Acclimation of Cyanobacterial Communities in Rice Fields and Response of Nitrogenase Activity to Light Regime

摘要: The short-term and long-term effects of light regime on nitrogenase activity (NA) cyanobacterial communities in rice fields (Valencia, Spain) were examined. Daily variation nitrogen fixation was measured during three periods the crop cycle: tillering (formation secondary stems plants), heading reproductive structures), maturity. Two locations examined over two consecutive years (1994 1995). Despite differences crop-cycle periods, location, year, a consistent pattern observed, with main peak morning another late evening. Short-term experiments, performed blooms (Nostoc sp. Anabaena sp.) exposed to natural under plant canopy (7% incidence irradiance), different intensities neutral density screens without cover (full sunlight, 43%, 26%, 13% incident indicated that dependent both intensity quality. In where cyanobacteria one month intensities, changes species composition genera heterocystous (Nostoc, Anabaena, Calothrix) observed. at which for became optimum irradiance NA each community. Assays higher or lower irradiances showed NA. Nitrogen followed seasonal along cycle. Values low beginning (May), reached maximum value end stage (June), declined thereafter until cultivation cycle (September).