The Influence of Light and Oxygen on Nitrogenase Activity in the Lichen Stereocaulon paschale

Abstract

AbstractThalli of the lichen Slereocaulon paschale (L.) Fr. were prctreated in the light (light activated) or in the dark (dark starved). In short‐time experiments with both light activated arid dark starved thalli, the nitrogenasc activity was higher in the light than in the dark, Light activated thalli had a very much higher rale of C2H2 reduction than dark starved thalli, both in the light and in the dark. The dark starved lhalli showed increasing nilrogenase activity when incubated in the light.Either light or oxygen was necessary for nitrogenase activity in light activated thalli. and up to about 10kPa oxygen they showed additive effects. Both in the light and in the dark the nitrogenase activity decreased when the oxygen partial pressure was lower than in normal air. The experimental data thus showed a short‐term effect of light on nilrogenase activity by provision of ATP and reductant, and a long term effect probably by build up of reserves that were later utilized. Any immediate effect of photorespiration on nitrogenase activity could not be found in light activated thalli.