Desempenho fisiológico de sementes de cultivares de algodão sob estresse hídrico

Abstract

The water stress represents a challenge for crop productivity and can substantially reduce yields. Therefore, the use of cotton cultivars adapted to deal with this abiotic stress becomes essential. The objective of this study was to evaluate the physiological performance of cotton cultivar seeds under water stress conditions. The experimental design used was completely randomized in a 3 x 5 factorial scheme, with three cultivars (FM 978GLTP, TMG 22GLTP and FM 970GLTP) and five osmotic potentials induced by polyethylene glycol solutions - PEG 6000 (0.0; -0.3; -0.6; -0.9 and -1.2 MPa), with four repetitions of 50 seeds. The variables analyzed were: water content, germination, root protrusion, first germination count, germination speed index, shoot length, root length and seedling fresh mass. The imbibition curve was conducted with four repetitions of 50 seeds distributed on Germitest paper moistened with two potentials (0.0 and -1.2 MPa) of PEG 6000. The seeds were weighed dry, and subsequently moistened at the following times: 0; 2; 4; 6; 8; 10; 12; 14; 16; 18; 20; 22 and 24 hours. The data were subjected to analysis of variance, with the means of osmotic potentials being compared using the F thesis (P<0,05), and the results from the weighing times were subjected to regression analysis. The results showed that severe water stress, in particular with osmotic potentials below -0.9 MPa, negatively affected the physiological performance of the studied cultivars. The FM 970GLTP cultivar was the least affected by water stress, while the TMG 22GLTP and FM 978GLTP cultivars were more sensitive, presenting lower germination and vigor results under water stress conditions. It was possible to observe the water absorption curve of the seeds of the studied cultivars only at 0.0 MPa potential, following the three-phase pattern.