Abstract Heat stress significantly constrains tomato ( Solanum lycopersicum ) productivity, necessitating the development of heat‐tolerant varieties to sustain production amid climate change. This study investigated the leaf anatomical adaptations of parthenocarpic tomato mutants iaa9‐3 and iaa9‐5 in response to heat stress to understand their tolerance mechanisms. The experiment was conducted in a greenhouse using a split‐plot design with four replications under two environmental conditions: normal and heat stress. Leaf anatomical characteristics, including stomatal, trichome, and mesophyll attributes, were observed using a digital microscope and compared between the mutants and the wild‐type (WT‐MT). Both mutants exhibited significant anatomical changes compared to WT‐MT. Under heat stress, iaa9‐3 and iaa9‐5 showed increased stomatal length but decreased width, guard cell thickness, and stomatal density. Additionally, both mutants displayed increased trichome length and density, reduced leaf cell density, and consistently higher thickness of the leaf, epidermis, palisade, and spongy layers than WT‐MT across both environments. These findings strengthen the understanding of the IAA9 gene's role in regulating plant anatomy and physiology under thermal stress. The superior anatomical traits of these mutants provide a scientific basis for breeding new tomato varieties that are more resilient to climate change‐induced heat stress.
Cartika et al. (Sun,) studied this question.