65ª Reunião Anual da SBPC

E. Ciências Agrárias - 1. Agronomia - 5. Agronomia

TOTAL SOLUBLE AMINO ACIDS IN TWO CULTIVARS OF Vigna unguiculata INDUCED DROUGHT AND INOCULATION.

Marcele de Cássia Henriques dos Santos Moraes - Núcleo de Pesquisa Vegetal Básica e Aplicada - UFRA Gélia Dinah Monteiro Viana - Núcleo de Pesquisa Vegetal Básica e Aplicada - UFRA Maria Antonia Machado Barbosa - Núcleo de Pesquisa Vegetal Básica e Aplicada - UFRA José Ricardo Santos Barbosa - Núcleo de Pesquisa Vegetal Básica e Aplicada - UFRA Kelly Nayara Nascimento Coelho - Núcleo de Pesquisa Vegetal Básica e Aplicada - UFRA Allan Klynger da Silva Lobato - Prof./Orientador - Núcleo de Pesquisa Vegetal Básica e Aplicada - UFRA

INTRODUÇÃO:

Cowpea (Vigna unguiculata [L.] Walp.) is a legume with high protein content, a large capacity of fixation of the atmospheric nitrogen (N2), which presents important agronomical characteristics, such as rusticity and early maturity, besides being considered a plant adapted to conditions of limited water availability. Water deficit is an abiotic factor that affects agricultural production, influencing aspects related to plant development. Cowpea plants are considered tolerant to water deficit, and important mechanisms have been developed by this species to tolerate inadequate water supply. For example, biochemical modifications in carbon metabolism, as well as interference in nitrogen metabolism, such as the increase in total amino acids contribute to osmotic adjustment of Vigna unguiculata plants. Beneficial effects provided by the inoculation on growth parameters as leaf, stem and root are well known in leguminous plants, but information on the specific aspects of this symbiotic process on essential compounds such as amino acids is limited.

OBJETIVO DO TRABALHO:

This study aimed to evaluate the effects of inoculation and water stress on relative water content and total soluble amino acids.

MÉTODOS:

The study was carried out in Instituto de Ciências Agrárias (ICA) of the Universidade Federal Rural da Amazônia (UFRA), Belém city, Pará state, Brazil. The plants remained in greenhouse environment under natural sunlight conditions. The experimental design used was a completely randomised factorial layout with 2 cultivars (tolerant and sensitive), 2 water regimes (water deficit and control), and 2 inoculation treatments (inoculated and non-inoculated), making up 8 treatments, with 6 replicates and 48 experimental units, in which each experimental unit consisted of 1 plant pot-1. Three seeds per pot were sowed and thinned out to 1 seedling after germination. Leaf relative water content was evaluated on leaf disks of 10 mm diameter from each plant; 40 disks were removed and the calculation was done using the formula: LRWC = [(FM – DM)/(TM – DM)] × 100. Determination of amino acids were performed using 50 mg of leaf dry matter powder, and incubated with 5 mL of sterile distilled water at 100ºC for 30 minutes. After incubation, the homogenised was centrifuged at 2.000 g for 5 minutes at 20ºC and supernatant was removed. Data were subjected to variance analysis and when significant differences were detected, Scott-Knott test at 5% level of error probability.

RESULTADOS E DISCUSSÃO:

The inoculation promoted attenuation of the negative effects induced by water deficit on leaf relative water content. The decrease of this variable can be explained by the reduction in water availability in substrate, because the water deficiency induces turgor loss and consequent stomatal closing, which will affect other physiological processes such as photosynthesis and transpiration. Inoculated drought tolerant plants showed increase in amino acids, and this can be attributed to biological fixation of nitrogen. In addition, the increased formation of amino acids is probably linked to an increase in activity of the enzyme glutamine synthetase (GS), which depends ATP (adenosine-5'-triphosphate), and glutamate synthase (GOGAT). In addition, the increase in amino acids of plants exposed to inoculation is due to greater flux and better assimilation of nitrogen in form of ammonium, concomitantly with higher activity of GS and GOGAT enzymes. The concentration of total soluble amino acids in plants under water deficit increased in all treatments. This increment probably occurred due to increase in activity of protease enzymes, responsible for the breakdown of proteins to adjust the plant osmotically.

CONCLUSÕES:

This research revealed an increase in the relative water content in plants Vigna unguiculata under inoculation. Additionally, the concentration of total soluble amino acids in plants under water deficit increased in all treatments.

Palavras-chave: Cowpea, Water déficit, Nitrogen metabolism.