Inhibition of photosystem II of nitrogen-fixing blue-green alga Nostoc linckia by the rice-field herbicide benthiocarb.

Effects of rice-field herbicide benthiocarb (S(4-chlorobenzyl)-N,N-diethyl thiolcarbamate) was studied on the nitrogen-fixing blue-green alga Nostoc linckia. The herbicide caused inhibition of growth and heterocyst formation, an increase in intensity of photoacoustic signals, and a four-fold reduction in oxygen evolution, but did not affect dark O2-uptake. The inhibition of growth and heterocyst formation was relieved by 500 micrograms/ml glucose. A Het-Nif- mutant of Nostoc muscorum failed to show an increase in reversion, frequency after treatment with 10 micrograms/ml benthiocarb for 1 hr.