Excessive P effects in the growth of Solanum lycopersicum related to stomatal closing mediated by ABA and ethylene.

Phosphorus (P) is an essential macronutrient for plant growth and development; however, both its deficiency and excess can be harmful. Although the effects of excess P are still poorly understood, research has shown that plants exposed to excessive levels of P exhibit reductions in stomatal conductance, photosynthesis, and growth. The aim of this study was to investigate the effect of different P concentrations on stomatal responses, photochemical parameters, growth, and development of three Solanum lycopersicum genotypes: wild type, Never ripe (lower sensitivity to ethylene), and Notabilis (deficient in ABA production). The plants were grown in a growth room, and stomatal traits, photochemical parameters, stomatal conductance, transpiration, and H₂O₂ content in the leaves were analyzed. Excessive P concentrations promoted stomatal closure, reduced stomatal conductance and transpiration, but did not cause significant changes in photochemical parameters in S. lycopersicum, indicating that the negative effects of excess P may be related to limitations in CO₂ acquisition. Furthermore, excess P increased leaf H₂O₂ content. The absence of negative effects of excess P in the Never ripe and Notabilis genotypes suggests that stomatal closure related to excess P depends on ABA and ethylene signaling to guard cells.