Physiological potential of soybean seeds during maturation and submitted to artificial drying

This study evaluated the physiological potential of soybean seeds harvested during two seasons, on different maturation stages, and subjected to different drying temperatures. The first season was between October (2013) and February (2014) and the second season was between January and May (2014). The seeds were harvested at the maturations stages R7, R7 + 2 days, R7 + 3 days, R7 + 5 days, R7 + 6 days, R7 + 7 days, R7 + 10 days and R7 + 12 days, corresponding to the seeds with the following moisture contents: 55, 50, 45, 40, 35, 30, 25, and 20%, respectively. For each maturation stage, seeds were divided into three parts: one part was used to directly evaluate the physiological potential (control), and the other parts were dried at 40 °C and 50 °C, until reaching the moisture content of 11.5%. The physiological potential was evaluated through germination test, first count, accelerated aging, modified cold, electrical conductivity and seedlings emergence. Maintaining the seeds in the field caused a decrease in their physiological potential; the seeds became tolerant to artificial drying approximately at the moisture content of 30%. The maximum physiological potential of seeds was achieved at the moisture content of 55%, the point that the dry matter was absolute (253.62 mg seed -1 ). Seed germination and vigor reduced as the increase in drying temperature, and this effect was enhanced when the seeds showed moisture contents above 30%.