Horticultural crops are valued not only for their yield but also for their nutritional, sensory, and aesthetic qualities, which are crucial for consumer acceptance and marketability. Among the diverse processes influencing crop quality, leaf senescence, sugar metabolism, and nitrogen metabolism have emerged as pivotal factors determining the development and preservation of quality traits such as color, flavor, aroma, texture, and nutritional value. Leaf senescence is intricately linked to the remobilization of nutrients and the degradation or accumulation of critical metabolites, impacting both harvest quality and postharvest longevity. Sugar metabolism regulates not only the sweetness, taste, and energy supply but also acts as a signaling hub orchestrating secondary metabolite biosynthesis and stress responses. Nitrogen metabolism underpins protein content, amino acid composition, and is tightly coordinated with carbon metabolism to shape both primary and secondary quality attributes.

Environmental stresses, suboptimal nutrient management, and inappropriate postharvest handling can accelerate or delay senescence, disrupt sugar accumulation and partitioning, as well as alter nitrogen assimilation, ultimately threatening the consistent quality of horticultural produce. Recent advances in omics-based profiling and molecular dissection of senescence-associated, sugar metabolic, and nitrogen regulatory genes and pathways have greatly enhanced our knowledge of the underlying mechanisms. However, significant gaps remain in understanding how external cues (such as light, temperature, water, and nutrient supply) and internal regulatory networks (including hormones, transcription factors, and epigenetic modifications) coordinately control leaf aging, sugar allocation, and nitrogen remobilization, thus impacting overall crop quality.

This Research Topic aims to provide a comprehensive overview of the mechanisms governing quality formation and maintenance through the lens of leaf senescence, metabolic mechanisms in horticultural plants, spanning from cultivation practices to postharvest stages. We welcome articles addressing, but not limited to, the following themes:

1. Genetic and molecular regulation of leaf senescence, sugar metabolism, and nitrogen metabolic pathways

2. Environmental modulation of quality: Effects of light quality, drought, salinity, and temperature on secondary metabolite accumulation (e.g., anthocyanins, carotenoids, polyphenols).

3. Phytohormonal regulation: Cross-talk between hormones (e.g., auxins, gibberellins, ethylene) in quality trait development.

4. Omics approaches: Genomics, transcriptomics, proteomics, and metabolomics insights into quality formation.

5. Pre- and postharvest interventions: Biostimulants, edible coatings, controlled atmosphere storage to maintain quality.

6. Consumer-driven quality: Sensory evaluation, bioactive compound bioavailability, and breeding for improved organoleptic properties.

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Integrating Environment and Metabolism: Leaf Aging, Carbon–Nitrogen Dynamics, and Quality Traits in Horticultural Crops