Germinação de sementes e crescimento de plântulas de algodão sob diferentes concentrações de zinco

Abstract

Zinc is naturally present in soils and comes from the weathering of the source material, being an essential element for the good development of plants. However, due to natural factors and the influence of man on the environment, the concentrations of Zn in the soil are very variable, and may be in insufficient concentrations to assist in the good development of the plant or without high concentrations that end up being toxic to them. The objective of this work was to analyze the effect of zinc on germination and development of cotton seedlings at different concentrations of the element. The experiment was conducted in the Seeds and Grains laboratory located at the Federal Institute of Education, Science and Technology of Mato Grosso on the campus of Lucas do Rio Verde - MT, in a split-plot scheme in time and a randomized block experimental design, with classification cross and 4 blocks. The seeds were divided into 4 lots of 16 replicates of 50 seeds, each repetition being sown in germitest® paper, previously moistened with a volume of water corresponding to 2.5 times the weight of the paper. The water used for the imbibition of the 4 batches was added with different concentrations of zinc sulfate (ZnSO4), so that the final zinc concentrations were 0, 100, 200 and 400 mg/L, generating four different treatments. The rolls of paper were kept in germinators at a constant temperature of 20ºC and with 24 hours of available light, and evaluations of vigor, germination and seedling length were carried out on the fifth, sixth, seventh and eighth days after sowing. On the eighth day, the seedlings were placed in paper bags and subjected to drying in an oven with forced air circulation, at 65°C for 72 hours, and subsequently weighed in mg per total repetition, determining the dry matter. It was possible to observe a significant effect of the application of doses of zinc in relation to germination, with a decrease in the percentage of germination of cotton seeds when treated with different doses of zinc. The dose of 400mg/L presented results below the levels established by the Standard National Seed Marketing. For seed vigor it was not possible to verify the effect of zinc doses along the treatments. In the length of roots, the point of maximum efficiency at the dose of 100 mg L-1, reducing this effectiveness at the highest doses. In the evaluations of Fresh Pasta and Dry Pasta, it was observed that as the doses of zinc increased, there was a tendency for these variables to fall.