Benzimidazole Effect in Chloroplasts of Wheat Leaves

Abstract

Chloroplasts isolated from wheat leaves in nonaqueous media contained 399,22.7, 113, and 17. 6 mumoles/gm dry weight of NAD, NADH, NADP respectively. Chloroplasts isolated in the same manner from leaves floated for 6 days on water had lost 80% of the total pyridine nucleotide content, including a complete loss of NADP. The reduced forms remained relatively unchanged. When leaves were floated on 50 mg/ liter benzimidazole for 6 days there was a 20% loss of total pyridine nucleotide in the chloroplasts, but the NADP level had risen 2-fold, mainly at the expense of NAD. Photophosphorylation of aqueous chloroplasts isolated in aqueous media gradually decreased when leaves were floated on water, but benzimidazole treatment brought about an initial rise followed by a similar decline. Electron micrographs of chloroplasts from leaves floated on water showed a marked change in shape, deterioration of intergrana lamella, and loss of electron-dense particles. In the benzimidazole-treated leaves chloroplasts retained their shape, the grana and intergrana lamellae were more abundant and more closely spaced. Electron-dense particles were present and polysaccharide synthesis appeared to have been initiated.