Gas exchanges and growth of soybean cultivars submitted to water deficiency

Abstract

<jats:p>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 &lt; 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.</jats:p>

Gas exchanges and growth of soybean as affected by irrigation depths and soil compaction

“…At 45, 55, 65 and 75 DAE, gas exchange was determined using a portable infrared gas analyzer (IRGA-LICOR 6400, LiCOR, Lincoln, Nebraska, USA), carried out between 09:00-10:30 h, in two plants per pot using the third fully expanded leaf from top to bottom, photosynthetically active and without lesions, located in the third trefoil from top to bottom. Photosynthetically active radiation was standardized in artificial saturating light of 1000 μmol•m -2 s -1 (equivalent to natural light) and ambient CO2 concentration (Silva et al, 2020). We measured stomatal conductance rate (gs, mol H2O•m -2 s -1 ), transpiration rate (E, mmol H2O•m -2 s -1 ), internal CO2 concentration (Ci, μmol CO2•mol -1 ), as well as the net photosynthesis rate (A, μmol CO2•m -2 s -1 ), leaf temperature (Tf) and vapor pressure deficit (VPD).…”