Akj. Sallal et al., EFFECT OF GIBBERELLIC-ACID ON PHOTOSYNTHETIC ELECTRON-TRANSPORT REACTIONS AND NITROGENASE ACTIVITY IN ANABAENA-CYLINDRICA, Microbios, 78(314), 1994, pp. 17-25
Various concentrations of gibberellic acid (GA) were tested for their
effects on photosynthetic reactions and dinitrogen-fixation (acetylene
reduction) in Anabaena cylindrica. The optimum concentration of GA fo
r growth and oxygen evolution was 10(-4) M, and NADP photoreduction wa
s also enhanced. A pronounced effect was evident on the photosystem It
-Hill reaction, while the effect on the photosystem I-Mehler reaction
was much less. A concentration of 10(-6) M GA exerted some inhibition
on growth and photosynthetic reactions, while 10(-2) and 10(-3) M conc
entrations led to complete lysis. The optimum concentration of GA for
maximum nitrogenase activity was 10(-5) MI which also increased hetero
cyst differentiation.