Starch Metabolism During Leaf Senescence in Two Rice Varieties on Exposure to Aluminium

摘要

Rice (Oryza sativa) is an important food crop in India as well as in other Asian countries. It is well known that compounds of heavy metals are known to harm land plants, and plant parts and aluminium is one such an element causing toxic effects in plants particularly in plant growing in marshy and acidic soils. Senescence is characterized by the results of many sequential molecular events and these are influenced by bio tic and abiotic factors. The present study was carried out systematically on the toxic effects of aluminium in the detached rice leaves during leaf senescence with reference to starch metabolism and its associated enzymes. In our study reducing and non-reducing sugars were increased and starch content decreased. Significant increases were observed in reducing and non-reducing sugars and their associated enzymes such as starch phosphorylase and sucrose synthase in both Aduthurai 43 (ADT-43) and Pro Agro 6129 (PA6129) varieties and decreased activity of a-amylase was observed with the increasing periods of exposure and increasing concentration of aluminium in leaves of rice varieties in detached leaves during leaf senescence. However, the shifts in the non-reducing sugars were greater in ADT 43, when compared to PA6129. The shifted carbon partitioning from non-soluble carbohydrate to soluble carbohydrates significantly contributed to osmotic adjustment in ADT 43 and it indicates that it is tolerant to aluminium toxicity.