1 Introduction

Pears (Pyrus spp.) are one of the world’s most important fruits. Their size and sweetness decide how popular they are, and how much they sell for. In local markets and in exports, big and sweet pears are always in demand. They bring farmers more money and keep the pear industry steady and growing (Liu et al., 2019; Zhang et al., 2024). But just planting more trees or only chasing higher yields is not enough to keep the pear industry strong. People now want better fruit, not just more fruit. This change is pushing farmers to rethink how they grow pears. To make the fruit taste better and look better, farmers need to keep looking for new ways and new tools.

The economic value of pears is high, but growing big and sweet fruit all the time isn’t easy. Things like genetic differences, lack of nutrients, bad weather, and plant diseases, can make pears smaller or less sweet (Sete et al., 2019; Zhang et al., 2024). Too much fertilizer or using it the wrong way can make the problem worse. It not only hurts the quality of the fruit, but also causes harm to the environment (Prasad and Bora, 2015).

N, P and K, along with trace elements like boron, zinc and copper, are all important for pear growth. Among them, K is the most critical. It helps plants make, move and store sugar, which makes the fruit sweeter and helps pears grow bigger (Shen et al., 2016; Zhang, 2019). N and P also help fruit develop and boost yield, but their effect on sugar levels is not always the same. This means, farmers need to manage them carefully (Sete et al., 2019; Li et al., 2024). Trace elements, like boron and copper, are often sprayed on the leaves. They help flowers turn into fruit, support sugar buildup, and improve the overall quality of the pears (Gilani et al., 2021; Sajid et al., 2022).

For pears to grow smoothly and become sweet, nutrients and sugar must be transported smoothly from the "source" (leaves) to the "reservoir" (fruits). In this process, P not helps plants build nutrient transport channels, activates key transport genes such as SUT, SOT and SWEET (Shen et al., 2018; 2019; Gu et al., 2021; Wang et al., 2022a). These genes work together to transport sugar and minerals to the fruit. When they operate in balance, the fruit can grow larger at the right time and accumulate more sugar.

This study explores how to better manage macronutrients and trace elements, incorporating the use of bio-organic fertilizers to enhance nutrient regulation. It integrates concepts from plant physiology, molecular research, and agricultural management methods, to identify practical approaches to improve pear quality. Through more scientific management, pear yields can be increased while also enhancing taste and nutritional value. This not only increases income for farmers, but allows consumers to enjoy higher-quality pears.

2 Physiological Basis of Fruit Size Formation

2.1 Mechanisms of cell division and expansion

N and P are key nutrients that influence pear cell growth and division, which directly determine the final fruit size. It has been reported that, providing adequate nitrogen and phosphorus during early fruit growth, can increase the length, width, weight, and overall volume of pears by promoting cell division and expansion (Arba et al., 2017). Field trials have found that pear yield and quality are optimal when farmers apply approximately 337.5 kg of nitrogen and 262.5 kg of phosphorus per hectare (Li et al., 2024).

The nutritional status of plants also affects the function of hormones in the body. Hormones such as auxin (IAA), zeaxin nucleoside (ZR), gibberellin (GA), and abscisic acid (ABA) are all related to the number of cell formation and fruit size (Tian et al., 2021; Liu et al., 2024). Research shows that higher levels of ZR and a more ideal balance of IAA/ABA, ZR/ABA and GA/ABA help to produce more cells and promote fruit enlargement. On the contrary, ABA inhibits cell division (Tian et al., 2021).

Nutrient regulation of plant hormones helps maintain a balanced growth process. Furthermore, external application of plant growth regulators (e.g., gibberellins and cytokinins), can further promote cell division and expansion, resulting in larger pear fruits and improving their quality (Mosa et al., 2022; Al-Saif et al., 2024; Liu et al., 2024).

