Inorganic pyrophosphatase activity in water stressed excised rice leaves

Abstract

Changes in the inorganic pyrophosphatase (EC 3.6.1.1) activity and the chlorophyll and α-amino nitrogen levels were studied in excised leaves of rice (Oryza sativa L. cv. Ratna) subjected to various degrees of water stress. Chlorophyll level decreased and a-amino nitrogen level increased in the turgid leaves floating on water; these changes were accelerated when the leaves were subjected to water stress (Figs. 2, 3). The decrease with time in the activity of alkaline inorganic pyrophosphatase and the increase with time in the activity of acid inorganic pyrophosphatase in water-floated turgid leaves were accelerated following water stress (Figs. 4, 5). There was an accelerated decline in the ratios of alkaline to acid inorganic pyrophosphatase activity in stressed compared to turgid leaves (Fig. 6). It was concluded that water stress enhances the senescence of excised rice leaves and that the changes in the activities of alkaline and acid inorganic pyrophosphatases can be taken as indicators of water stress in rice leaves.