Laboratory Evaluation of Mefluidide Effects on Elongation of Hydrilla and Eurasian Watermilfoil

The potential of mefluidide (N-(2,4-dimethyl-5[[trifluromethyl) sulfonyl] amino] phenol) acetamide) to act as a submersed aquatic plant growth regulator was evaluated using a laboratory bioassay system. Main stem elongation of hydrilla (Hydrilla verticillata (L.f.) Royle) and Eurasian watermilfoil (Myriophyllum spicatum L.) was effectively reduced by mefluidide at low concentrations. The lowest effective concentration of mefluidide that reduced stem length in Eurasian watermilfoil (100 yg a.i./L) was 5 times lower than that for hydrilla (500 yg a.i./L). Short-term net photosynthetic rates of these plants were not affected by mefluidide at concentrations as high as 1000 yg a.i./L. The minimum exposure time required to maintain an inhibitory effect for at least 28 days at a concentration of 500 yg ai.i./L was 3 to 7 days for Eurasian watermilfoil and 7 to 14 days for hydrilla. The results suggest that mefluidide is a more effective growth regulator for Eurasian watermilfoil than hydrilla. Exogenously applied gibberellic acid (GA) did not completely overcome the inhibitory effect of mefluidide even when GA was added at a high concentration (10-5 M). In addition, the internodal lengths of stems treated with mefluidide were not reduced as they were when treated with gibberellin synthesis inhibitors. The reduction of main stem elongation by mefluidide appeared to be due to the inhibition of new cell and tissue development at the stem tip rather than from inhibition of GA biosynthesis.

Effect of fertilizer carbamide on proteolytic enzymes of fish Labeo rohita

Specific activities of acid, alkaline and neutral proteases in liver, muscle, brain, and gill of fish exposed to 50 ppm ambient carbamide for 15, 30 and 60 days and in control were estimated. It was observed that carbamide even at low concentration of 50 ppm inhibited proteolysis and favoured protein synthesis.

Effect of copper, cadmium and Cu.Cd mixture on amino acid content in the poslarvae of penaeid shrimp, Penaeus monodon and P. penicillatus

This study document effects of short-term (96h) sublethal levels of copper, cadmium and their mixture on the amino acid composition of postlarvae of the penaeid shrimp, P.monodon and P.penicillatus . All experimental conditions were kept constant, temperature between 25-27•C and salinity 21-22 ppt. The estimated LD50 for Cu was 200 ug/L, for Cd 177.5 ug/L and for Cu.Cd mixture 250ug/L. In P. penicillatus at the same concentration of each metal, there was significant reduction in amino acid content, which was 8.01% higher than the control. Almost similar reduction in some amino acids was observed in P.monodon. At the maximum concentration of 400 ug/L, cadmium caused higher reduction in amino acid composition than did copper. Thus, amino acid composition may be regarded as a sensitive biochemical indicator of Cu and Cd toxicity because of the effect of these metals on protein synthesis, a signal of physiological stress in marine organisms subjected to heavy metal pollution.