1 Introduction

Tetrastigma hemsleyanum is a high-value Chinese medicinal vine, and both its roots and aerial parts are widely used. With increasing market demand and intensified overharvesting, the utilization of T. hemsleyanum resources is rapidly shifting from wild collection to artificial cultivation (Hu et al., 2021). Its medicinal quality largely depends on light-sensitive secondary metabolites; therefore, shading management has become a key issue in standardized and high-quality production (Zhang et al., 2021). Traditionally, T. hemsleyanum has been used to treat fever, pneumonia, asthma, hepatitis, rheumatism, and other inflammatory and infectious diseases, and it is known in folk practice as a “natural plant antibiotic” (Ji et al., 2020). Modern studies have identified more than 140 compounds in this species, among which flavonoids and polysaccharides are representative active components, exhibiting antitumor, anti-inflammatory, antioxidant, immunomodulatory, and antipyretic activities. Total flavonoids from the roots of T. hemsleyanum can inhibit colorectal tumor growth and regulate gut microbiota (Han et al., 2023), while polysaccharides from the roots and aerial parts show significant antitumor, antipyretic, and immunomodulatory effects in vivo. These findings indicate that T. hemsleyanum is a potential resource for developing novel antitumor and immunomodulatory products and also provide strong impetus for its industrial development.

For medicinal plants, light environment regulation is a core agronomic measure that simultaneously affects biomass and secondary metabolite accumulation (Zhang et al., 2021). In many medicinal plants, shading or light intensity regulation has been shown to alter photosynthesis, pigment content, and the levels of phenolics, flavonoids, and other bioactive compounds. The optimal state often occurs under moderate shading rather than full sunlight or deep shading (Xu et al., 2020; Gao et al., 2025). In shade-tolerant or understory herbaceous medicinal plants, appropriate shading can simultaneously increase aboveground yield and enhance the accumulation of specific medicinal metabolites, thereby improving overall medicinal value. However, plant responses to the light environment are highly species-specific and are jointly affected by light intensity, spectral quality, and duration. Therefore, it is difficult to directly apply a universal “light formula” to all medicinal crops.

This study explores the mechanisms by which shading environments affect the growth and medicinal quality formation of T. hemsleyanum. Existing studies on the physiological characteristics of T. hemsleyanum have only briefly addressed light effects, and there remains a clear knowledge gap regarding how the light environment shapes its growth process and medicinal quality formation. Given the increasing scarcity of wild resources and the rapid expansion of cultivated areas, it is necessary to clarify the mechanisms by which shading environments regulate the growth of T. hemsleyanum and the accumulation of key active components. On the one hand, standardized light and shading management is important for improving biomass, stabilizing quality markers such as flavonoids and polysaccharides, supporting quality control, and promoting industrial upgrading. On the other hand, clarifying how light intensity and shading affect photosynthesis, antioxidant defense, and secondary metabolism in this species will enrich the theoretical basis for precise light environment regulation in medicinal plants. This study focuses on analyzing the mechanisms by which shading environments influence the growth and medicinal quality formation of T. hemsleyanum, aiming to provide scientific reference for its standardized cultivation, quality evaluation, and sustainable industrial development.

2 Ecological Habits and Shading Adaptation Basis of Tetrastigma hemsleyanum

2.1 Natural habitat and low-light adaptation characteristics of Tetrastigma hemsleyanum

Tetrastigma hemsleyanum is a perennial herbaceous climbing vine belonging to the genus Tetrastigma in the family Vitaceae, and it is one of the important medicinal plant resources in China. Its natural distribution is mainly concentrated in warm evergreen forests in subtropical and tropical regions of China. It is commonly found in understory habitats, forest edges, valleys, streamside areas, and hillside shrublands at altitudes of 300-1300 m, and may also extend to regions such as Hainan and Taiwan (Ren et al., 2025). From an ecological perspective, T. hemsleyanum prefers cool and humid environments, relatively high air humidity, loose soils rich in humus, and yellow or yellow-brown soils. Its natural habitats are generally characterized by sufficient scattered light, weak direct sunlight, and relatively stable hydrothermal conditions (Ji et al., 2020; Hu et al., 2021). This indicates that T. hemsleyanum is not a typical heliophilous plant, but is more suitable for growth in semi-shaded and humid environments with a certain degree of canopy cover. This also provides an ecological basis for its application in understory cultivation, trellis cultivation, and intercropping systems.

During long-term adaptation to understory or semi-shaded environments, T. hemsleyanum has developed a series of low-light adaptation characteristics. The plant mainly grows as a climbing vine and can extend outward by relying on surrounding vegetation or supports, thereby obtaining suitable scattered light resources. As the main photosynthetic organs, leaves are highly sensitive to changes in light conditions. Under low-light conditions, they can improve light interception capacity by regulating leaf area, chlorophyll content, and spatial leaf distribution. Ensemble habitat modeling further indicates that the current highly suitable habitats of T. hemsleyanum are mainly concentrated in subtropical regions jointly constrained by specific temperature and precipitation conditions, showing strong climatic adaptation specificity. Genomic and landscape genomic studies also show that T. hemsleyanum exhibits obvious local adaptation to heterogeneous climates. Winter precipitation and other climatic factors can explain a considerable proportion of its genomic variation, and many adaptive loci are associated with stress responses and environmental adaptation (Ren et al., 2025). Although direct measurements of the natural canopy light environment of T. hemsleyanum remain limited, its distribution in evergreen forests, preference for cool and humid environments, and the need to avoid strong light in bionic cultivation collectively support the view that it has a shade-adapted, low-light ecological strategy (Xu et al., 2018; Hu et al., 2021).

2.2 Fundamental role of light intensity in the growth and development of Tetrastigma hemsleyanum

Light is one of the most important ecological factors in the growth and development of T. hemsleyanum. It not only provides energy for photosynthesis, but also acts as an environmental signal involved in regulating plant morphogenesis, substance accumulation, and metabolic activities. Suitable light intensity is beneficial for improving leaf photosynthetic efficiency, promoting organic matter synthesis and transport, and providing a material basis for vine elongation, leaf expansion, and tuberous root enlargement. Shading experiments have shown that light intensity is a key factor regulating the growth, photosynthesis, and pigment accumulation of T. hemsleyanum. Under different shading levels, leaf size and net photosynthetic rate (Pn) reach relatively high levels under approximately 67%~70% shading, whereas stronger light and excessive shading both reduce plant growth and carbon assimilation capacity (Dai et al., 2009; Xu et al., 2018). This suggests that T. hemsleyanum has a clear suitable range of light intensity, and that either excessively strong or insufficient light is unfavorable for its sustained growth and formation of medicinal organs.

Both excessively high and excessively low light intensity may adversely affect T. hemsleyanum. Under strong light conditions, leaf transpiration increases and plant water consumption accelerates. When accompanied by high temperature and insufficient soil moisture, this may easily lead to leaf wilting, scorching, or photoinhibition, thereby reducing photosystem stability and photosynthetic efficiency. Studies have shown that under full sunlight and low-shading conditions, electron transport rate and photochemical quenching in T. hemsleyanum are inhibited, while non-photochemical quenching increases, indicating that excessively strong light can induce photoinhibition and reduce light-use efficiency. Conversely, under long-term excessive shading or insufficient low-light conditions, although T. hemsleyanum can enhance low-light capture capacity by increasing chlorophyll a, chlorophyll b, and total chlorophyll contents and reducing the chlorophyll a/b ratio, the accumulation of net photosynthetic products remains limited due to insufficient photosynthetically active radiation (Dai et al., 2009). Light response curve studies also indicate that the net photosynthetic rate of T. hemsleyanum increases rapidly under moderate photon flux density, then tends to become saturated, and decreases under high-light conditions, while the suitable light saturation point and maximum net photosynthetic rate mainly occur under moderate shading conditions (Xu et al., 2018). Therefore, the effect of light intensity on T. hemsleyanum is clearly dual in nature, and the key lies in maintaining a dynamic balance among light energy utilization, carbon assimilation, and stress alleviation.

