Emerging Insights into Horticultural Crop Ecophysiology

Highlights

What are the main findings?

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Nine studies elucidate biostimulants, stress memory, and gene regulation across horticultural species.

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Exogenous regulators, plant extracts, and seed priming mitigate drought, heat, and salinity stresses.

What are the implications of the main findings?

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Targeted physiological and metabolic tuning offers sustainable solutions for climate-resilient agriculture.

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Multi-omics and multi-stress field trials are crucial future priorities.

Abstract

Abiotic stressors driven by climate change increasingly threaten global horticultural productivity and crop quality. This closing editorial synthesizes nine multidisciplinary articles published in the Special Issue, focusing on physiological, biochemical, and molecular mechanisms governing crop resilience and secondary metabolite biosynthesis. Through comprehensive assessments of biostimulant applications, seed priming memory, and sugar-mediated signaling, the featured studies demonstrate that targeted exogenous treatments such as amino-acids, seaweed extracts, and melatonin effectively alleviate heat, drought, and salinity damage. Furthermore, research highlights the role of genetic regulators like flavonol synthase (ZjFLS) and tissue culture stress in metabolic reprogramming. Long-term studies reveal persistent physiological benefits of seed priming on photosynthetic efficiency and dry matter allocation in fruit crops. Altogether, this Special Issue addresses the knowledge gaps by bridging fundamental cellular responses with applied agronomic practices. To ensure sustainable horticultural production under escalating environmental pressures, future research must prioritize multi-stress field trials, epigenetic mechanisms underlying stress memory, multi-omics integration, and standardized field protocols for biostimulant management.

1. Introduction

Horticultural production currently confronts critical challenges as climate change and resource scarcity threaten the stability of the global food systems [1,2]. Environmental stressors, including extreme temperatures, drought, and soil salinity, have been shown to reduce potential crop yields by 50% to 70%, necessitating a deeper understanding of plant adaptation mechanisms [3,4]. To mitigate these impacts, contemporary research increasingly integrates physiological and molecular strategies to elucidate complex signaling pathways and regulatory gene networks that govern resilience [5]. Beyond survival, these adaptive mechanisms actively influence the biosynthesis of secondary metabolites, which serve as essential markers of producing quality and nutritional density in response to environmental fluctuations [6,7]. By utilizing techniques such as regulated deficit irrigation and targeted eustress stimuli, producers can optimize these biochemical pathways to enhance antioxidant profiles and sensory traits without compromising yield [8]. This holistic framework underscores the dual role of plant metabolism, where stress-induced signaling not only facilitates environmental acclimation but also modulates the accumulation of bioactive compounds critical for human health [9]. Consequently, unraveling the crosstalk between stress perception and secondary metabolic fluxes is pivotal for developing climate-smart cultivars that balance robust physiological acclimation with high-value nutritional attributes [10,11]. The escalating frequency and intensity of these environmental perturbations necessitate a shift toward multi-omics approaches to decipher the intricate transcriptional and metabolic adjustments required for simultaneous stress tolerance [12,13]. Integrated investigations into the plant stress response pathway, regulated through highly coordinated signaling mechanisms, are essential for identifying the master transcriptional regulators of these metabolic adaptations [14]. These efforts are further advanced by identifying physiological, biochemical, and molecular markers that correlate stress tolerance with the enhanced accumulation of nutraceuticals [15].

Modern horticulture operates at the intersection of climate change pressures, resource scarcity, and growing global demand for high-quality food, medicinal, and ornamental crops. Rising global temperatures, erratic precipitation patterns, soil salinization, and urban environmental stressors increasingly compromise crop growth, yield stability, and metabolic profiles [16,17]. In response, recent research in horticultural science has shifted from purely agronomic observations toward integrative physiological, biochemical, and molecular frameworks [18]. Key developments include the exploration of biostimulants and exogenous protective substances to enhance stress tolerance [19], the elucidation of seed priming and micropropagation stress responses [20,21], and the characterization of gene regulatory networks and signaling metabolites involved in secondary metabolite synthesis [22]. Understanding these mechanisms is essential for breeding and cultivating climate-resilient crops capable of maintaining functional quality under stress [23].

