Efeito do tratamento de sementes de gergelim com molibdênio e zinco sobre a germinação, desenvolvimento inicial das plantas e resposta ao déficit hídrico

Abstract

Sesame is a crop of great relevance, especially in the Brazilian Cerrado, where it is mostly grown as a second crop. However, this growing season exposes the plant to "veranicos" (dry spells), periods of water scarcity that can severely compromise seed productivity and physiological quality. The objective of the study was to evaluate the effect of this treatment on initial development, focusing especially on rooting and the capacity to respond to low water availability. The methodology consisted of conducting bibliographic research and two experimental trials using the BRS Anahi cultivar. The first, in the laboratory, used a 4 x 4 factorial scheme (four doses of Zn and four of Mo: 0; 0.5; 1; and 1.5 g kg⁻¹ of seeds) in a completely randomized design with four replicates. Physiological quality was assessed through germination tests on paper and emergence in sand, also determining the lengths and dry masses of the shoots and the root system. Based on ANOVA and mean tests, doses of 0.5 g kg⁻¹ of both nutrients were selected for the second trial, conducted in a greenhouse. This second trial adopted a 4 x 2 factorial scheme, comparing four treatments (T1: 0 Mo/0 Zn; T2: 0.5 g kg⁻¹ Mo/0 Zn; T3: 0 Mo/0.5 g kg⁻¹ Zn; T4: 0.5 g kg⁻¹ Mo/0.5 g kg⁻¹ Zn) under two water regimes: full irrigation and water deficit applied for seven days starting at 20 days after emergence (DAE). At 35 DAE, height, leaf number, and fresh and dry masses were evaluated. The results demonstrated that seed treatment affected germination but did not impair seedling emergence, even at the maximum dosages of 1.5 g kg⁻¹. Although the micronutrients did not increase tolerance to water deficit in isolation per se, they promoted significant benefits in initial growth and root system development under both water conditions. Zinc, in particular, is recognized for its role in auxin synthesis and membrane stability under stress. It is concluded that seed treatment with Zn and Mo is a promising technique to accelerate the crop's initial development. For vigorous establishment in greenhouse conditions, the most effective results were obtained with the dose of 0.5 g kg⁻¹ of Mo, applied alone or in combination with 0.5 g kg⁻¹ of Zn, regardless of water availability.