Impact of tetraploidization on morphophysiological leaf traits in the drought tolerant 'de Ramellet' tomato landrace

Tetraploidization was induced in the drought-tolerant tomato landrace 'de Ramellet' to evaluate its physiological and anatomical response under well-watered (WW) and water-deficient (WD) conditions. Under WW, tetraploid plants exhibited approximately 40% lower stomatal density and approximately 80% larger stomata than diploids. Net photosynthetic rate (<i>P</i>_N), intrinsic water-use efficiency, and intercellular CO₂ concentration remained unchanged between diploids and tetraploids. Under WD, both genotypes reduced <i>P</i>_N and stomatal conductance by similar proportions; however, only diploids decreased leaf area and adjusted stomatal density and size, whereas the tetraploid maintained stomatal traits similarly to those in WW conditions. However, both genotypes maintained similar photosynthetic capacity under WD despite different stomatal display and total pore area, which suggests the involvement of morphophysiological mechanisms beyond stomatal traits, such as root traits and hydraulic regulation.