2.3 Significance of shading environment for adaptation to artificial cultivation

The shading environment has important ecological regulatory significance in the artificial cultivation of T. hemsleyanum. Since the natural habitat of T. hemsleyanum is mostly semi-shaded and humid, exposing artificially cultivated plants completely to strong light may easily create a mismatch between their ecological niche requirements and the cultivation environment. In recent years, with the decline of wild T. hemsleyanum resources and increasing demand for medicinal materials, artificial cultivation has expanded rapidly, making light environment management a core issue for sustainable production. Based on the fact that T. hemsleyanum naturally grows in forest environments and is sensitive to strong light, bionic cultivation has been considered an important approach to meeting medicinal material demand and improving cultivation adaptability (Xu et al., 2018). By using shading nets, trellises, understory intercropping, or intercropping with tall-stemmed crops, direct light intensity can be reduced, the proportion of scattered light can be increased, and the field microclimate can be improved, thereby creating a growth environment close to its natural habitat. Relevant studies suggest that shading measures capable of achieving approximately 67%~70% shading may be adopted in cultivation, because higher light intensity inhibits its photosynthetic activity and growth, while excessive shading restricts carbon assimilation (Dai et al., 2009).

From the perspective of production practice, the value of shading treatment lies not only in promoting the growth of T. hemsleyanum, but also in regulating the relationship between yield and quality. Under suitable shading conditions, T. hemsleyanum can affect the formation and accumulation of active components such as flavonoids, polysaccharides, and phenolic compounds by improving leaf photosynthetic function, maintaining antioxidant system activity, regulating carbon-nitrogen metabolism, and promoting secondary metabolic processes. Studies on other shade-tolerant medicinal plants also support this pattern, indicating that moderate shading can improve growth, photosynthetic performance, and secondary metabolite accumulation, whereas full sunlight and deep shading may both have adverse effects. For example, in medicinal plants such as Eleutherococcus senticosus, Pinellia ternata, Paris polyphylla var. chinensis, and Polygala fallax, moderate shading can increase chlorophyll content, optimize photosystem function, and increase biomass or certain active components, whereas excessively strong or weak light may lead to growth inhibition, light damage, or reduced accumulation of active components (Xu et al., 2020; Liang et al., 2022; Gao et al., 2025; Liu et al., 2026). Reviews on light-regulated secondary metabolism further indicate that precise control of light intensity and light quality is an important means of enriching valuable medicinal metabolites, which also highlights the importance of shading regimes in quality-oriented cultivation of T. hemsleyanum (Zhang et al., 2021).

Therefore, establishing a rational shading management model not only helps improve the adaptability of T. hemsleyanum to artificial cultivation environments, but also provides important technical support for high-quality, efficient, and standardized cultivation. Especially in medicinal plant cultivation, yield improvement does not necessarily equate to quality enhancement. How to achieve coordination among tuberous root yield, active component content, and commercial traits of medicinal materials is a core issue in optimizing T. hemsleyanum cultivation technology. In the future, shading cultivation of T. hemsleyanum should be based on a clear understanding of its ecological habits and photosynthetic adaptation mechanisms, and should further integrate shading intensity, light quality regulation, cultivation models, and quality evaluation indicators to establish a widely applicable standardized light environment management scheme, thereby supporting resource conservation, stable medicinal material quality, and industrial development of T. hemsleyanum.

3 Effects of Shading Environment on Morphogenesis and Biomass Accumulation of Tetrastigma hemsleyanum

3.1 Effects on plant height, vine growth, and branching

The shading environment first affects the aboveground morphogenesis of Tetrastigma hemsleyanum, especially in terms of plant height, vine elongation, and branch growth. As a perennial vine, T. hemsleyanum often grows in understory or semi-shaded and humid environments in the wild, where it receives scattered light filtered through the forest canopy. Therefore, its artificial cultivation also requires light regulation to approximate its natural ecological niche requirements as closely as possible (Ji et al., 2020). Vine growth capacity is directly related to spatial expansion, leaf distribution, and light resource acquisition in T. hemsleyanum. Under moderate shading conditions, plants can enhance their utilization of scattered light by increasing vine length, adjusting internode distance, and improving the spatial arrangement of leaves. This morphological change represents an adaptive response to low-light environments, which helps expand the photosynthetic area and improve the light interception efficiency of the plant canopy under limited light resources.

The effects of shading on vine growth in T. hemsleyanum vary significantly with shading intensity. Shading experiments have shown that under full sunlight or only 50% shading, photosynthetic electron transport and photochemical quenching in T. hemsleyanum are inhibited, while photosynthetic activity and plant growth decline, indicating that strong light conditions suppress overall plant growth. In contrast, when light is reduced to approximately 67%~70% shading, the net photosynthetic rate, light saturation point, and maximum photosynthetic rate are higher than those under weaker shading treatments, indicating that this shading level is more conducive to carbon assimilation and vegetative vine growth (Xu et al., 2018). However, if shading is excessive, such as reaching 75%-90% or higher, insufficient photosynthetically active radiation restricts carbon assimilation and slows growth (Dai et al., 2009). Therefore, plant height, vine elongation, and branch formation in T. hemsleyanum are jointly constrained by photoinhibition under strong light and insufficient carbon supply under deep shading, while moderate to relatively high shading is more favorable for vine extension and coordinated plant structure formation.

From the general perspective of plant responses to shading, reduced light or a decreased red/far-red ratio can induce shade-avoidance responses, manifested as stem and internode elongation, but often at the cost of reduced branching and limited development of harvestable organs (Yang and Li, 2017). Similar phenomena have also been observed in leguminous plants, where shading can promote taller and thinner plants while reducing the number of lateral branches and aboveground biomass. For naturally shade-tolerant T. hemsleyanum, moderate shading is more likely to result in adaptive elongation and canopy optimization rather than simple etiolation. However, under excessive shading, excessive vine elongation, overly extended internodes, weak stems, and suppressed lateral branching may still occur, ultimately affecting leaf area formation and photosynthetic product accumulation. Therefore, in cultivation, “vine elongation” should not be simply equated with “good growth”; instead, branch number, leaf distribution, vine robustness, and underground tuberous root development should be comprehensively evaluated.

3.2 Effects on leaf morphology and leaf area expansion

Leaves are the main organs through which T. hemsleyanum performs photosynthesis and senses changes in the light environment. Therefore, changes in leaf morphology under shading conditions are important manifestations of its low-light adaptation. Leaf traits of T. hemsleyanum are sensitive to shading environments and reflect typical shade-leaf characteristics. As shading increases, chlorophyll a, chlorophyll b, and total chlorophyll contents increase, while the chlorophyll a/b ratio decreases, indicating adaptive adjustment of the light-harvesting antenna system to capture limited photons more efficiently under low-light conditions (Dai et al., 2009; Xu et al., 2018). In general, under moderately low-light environments, T. hemsleyanum can enhance light capture capacity by expanding individual leaf area, increasing total leaf area, and increasing photosynthetic pigment content. Studies have shown that leaves of T. hemsleyanum reach their largest size under approximately 67% shading, whereas full sunlight, 50% shading, and deep shading of approximately 90% all result in smaller leaves (Dai et al., 2009).

Leaf area expansion can increase the plant’s absorption range of scattered light, helping compensate for the decrease in light intensity per unit leaf area. These changes are consistent with general patterns observed in shade-tolerant medicinal plants and forest plants, in which moderate shading, compared with no shading or excessive shading, is more conducive to increasing leaf area, improving seedling quality, and enhancing leaf function (Xue et al., 2023; Liu et al., 2026). In other shade-tolerant medicinal plants, low to moderate shading can thin the palisade tissue, increase total leaf thickness, and improve mesophyll structure, thereby promoting light absorption and carbon dioxide diffusion (Li et al., 2025). In T. hemsleyanum, increased chlorophyll content under approximately 67%~70% shading, together with improved net photosynthetic rate and other photosynthetic parameters, suggests that its leaf structure and function may also undergo optimization favorable for low-light utilization (Dai et al., 2009; Xu et al., 2018).

However, leaf area expansion does not necessarily indicate increased biomass accumulation. If shading intensity is too high, leaves may show certain shade-adaptive characteristics, such as deeper green color, increased chlorophyll content, or thinner leaf blades. Nevertheless, due to insufficient photosynthetically active radiation, net photosynthetic capacity per unit leaf area may decline, causing leaves to shift from highly efficient production organs to organs with relatively high maintenance costs. Long-term deep shading may also reduce leaf structural stability and stress resistance and increase the risk of disease occurrence. When shading is excessive, the decline in light saturation point and photosynthetic capacity in T. hemsleyanum limits carbon acquisition, thereby restricting leaf expansion and total leaf area formation (Xu et al., 2018). Therefore, the effects of shading on leaf morphology should be evaluated comprehensively from three aspects: leaf area expansion, leaf functional maintenance, and photosynthetic efficiency improvement. Among these, moderate shading regimes are more conducive to allowing T. hemsleyanum to fully express shade-leaf morphological potential, improve canopy light interception, and promote biomass accumulation.

