Seed germination and antioxidant enzyme activity in seedlings of diploid and tetraploid bahiagrass under water restriction.

EnglishThe objective of the following research was to investigate the physiological responses of two bahiagrass genotypes (Paspalum notatum Flugge) submitted to water restriction, induced by polyethylene glycol (PEG6000), during seed germination. Seeds of cv. Pensacola (diploid) and Bagual ecotype (tetraploid) were placed on paper moistened with osmotic solutions at potentials of 0.0; -0.1; -0.2 and -0.3 MPa. Composed of two subsamples of 100 seeds and four experimental units per treatment, the germination test was conducted in a germination chamber under alternating temperatures of 30 °C (8 hours) and 20 °C (16 hours), with presence of light during the higher temperature. Final germination percentage and germination speed index of the seeds, as well as early growth, activity and expression of antioxidant enzymes of seedlings were evaluated. The water restriction induced by PEG6000 reduced the percentage of germination in Pensacola (from 74% to 59%) and Bagual (34% to 10%). For the latter, the evaluation of seedlings showed higher dry mass in relation to cv. Pensacola (1.7 times higher in root and 1.6 times in shoot). In response to moderate water restriction, the genotypes showed increases in root growth (1.7 times higher in -0.1 compared to 0.0 MPa), both in expression and enzymatic activity (superoxide dismutase and catalase) portuguesO presente estudo objetivou avaliar as respostas fisiologicas de dois genotipos de grama forquilha (Paspalum notatum Flugge) sob restricao hidrica induzida por polietileno glicol (PEG6000) durante a germinacao de sementes. Sementes da cv. Pensacola (diploide) e do ecotipo Bagual (tetraploide) foram colocadas em papel umedecido com solucoes osmoticas nos potenciais de 0,0; -0,1; -0,2 e -0,3 MPa. Composto de duas subamostras de 100 sementes e quatro unidades experimentais por tratamento, o teste de germinacao foi conduzido em câmara de germinacao sob temperatura alternada de 30-20 oC, com presenca de luz durante a maior temperatura. Foram avaliados a porcentagem final e o indice de velocidade de germinacao das sementes, assim como o crescimento inicial, a atividade e a expressao de enzimas antioxidantes das plântulas. A restricao hidrica induzida por PEG6000 reduziu o percentual de germinacao em Pensacola (de 74 para 59%) e Bagual (34 para 10%). Este ultimo, na avaliacao de plântulas, apresentou massa seca superior em relacao a cv. Pensacola (1.7 vezes superior em raiz e 1.6 vezes superior em parte aerea). Em resposta a restricao hidrica moderada, os genotipos apresentaram aumentos tanto do crescimento radicular (1.7 vezes superior em -0.1 em comparacao com 0.0 MPa), quanto da expressao e da atividade enzimatica (superoxido dismutase e catalase)