2.2 Vascular structure and sink strength modulation

For pear fruits to grow big and sweet, the sugar in the leaves must be smoothly delivered to the fruit. However, if the transport function of the transport channel, that is, the vascular tissue, is poor, sugar will block the road (Shen et al., 2019; Wang et al., 2022). The role of K can be manifested at this time: it can make the vascular tissues of petioles and fruit stalks more developed, and also make sugar transport genes, such as SUT and SOT, more active. Thus, glucose, fructose, sorbitol and sucrose will accumulate rapidly in the fruit. With the enhancement of transportation capacity, the "reservoir strength" of fruits will also be stronger, the ability to absorb and store sugar will be better, and the fruits will be larger and sweeter (Cheng et al., 2018).

Of course, potassium is not the only key. Calcium (Ca) and boron (B) are also indispensable. Calcium can make the cell walls and cell membranes more stable, supporting the continuous growth of fruits. Boron maintains cell wall structure and vascular function at the back (Pessoa et al., 2022). Only when both calcium and boron are sufficient can the vascular system remain smooth, allowing sugar and nutrients to continuously flow into the fruit, and enabling the pear to grow to the desired size and quality.

2.3 Interactions between nutrition and environmental factors

Water and temperature play a big role in how well pear trees take in and use nutrients. When there isn’t enough water, sugars and nutrients can’t move into the fruit. When it gets too hot, the tree’s normal metabolism is thrown off, and even its nutrient needs can change (Shen et al., 2019). Pear trees will try to adjust by doing things, like boosting root activity or changing how transport proteins work. But if these fixes go on for too long, the fruit won’t grow well, and the pears will end up smaller (Nishio et al., 2021).

Nutritional imbalance is also a problem. Too little fertilizer, or the wrong mix, can slow cell division, and block the growth of vascular tissue. It also weakens the “sink strength”, which makes fruits smaller and less sweet (Shen et al., 2019). On the other hand, using fertilizer the right way—with a good balance of N, P, K, Ca and B—can ease these stresses, and help pears grow better and taste better (Nishio et al., 2021).

3 Regulatory Mechanisms of Sugar Accumulation in Pear Fruit

3.1 Metabolic pathways of sucrose and sorbitol

In pear fruit, sugar accumulation primarily occurs via sucrose and sorbitol, a common transport pathway in Rosaceae plants. Sorbitol dehydrogenase (SDH) converts sorbitol to fructose, a step that directly impacts sweetness. Numerous studies have found that, the application of bio-organic fertilizers that enhance SDH expression significantly increases fructose content (Wang et al., 2022a; Jiang et al., 2023).

Sucrose breakdown involves not only one enzyme. Invertase hydrolyzes sucrose into glucose and fructose, and its activity varies with fruit development. Acid invertase (AI) is more active in the later stages, helping to accumulate hexoses, while sucrose synthase (SS) and sucrose phosphate synthase (SPS) are more important early in the fruit (Kou et al., 2017; 2018; Min et al., 2020). Interestingly, some studies suggested that in developing pears, sucrose synthase may even play a greater role in sucrose breakdown than invertase (Reuscher et al., 2016).

Nutrient supply, especially potassium (K), boosts the activity of genes like SDH, S6PDH, SPS, and SUS in leaves and fruits. This helps sugar build up in the fruit (Shen et al., 2018; Wang et al., 2022a). Sugar itself can also “push back” and activate SDH. When sorbitol, glucose, or sucrose is sprayed on the plant, SDH expression and activity go up even more. Researchers also found that, transcription factors like PbrbZIP15, PuMYB12, and PuWRKY31, as well as epigenetic changes such as histone acetylation, affect how sugar metabolism and transport genes are expressed (Li et al., 2020; Gao et al., 2023; Jia et al., 2024).

3.2 Key nutritional factors influencing sugar content

Potassium (K) is very important for helping pears move and store sugar. It makes the plant’s veins grow better and turns on sugar transport genes like SUT and SOT. This helps sugars move smoothly from the leaves, or the “source”, to the fruit, or the “sink” (Shen et al., 2018; 2019). When the plant has plenty of potassium, the leaves and fruit hold more sorbitol, sucrose, and total sugar, which makes the fruit sweeter. Mg hasn’t been studied as much, but it also matters because it helps leaves keep up photosynthesis and might work together with potassium to move sugars. Shen et al. (2019) found that when potassium is low, the plant makes more magnesium transporter proteins to make up for it a little.

