The Effects of Light Intensity on Acetylene Reduction by Blue‐green Algal Mats in Sub‐tropical Grassland

Abstract

SUMMARYHigh light intensities such as those found during the middle of the day in southern Africa are not responsible for inhibition of acetylene reduction by mats of blue-green algae in kikuyu lawns. Similar results were obtained with uni-algal cultures of Nostoc isolated from the algal mats. Short term experiments (3 h) with both cultures and algal mats showed a direct relationship between acetylene reduction and light intensities of up to 323 lux but no significant increase in acetylene reduction for light intensities above this. The amount of acetylene reduction by algae in the dark is determined by the light intensity received prior to darkness.

Potential nitrogen fixation activity of different aged biological soil crusts from rehabilitated grasslands of the hilly Loess Plateau, China

“…Previous studies have shown that potential nitrogen fixation in biocrusts is highly dependent on past and present water and light regimes, ambient temperature, water content and light intensity (Belnap, 2003;Jones, 1977bJones, , 1977cJones, , 1977dKallio and Kallio, 1978;Rychert et al, 1978). In addition, some studies have also demonstrated that potential fixation rates vary with the successional stage of biocrusts (Belnap, 1996(Belnap, , 2002Housman et al, 2006;Marsh et al, 2006), as both species and biomass of N-fixing organisms change during the successional process (Belnap, 2003;Kallio and Kallio, 1978;Marsh et al, 2006).…”

The Effects of Temperature on Acetylene Reduction by Mats of Blue‐green Algae in Sub‐tropical Grassland

“…A species of Nostoc isolated from the algal mats was also used (Jones, 1977c). Acetylene reduction was measured as described previously (Jones, 1977c).…”

“…The highest rates of diurnal acetylene reduction are found in the afternoon when both soil temperature and light intensity are below the levels at midday when acetylene reduction is low. Light intensity does not appear to contribute to this midday drop in acetylene reduction (Jones, 1977c) hence there is the need for an investigation into the effects of temperature on acetylene reduction by the algal mats.…”