3.3 Effects on tuberous root enlargement and biomass allocation

The main medicinal organs of T. hemsleyanum are enlarged spindle-shaped tuberous roots. These tuberous roots serve both as storage tissues and as pharmacologically active tissues, and their enlargement and dry matter accumulation are directly related to medicinal yield and commercial value (Figure 1) (Ji et al., 2020). The effect of shading environment on tuberous root formation essentially depends on the coordination between aboveground photosynthetic product supply and underground assimilate allocation. At present, direct studies on the relationship between shading and tuberous root enlargement in T. hemsleyanum remain limited, and existing research has mainly focused on changes in aboveground photosynthesis under different light intensities (Hu et al., 2021). Current data indicate that unsuitable light environments, such as strong light, high temperature, and low humidity, reduce photosynthetic activity and slow plant growth in T. hemsleyanum, thereby indirectly limiting carbohydrate supply to the roots (Xu et al., 2018). In contrast, 67%~70% shading can maintain relatively high maximum net photosynthetic rate and quantum efficiency, creating favorable conditions for sustained assimilate production and its storage in tuberous roots (Dai et al., 2009).

Studies on other medicinal plants with storage organs help explain the possible biomass allocation patterns of T. hemsleyanum under different shading regimes. In shade-responsive species, moderate shading generally increases total biomass more effectively than full sunlight or deep shading, and may also increase root or storage organ biomass (Liang et al., 2022; Xue et al., 2023). Comprehensive studies of biomass allocation have shown that plants under environmental stress or resource limitation often allocate a relatively greater proportion of biomass to underground parts, thereby increasing the root-shoot ratio. However, this does not necessarily mean improved medicinal yield, because increased underground allocation may be accompanied by damage to aboveground photosynthetic structures and a decline in total biomass (Qi et al., 2019). In medicinal herbaceous plants, light shading may reduce the root-shoot ratio while increasing leaf biomass and total yield; in contrast, high light and dense planting may promote biomass allocation to roots, but at the expense of restricted aboveground growth (Ahmed et al., 2024). In storage tuber crops such as potato, simulated shading promotes stem elongation but reduces tuber yield, indicating that excessive shading may redirect assimilates from storage organs toward stem elongation (Gómez-Ocampo et al., 2023).

Therefore, from the perspective of medicinal material production, an ideal shading environment should not simply promote stem and leaf growth, nor should it simply increase the root-shoot ratio. Instead, it should maintain a dynamic balance between aboveground photosynthetic structure formation and underground medicinal organ accumulation. T. hemsleyanum likely has an optimal shading range close to the 67%~70% shading level identified in photosynthetic performance studies. Within this range, aboveground assimilation and underground storage processes can be well coordinated, thereby simultaneously supporting vigorous vine growth and effective tuberous root enlargement. In contrast, both strong light stress and excessively deep shading may lead to unfavorable biomass allocation and reduced medicinal yield. Therefore, in T. hemsleyanum cultivation, shading intensity should be reasonably controlled according to different growth stages so as to maintain good vegetative growth while ensuring tuberous root formation and medicinal yield improvement.

4 Effects of Shading Environment on Photosynthetic Physiology and Stress Resistance of Tetrastigma hemsleyanum

4.1 Effects on photosynthetic pigments and light-harvesting capacity

Photosynthetic pigments are an important material basis for light energy absorption, transfer, and conversion in Tetrastigma hemsleyanum, and changes in their content and composition directly reflect the plant’s adaptability to shading environments. Shading treatment can significantly alter the pigment system of T. hemsleyanum and related shade-tolerant plants, thereby reshaping their light-harvesting capacity. Studies have shown that, in T. hemsleyanum, chlorophyll a, chlorophyll b, and total chlorophyll contents gradually increase with increasing shading intensity, while the chlorophyll a/b ratio decreases, indicating a typical shade-leaf adaptive expansion of the light-harvesting complex. This adjustment helps enhance the absorption of scattered and weak light under low-light conditions (Dai et al., 2009; Xu et al., 2018). In particular, the increase in chlorophyll b content is important for expanding the light-harvesting antenna system and improving light energy utilization efficiency under weak light. Similar phenomena have also been observed in other shade-managed crops, in which shading promotes the accumulation of chlorophyll and carotenoids and, compared with full sunlight, helps maintain greener leaves and a higher net photosynthetic rate (Elango et al., 2023).

In addition to chlorophylls, auxiliary pigments such as carotenoids also participate in light absorption, energy transfer, and photoprotection. Under suitable shading conditions, increases in chlorophyll and carotenoid contents can enhance light absorption capacity and improve the processing efficiency of absorbed light energy. At the same time, they reduce strong light-induced photooxidative pressure and decrease damage caused by excessive light energy accumulation in leaves. Shade-grown leaves usually show a reduced chlorophyll a/b ratio along with structural adjustments, which helps improve the utilization of transmitted light and avoid photoinhibition (Sagun et al., 2022). In overwintering tea plants and other shade-managed crops, shading can also upregulate genes related to chlorophyll and carotenoid metabolism as well as core photosystem protein genes, thereby enhancing light-harvesting capacity under low-light conditions (Simkin et al., 2022; Han et al., 2023). Therefore, moderate shading can enhance the adaptability of T. hemsleyanum to weak-light environments by optimizing pigment composition and the light-harvesting system. However, if shading is excessive, although leaves may exhibit apparent features such as deeper green color and increased chlorophyll content, insufficient incident light energy will still restrict light reactions and carbon assimilation, ultimately reducing photosynthetic production capacity.

4.2 Effects on photosynthetic efficiency and stomatal regulation

Photosynthetic efficiency is an important indicator for evaluating the growth potential of T. hemsleyanum under different light environments. Moderate shading can alleviate physiological stress caused by strong light, high temperature, and excessive water transpiration, helping maintain favorable stomatal opening and photosynthetic system activity. Across a series of shading treatments, the net photosynthetic rate, stomatal conductance, transpiration rate, light saturation point, and maximum net photosynthetic rate of T. hemsleyanum all increased with enhanced shading and reached relatively high levels under approximately 70% shading, before declining under deeper shading. Across different growth stages, the 70% shading treatment consistently showed superior photosynthetic characteristics (Xu et al., 2018). Another shading experiment also showed that under 67% shading, T. hemsleyanum had the largest leaves, the highest net photosynthetic rate, and a light saturation point of 600 μmol·m⁻²·s⁻¹, whereas stronger light and excessive shading both reduced carbon assimilation capacity and plant growth (Dai et al., 2009). These findings indicate that the photosynthesis of T. hemsleyanum exhibits an obvious “moderate optimum” response to shading intensity.

Shading also reshapes stomatal regulation and photochemical processes in T. hemsleyanum. Under suitable shading conditions, stomatal conductance and transpiration rate remain relatively coordinated, which helps ensure carbon dioxide entry into leaves for carbon assimilation. Meanwhile, the milder microclimate under shading can reduce leaf water deficit and decrease photosynthetic limitation caused by stomatal closure. Studies have shown that stomatal conductance and transpiration rate in T. hemsleyanum increase as shading rises to 70%, and then decline; unsuitable conditions such as strong light and high temperature reduce photosynthetic activity and slow plant growth (Xu et al., 2018). Under full sunlight and low-shading conditions, electron transport rate and photochemical quenching in T. hemsleyanum decrease, while non-photochemical quenching increases, indicating the occurrence of photoinhibition. Moderate shading, by contrast, can maintain relatively high photochemical efficiency (Dai et al., 2009). Similar patterns have also been reported in other woody and medicinal plants: net photosynthetic rate is relatively high under moderate shading, the functions of photosystem II and photosystem I are more coordinated, whereas strong light or heavy shading may cause photosystem functional imbalance (Barazetti et al., 2021).

However, the effect of shading on photosynthetic efficiency is dual in nature. When shading is too strong, insufficient photosynthetically active radiation becomes the main factor limiting photosynthesis in T. hemsleyanum. Under such conditions, even if stomatal conductance does not decline significantly, insufficient light energy received by leaves will restrict both light and dark reactions, resulting in a decrease in net photosynthetic rate. Long-term heavy shading reduces organic matter synthesis, disrupts the balance between respiratory consumption and material accumulation, and further affects robust vine growth, leaf functional maintenance, and underground tuberous root enlargement. Therefore, the key to shading cultivation is not simply to reduce light exposure, but to regulate light intensity rationally so that T. hemsleyanum can avoid strong light stress while obtaining sufficient light energy to support biomass accumulation and medicinal quality formation.