For pears, Boron (B) and zinc (Zn) are important micronutrients. They help sugars build up by keeping cell walls strong, cell membranes stable, and enzymes working well. B is key for sugar transporters and vascular tissues to work normally. While Zn helps enzymes that take part in carbohydrate metabolism (Pessoa et al., 2022; Zhang et al., 2022). When pears get enough boron and zinc, sugar moves and gathers more easily, which makes the fruit taste better and improves its quality.

3.3 Interactive regulation with photosynthesis and source-sink dynamics

The nutritional status of leaves, especially the potassium (K) content, has a significant impact on photosynthesis. After the increase of potassium, the photosynthetic efficiency of leaves is enhanced, sugar production is also greater, and the "raw materials" transported to the fruit are naturally more abundant (Shen et al., 2018). The addition of organic and bio-organic fertilizers can also enhance photosynthesis and promote the expression of genes related to glucose metabolism, making the accumulation of sucrose in fruits more obvious (Wang et al., 2022a).

The way fruits get sugar is not simple. Phloem unloading and sugar storage rely on sugar transporters, like SUT, SOT, SWEET, and TMT, along with metabolic enzymes. Transcription factors such as PuWRKY31 and PbrbZIP15, plus epigenetic changes, also take part in this process (Li et al., 2020; Gao et al., 2023; Jia et al., 2024). There are also genes like PbCPK28 and PbTST4. Their natural variations can change how well sugar moves into the vacuole, which then affects how sweet the fruit becomes (Cheng et al., 2018; Li et al., 2023).

4 Nutrient Metabolic Regulatory Network in Pear Fruit

4.1 Signal transduction and transcription factor regulation

In the metabolic regulation of pears, transcription factors (TFs), like members of the bZIP, WRKY, and MYB families, all play a role. Take PpbZIP44 as an example, it can directly regulate the genes involved in the biosynthesis of carbohydrates, amino acids and flavonoids, redistribute the metabolic flow direction, and allow more fructose and phenylalanine to accumulate in the fruit (Wang et al., 2023). Members of the WRKY family, such as PbWRKY26, regulate organic acid metabolism by activating malate dehydrogenase-related genes, and ultimately affect malic acid levels and fruit acidity (Yang et al., 2023). MYB is more involved in the regulation of secondary metabolites and structural components, and has an impact on both flavor and quality (Xue et al., 2023).

Nutrient signals and hormone signals are closely linked in pears. For example, MeJA treatment can start changes in carbohydrate and amino acid metabolism. This process involves ceRNAs, miRNAs, and transcription factors (Yuan et al., 2024). ABA signaling has its own chain of control. It is shaped by DNA methylation, and transcription factors like PbZFP1. These signals affect how metabolic genes work, which then sets the pace for fruit ripening and the overall metabolic state (Gu et al., 2024).

4.2 Mechanisms of carbon-nitrogen balance regulation

Nitrogen supply not only determines the growth of leaves, but also affects the expression of genes related to sugar metabolism, thereby influencing the balance between carbon and nitrogen compounds. Transcriptome analysis revealed that, nitrogen-responsive transcription factors and metabolic genes were co-expressed with sucrose biosynthesis genes, suggesting that there was not an indirect relationship between nitrogen status and sugar accumulation, but a direct regulatory connection (Lu et al., 2020; Wang et al., 2023).

Lü et al. (2020) conducted a comparative transcriptome analysis of three developmental stages of the low-sucrose cultivar ‘Korla’ and the high-sucrose cultivar ‘Fengshui’, identifying seven key genes closely related to sucrose synthesis (SPS, SUS, FRK, and PGI, etc.) along with 42 transcription factors. They constructed a regulatory model linking signals, transcription factors, and target genes to explain how gene regulation and metabolic flux jointly drive differences in sweetness (Figure 1). This provides a valuable reference for understanding the molecular basis of sugar accumulation under nitrogen influence and also demonstrates that by regulating the expression of relevant genes, carbon–nitrogen metabolism can be coordinated to optimize fruit quality.

