Lipid, carbohydrate, and protein accumulation in Mn-treated rice

The accumulation of lipids, carbohydrates, and proteins was investigated in manganese (Mn)-treated rice (Oryza sativa L. cv. Safari). Rice plants were grown over a 15, 21, and 28-day period in nutrient solutions containing Mn concentrations varying between 0.125 and 32 m 1(-1). In all the experimental periods rice root and shoot concentrations of Mn increased continuously until the highest Mn treatment. The contents of acyl lipids did not vary significantly with increasing Mn concentrations. The levels of starch increased only after the 2 mg 1(-1) Mn treatment and from day 21 after germination onwards. In all the experimental periods the concentration of soluble carbohydrates decreased in the shoots after the 2 mg 1(-1) Mn treatment. In the roots, this tendency was also detected in 21 and 28-days-old plants. In these tissues, the protein content did not vary significantly until 28 days after germination, but in the shoots a decrease was found in 21 and 28-day-old plants, from 0.5 mg 1(-1) onwards. In both root and shoot tissues, protease activity remained unchanged in 15-day-old plants, but in the following experimental periods an increase was found in the highest Mn treatment. In the shoot, the acid RNAse activity increased in 21 and 28-day-old plants, from 0.5 mg 1(-1) onwards. The interaction between excess Mn and lipids, carbohydrates, and proteins before and after the end of the mobilization of seed reserves was evaluated.