4.3 Effects on the antioxidant system and cellular homeostasis

The shading environment also regulates stress resistance and cellular homeostasis in T. hemsleyanum by affecting the production and scavenging of reactive oxygen species. Regulation of the antioxidant system is an important mechanism by which plants cope with light stress. Although direct studies on antioxidant enzyme activities in T. hemsleyanum remain relatively limited, related studies in model shade-tolerant plants and medicinal plants are more abundant. Under strong light, high temperature, water stress, or other unfavorable light environments, the photosynthetic electron transport chain in leaves is prone to over-reduction, resulting in the accumulation of reactive oxygen species (ROS), which can further induce membrane lipid peroxidation, protein damage, and destruction of photosynthetic structures (García-Caparrós et al., 2020; Mishra et al., 2023). Therefore, plants must rely on enzymatic and non-enzymatic antioxidant systems to remove excess ROS, protect cellular structures, and maintain metabolic stability.

The main enzymatic antioxidant components include superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR). These enzymes act cooperatively to convert reactive oxygen species such as superoxide anions and hydrogen peroxide into less harmful products. Meanwhile, non-enzymatic antioxidants such as ascorbic acid, glutathione, carotenoids, and flavonoids can also provide additional redox buffering capacity (García-Caparrós et al., 2020; Rajput et al., 2021). Moderate shading can reduce excessive light energy input, alleviate photooxidative pressure, and help maintain coordinated operation of antioxidant enzyme systems, thereby improving the plant’s buffering capacity against environmental fluctuations.

Under different light conditions, many plants can maintain ROS homeostasis by upregulating antioxidant-related gene expression and increasing antioxidant enzyme activities. In the shade-tolerant plant Solidago canadensis, increased shading can induce high expression of SOD, POD, CAT, APX, and GPX genes, thereby enhancing ROS scavenging capacity under shading stress. In shade-tolerant Panax notoginseng, strong light stress increases SOD, POD, and CAT activities, while non-photochemical quenching dissipates excess energy to prevent photooxidative damage (Cun et al., 2023). Jasmine shows rapid changes in SOD, POD, APX, and CAT activities under different shading levels, and these changes are affected by both shading intensity and duration. Moderate shading generally supports more efficient antioxidant responses and reduces membrane lipid peroxidation compared with full sunlight or heavy shading (Deng et al., 2018). Based on these findings, it can be inferred that, in T. hemsleyanum, suitable shading environments may reduce excessive ROS production caused by strong light or extreme shading, support balanced antioxidant enzyme activity, and maintain membrane integrity, osmotic regulation capacity, and redox homeostasis, thereby providing a physiological basis for enhanced stress resistance and stable medicinal quality formation.

5 Effects of Shading Environment on Substance Metabolism and Active Component Accumulation in Tetrastigma hemsleyanum

5.1 Effects on carbohydrate accumulation and transport

Carbohydrates are an important material basis for the growth, development, and medicinal organ formation of Tetrastigma hemsleyanum. Their accumulation level is directly affected by photosynthetic intensity, sugar metabolic activity, and the transport efficiency of assimilates. By altering the light intensity received by leaves, the shading environment further affects the synthesis, allocation, and transport of carbohydrates such as soluble sugars, sucrose, and starch. Studies on light-regulated sugar metabolism indicate that light intensity and light quality can influence starch granule formation, sucrose synthesis, and vascular transport, thereby determining the amount of carbon sources available for plant growth, storage organ development, and secondary metabolism. Under moderate shading conditions, leaves of T. hemsleyanum are expected to maintain relatively stable photosynthetic activity while reducing physiological consumption caused by strong light and high temperature, which is conducive to the continuous formation and effective transport of photosynthetic products. At this stage, leaves function as “source” organs and can provide sufficient carbon support for vine growth and underground tuberous root enlargement.

Carbohydrate accumulation is highly sensitive to shading intensity. If shading is excessive, insufficient photosynthetically active radiation restricts carbon assimilation, reducing the production of photosynthetic products in leaves and subsequently affecting sucrose transport to underground tuberous roots and the accumulation of storage substances. In medicinal underground bud plants such as Bletilla striata and Bletilla ochracea, moderate shading or medium light intensity can increase aboveground and tuber dry weight, net photosynthetic rate, and total polysaccharide content, whereas excessive shading leads to a significant decline in these indicators (Xu et al., 2024). Suitable light intensity can promote sucrose production in leaves and improve its transport efficiency to storage organs. In storage organs, sucrose is further converted into key intermediates such as sucrose-6-phosphate, fructose-6-phosphate, glucose-6-phosphate, GDP-mannose, and UDP-glucose, which subsequently participate in polysaccharide biosynthesis (Zhu et al., 2024; Zhu et al., 2025). Conversely, under low-light or long-term shading conditions, glycolysis, galactose metabolism, the pentose phosphate pathway, and the tricarboxylic acid cycle are inhibited in many plants, resulting in reduced sugar reserves and causing plants to shift toward consuming stored carbohydrates (Liu et al., 2020; Shao et al., 2022). Therefore, the regulation of carbon metabolism by shading in T. hemsleyanum is not simply promotive or inhibitory; rather, it depends on whether shading intensity can maintain a balance among photosynthesis, respiratory consumption, and assimilate transport.

5.2 Effects on nitrogen metabolism and carbon-nitrogen balance

Nitrogen metabolism is an important basis for vegetative growth and physiological function maintenance in T. hemsleyanum, and it is closely associated with chlorophyll synthesis, protein formation, enzyme activity regulation, and secondary metabolism. Under shading conditions, T. hemsleyanum often needs to adjust leaf structure and photosynthetic pigment composition to adapt to weak-light environments, while chlorophyll, Rubisco, and other photosynthesis-related proteins all require nitrogen for their formation. General studies on carbon-nitrogen regulation have shown that increasing nitrogen allocation in leaves can enhance chlorophyll and Rubisco contents, photosynthetic nitrogen-use efficiency, and carbon assimilation capacity, and can help improve plant growth and carbon storage even under nitrogen-limited conditions (Perchlik and Tegeder, 2018). Therefore, under moderate shading conditions, T. hemsleyanum may enhance light absorption and utilization under weak light by optimizing nitrogen allocation for leaf functional maintenance and photosynthetic system construction, thereby providing a metabolic basis for subsequent substance synthesis and medicinal component accumulation.

Shading can also reshape nitrogen metabolism and carbon-nitrogen (C-N) balance, both of which jointly determine photosynthetic capacity, vegetative growth, and secondary metabolite biosynthesis in plants. In tea plants, short-term shading can promote leaf nitrogen metabolism and increase amino acid accumulation, whereas long-term or high-intensity shading inhibits sugar metabolism and alters flavonoid metabolic pathways (Li et al., 2020). Under shading conditions, protein hydrolysis and nitrogen redistribution can increase free amino acid content, while catechin and other phenolic compound levels decline, reflecting a shift in carbon-nitrogen allocation direction (Shao et al., 2022). Shading experiments in forest plants have shown that, as shading increases, the leaf C:N ratio decreases while the N:P ratio increases, and non-structural carbohydrates are closely associated with C: N: P stoichiometric characteristics, suggesting a dynamic trade-off between carbon storage and nutrient utilization under low-light environments (Liu et al., 2020). For T. hemsleyanum, if shading is appropriate, carbon supply and nitrogen utilization can remain relatively coordinated, which is beneficial for protein synthesis, enzymatic reactions, and normal operation of metabolic pathways. If shading is excessive, however, carbon assimilation becomes restricted while nitrogen metabolic demand remains, potentially causing C-N imbalance and affecting plant dry matter accumulation and substrate supply for secondary metabolism.

5.3 Effects on the accumulation of flavonoids, polysaccharides, and phenolic compounds

Flavonoids, polysaccharides, and phenolic acids are important active components for evaluating the medicinal quality of T. hemsleyanum, and they are also representative pharmacologically active substances in its tuberous roots and leaves (Hu et al., 2021). The accumulation of these components is jointly regulated by multiple factors, including light intensity, spectral composition, temperature, water availability, nutrient status, and growth stage. The shading environment can influence the operation of secondary metabolic pathways in T. hemsleyanum by altering light signal input, photosynthetic product supply, and cellular redox status. Moderate shading can alleviate strong light stress and maintain a relatively stable physiological metabolic state, thereby providing a favorable cellular environment for active component synthesis. Meanwhile, suitable weak light or specific light quality stimulation may also induce plants to adjust phenylpropanoid metabolism and flavonoid biosynthesis, thereby affecting the accumulation of flavonoids and phenolic compounds.