Figure 1 A proposed model of sucrose content difference in pear fruits. Several types of TFs are involved in the upregulated transcription of FRK, PGI, SPS and SUS genes in the nucleus, and high sucrose then accumulates in vacuoles. Sucrose accumulation is affected by multiple signals, such as plant hormones. CINV, cytoplasmic invertase or neutral invertase; Glc, glucose; SDH, sorbitol dehydrogenase (Adopted from Lü et al., 2020) Image caption: The figure illustrates the metabolic pathways at the cellular level in high- and low-sucrose cultivars. In high-sucrose types, the upregulation of genes such as SPS, SUS, FRK, and PGI promotes sucrose synthesis and its accumulation in vacuoles within fruit cells, while being regulated by transcription factors like bZIP and WRKY as well as plant hormone signals. In contrast, low-sucrose types lack this efficient pathway, resulting in limited sucrose deposition (Adapted from Lü et al., 2020)

The balance of nutrients, especially the carbon-to-nitrogen ratio, also affects how pear trees work inside. Studies using different “omics” methods show that when this ratio changes, it can turn certain genes on or off. These genes are linked to how the plant handles sugars and amino acids. As a result, the amount of sugar, organic acids, and amino acids in the fruit also changes (Wang et al., 2023; Yuan et al., 2024).

5 Fertilization Strategies for Improving Fruit Quality

5.1 Balanced fertilization schemes for coordinated trait improvement

Studies have shown that moderate application of nitrogen fertilizer can increase fruit quantity and yield. However, excessive application not only fails to further improve fruit quality, but may also lead to nutrient excess and environmental risks (Chen et al., 2018; Sete et al., 2019; Liang et al., 2022). Especially, the role of potassium fertilizer is more prominent. It can not only enhance fruit hardness, soluble solid content and storability, but also promote sugar accumulation, thereby comprehensively improving fruit quality (Brunetto et al., 2015; Shen et al., 2016; Sete et al., 2020).

The optimal NPK ratio should be adjusted based on local soil conditions and tree needs. For example, studies have shown that in North China, moderate irrigation combined with high nitrogen application yields the best results (Liu et al., 2023; Li et al., 2024). Balanced fertilization can also increase the mineral and vitamin C content of fruit, improving flavor and nutritional value (Gill et al., 2017).

Slow-release and controlled-release fertilizers give the trees a steady flow of nutrients through the whole growing season. This cuts down on nutrient loss and helps the plant use the fertilizer better. These fertilizers can make pears have more soluble solids, more vitamin C, and a better sugar–acid balance. They also save money on fertilizer and are better for the environment (Shen et al., 2018). For example, studies show that bagged controlled-release fertilizers, compared to regular compound fertilizers, make the fruit taste better and boost its nutrition, giving farmers a good option for growing high-quality pears.

5.2 Timing and methods of nutrient application

The advantages of foliar fertilization are quite obvious, especially when there is a deficiency of trace elements. It works quickly and can also enhance the hardness, sugar content and soluble solids of fruits. It works best during critical periods, when the fruit is developing (Gilani et al., 2021; Sajid et al., 2022; Seo et al., 2024; Yuan et al., 2024). However, root (soil) fertilization remains the main force. It provides a large amount of nutrients and supports the entire process of pear trees from vegetative growth to reproductive growth (Jiang et al., 2020; Colpaert et al., 2021). When the two methods are used in combination, the improvement of nutrient absorption and fruit quality will be more obvious. When soil nutrient supply is insufficient or stress occurs, foliar spraying becomes more important (Zargar et al., 2019).

The timing of fertilization is also very important. Giving the right nutrients during flowering, fruit setting, and fruit expansion helps pears grow bigger and build up more sugar (Liu et al., 2019; Jiang et al., 2020). For example, nitrogen fertilizer added in spring mostly goes to the young fruits. Fertilizers used in summer and autumn are stored in the roots, and later moved through the plant (Colpaert et al., 2021). During fruit setting and expansion, spraying regulators and trace elements can improve both the quality, and the yield of the pears (Li et al., 2023).

