Alterações fisiológicas e bioquímicas de genótipos transgênicos de soja submetidos à condição de alagamento

Abstract

Soil flooding occurs in many parts of the world, especially in regions with shallow soils or drainage problems. When it occurs in agricultural areas, flooding directly interferes with plant cultivation, severely limiting crop production, causing oxygen deprivation (hypoxia) in roots, triggering metabolic changes in the entire plant, affecting essential processes. The objective of this work was to evaluate the physiological and biochemical characteristics of transgenic soya genotypes submitted to hypoxia and reoxygenation in the V4 and R2 stages. For this purpose, an experiment was carried out in polyethylene boxes installed in the field, under natural light and temperature conditions, using two GM lines: NCED and GOLS and background cv. BRS184. Biochemical, phenotypic and production studies were performed, such as gas exchange, photosynthetic pigment contents, antioxidant enzymes activity, hydrogen peroxide content, lipid peroxidation, alcohol dehydrogenase (ADH) and alanine aminotransferase (AlaAT) activity, stature of plants at maturity, weight of one hundred seeds and yield of grains. In general, genotypes have different mechanisms to overcome hypoxic stress. In leaves, both GM genotypes showed reduction in stomatal conductance and transpiration. The NCED strain is able to maintain photosynthetic rates at control levels during flooding in both V4 and R2. The content of H2O2 identified in all genotypes during the flooding period is possibly not produced by SOD, since the enzymatic antioxidant defense system is generally poorly active for GM and isoline strains. The GOLS line is able to withstand hypoxic stress with low damage to lipid peroxidation. In roots, genotypes NCED and BRS184 are able to induce the enzymatic antioxidant defense system in soybean roots under O2 deficiency, reducing oxidative damages during the period of hypoxia and recovery. The BRS184 genotype shows less damage caused by lipid peroxidation than the GM NCED lineage. The hypoxia imposed at the vegetative stage promotes an increase in grain yield in BRS184 and reduction in NCED. The activity of the AlaAT enzyme is responsive to hypoxic stress in NCED, presenting activity variations when compared to BRS184 as a function of the developmental stage - greater intensity of response during the reproductive stage, but returning to the control levels during the recovery period.