Different active components do not respond uniformly to shading environments. In T. hemsleyanum cultivated under different colored films, blue film promoted vegetative growth and soluble amino acid accumulation, whereas red film significantly increased flavonoid content and the activity of key enzymes such as phenylalanine ammonia-lyase (PAL). This indicates that changes in light quality under shading environments may lead plants to exhibit different metabolic orientations between yield and quality (Bai et al., 2021). Long-term low-intensity blue light treatment of T. hemsleyanum tuberous roots can simultaneously increase tuberous root yield and total flavonoid content, enhance antioxidant activity, and upregulate genes related to flavanol biosynthesis (Zhao et al., 2024). In addition, seasonal analysis has shown that flavonoid content, as well as the antioxidant activities of major phenolic compounds and polysaccharides in T. hemsleyanum, fluctuate with changes in sunshine duration, temperature, and humidity, while suitable shading conditions help enhance the accumulation of medicinally relevant phenolic compounds and polysaccharides (Figure 2) (Shi et al., 2022). These results indicate that the accumulation of active components in T. hemsleyanum is sensitive to both light intensity and spectral composition, and shading management affects not only yield but also the intrinsic quality of medicinal materials.

Polysaccharide accumulation is usually closely related to carbohydrate metabolism, tuberous root development, and storage substance formation. Therefore, when excessive shading causes carbon source insufficiency, polysaccharide accumulation may be inhibited. Shading studies on Bletilla species have shown that moderate shading or medium light intensity can result in relatively high polysaccharide content, accompanied by increases in precursor substances such as sucrose-6-phosphate and glucose-6-phosphate. In contrast, excessive shading or strong light reduces polysaccharide levels and disrupts carbon metabolism (Xu et al., 2024; Zhu et al., 2024). Flavonoids and phenolic compounds are more strongly affected by light signals, oxidative stress, and secondary metabolic enzyme activities. Studies on tea plants have shown that strong shading generally inhibits flavonoid and catechin biosynthesis while increasing free amino acid content, indicating that reduced light can alter the balance between nitrogen-rich and carbon-rich metabolites (Li et al., 2020; Shao et al., 2022). Therefore, the effects of shading environments on the medicinal quality of T. hemsleyanum are component-specific, light quality-sensitive, and intensity-dependent. An ideal shading regime should promote the coordinated accumulation of major active components such as flavonoids, polysaccharides, and phenolic compounds while ensuring tuberous root yield, thereby achieving simultaneous improvement in medicinal yield and intrinsic quality.

6 Mechanisms by Which Shading Regulates Medicinal Quality Formation in Tetrastigma hemsleyanum

6.1 Light signal perception and transduction mechanisms

Shading simultaneously alters light intensity and spectral composition, such as reducing the proportions of UV-B, blue light, and red light while enriching far-red light. Therefore, Tetrastigma hemsleyanum is expected to perceive shading environments through a series of photoreceptors similar to those identified in other plant species. Under canopy or shaded conditions, plants use phytochromes to perceive red and far-red light, cryptochromes and phototropins to perceive blue light/UV-A, and UVR8 to perceive UV-B, thereby recognizing changes in light quality and quantity and correspondingly regulating morphology and metabolism (Liu et al., 2018). These photoreceptors converge on core regulatory hubs such as the COP1-SPA E3 ubiquitin ligase complex and the bZIP transcription factor HY5, integrating multi-wavelength signals and reprogramming gene expression (Tissot and Ulm, 2020).

In shaded tea plants, UVR8-, HY5-, and COP1-related genes show co-expression relationships with flavonoid biosynthesis genes, and their expression levels decrease synchronously with catechin and flavonol contents, indicating that weakening of UV-B and its related signaling directly affects secondary metabolism (Liu et al., 2018). More broadly, different wavelengths of light can activate HY5 and related factors through UVR8, cryptochromes, and phytochromes, thereby inducing the synthesis of phenylpropanoid “sunscreen” metabolites and other protective metabolites (Leonardelli et al., 2024). Therefore, in T. hemsleyanum, shading-induced changes in the UVR8-HY5-COP1 signaling pathway are likely to be key upstream mechanisms regulating the accumulation of medicinal phenylpropanoid and flavonoid compounds.

6.2 Regulatory mechanisms of secondary metabolic pathways

Light regulates the biosynthesis of phenolic compounds, terpenoids, alkaloids, and other substances through conserved transcriptional regulatory networks. Specific photoreceptors can activate signaling cascades and regulate the expression of genes involved in phenylpropanoid and flavonoid metabolic pathways, such as PAL, C4H, 4CL, CHS, CHI, F3H, F3′H, FLS, DFR, ANS, ANR, and LAR, thereby leading to tissue- and condition-specific accumulation of catechins, flavonols, anthocyanins, and other metabolites (Liu et al., 2023). In tea plants, shading treatment, namely 20%-25% light transmittance, reduces catechin and flavonol contents by more than 40%-50%, accompanied by coordinated downregulation of multiple flavonoid structural genes and UVR8 pathway components, directly demonstrating a link between shading and reduced phenylpropanoid metabolic flux (Liu et al., 2018).

Comprehensive reviews indicate that the effect of shading on medicinal quality depends on species shade tolerance and light level: moderate shading can increase total phenols, flavonoids, and specific compounds, whereas deep shading usually downregulates genes related to phenylpropanoid and terpenoid biosynthesis and reduces metabolite accumulation. Reviews of phenylpropanoid metabolism emphasize that this pathway generates thousands of metabolites, including flavonoids and phenolic acids with strong antioxidant and defensive functions, and that it is strictly regulated at both transcriptional and post-transcriptional levels to adapt to changing environmental conditions (Deng and Lu, 2017; Ninkuu et al., 2025). For T. hemsleyanum, its key medicinal components mainly include flavonoids and related compounds derived from the phenylpropanoid pathway. Therefore, shading is expected to reshape metabolic pathway flux by altering photoreceptor signaling and the expression of core biosynthetic genes.

6.3 Regulation of key enzyme genes and transcription factors

Light signals regulate medicinal quality not only through structural genes, but also through complex transcription factor networks. Core light-responsive regulators such as HY5, PIFs, BBX proteins, and COP1 can integrate photoreceptor input signals and interact with transcription factors such as MYB, bHLH, WRKY, bZIP, and NAC, thereby directing the expression of genes related to secondary metabolism (Liu et al., 2023; Chen et al., 2025). In shaded tea plants, photoreceptor genes and UVR8-HY5 pathway genes show co-expression relationships with MYB12, MYB4, and MYB111, supporting a model in which light-regulated MYB transcription factors control catechin and flavonol biosynthesis (Liu et al., 2018). In medicinal and horticultural plants, MYB, bHLH, WRKY, and related transcription factors serve as “master switches” of phenylpropanoid and flavonoid metabolic pathways and respond strongly to changes in the light environment. In yam, light exposure can increase anthocyanin and flavonoid contents, and light-induced MYB and WRKY transcription factors are highly correlated with anthocyanin metabolites and structural gene expression.

In pear, the light-responsive WRKY transcription factor PpWRKY44 is activated by BBX18 and can directly bind to the PpMYB10 promoter, thereby driving anthocyanin accumulation (Alabd et al., 2022). Multi-omics studies further show that blue light can upregulate MYB transcription factors as well as key structural genes such as PAL, CHS, CHI, F3H, and FLS, thereby enhancing flavonoid accumulation. Reviews on medicinal plants also point out that the MYB, WRKY, bHLH, AP2/ERF, and NAC families are core regulatory factors mediating stress- and light-induced secondary metabolite biosynthesis (Tong et al., 2024; Rabeh et al., 2025). Based on these conserved mechanisms, it can be inferred that shading effects in T. hemsleyanum are likely mediated by regulating light-signaling hubs such as UVR8-COP1-HY5, which further control MYB/WRKY/bHLH regulatory networks and the expression of key enzyme genes in phenylpropanoid and flavonoid metabolic pathways, ultimately influencing medicinal quality formation.