5.3 Use of organic and biological inputs

Organic fertilizers, like compost, farmyard manure, and biogas slurry, can make the soil better by improving its structure, helping it hold water, and boosting microbial activity. This helps pears grow bigger, get sweeter, and store longer (Wang et al., 2022a; Ye et al., 2020; 2022; Butcaru et al., 2024). Bio-organic fertilizers with helpful microbes can go even further-they help pears make more sucrose, balance sugar and acid better, and improve overall fruit quality by affecting the genes that control sugar and acid metabolism (Kang et al., 2021; Wang et al., 2022a; b). Using organic fertilizers for many years, also builds up organic matter in the soil and makes nutrients easier for the trees to use, helping orchards keep producing in the long run.

Soil microbial inoculants like Bacillus subtilis and Trichoderma can help pear trees take in more nutrients. They boost enzyme activity, improve soil health, raise fruit yield, and keep the sugar-acid balance better (Kang et al., 2021; Shi et al., 2023). These biofertilizers change the microbes around the roots, encouraging good bacteria and fungi to grow. This helps nutrients move through the soil and supports plant growth (Wang et al., 2022b; Yanwei et al., 2025). When organic matter is used together with these inoculants, the effect is even stronger. It can stop leaves from dropping too early, raise yields even in bad weather, and make the fruit better in quality.

6 Variety Differences and Nutrient Regulation Adaptability in Pear

6.1 Nutrient response characteristics of different pear varieties

Different pear species take in nutrients and store minerals in their own ways. This changes how big and how sweet the fruit becomes. Pyrus bretschneideri, P. pyrifolia, and P. ussuriensis each have different patterns of sugar buildup, organic acid levels, and mineral content. For example, P. ussuriensis fruits have more potassium, calcium, and magnesium than P. pyrifolia or P. bretschneideri. Wild pears also usually hold more minerals than the pears grown in orchards (Liu et al., 2023).

Metabolomic studies, further elucidate these differences, revealing distinct patterns in phenylalanine metabolism, and other pathways related to fruit quality between white pears and sand pears (Zheng et al., 2022). Northeast pears exhibit higher potassium efficiency and greater tolerance to potassium-deficient environments, which is associated with the regulation of genes like PbNRT2.4, that is upregulated under potassium deficiency or exogenous sugar conditions (Yang et al., 2025).

The sensitivity of different varieties to nutrient management also varies. The high sugar type "Fengshui" upregulates sucrose synthesis related genes under nutrient supply, while the low sugar type "Korla Fragrant Pear" shows another expression pattern (Lü et al., 2020). Some varieties with larger fruits and higher sugar to acid ratios, like "Niitaka" and "Hanareum", have stronger nutrient absorption and accumulation abilities for sugars, amino acids, and minerals, making them suitable for both fresh and processed consumption. Some varieties can exhibit stronger tolerance or metabolic compensation ability, when they are deficient in potassium or iron (Melaouhi et al., 2022; Liu et al., 2025).

6.2 Breeding basis of traits related to nutrient regulation

Modern breeding increasingly values high-sugar and large-fruit traits, which are underpinned by both genetic and metabolic factors. QTL mapping and transcriptome analysis have identified a number of important loci and candidate genes, related to sugar accumulation and fruit enlargement, including PpSUT, PpSDH, SPS, SUS, etc. (Lu et al., 2020; Zhang et al., 2021; Jiang et al., 2023). Metabolomics studies supplemented more information, to help breeders screen varieties with better performance in sugar, organic acids and polyphenols (Zheng et al., 2022). The pollination effect (xenia), can also change fruit size and sweetness, indicating that breeding strategies cannot ignore the interaction between genetic background and reproductive biology (Qiao et al., 2025).

