Respostas morfofisiológicas à adição de nutrientes em Pavonia varians Moric. (Malvaceae) e Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs (Poaceae) sob restrição hídrica

Abstract

Drought is one of the main factors limiting plant growth and establishment in environments such as the Caatinga, and demands from species a sufficient biochemical, physiological and morphological apparatus to enable them to overcome the challenges encountered in a semi-arid environment of a Seasonally Dry Tropical Forest. Anthropogenic actions have directly impacted the plant structure of this area, contributing to the intensification of the severity of conditions, such as nutritional availability and access by plants. The work aimed to analyze the morphophysiological responses of Pavonia varians and Megathyrsus maximus, species present in the Caatinga of Pernambuco, under nutritional supplementation with Nitrogen – N, Phosphorus – P, and Potassium – K under a regime of water restriction and rehydration. The study was carried out in a greenhouse with young individuals of P. varians and M. maximus collected in the Catimbau National Park in Pernambuco. Nutritional supplementation was carried out through the application of 4 doses (40ml/pot) of a solution of N (6mM), P (2mM) and K (6mM), starting 31 days after transplantation (DAT) of the plants. Until 51 DAT, the plants are maintained under watering, keeping them at 70% humidity of the pot capacity (control). 52 DAT, watering was suspended for 10 days and the first collection was carried out and irrigation was reestablished for another 20 days, ending with a second collection of plants. Through growth, physiological, oxidative, metabolic and nutritional stress analyses, it was possible to verify the action of NPK in the responses to water restriction and rehydration in P. varians and M. maximus. Proline was the main response modulated by nutritional supplementation with NPK to water restriction in both species. P. varians and M. maximus demonstrate responses to the NPK offered, however, recruiting different antioxidant defense pathways to water restriction. P. varians mobilized a non-enzymatic pathway, with emphasis on the action of proline, managing to reduce oxidative damage. M. maximus, in turn, also benefited through the enzymatic activity of APX, however it was not possible to observe a reduction in the levels of membrane damage. The study showed that the species demonstrate different behaviors in response to drought due to the suspension of irrigation, especially when supplemented with NPK. Nutritional supplementation favored the physiological strengthening of the species, contributing to more effective coping with oxidative damage caused by drought, and its consequent effective recovery after rehydration, proving to be an effective tool for combating water deficit.