ABSTRACT
A low availability of water in the soil may alter morphological traits and physiological processes in soybean, limiting its development, mainly at late sowings. This study aimed to evaluate the leaf gas exchanges and dry matter accumulation in soybean cultivars under low water availability at late sowing. An Oxisol with a very clayey texture was employed. A completely randomized design, in a 5 × 3 factorial scheme, with four replications, was used. The treatments were five water tensions (10 kPa, 15 kPa, 25 kPa, 40 kPa and 60 kPa) combined with three soybean cultivars (BRS Favorita, BRSMG 820 and BRSMG 850). The response variables were measured at 55 days after the emergence. The values for stomatal conductance, transpiration, photosynthesis rate, intercellular CO2 concentration and instantaneous carboxylation efficiency were significantly reduced (p < 0.05) with the increase of the water tension in the soil. The gas exchanges in the soybean plants were also reduced with the increase of the water tension in the soil, being the most critical ones observed from 25 kPa. BRSMG 850 showed the best performance for production of root dry matter in this water tension in the soil.
KEYWORDS:
Glycine max; instantaneous carboxylation efficiency; water tension in the soil
