Ácido giberélico associado ao tratamento fitossanitário no uso imediato e armazenado sobre a qualidade de sementes e desenvolvimento inicial de arroz

Abstract

The early sowing of rice crops can lead to irregular seedling emergence due to low soil temperatures, uniform seed germination is essential for proper crop establishment and successively better efficiencies in crop management. The goal of this study was to evaluate the physiological response of irrigated rice seeds submitted to different concentrations of gibberellic acid (GA3) applied along with fungicide and insecticide in seed treatment, and the performance of these seeds with and without storage after treatment. The experiment conducted in the laboratory was completely randomized design (CRD) with four repetitions, in a simple factorial scheme (5x3), five doses of gibberellic acid (GA3): 0, 250, 500, 750 and 1000 mg of the commercial product ProGibb 40%, and three conditions of seed treatment: (i) seeds treated with gibberellic acid only; (ii) seeds treated with gibberellic acid with the addition of fungicide and insecticide; (iii) seeds treated with gibberellic acid with the addition of fungicide and insecticide and stored for a period of 30 days. The physiological quality was evaluated by germination tests, first germination count, seedling length and seedling dry weight. The field experiment was conducted in a randomized block design (RBD) with four repetitions, in a simple factorial (5x2), with the same doses of gibberellic acid (GA3) and two seed handling conditions: i) treated seeds (gibberellic acid and fungicide and insecticide) and after 24 hours sown in pots; and ii) treated seeds (gibberellic acid and fungicide + insecticide) and stored for 30 days at room temperature. The plants were evaluated on four dates for length, leaf area, dry mass of the aerial part, and growth analysis: i) crop growth rate - CGR (mg.pl-1 day-1); ii) relative growth rate - RGR (mg. g-1 day-1); and iii) net assimilation rate - NET (mg.cm2 day-1). The association of the plant regulator gibberellic acid (GA3) is compatible with fungicide and insecticide. It is advantageous to treat seeds with these products 30 days before rice sowing, because in this way the seeds can already leave the seed producing companies with this combination of products along with industrial seed treating (GA3 + fungicide + insecticide), thus avoiding the risks of "on farm" treatment by farmers.