O mutante insensível ao etileno Never ripe apresenta respostas diferenciais aos estresses por fósforo

Abstract

Phosphorus (P) is a macronutrient required as a structural and functional component of several biomolecules. This element interacts with phytohormones, such as ethylene, generating responses that impact plant growth and development. Tomato (Solanum lycopersicum L.) has been used as a model for physiological and biochemical studies, and the mutant with reduced ethylene perception, Never ripe (Nr), can help to understand how this hormone interferes and coordinates biological processes, including response to stresses, such as nutritional ones. This work aimed to understand how the ethylene-insensitive mutant tomato plant Never ripe responds to phosphorus (P) stresses (absence and excess). The experiment was conducted in the growth room, where tomatoes (cv. Micro-Tom) of wild type (WT) and Nr were subjected to fertigation with adapted Hoagland solution. Plants were distributed in six treatments, in double factorial 2 (genotypes) x 3 (levels of P): (i) WT in P optimal; (ii) WT in absence of P; (iii) WT in excess of P; (iv) Nr in P optimal; (v) Nr in absence of P; and (vi) Nr in excess of P. Biometric, photosynthetic, biochemical and nutritional parameters of plants in the vegetative stage and at the end of the experiment were quantified. The highest values of the biometric parameters were found in Nr, in all treatments, except the root-shoot ratio. Fruit production was widely affected, being lower in WT in the absence of P. Curiously, several photosynthetic parameters such as Fv/Fm, and CO2 assimilation were higher in the absence of P for both genotypes. Nr plants showed fewer carbohydrates and more amino acids and proteins; in addition to having better nutritional aspects of P accumulation in plant organs and P use efficiency. These Nr plants also demonstrated greater phenotypic stability when exposed to P stresses, verified by their greatest biometric attributes. The results indicate that ethylene plays an essential role in the signaling of nutritional stresses and that it’s reduced perception can mitigate these effects. The ethylene insensitivity led to a better resistance of plants to adverse conditions to which they were submitted (absence and excess of P). However, higher levels of nitrogen compounds in Nr may indicate that these plants are perceiving P stress and responding differently in relation to WT.