Effect of Temperature on the Nitrogenase Activity of Intact and Detached Nodules inLotusandStylosanthes

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Abstract
Temperature and plant age influenced the nitrogenase activity of Lotus and Stylosanthes nodules. Time course studies using nodulated plants in closed vials showed a decline in activity after 48 h; regassing with 10% (v/v) acetylene in air partially restored the activity. Transfer of plants from 15, 20, 25, and 30 °C to 40 °C immediately stopped activity; this was completely restored within 1 h after return to original temperatures. Detached nodules cultured on nitrogen-free agar medium exhibited a sucrose concentration (2–8%, w/v)-dependent nitrogenase activity at each temperature. With 6% sucrose prolonged activity, up to 96 h, was obtained. Decline in nitrogenase activity in detached nodules was due partly to exposure to air during excision and transfer to the medium.