63ª Reunião Anual da SBPC

E. Ciências Agrárias - 1. Agronomia - 4. Fitotecnia

Impact of the water deficit and rehydration on abscisic acid and proline in Vigna unguiculata plants

Robson de Lima Silva 1 Maria Luiza Martins de Lima 1 Ruy Guilherme Correia 1 Cândido Ferreira de Oliveira Neto 1 Allan Klynger da Silva Lobato 1 Roberto Cezar Lobo da Costa 1

1. Núcleo de Pesquisa Vegetal Básica e Aplicada, Universidade Federal Rural da Amazônia

INTRODUÇÃO:

Proline is an amino acid that is normally synthesized in large amounts under conditions of biotic stress like pathogen infection and abiotic stress like water deficiency, salt stress, and heavy metal stress. Therefore, this accumulation is associated with functions of osmoprotection and osmotic adjustment. The abscisic acid (ABA) hormone is synthesized into plastids, as well as linked to stomatal mechanism and other physiological processes, besides it is quickly responsive in conditions of water deficiency. The ABA can be produced in roots and/or shoots, but this hormone is normally synthesized under water deficiency in roots and translocated to leaves aiming to improve stomatal control. The ABA signalization pathway depends on the Ca+ influx into the cytosol activating the K+ , Cl-, and malate-2 efflux channels to extern medium, through plasmatic membranes and concomitantly blocking the K+ entrance to cytosol. Therefore, the cytosol solute flux in direction to the cellular wall results in a decrease of turgescence pressure in guard cells, so consequently the stomata are closed. The aim of the study was to investigate impact of the water deficit and rehydration on abscisic acid and proline in Vigna unguiculata plants.

METODOLOGIA:

The study was carried out in the Laboratory of Metabolism and Plant Stress of the Universidade Federal do Ceará (UFC), Fortaleza, Ceará State, Brazil. The plants were grown in a glasshouse. The Vigna unguiculata seeds of the Vita 7 cultivar were used in this study. The experimental design used was entirely randomized in a factorial scheme, with 2 water conditions (control and stress) combined with 7 evaluation periods (0, 1, 2, 3, and 4 days under water deficit, followed by 5th and 6th day under rehydration. The treatments (control and stress) were watered with a nutritive solution of Hoagland and Arnon (1950). All the plants were grown until the 28th day, and subsequently plants under the stress treatment were submitted to 4 consecutive days without nutritive solution, and after this period, rehydrated with distilled water during 2 days. In this study were determined abscisic acid concentration and proline according to Norman et al. (1990) and Bates et al. (1973), respectively. The data were submitted to variance analyses and when significant differences occurred the Tukey test was applied at 5% level of error probability. The standard errors were calculated in all evaluated treatments.

RESULTADOS:

Water deficit simulation promoted a significant increase in the abscisic acid concentration, and values verified in the stress treatment were 2.4, 45.9, 42.6, 47.9, 66.9, 9.2, and 5.5 mg Kg-1 DM on days 0, 1, 2, 3, 4, 5 and 6, respectively. In addition, the control treatment presented the values oscillating between 2.4 and 5.2 mg Kg-1 DM. The rehydration induced a rapid decrease in the abscisic acid concentration, but the concentration of the treatment stress was equal to the control only on the 6th day Proline levels of the plants under stress increased due to water restriction, in which the stress treatment presented significant increases at 67, 354, 423, and 532% on the 1st, 2nd, 3rd, and 4th day, respectively, when comparing plants of the stress treatment to the control. After rehydration, the proline levels of the plants submitted to water deficit were reduced; however only on the 6th day was it statistically similar to the control.

CONCLUSÃO:

This study suggests a negative interference of water deficit and fast recuperation after rehydration, in which were showed increases in abscisic acid concentration and proline with the objective to relieve water loss in Vigna unguiculata induced to water deficiency.

Palavras-chave: ABA, proline, Vigna unguiculata.