Long‐term effects of herbicides on the photosynthetic apparatus II. Investigations on bentazone inhibition

Summary: Non‐cyclic electron transport by isolated chloroplasts from the alga Bumilleriopsis is inhibited by bentazone, while the activity of photosystem I is not affected. Chloroplast material isolated from cells grown for several days in the presence of bentazone also shows inhibition of photosystem II activity, similar to the decreased cellular photosynthesis. A slow partial recovery is possible, whereas it is fast and complete after exposure of cells or isolated chloroplasts to the herbicide for some hours only. Irreversibility of longterm inhibition could be a metabolic process which brings about the binding of bentazone (or an active derivative) to the thylakoids in vivo , but not in vitro .