Growth and nitrogenase activity of Azolla pinnata var. pinnata R. Brown asaffected by some environmental factors

Effects of pH, light, diel changes, temperature and shaking on the growth a nd nitrogenase activity of a local strain of Azolla pinnata var. pinnata Dh 101 have been studied in the controlled laboratory conditions. It appeared that pH 5 to 6 were favourable for growth and nitrogenase activity. With de creasing light quantities the growth and nitrogenase activity gradually dec reased. Adaptation to changed Light flux takes place within one and one and a half-hour of transfer. Mimicking day and night in the laboratory it was observed that about 20% nitrogenase activity of the 24h total occurred at n ight. Azolla showed two peak activities, after 6 and 10 h of re-illuminatio n, In continuously illuminated Azolla the activity also showed ups- and dow ns in every 3-4 h time. A temperature rise up to 33 from 25 degreesC (durin g the photoperiod of 80 muE m(-2) s(-1)) reduced both the growth and nitrog enase activity by about 50%. A high light flux of 150 muE m(-2) s(-1) sever ely affected only chlorophylls. Shaking did not have any effect on the grow th and nitrogenase activity.