While individual strategies for stress mitigation have been reported, significant gaps remain regarding taxa-specific responses, long-term physiological memory, trade-offs between biomass and secondary metabolite accumulation, and the precise molecular pathways governing metabolic reprogramming [24,25]. This Special Issue addresses these gaps through nine multidisciplinary contributions categorized in four thematic clusters. To address these knowledge gaps, research must go beyond isolated single-factor treatments to investigate the interactive effects of multiple environmental signals under field and controlled conditions. Crop response to abiotic stress is governed by non-linear dynamics, where metabolic flux allocation between primary growth processes and protective secondary pathways dictates overall yield stability and crop quality [26]. Understanding how signaling cascades, such as phytohormone crosstalk, reactive oxygen species (ROS) scavenging systems, and transcriptional activation networks, modulate plant phenotype across different ontological stages is vital for modern crop management.

2. Biostimulants and Exogenous Protectants for Stress Mitigation

The application of natural and synthetic biostimulants offers a sustainable alternative to conventional inputs for improving stress resilience.

Regarding amino acid-based promoters, Peña-Calzada et al. provided a quantitative systematic review evaluating the amino-acid-based biostimulant VIUSID^® agro across diverse crop groups, demonstrating its capacity to modulate photosynthetic performance, enhance enzymatic antioxidant defenses and maintain ionic homeostasis, and mitigate salt stress [27].

Natural plant and seaweed extracts were also discussed. In Ocimum basilicum ‘Rokoko’, Kisvarga et al. demonstrated that foliar applications of Equisetum arvense (horsetail) and Ecklonia maxima (seaweed) extracts significantly enhanced leaf number, leaf area, chlorophyll content, and essential oil grand density under greenhouse conditions, whereas soil-applied humic acids reduced peroxidase (POD) activity and overall physiological stress [28].

Exogenous regulators under heat stress were studied by Bai et al. This study assessed five Asian lily cultivars in Chongqing, identifying ‘Tiny Diamond’ as highly heat-sensitive, and showed that exogenous applications of calcium chloride (CaCl₂), potassium fulvic acid (PFA), and melatonin (MT) effectively alleviated thermal damage by boosting superoxide dismutase (SOD) activity, osmoprotectant levels, and membrane stability, with 40 mmol/L CaCl₂ providing the most effective treatment [29].

3. Drought Physiology, Ecophysiology, and Secondary Metabolite Dynamics

Understanding how water deficit impacts crop growth versus secondary metabolite accumulation is crucial for optimizing cultivation under climate change.

The genotypic variation was highlighted by Mulugeta et al. in a two-year open-field study across five Ocimum genotypes (O. basilicum L. ‘Ohˇre,’ O. basilicum L. ‘Genovese,’ O. × africanum Lour., O. americanum L., and O. sanctum L.). This study reveals that while drought stress consistently reduced biomass yield across all taxa, its effect on essential oil content, total phenolic content (TPC), and antioxidant capacity (AOC) was strongly taxa-dependent, with O sanctum displaying the highest drought tolerance [30].

Field ecophysiology was assessed for newly introduced crops in a specific area. Here Stoian et al. assessed the ecophysiological adaptability of three sweet potato (Ipomoea batatas) cultivars (‘KSC’, ‘Koretta’ and ‘Hayanmi’) across three distinct phenophases in Romania, revealing variety-specific physiological strategies where ‘Hayanmi’ prioritized early leaf biomass and dry matter, while ‘KSC’ achieved superior tuber weight late in the vegetation season [31].

4. Seed Priming, Tissue Culture Stress, and Cellular Adaptation

Optimizing propagation techniques and including stress memory can significantly enhance plant establishment and resilience.

