Tolerance of finger millet to propanil. 2 Recovery from propanil inhibition of photosynthesis.

Abstract

The effects of propanil on both photosynthesis and respiration of intact plants of rice, barnyardgrass and finger millet were investigated. Immediately after its application, both photosynthesis and respiration of the three species were inhibited, and only rice plant recovered from the inhibition of photosynthesis almost completely in a relatively short period. Photosynthesis of finger millet plants was recovered gradually, and no recovery was found in barnyardgrass. There were no significant differences in recovery of respiration among the three plant species. In leaf discs, quick recovery from the inhibition of photosynthesis of leaf discs was observed in rice and slower recovery in finger millet. Only slight recovery was shown in barnyardgrass.On the other hand, quick release from leaf discs of 14C-radioactivity, which had been applied as 14C-propanil was observed within one hour. Although immediately after exposure to 14C-propanil for various periods, amounts of 14C-radioactivity found in the discs of all three plant species were similar, when the discs were kept in propanil-free solution after exposure, detected 14C-radioactivity amounts were different, and there was particularly more in rice. But propanil in rice rapidly decreased, and was ultimately significantly less than in barnyardgrass and finger millet.In conclusion, selectivity of propanil in leaf discs was similar to the result from intact plant and the mechanism of tolerance of rice to the herbicide could be explained by its metabolic change in leaf discs as in intact plants, even if the reaction time was very short. The recovery of photosynthesis in finger millet was also observed in intact plant but in leaf discs it was observed only following treatment for relatively short periods.