Selecting genotypes with high nutrient utilization efficiency is also a key point. The ability of different rootstock and scion combinations to absorb and utilize nutrients such as nitrogen and potassium varies. Rootstocks such as "Pyrodwarf" and "OHF", have differences in the levels of required nutrients (Jamshidi et al., 2016). Some genotypes exhibit higher nutrient absorption efficiency, such as the nitrogen-efficient "971" selection and potassium-efficient Northeast pear, which is of great significance for sustainable production and quality improvement (Sete et al., 2020; Liu et al., 2023; Yang et al., 2025).

6.3 Genotype × nutrient interaction mechanisms

QTL mapping has identified many key sites related to sugar, organic acid and nutrient utilization efficiency. For instance, in pyrifolia, qSugar-LG6-Chr7 and qSugar-LG12-Chr3 are closely related to the total sugar content. The candidate genes include sorbitol dehydrogenase (PpSDH) and sucrose transporter (PpSUT). They play a core role in sugar accumulation (Jiang et al., 2023). GWAS analysis also identified more loci related to fruit quality, involving genes such as stone cell formation, organic acid and sugar accumulation (Zhang et al., 2021), providing a genetic basis for breeding material selection.

Research has also found that different genotypes respond differently to fertilization systems. Some varieties are particularly sensitive to potassium supply. For example, a comparative study of "Crown" pear shows that potassium treatment can change gene expression and sugar accumulation, indicating that the fertilization plan must match the genotype (Shen et al., 2019). In addition, the improvements in sugar content, fruit size and metabolic characteristics brought about by bio-organic fertilizer or canopy structure adjustment vary among different genotypes (Wang et al., 2022a; Liu et al., 2024).

7 Case Studies of Nutrient Regulation in Pear Production

7.1 Practices for pear fruit enlargement

In the pear industry, rational nutrient regulation is key to increasing fruit yield and commercial value. In recent years, researchers have focused on the role of traditional chemical fertilizers and single nutrients, and also incorporated sustainable inputs, such as organic fertilizers and bio-organic fertilizers, into their experiments to explore more efficient and environmentally friendly pathways to increase yield. Wang et al. (2022a) demonstrated that the application of bio-organic fertilizers (BF) provides a new practical example for increasing pear fruit size. Field trials showed that, BF treatment significantly increased per-plant yield (by 10.6%) compared to chemical fertilizers. The fruit also increased in both longitudinal and transverse diameters, resulting in larger fruit size without affecting firmness (Figure 2).

Figure 2 Effect of different fertilization treatments on fruit weight per tree (A), fruit hardness (B), fruit vertical (C), horizontal (D) diameter and phenotype (E) of Pear. CF: chemical fertilizers application; BF: bio-organic fertilizers application; OF: organic fertilizers application. Values followed by different letters differ significantly (Duncan’s test, P< 0.05, n=5) (Adopted from Wang et al., 2022a)

In field trials of Asian pear varieties, including ‘Yali’ and ‘Xinli No. 7’, increasing potassium (K) fertilizer application rates has been shown to effectively improve fruit size and quality. Potassium fertilizer increases potassium concentrations in leaves and fruits and enhances net leaf photosynthetic rate, thereby promoting fruit growth. High levels of potassium fertilizer can upregulate the expression of genes involved in sugar metabolism (such as AIV, S6PDH, SPS, SUS, and SUT), promote soluble sugar accumulation, and increase fruit size during ripening (Shen et al., 2018; 2019).

Multiple foliar potassium sprays during fruit development, such as three sprays of 1.5%-2.0% potassium nitrate (KNO₃) or potassium sulfate (K₂SO₄) during the fruiting period, can further enhance these effects (Prasad and Bora, 2015). Economic analysis also shows that high-potassium fertilization can increase yield by 16%-17%, improve soluble solids and sugar content, and enhance market value and crop profitability. However, the amount and timing of fertilizer application must be precisely controlled to avoid over-investment or diminishing returns (Shen et al., 2016).

7.2 Enhancement of pear flavor quality

The flavor and commercial value of pears mainly depend on the balance of sugar and acid, as well as the accumulation of secondary metabolites. In recent years, the role of transcription factors in the regulation of fruit quality has attracted much attention. As research has found, PpbZIP44, a member of the S1-bZIP family, plays a key role in the multiple metabolic regulation of fruits.