7 Optimization Strategies for Shading Cultivation of Tetrastigma hemsleyanum

7.1 Reasonable determination of shading intensity

Physiological studies on Tetrastigma hemsleyanum provide clear evidence for determining an appropriate shading level. Under five light intensity treatments ranging from full sunlight to 90% shading, photosynthetic pigments and most photosynthetic indicators increased with increasing shading intensity and reached their peak at approximately 70% shading before declining. This indicates that 70% shading can maintain the highest net photosynthetic rate (Pn), maximum photosynthetic rate (Pmax), light saturation point, and stomatal conductance during both the rapid and slow growth stages (Xu et al., 2018). Another experiment conducted under full sunlight, 50% shading, 67% shading, and 90% shading showed that 67% shading produced the largest leaves and the highest photosynthetic rate. Light stronger than that under 50% shading inhibited photosynthesis and growth, whereas irradiance below that under 75% shading restricted carbon assimilation (Dai et al., 2009). Together, these findings suggest that approximately 65%-70% shading can serve as a reasonable baseline for field and greenhouse cultivation.

Experience from other medicinal plants also supports this principle, namely that moderate shading or medium light intensity can usually optimize both biomass and active component accumulation. In the shade-loving medicinal plant Panax notoginseng, the combination of three-layer shading, an appropriate red-blue light ratio, and moderate soil moisture produced the highest biomass and saponin content; in contrast, light under single-layer shading was still “excessive” relative to its physiological requirements and could damage photosynthesis and secondary metabolism. In Pinellia ternata, 55% full sunlight treatment increased chlorophyll content, photosynthetic rate, and succinic acid content compared with full sunlight, with succinic acid increasing by 27%, indicating that moderate shading can improve medicinal quality (Gao et al., 2025). Meanwhile, excessive shading, such as 72%-90% shading, may significantly reduce biomass and active component content in certain species (Deng et al., 2024). Therefore, for T. hemsleyanum, using 65%-70% shading as the core target and making slight adjustments within this range according to local light climate and quality objectives is a relatively reasonable cultivation strategy.

7.2 Stage-specific light environment regulation

The light requirements of T. hemsleyanum differ among developmental stages, and therefore a dynamic shading strategy is needed. The photosynthetic indicators of this species during the rapid growth stage are 41%-67% higher than those during the slow growth stage, yet 70% shading remains suitable in both stages. This suggests that, while maintaining the same basic shading intensity, other factors such as temperature and humidity can be further adjusted (Xu et al., 2018). However, studies on other herbaceous medicinal plants indicate that using full sunlight or relatively high light intensity at the early growth stage, followed by increased shading or spectral adjustment at later stages, may better coordinate biomass accumulation and quality formation. In Origanum majorana, 100% light produced the highest dry weight, whereas essential oil content peaked under 70% light; therefore, researchers suggested using high light during the early growth stage and 70% light transmittance shading treatment during the later growth cycle (Hashemifar et al., 2024).

Studies on understory medicinal plants and shade-tolerant plants further emphasize the importance of stage-specific light quality regulation. In Scutellaria baicalensis, compared with UV-A, green light, or mixed blue-red light treatments, monochromatic blue light (R0B4) better promoted growth and flavonoid accumulation, indicating that enhancing the blue-light component during stages targeting flavonoid synthesis may improve quality. For T. hemsleyanum, when cultivated under different colored films at 70% total light transmittance, blue film (BF) was most favorable for promoting growth and yield formation, whereas red film (RF) was most effective in increasing PAL activity and flavonoid content (Bai et al., 2021). These results suggest that, on the basis of relatively stable 65%~70% shading, blue-enriched light spectra may be used during the vegetative expansion stage, while red-enriched spectra or films may be applied during the later medicinal quality formation stage to achieve stage-specific coordination between growth promotion and quality enhancement.

7.3 Optimization of cultivation models and quality evaluation systems

In addition to adjusting shading nets and spectral composition, optimizing cultivation models is also important for stabilizing the yield and quality of T. hemsleyanum. Comparative studies of different planting bases and cultivation modes have shown that greenhouse cultivation produces the thickest stems, longest leaves, and greatest aboveground and underground biomass, and that the total flavonoid content in tuberous roots under greenhouse cultivation is higher than that under understory cultivation. Under greenhouse conditions, the stereoscopic cultivation mode further increases the contents of indicator compounds, including polydatin, resveratrol glycoside, resveratrol, and kaempferol, compared with creeping cultivation (Hu et al., 2023). These findings suggest that “greenhouse + stereoscopic structure + optimized shading” may be a comprehensive cultivation model with strong potential for industrial production of T. hemsleyanum.

To support the above cultivation models, a systematic quality evaluation system and light regulation decision-making tools are also needed. A review on T. hemsleyanum pointed out that a scientific, universal, and measurable quality control system is still lacking, and called for the establishment of quality markers related to antitumor and anti-inflammatory activities (Hu et al., 2021). In other medicinal plants, comprehensive evaluation methods such as entropy-weighted TOPSIS have been used to screen combinations of red-blue light ratios, field water-holding capacity, and shading treatments, and to identify optimal cultivation conditions by comprehensively scoring growth, photosynthesis, and saponin content. Similar multi-index evaluation models can also be applied to T. hemsleyanum, using biomass and key components, such as flavonoids, resveratrol-like compounds, and polysaccharides, as core indicators. Combined with controlled shading regimes, such models can help establish standardized cultivation protocols, guide the construction of regional planting models, and support traceable quality evaluation from field production to market circulation.

8 Conclusion and Prospects

Existing studies clearly indicate that the light environment is a core ecological factor determining the growth performance and medicinal quality of Tetrastigma hemsleyanum. As an understory vine adapted to shaded environments, T. hemsleyanum exhibits systematic changes in photosynthetic pigments, gas exchange, and light-response parameters along shading gradients; unsuitable conditions such as strong light, high temperature, and low humidity can reduce photosynthetic activity and slow plant growth. Light quality is equally important. Under different colored film treatments, blue film can promote vegetative growth and yield formation, whereas red film enhances PAL activity and flavonoid accumulation, directly indicating that spectral composition is closely associated with biomass formation and active component accumulation. At the cultivation system level, compared with understory cultivation, greenhouse cultivation with a stereoscopic structure can significantly increase aboveground and underground biomass and improve total flavonoid content in tuberous roots, further confirming that integrated light environment regulation is a key approach for simultaneously improving yield and medicinal quality.

Multiple experiments have shown that moderate shading is the most effective strategy for coordinating vegetative growth, photosynthetic performance, and active component accumulation in T. hemsleyanum and similar shade-tolerant medicinal plants. In T. hemsleyanum, photosynthetic pigments and most photosynthetic indicators increase with enhanced shading and reach maximum values under approximately 70% shading during both rapid and slow growth stages; thereafter, excessive shading reduces photosynthetic capacity. Therefore, 70% shading has been considered suitable for different growth stages. Similarly, 67% shading results in the highest leaf area and net photosynthetic rate, whereas light stronger than that under 50% shading inhibits photosynthesis, and irradiance below that under 75% shading restricts carbon assimilation and plant growth. This suggests that an appropriate window may exist near approximately two-thirds shading. From broader research on medicinal plants, moderate reduction of light intensity or optimization of scattered light proportion generally improves biomass and key metabolite contents, whereas excessively strong or weak light impairs survival, photosynthesis, and secondary metabolism. This further indicates that precise calibration of shading conditions is necessary to achieve the dual goals of high yield and stable medicinal quality.

Although existing studies have clarified the suitable shading range for T. hemsleyanum and demonstrated that light quality and cultivation mode strongly affect its growth and flavonoid accumulation, research on its intrinsic mechanisms and standardized application remains limited. Recent reviews have pointed out that current physiological studies of T. hemsleyanum mainly focus on light and fertilizer effects, with relatively few investigations into deeper regulatory processes or systematic quality control. They also emphasize that this species still lacks a scientific, universal, and measurable quality evaluation system. In contrast, integrated phenotypic, physiological, and transcriptomic analyses of other medicinal plants under light gradients have revealed how moderate light reallocates carbon sources, reshapes membrane structures, and directs metabolic flux toward photoprotection and bioactive compound production, providing a useful theoretical framework for mechanistic studies of T. hemsleyanum. Therefore, future research should integrate omics-based analyses of light signaling, carbon-nitrogen metabolism, and secondary metabolic networks with multifactorial cultivation experiments involving shading intensity, spectrum, cultivation mode, nutrient management, and water management. Multi-index evaluation or decision-making models should also be applied to construct standardized and scalable shading cultivation systems and quality evaluation systems suitable for resource conservation and industrial development of T. hemsleyanum.

