Physiological and Photosynthetic Variability among Tomato (Solanum lycopersicum L.) Genotypes under Pot Culture in Temperate Kashmir

Tomato (Solanum lycopersicum L.) is one of the most widely cultivated vegetable crops and is valued for its nutritional, economic and dietary importance. Its fruits are important sources of vitamins, minerals, carotenoids and other bioactive compounds, while the crop has considerable significance for fresh consumption and processing industries. However, tomato growth, development and productivity are strongly influenced by genotype and environmental conditions, making the identification of genotypes with superior adaptation and physiological performance an important component of crop improvement programmes. Recent studies have demonstrated substantial genetic variation among tomato germplasm for plant growth, biomass production, root characteristics and other agronomic traits, highlighting the value of physiological and phenotypic characterization for genotype selection (Roohanitaziani et al., 2020; Tripodi et al., 2022).

Photosynthesis is a major determinant of plant carbon gain and biomass accumulation and is influenced by the coordinated functioning of photosynthetic pigments, stomatal regulation, carbon assimilation and the photosynthetic apparatus. Chlorophylls are central to light harvesting and energy conversion, whereas carotenoids contribute to light harvesting and photoprotection. Leaf gas-exchange attributes, particularly net photosynthetic rate, stomatal conductance and transpiration rate, provide important indicators of carbon assimilation and plant water relations. Recent advances in tomato research have emphasized the genetic basis of photosynthetic variation and the potential for exploiting photosynthetic traits in crop improvement (Dong et al., 2025). Differences among genotypes in gas exchange and photosynthetic responses may also become particularly important under environmental constraints, because tomato genotypes can employ contrasting physiological strategies for maintaining growth and photosynthetic function (Francesca et al., 2024; Bhattarai et al., 2024).

Genotypic variation in physiological traits is closely associated with differences in biomass accumulation and resource acquisition. Biomass partitioning between shoots and roots reflects the allocation of assimilates towards above- and below-ground organs and may influence plant establishment, nutrient acquisition and overall growth. Recent evaluation of diverse tomato accessions under contrasting nitrogen regimes demonstrated substantial variation in growth, biomass traits and pigment-related characteristics, with root biomass identified as one of the useful traits associated with nutrient-use efficiency (Flores-Saavedra et al., 2024). Similarly, comparative studies involving diverse tomato genotypes have shown that genotype, environment and their interaction can substantially influence morpho-physiological performance (Tripodi et al., 2022). Such variation provides an opportunity to identify genotypes with favourable physiological attributes for subsequent breeding and adaptation studies.

The importance of physiological characterization is further increased under changing climatic conditions. Temperature extremes can markedly affect photosynthesis, stomatal behaviour, growth and reproductive performance in tomato, with genotypes differing considerably in their physiological responses to environmental stress (Francesca et al., 2024; Bhattarai et al., 2024). Recent studies have shown that physiological and photosynthetic traits can contribute to the identification of contrasting tomato genotypes under temperature stress and other environmental constraints, although individual physiological traits may not always provide sufficient information for genotype selection when considered independently (Francesca et al., 2024; Bhattarai et al., 2024). Therefore, an integrated assessment of growth, biomass allocation, photosynthetic pigments and gas-exchange characteristics can provide a more comprehensive understanding of genotypic physiological performance.

Under the temperate agro-climatic conditions of Kashmir, evaluation of tomato genotypes is particularly relevant because environmental conditions differ from those of the major tomato-growing regions of India. Earlier work under Kashmir conditions reported significant variability among tomato genotypes for plant growth, fruit yield and quality attributes (Bhat et al., 2022). However, the physiological basis underlying such genotypic differences, particularly with respect to biomass partitioning, photosynthetic pigments and leaf gas exchange, remains insufficiently characterized. In particular, there is limited information on the simultaneous evaluation of these physiological attributes among the tomato genotypes evaluated under Kashmir conditions. Such information can complement conventional yield and quality evaluation and help identify genotypes possessing favourable physiological traits for further adaptation and breeding studies.

Therefore, the present study was undertaken to evaluate the physiological and photosynthetic variability among twelve tomato genotypes under pot culture conditions in the temperate climate of Kashmir, with particular emphasis on plant growth, shoot and root biomass, biomass partitioning, photosynthetic pigments and leaf gas-exchange characteristics. It was hypothesized that the tomato genotypes would differ significantly in biomass allocation, photosynthetic pigment concentration and gas-exchange activity, and that genotypes exhibiting superior physiological performance could be identified for further evaluation under temperate conditions of Kashmir.