Boro melhora a fotossíntese, alivia os danos da restrição hídrica, promove o crescimento e produtividade em soja.

Abstract

The availability of B in the soil can influence the water condition of the plants in different ways, so that the concentration of this element can be a fundamental factor for the plant to be able to attenuate the effects of the water restriction. Thus, the supply of B can favor the water relations of plants, improving the absorption of water and nutrients, transport through the xylem, and relieve the wilt of plants. In this context, the objective was to evaluate the effects of B doses and their influence on gas exchange in the vegetative phase; the fluorescence of chlorophyll a, gas exchange, growth and productivity in the reproductive stage of soybean cultivated with different water contents in the soil. For this, a greenhouse experiment was carried out in two different phases. In the first phase, treatments were 4 doses of B (0.0, 1.5, 3.0 and 6.0 mg dm- 3) and five replications in randomized blocks. In the second, the treatments consisted of the combination of the same doses of B of the first phase and three leveis of water in the soil [60, 80 and 100% of the moisture in the field capacity (Ucc)], in a 4 x 3 factorial scheme, with five replications distributed in a randomized block design. The results revealed that: i) the application of B promoted improvement in gas exchange by stomatal control, greater photosynthetic activity and better osmotic adjustment; ii) the B supply in plants under 60% Ucc promoted greater photosynthetic efficiency due to improvements in the photochemical phase, evidenced by the chlorophyll a fluorescence; (iii) The application of B contributed to improving the efficiency of water use, reducing water loss through transpiration and producing more dry matter per gram of transpired water; iv) the supply of B in condition of water restriction promoted an increase in biomass production and grain yield.