Metal toxicity in acid soils of Kerala —effect of manganese on growth and physiology of rice(Oryza Sativa L.)cv. Jaya

Abstract

A study was conducted to evaluate the effect of manganese on growth and physiology of Oryza sativa L. cv. Jaya in a hydroponic system containing 2 to 200 ppm manganese for 40 days. The study indicated that manganese do not inhibit seed germination even at 200 ppm. There was no manifestation of growth retardation up to 10th day, but notable reduction in shoot length was recorded by 26.3% and 37.8% for 100 ppm and 45.8% and 52% for 200 ppm on 25th and 40th day respectively. On the 40th day the root system of 200 ppm got completely damaged. There was a progressive reduction in total chlorophyll content, varying from 8.6% to 31.9%, 6% to 54.6% and 61.4% to 99% on the 10th, 25th and 40th day, respectively, for 2 to 200 ppm compared to the control. Prolonged manganese toxicity beyond 25 days drastically affected the chlorophyll content, resulting in chlorosis, necrosis and drying up of leaves. The total soluble sugars showed reduction from 26.9% to 77.2%, 2.7% to 35% and 16% to 50% for 2 to 200 ppm on the 10th, 25th and 40th day, respectively. Total protein content also showed a reduction from 2.4% to 52.2%, 0.4% to 28.4% and 7% to 36.4% for 2 to 200 ppm on the 10th, 25th and 40th day, respectively. The results indicate that manganese toxicity resulted in a progressive reduction in chlorophyll, soluble sugars and total proteins.