Gradative effect of phosphorus in stomatal traits regulated by ethylene and aba affecting photosynthesis and growth of Solanum Lycopersicum L.

Abstract

This study investigates the effects of excess phosphorus (P) on the stomatal closure and growth of Solanum lycopersicum L., focusing on the stomatal effects signaled by the phytohormones ethylene and abscisic acid (ABA). The excessive use of phosphate fertilizers in modern agricultural practices can increase P concentrations in the soil, leading to negative environmental impacts, such as the eutrophication of soils and waters, damaging the environment, its organisms and even human activities. Although several studies have investigated the effects of P deficiency on plants, the effects of excess P on plants are still poorly understood. Research has shown that plants exposed to excessive concentrations of P show reductions in stomatal conductance, photosynthesis and growth. The first article in this thesis examines phosphate-triggered and ethylene-mediated stomatal closure in S. lycopersicum mutants. It was observed that exogenous application of P directly to the leaf epidermis promoted stomatal closure and reduced stomatal conductance in all the genotypes studied, with the Notabilis mutant (deficient in ABA) being the most responsive and the Never ripe mutant (low sensitivity to ethylene) being the least responsive. The second article investigates how excess P reduces growth in S. lycopersicum, highlighting the role of stomatal closure mediated by ethylene and ABA. Excess P caused a reduction in stomatal conductance, transpiration and plant growth, 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. In addition, excess P increased the H₂O₂ content in the leaves. The responses varied between genotypes, suggesting that ethylene and ABA signalling are crucial to plant responses to excess P. The results of this study are fundamental to understanding the impacts of excess phosphorus on plants and can contribute to more sustainable agricultural practices, minimizing environmental risks and maximizing the efficiency of fertilizer use.