Conflict of Interest Disclosure

The author affirms that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

References

Ahmed O.A., Yusoff M.M., Misran A., Wahab P.E.M., and Muttaleb Q.A., 2024, Root-shoot ratio and its relationships with physiological characteristics, growth and biomass yield of Gynura procumbens under different shade levels and plant density, Bionatura, 9(1): 52.

https://doi.org/10.21931/rb/2024.09.01.52

Alabd A., Ahmad M., Zhang X., Gao Y., Peng L., Zhang L., Ni J., Bai S., and Teng Y., 2022, Light-responsive transcription factor PpWRKY44 induces anthocyanin accumulation by regulating PpMYB10 expression in pear, Horticulture Research, 9: uhac199.

https://doi.org/10.1093/hr/uhac199

Bai Y., Chen W., Liu S., Xu L., Li Z., and Liu B., 2021, Physiological responses of the Tetrastigma hemsleyanum plant under different color films, HortScience, 56(10): 672-677.

https://doi.org/10.21273/HORTSCI15690-21

Barazetti V.M., Gross E., Sodré G., Dalmolin Â., Costa L.C., and Ribeiro M.A., 2021, Growth, leaf gas exchange and mycorrhizal colonization of three medicinal species submitted to different irradiance levels, Ciência Rural, 52(4): e20200633.

https://doi.org/10.1590/0103-8478cr20200633

Chen Y.D., Shi L.X., Xu Q.T., Zhang C., Wang L., and Li W., 2025, Light signal transduction networks regulating phenylpropanoid, terpenoid and alkaloid biosynthesis in horticultural plants, Journal of Plant Physiology, 18: 154681.

https://doi.org/10.1016/j.jplph.2025.154681

Cun Z., Xu X.Z., Zhang J.Y., Shuang S.P., Wu H.M., An T., and Chen J.W., 2023, Responses of photosystem to long-term light stress in a typically shade-tolerant species Panax notoginseng, Frontiers in Plant Science, 13: 1095726.

https://doi.org/10.3389/fpls.2022.1095726

Dai Y.J., Shen Z.G., Liu Y., Wang L.L., Hannaway D., and Lu H.F., 2009, Effects of shade treatments on the photosynthetic capacity, chlorophyll fluorescence, and chlorophyll content of Tetrastigma hemsleyanum diels et gilg, Environmental and Experimental Botany, 65(2-3): 177-182.

https://doi.org/10.1016/j.envexpbot.2008.12.008

Deng C.N., Zhang Z.Z., Da Silva F.S.B., Hashem A., Abd_Allah E.F., Zou Y., and Wu Q., 2024, Shading impairs mycorrhizal benefits on plant growth, leaf gas exchange, and active ingredients in Polygonum cuspidatum, Horticulturae, 10(10): 1078.

https://doi.org/10.3390/horticulturae10101078

Deng Y.X., and Lu S.F., 2017, Biosynthesis and regulation of phenylpropanoids in plants, Critical Reviews in Plant Sciences, 36(4): 257-290.

https://doi.org/10.1080/07352689.2017.1402852

Deng Y.M., Jia X.P., Sun X.B., Liang L., and Su J., 2018, Comparison of jasmine antioxidant system responses to different degrees and durations of shade, Acta Physiologiae Plantarum, 40: 1-6.

https://doi.org/10.1007/s11738-018-2618-7

Elango T., Jeyaraj A., Dayalan H., Arul S., Govindadamy R., Prathap K., and Li X., 2023, Influence of shading intensity on chlorophyll, carotenoid and metabolites biosynthesis to improve the quality of green tea: a review, Energy Nexus, 12: 100241.

https://doi.org/10.1016/j.nexus.2023.100241

Gao L.L., Dong Y., Cun Z., Zhang J.Y., and Chen J.W., 2025, Moderate shading elicits succinic acid accumulation aligning with simultaneous expression of genes involved in TCA cycle and photosynthetic pathway in a medicinal plant Pinellia ternata, Plant Physiology and Biochemistry, 224: 109911.

https://doi.org/10.1016/j.plaphy.2025.109911

García-Caparrós P., De Filippis L., Gul A., Hasanuzzaman M., Ozturk M., Altay V., and Lao M.T., 2020, Oxidative stress and antioxidant metabolism under adverse environmental conditions: a review, The Botanical Review, 87(4): 421-466.

https://doi.org/10.1007/s12229-020-09231-1

Gómez-Ocampo G., Cascales J., Medina-Fraga A. L., Ploschuk E., Mantese A., Crocco C.D., Matsusaka D., Sánchez D.H., and Botto J., 2023, Transcriptomic and physiological shade avoidance responses in potato (Solanum tuberosum) plants, Physiologia Plantarum, 175(4): e13991.

https://doi.org/10.1111/ppl.13991

Han X., Shen Y.Z., Wang Y., Shen J.Z., Wang H., Ding S.B., Xu Y., Mao Y., Chen H., Song Y., Ding Z., and Fan K., 2023, Transcriptome revealed the effect of shading on the photosynthetic pigment and photosynthesis of overwintering tea leaves, Agronomy, 13(7): 1701.

https://doi.org/10.3390/agronomy13071701

Hashemifar Z., Sanjarian F., Badi N. H., and Mehrafarin A., 2024, Varying levels of natural light intensity affect the phyto-biochemical compounds, antioxidant indices and genes involved in the monoterpene biosynthetic pathway of Origanum majorana L., BMC Plant Biology, 24: 676.

https://doi.org/10.1186/s12870-024-05739-5

Hu W.Y., Jiang M.D., Liang Z.S., and Xia P.G., 2023, The stereoscopic planting mode improved the quality and yield of Tetrastigma hemsleyanum, South African Journal of Botany, 157: 221-229.

https://doi.org/10.1016/j.sajb.2023.03.048

Hu W., Zheng Y.J., Xia P.G., and Liang Z.S., 2021, The research progresses and future prospects of Tetrastigma hemsleyanum diels et gilg: a valuable Chinese herbal medicine, Journal of Ethnopharmacology, 271: 113836.

https://doi.org/10.1016/j.jep.2021.113836

Ji T., Ji W.W., Wang J., Chen H.J., Peng X., Cheng K.J., Qiu D., and Yang W.J., 2020, A comprehensive review on traditional uses, chemical compositions, pharmacology properties and toxicology of Tetrastigma hemsleyanum, Journal of Ethnopharmacology, 264: 113247.

https://doi.org/10.1016/j.jep.2020.113247

Leonardelli M., Tissot N., Podolec R., Ares-Orpel F., Glauser G., Ulm R., and Demarsy E., 2024, Photoreceptor-induced sinapate synthesis contributes to photoprotection in Arabidopsis, Plant Physiology, 196(2): 1518-1533.

https://doi.org/10.1093/plphys/kiae352

Li Q., Zhang L., He J.N., Li J.A., Zhang H., Li Y.M., Gu Y.Y., Luo H., Lu M., Lu K., and Xiong L., 2025, Effects of different shade treatments on Melaleuca seedling growth and physiological properties, BMC Plant Biology, 25: 545.

https://doi.org/10.1186/s12870-025-06218-1

Li Y.C., Jeyaraj A., Yu H.P., Wang Y., Ma Q.Q., Chen X., Sun H.W., Zhang H., Ding Z.T., and Li X.H., 2020, Metabolic regulation profiling of carbon and nitrogen in tea plants [Camellia sinensis (L.) O. Kuntze] in response to shading, Journal of Agricultural and Food Chemistry, 68(11): 3438-3448.

https://doi.org/10.1021/acs.jafc.9b05858

Liang H.L., Liu B.Y., Wu C., Zhang X.J., Wang M.L., Huang X.Y., Wan L., and Tang H., 2022, Effects of light intensity on the growth of Polygala fallax hemsl. (Polygalaceae), Frontiers in Plant Science, 13: 985628.

https://doi.org/10.3389/fpls.2022.985628

Liu B.Y., Wang S.W., Li J.J., Wang J., Hou X.Y., Zhang Y., and Wang L., 2026, Effects of different light intensities on the growth and photosynthetic physiological characteristics of Cremastra appendiculata (D. Don) makino seedlings, Plants, 15(3): 388.

