Potencial fisiológico de sementes escuras e claras de Euphorbia hyssopifolia Lam. em função dos estresses hídrico e salino e de condições químicas do substrato

Abstract

Euphorbia hyssopifolia is a weed species that occurs in several states in Brazil, including Alagoas, where it has been found in areas occupied by soybeans, corn, sugar cane and pastures, causing direct and indirect problems. Therefore, there is a need for studies that can generate information for use in controlling this weed in the field. Thus, the present work was conducted at the Campus of Agricultural Engineering and Sciences (CECA/UFAL) with the objective of studying the physiological potential of E. hyssopifolia seeds depending on their color and interaction with water and saline stress, pH, and of aluminum and calcium content in the substrate. Thus, dark and light colored seeds were allowed to germinate under water stress conditions. Using PEG 6000 solutions at different water potentials (-0.3; - 0.6; -0.9 and -1.2 MPa); salt stress, using NaCl (isotonic potential 1.8) to obtain potentials 0.0; -0.3; -0.6; -0.9 and - 1.2 MPa., under different pH conditions (2.5, 4.0, 5.5, 7.0, 8.5 and 10); aluminum content prepared from aluminum sulfate - Al2(SO4)3 at concentrations of 0; 1.5; 3.0; 4.5; and 6.0 mmolc.dm-3 different doses of calcium (0.0; 1.5; 3.0; 4.5; and 6.0 meq 100 ml-1) and doses of magnesium (0.0; 3 .0; 6.0; 9.0; and 12.0 meq 100 ml-1). The experiments were carried out in a completely randomized design (DIC), with the data subjected to analysis of variance, whose means were evaluated by the Tukey test at 5% and regression analysis for quantitative variables. For each experiment, four replications of 25 seeds were used, placed on blotting paper moistened with solutions according to the experiment and treatment, placed in a germination chamber (B.O.D.), regulated at an alternating temperature of 20-30oC and constant of 20oC for water and saline stress experiments, with a photoperiod of eight hours in all tests. The tests lasted 21 days, considering seeds with a 2 mm long root protrusion to be germinated. At the end of the experiments, the seedlings obtained were measured and then dried in an oven to determine the dry mass. From the daily count data, the percentage and speed of germination (average time and IVG) were calculated. According to the results obtained, it was found that the behavior of seeds under the influence of salinity levels showed a decrease in germination with increasing osmotic pressures. The ideal pH for maximum germination was 7.0, regardless of color. Germinability was affected from 1.5 mmolc.dm-3 of Al3+. The levels of PEG 6000 and NaCl studied showed an influence on germinability from -0.3 Mpa. The germination process was completely inhibited from a concentration of 9.0 (cmolc.dm-3) of Calcium Chloride and 9.0 (cmolc.dm-3) of Magnesium Chloride in E. hyssopifolia seeds. Keyword: Dairy donkey; Weed; Euphorbiaceae.