Effect of Chromium(VI) Toxicity on Enzymes of Nitrogen Metabolism in Clusterbean (Cyamopsis tetragonolobaL.)

Abstract

Heavy metals are the intrinsic component of the environment with both essential and nonessential types. Their excessive levels pose a threat to plant growth and yield. Also, some heavy metals are toxic to plants even at very low concentrations. The present investigation (a pot experiment) was conducted to determine the affects of varying chromium(VI) levels (0.0, 0.5, 1.0, 2.0, and 4.0 mg chromium(VI) kg−1 soil in the form of potassium dichromate) on the key enzymes of nitrogen metabolism in clusterbean. Chromium treatment adversely affect nitrogenase, nitrate reductase, nitrite reductase, glutamine synthetase, and glutamate dehydrogenase in various plant organs at different growth stages as specific enzyme activity of these enzymes decreased with an increase in chromium(VI) levels from 0 to 2.0 mg chromium(VI) kg−1 soil and 4.0 mg chromium(VI) kg−1 soil was found to be lethal to clusterbean plants. In general, the enzyme activity increased with advancement of growth to reach maximum at flowering stage and thereafter decreased at grain filling stage.

Hexavalent Chromium Induced Alteration of Carbohydrate Bioenergetics: A Dose-dependent Study

“…The SDH activity was measured spectrophotometrically by following the reduction of K 3 Fe(CN) 6 at 420 nm according to the method of Dutta et al [21]. 1 ml of the assay mixture contained 50 mM phosphate buffer (pH 7.4), 2% (w/v) BSA, 4 mM succinate, 2.5 mM K 3 Fe(CN) 6 and a suitable aliquot of the enzyme.…”

“…1 ml of the assay mixture contained 50 mM phosphate buffer (pH 7.4), 2% (w/v) BSA, 4 mM succinate, 2.5 mM K 3 Fe(CN) 6 and a suitable aliquot of the enzyme. The enzyme activity was expressed as units/min/mg of tissue protein.…”

“…Cr (VI) can penetrate through the cell membrane more easily than the other chromium compounds thus executing its potential toxic manifestation, and the severity of chromium toxicity depends on its valence state [6]. Chromate and dichromate are highly soluble in the water and thus readily absorbed by the gastrointestinal tract due to its high diffusional capacity through all types of the cell membrane [7].…”

Interactive effects of salicylic acid on enzymes of nitrogen metabolism in clusterbean (Cyamopsis tetragonoloba L.) under chromium(VI) toxicity

“…Nitrogenase (E.C.1.7.99.2), nitrate reductase (NR; E.C.1.6.6.1), nitrite reductase (NiR; E.C. 1.7.7.1), glutamine synthetase (GS; E.C.6.3.1.2), glutamate dehydrogenase (GDH; E.C.1.4.1.4) and glutamate synthase (GOGAT; E.C.1.4.1.14) in leaves, shoot and root (Nitrogenase activity in nodules only) at different growth stages were measured by the standard methods as described in Sangwan et al (2014). All observations were measured up to 2.0 mg kg À 1 soil because plants treated with more than 2.0 mg Cr(VI) kg À 1 soil concentration did not survive 20 days after sowing.…”

“…Cr (VI) treatments adversely affected the growth of forage sorghum as a result of its interference with photosynthetic pigments and key enzymes of NH 4 + assimilation (Kumar and Joshi, 2008). Cr(VI) treatments were also reported to affect the enzymes of nitrogen metabolism in clusterbean (Sangwan et al, 2014).…”