https://doi.org/10.3390/plants15030388

Liu L.L., Li Y.Y., She G.B., Zhang X.C., Jordan B., Chen Q., Zhao J., and Wan X.C., 2018, Metabolite profiling and transcriptomic analyses reveal an essential role of UVR8-mediated signal transduction pathway in regulating flavonoid biosynthesis in tea plants (Camellia sinensis) in response to shading, BMC Plant Biology, 18(1): 233.

https://doi.org/10.1186/s12870-018-1440-0

Liu Q.Q., Huang Z.J., Wang Z.G., Chen Y.F., Wen Z.M., Liu B., and Tigabu M., 2020, Responses of leaf morphology, NSCs contents and C:N:P stoichiometry of Cunninghamia lanceolata and Schima superba to shading, BMC Plant Biology, 20: 514.

https://doi.org/10.1186/s12870-020-02556-4

Liu Y., Singh S.K., Pattanaik S., Wang H.X., and Yuan L., 2023, Light regulation of the biosynthesis of phenolics, terpenoids, and alkaloids in plants, Communications Biology, 6(1): 1055.

https://doi.org/10.1038/s42003-023-05435-4

Mishra N., Jiang C.K., Chen L., Paul A., Chatterjee A., and Shen G.X., 2023, Achieving abiotic stress tolerance in plants through antioxidative defense mechanisms, Frontiers in Plant Science, 14: 1110622.

https://doi.org/10.3389/fpls.2023.1110622

Ninkuu V., Aluko O.O., Yan J., Zeng H., Liu G., Zhao J., Li H., Chen S., and Dakora F.D., 2025, Phenylpropanoids metabolism: recent insight into stress tolerance and plant development cues, Frontiers in Plant Science, 16: 1571825.

https://doi.org/10.3389/fpls.2025.1571825

Perchlik M., and Tegeder M., 2018, Leaf amino acid supply affects photosynthetic and plant nitrogen use efficiency under nitrogen stress, Plant Physiology, 178(1): 174-188.

https://doi.org/10.1104/pp.18.00597

Qi Y.L., Wei W., Chen C.G., and Chen L.D., 2019, Plant root-shoot biomass allocation over diverse biomes: a global synthesis, Global Ecology and Conservation, 18: e00606.

https://doi.org/10.1016/j.gecco.2019.e00606

Rabeh K., Hnini M., and Oubohssaine M., 2025, A comprehensive review of transcription factor-mediated regulation of secondary metabolites in plants under environmental stress, Stress Biology, 5(1): 15.

https://doi.org/10.1007/s44154-024-00201-w

Rajput V.D., Harish H., Singh R.K., Verma K.K., Sharma L., Quiroz-Figueroa F.R., Meena M., Gour V.S., Minkina T., Sushkova S., and Mandzhieva S., 2021, Recent developments in enzymatic antioxidant defence mechanism in plants with special reference to abiotic stress, Biology, 10(4): 267.

https://doi.org/10.3390/biology10040267

Ren C., Comes H.P., Zhu S.S., Zhang X.Y., Jiang W.M., Fu C.X., Chen J., Ma Y.Z., and Qiu Y.Q., 2025, Genome-wide patterns of local adaptation associated with transposable elements in Tetrastigma hemsleyanum (Vitaceae), New Phytologist, 247(2): 731-747.

https://doi.org/10.1111/nph.70264

Sagun J.V., Chow W., and Ghannoum O., 2022, Leaf pigments and photosystems stoichiometry underpin photosynthetic efficiency of related C3, C3-C4 and C4 grasses under shade, Physiologia Plantarum, 174(6): e13819.

https://doi.org/10.1111/ppl.13819

Shao C.Y., Jiao H., Chen J.H., Zhang C., Liu J., Chen J., Li Y., Huang J., Yang B., Liu Z., and Shen C., 2022, Carbon and nitrogen metabolism are jointly regulated during shading in roots and leaves of Camellia sinensis, Frontiers in Plant Science, 13: 894840.

https://doi.org/10.3389/fpls.2022.894840

Shi Y.S., Yang L., Yu M.F., Li Z., Ke Z.Q., Qian X.L., Ruan X., He L., Wei F., Zhao Y., and Wang Q., 2022, Seasonal variation influences flavonoid biosynthesis path and content, and antioxidant activity of metabolites in Tetrastigma hemsleyanum Diels and Gilg, PLOS ONE, 17(4): e0265954.

https://doi.org/10.1371/journal.pone.0265954

Simkin A.J., Kapoor L., Doss C.G.P., Hofmann T.A., Lawson T., and Ramamoorthy S., 2022, The role of photosynthesis-related pigments in light harvesting, photoprotection and enhancement of photosynthetic yield in planta, Photosynthesis Research, 152(1): 23-42.

https://doi.org/10.1007/s11120-021-00892-6

Tissot N., and Ulm R., 2020, Cryptochrome-mediated blue-light signalling modulates UVR8 photoreceptor activity and contributes to UV-B tolerance in Arabidopsis, Nature Communications, 11(1): 1323.

https://doi.org/10.1038/s41467-020-15133-y

Tong Y.Q., Xue J.P., Li Q.Z., and Zhang L., 2024, A generalist regulator: MYB transcription factors regulate active ingredient biosynthesis in medicinal plants, Journal of Experimental Botany, 75(16): 4729-4744.

https://doi.org/10.1093/jxb/erae225

Xu LY., Liu S.Z., Bai Y., Ding H., Hu X.T., Wu X.Q., Xu H.S., and Zheng B.S., 2018, Effects of light intensity treatments on photosynthetic characteristics in Tetrastigma hemsleyanum, Journal of Zhejiang A&F University, 35(3): 467-475.

https://doi.org/10.11833/j.issn.2095-0756.2018.03.010

Xu M.Y., Wu K.X., Liu Y., Liu J., and Tang Z.H., 2020, Effects of light intensity on the growth, photosynthetic characteristics, and secondary metabolites of Eleutherococcus senticosus Harms, Photosynthetica, 58(4): 881-889.

https://doi.org/10.32615/ps.2020.045

Xu S.P., Zhang Y., Liang F., Jiang S.H., Niu S.Y., Wang X.M., Zhou Y.R., Cui B., and Yuan X.Y., 2024, Metabolomic and transcriptomic analyses reveal the mechanism of polysaccharide and secondary metabolite biosynthesis in Bletilla striata tubers in response to shading, International Journal of Biological Macromolecules, 269: 135545.

https://doi.org/10.1016/j.ijbiomac.2024.135545

Xue G.Y., Wu J.D., Zhou B.J., Zhu X.P., Zeng J., Wang Y.N., and Jia H.Y., 2023, Effects of shading on the growth and photosynthetic fluorescence characteristics of Castanopsis hystrix seedlings of top community-building species in southern subtropical China, Forests, 14(8): 1659.

https://doi.org/10.3390/f14081659

Yang C.W., and Li L., 2017, Hormonal regulation in shade avoidance, Frontiers in Plant Science, 8: 1527.

https://doi.org/10.3389/fpls.2017.01527

Zhang S.C., Zhang L., Zou H.Y., Qiu L., Zheng Y.W., Yang D.F., and Wang Y.P., 2021, Effects of light on secondary metabolite biosynthesis in medicinal plants, Frontiers in Plant Science, 12: 781236.

https://doi.org/10.3389/fpls.2021.781236

Zhao G., Liu W.L., Zhu H., Duan H.P., Nie J.N., Hong S.R., and Wen J., 2024, The influence of prolonged but low intensity blue light on the physiological properties of root tubers and the accumulation of flavonoids in Tetrastigma hemsleyanum diels et gilg, Plant Physiology and Biochemistry, 213: 108824.

https://doi.org/10.1016/j.plaphy.2024.108824

Zhu J., Cai Y.M., Li X., Yang L.Y., and Zhang Y., 2024, Integrated multi-omic analysis reveals the carbon metabolism-mediated regulation of polysaccharide biosynthesis by suitable light intensity in Bletilla striata leaves, Plant Physiology and Biochemistry, 214: 108872.

https://doi.org/10.1016/j.plaphy.2024.108872

Zhu J., Yang L.Y., Cai Y.M., Zeng X.H., Zhang Y.C., and Huang W.C., 2025, Suitable light intensity stimulated polysaccharide biosynthesis in Bletilla striata pseudobulbs through regulating starch and sucrose metabolism, Plant Stress, 18: 101041.

https://doi.org/10.1016/j.stress.2025.101041