SOME EFFECTS OF MALEIC HYDRAZIDE ON LIGHT REACTIONS OF PHOTOSYNTHESIS IN ISOLATED CHLOROPLASTS FROM PHASEOLUS VULGARIS PLANTS

Abstract

The light reactions in leaf chloroplasts extracted from maleic hydrazide (MH)-treated and untreated snapbean plants (Phaseolus vulgaris L. ’Tendercrop’) were studied using three dye reduction tests. The intact plants were treated with a level of MH which caused little or no morphological alteration. The Hill reaction and dichlorophenol indophenol (DCPIP) reduction by pigment system II (PS II) were significantly decreased by the MH treatment. Ferricyanide reduction activity was significantly accelerated by the MH treatment. The Hill reaction and DCPIP reduction results suggest that there is not an uncoupling of photophosphorylation. The point of action for MH in photosynthesis appears not to be in PS II but between cytochrome f and plastocyanin.