This study aimed to evaluate the effect of exogenous phosphorus (P) and the abscisic acid (ABA) application on the stomatal physiology of three tomato genotypes: the wild type, ABA-deficient mutant notabilis, and the low ethylene sensitivity mutant Never ripe (Nr). The tomato genotypes were grown in a growth room for 60 days using Hoagland’s nutrient solution. Leaves were then collected, and fragments of the leaf epidermis were sampled and exposed to exogenous solutions of ABA and P for 10 min. The percentage of open and closed stomata, stomatal density, length, and width, and pore area were evaluated, and the maximum stomatal conductance was estimated. ABA promoted stomatal closure in all the genotypes, and the notabilis genotype was less responsive. P promoted stomatal closure in all genotypes, with notabilis being the most responsive and Nr the lowest. P reduced the pore area in all genotypes, with notabilis being the most responsive and Nr the least. P increased the stomatal length but reduced stomatal width in all genotypes. P reduced the stomatal conductance in all genotypes, with notabilis being the most responsive and Nr the least. Excessive P application on the leaf epidermis of tomato promotes stomatal closure and reduction of stomatal conductance, indicating that this closure is directly related to ethylene signaling.
Pádua et al. (Sat,) studied this question.