Wang et al. (2023) demonstrated that PpbZIP44 can alter the accumulation patterns of sugars, organic acids, amino acids, and flavonoids by transient overexpression and RNA interference in pear fruit, as well as by establishing a stable transgenic system in tomatoes. The experiments showed that overexpression of PpbZIP44 increased fructose in the fruit by 38%, decreased sorbitol by 26%, and reduced citric acid and malic acid by nearly 40% and 30%, respectively. This significantly increased the sugar-acid ratio, thereby improving flavor and marketability (Figure 3).

Figure 3 Transient transformation of PpbZIP44 in pear fruits. A. Multiple protein sequence alignments of PpbZIP44 and other S1-bZIP proteins in different species. B. Transient assays in ‘Sucui 1’ pear using overexpression (OE-) or RNAi (RNAi) or empty vector (Vector) of PpbZIP44. C. The expression levels of PpbZIP44 in the fleshy tissue around the infiltration sites of transformed pear fruits using qRT-PCR. The content of total SS (D) and TA (E), SS/TA ratio (F), individual soluble sugars contents (G), individual organic acids contents (H), and SDH activity (I) in transformed pear fruits and control pear fruits. Bars represented the mean value ± SE (n ≥ 3). The asterisks indicated values that were determined by the Dunnett t test to significantly differ from their empty vector or WT control (*P < 0.05, **P < 0.01, ***P < 0.001) (Adopted from Wang et al., 2023)

More importantly, PpbZIP44 regulates sugar conversion, proline decomposition, and the synthesis of aromatic amino acids and flavonoids by directly binding to the promoters of genes (e.g., PpSDH9, PpProDH1, PpADT, and PpF3H), promoting the flow of carbon towards fructose and flavonoid accumulation, while weakening the formation of some lignin. Thereby reducing the negative impact of "stone cells" on the taste. Metabolomic and transcriptomic analyses further confirmed that these treatments could enhance gene expression related to carbohydrate metabolism, ultimately achieving sweeter fruits and higher market acceptance (Wang et al., 2022a; Wang et al., 2023; Jia et al., 2024).

8 Conclusions and Perspectives

When talking about pear quality, it’s hard not to bring up nitrogen, potassium, and different trace elements. These nutrients pretty much decide the fruit’s shape, size, and even how it tastes. Sugar doesn’t come from just one process-it’s built through a whole network that also involves plant hormones like ethylene, gibberellins, and abscisic acid, plus many working genes. New research in genomics and molecular biology is now finding more and more of these key genes and pathways, giving clues on how to manage nutrients more precisely in the future.

Smart fertilization methods-like giving a balanced mix of nutrients, applying them in stages, and using both organic and mineral fertilizers-can help pears grow bigger and taste sweeter. In practice, this means adjusting the right nutrient ratios, spraying leaves at key growth times, and using new genomic research to plan fertilizer use for each specific variety.

However, the shortcomings of reality cannot be ignored either. Many studies still remain at the level of a few varieties or general mechanisms, and the understanding of the differences among various pear varieties is not deep enough. In the fields, the situation is always more complicated: soil differences, climate fluctuations, and even pests and diseases can all alter the effectiveness of fertilization. This gap makes the achievements in the laboratory not always smoothly enter the orchard, and it also reminds us that future management strategies must be flexible and adapted to local conditions.

Next, a more promising direction is to truly integrate molecular and genomic data into nutrition management and build a smarter system. Genomic selection, marker-assisted breeding, and even real-time monitoring technologies can all be incorporated. The ultimate goal is not only to make pears larger and sweeter, but also to take into account the environment and sustainability. Precise fertilization, organic improvement, and the breeding of new varieties that efficiently utilize nutrients may enable the pear industry to strike a balance between economic benefits and ecological protection.

Acknowledgments

The authors would like to express their sincere gratitude to Ms. Zhang for her assistance in organizing the literature materials. The authors also extend special thanks to the two anonymous peer reviewers for their comprehensive evaluation of the manuscript. 

Conflict of Interest Disclosure

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

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