The long-term memory of seed priming was assessed by Stoian et al., aiming to assess different seed preconditioning techniques like hydropriming and osmopriming on Citrus limon seeds, along with observations of three years of young tree growth and development. This study highlights that osmopriming treatment conferred sustained increases in relative chlorophyll content, leaf dry matter allocation (32%), and quantum yield of photosynthetic electron transport, accompanied by altered stomatal density and guard cell architecture [32].

Metabolic and structural changes in blueberry micropropagation were also noted. Barua et al. investigated hyperhydricity (HH) in micropropagated half-highbush blueberry hybrids (Vaccinium corymbosum × Vaccinium angustifolium), using scanning electron microscopy (SEM), histology, and ¹H NMR spectroscopy to reveal structural abnormalities in mesophyll tissue and altered accumulation patterns of catechin, chlorogenic acid, and fatty acid chains under high-humidity culture systems [33].

5. Molecular Regulation, Functional Genes, and Sugar Signaling

Unraveling the molecular circuitry governing secondary metabolite biosynthesis and nutrient signaling provides targets for genetic improvement.

The flavonol biosynthesis in Jujube, a species with a history spanning millennia in Asia, was characterized. Xue et al. cloned and functionally characterized the flavonol synthase gene (ZjFLS) from Chinese jujube (Ziziphus jujuba Mil.), demonstrating its tissue-specific expression, which was highest in young leaves and white-ripe fruits, and confirming via heterologous overexpression in Arabidopsis thaliana that ZjFLS directly promotes total flavonoid accumulation [34].

Sugar-mediated metabolic reprogramming was demonstrated by Li et al. through transcriptome profiling of sweet cherry rootstock roots (Prunus cerasus), establishing that exogenous glucose functions as a potent signaling molecule rather than merely an energy source. Their investigation revealed that glucose application induces sustained, systems-level transcriptional shifts that dynamically coordinate carbon, nitrogen, and sulfur (C-N-S) metabolic pathways alongside stress-responsive processes. By modulating key regulatory networks, transcription factors, and enzymatic components such as nitrate transporters, carbonic anhydrases, and glutamine synthases, glucose fine-tunes nutrient assimilation, cellular redox homeostasis, and lateral root system development. Ultimately, this sugar-induced rewriting of primary nutrient circuits underscores the pivotal role of sugar signaling in root physiological plasticity, offering a foundation for enhancing rootstock vigor and nutrient use efficiency in horticultural species [35].

6. Future Research Directions

Building upon the findings of this Special Issue, several priority research avenues should be pursued to advance sustainable horticultural production. Future studies must transition from single-factor stress experiments towards multi-stress scenarios like combined drought, heat, and salinity in open-field environments to evaluate the interactive effects of biostimulants and exogenous protective agents. Given the multi-year physiological memory observed in woody species following seed priming, investigating epigenetic markers will be essential to decode how early priming signals translate into lifelong stress resilience. Combining transcriptomics, metabolomics, and non-destructive metabolic profiling such as NMR spectroscopy will clarify the precise regulatory hubs balancing primary biomass accumulation with secondary metabolite biosynthesis. Translating greenhouse biostimulant findings into standardized, crop-specific field application protocols considering delivery models (foliar vs. soil fertigation), timing across phenophases, and economic feasibility will be vital for sustainable commercial adoption.

7. Conclusions

Altogether, these studies highlight the multifaceted strategies required to obtain horticultural productivity, stress resilience, and crop quality under changing global environments. By integrating insights across biostimulant interventions, seed priming memory, ecophysiological adaptability, and sugar-mediated metabolic reprogramming, the collected studies demonstrate that stress mitigation relies on the tight coordination between fundamental physiological mechanisms and secondary metabolic regulation. Translating these genetic, biochemical, and physiological discoveries into validated, field-scale agronomic solutions will be paramount to safeguarding crop yields, enhancing high-value secondary metabolites, and fostering sustainable agricultural systems for the future.