Chandra Prakash Sharma

Effect of heavy metals Co2+, Ni2+ and Cd2+ on growth and metabolism of cabbage

Abstract Exposure of cabbage plants to excess (500 μM) of Co 2+ , Ni 2+ and Cd 2+ in sand culture led to increased accumulation of the metals, inhibition of growth and induction of visible symptoms of metal toxicity. In addition to chlorosis, Co 2+ treated plants exhibited reddish purple coloration along leaf margins, Ni 2+ treated plants exhibited black spots near leaf margins, and Cd 2+ treated plants developed purple coloration along leaf margins. At equimolar concentration, inhibition of growth was most severe with excess Cd 2+ and induction of visible symptoms was most severe with excess Ni 2+ . Exposure to excess concentration of the heavy metals decreased the uptake of Fe and its translocation to leaves. Exposure to each Co 2+ , Ni 2+ and Cd 2+ decreased chlorophyll content (Ni 2+ >Cd 2+ >Co 2+ ), concomitant with decrease in the activities of the Fe enzymes—catalase and peroxidase, suggesting reduced availability of Fe for chlorophyll–heme biosynthesis. Each Co 2+ , Ni 2+ and Cd 2+ decreased water potential and transpiration rate, associated with increase in diffusive resistance showing development of water stress. This was further substantiated by enhanced accumulation of proline in the leaves of plants exposed to Co 2+ , Ni 2+ and Cd 2+ .

Chromium accumulation and its effects on wheat (Triticum aestivum L. cv. HD 2204) metabolism

Chromium accumulation and its effect at graded concentration on certain metabolic activities in wheat (Triticum aestivum L. cv. HD 2204) were investigated under controlled glasshouse conditions. Low concentrations of Cr(VI) supply induced interveinal chlorosis in the young leaves which turned to necrosis at later stages of growth. Chromium supply severely affected chlorophyll and Hill activity. The activity of catalase in young leaves was impaired by an increase in Cr(VI) supply from 0.05 to 1.0 mM. The concentration of protein nitrogen decreased and that of reducing sugars increased. Chromium accumulation was greater in stems followed by leaves at higher levels but at low levels of Cr(VI) supply, the accumulation was higher in the rachilla as compared to the stem. In response to chromium supply, grain yield was severely affected and even no seed formation was observed at 1.0 mM Cr(VI). In view of the above findings, it was concluded that chromium Cr(VI) is inhibitory to metabolism and a contributory factor in phytotoxicity of wheat.

Chromium interference in iron nutrition and water relations of cabbage

Abstract Cabbage (Brassica oleracea var. capitata cv. Snowball), known to be responsive to potentially toxic elements, was investigated for chromium (Cr3+) effect on iron metabolism and water relations. After 6 weeks growth in sand culture, a set of plants was supplied with 500 μM Cr3+ (CrCl3), superimposed over the full nutrient solution (control). Exposure to excess Cr3+ led to increased accumulation of Cr, more in roots than in leaves, and to the development of toxicity symptoms. In decreasing chlorophyll concentration and the activities of heme enzymes, catalase and peroxidase, the excess Cr3+ effect resembled Fe deficiency. These changes, associated with decrease in Fe accumulation in Cr3+ treated plants, indicate that by reducing absorption of Fe, Cr3+ impairs the Fe requiring steps of chlorophyll and heme biosynthesis. In spite of lower water saturation deficit, the leaves of Cr3+ treated plants showed decrease in leaf water potential, associated with increase in diffusive resistance and lowering of transpiration rate, indicating development of water stress. Enhanced accumulation of proline in Cr3+ treated plants also suggested this. Observed changes in water stress parameters in Cr3+ stressed plants indicate that plant exposure to excess supply of Cr3+ reduces the physiological availability of water.

Zinc deficiency and pollen fertility in maize (Zea mays)

Zinc deficiency decreased pollen viability in maize (Zea mays L. cv. G2) grown in sand culture. On restoring normal zinc supply to zinc-deficient plants before the pollen mother cell stage of anther development, the vegetative yield of plants and pollen fertility could be recovered to a large extent, but the recovery treatment was not effective when given after the release of microspores from the tetrads. If zinc deficiency was induced prior to microsporogenesis it did not significantly affect vegetative yield and ovule fertility, but decreased the fertility of pollen grains, even of those which visibly appeared normal. If the deficiency was induced after the release of microspores from the tetrads, not only vegetative yield and ovule fertility but pollen fertility also remained unaffected.

Development and enzymatic changes during pollen development in boron deficient maize plants

Abstract Maize (Zea mays L.) plants subjected to severe deficiency of boron (0.0026 ppm B) failed to produce tassels with functional flowers. In plants subjected to moderate deficiency of boron (0.013 ppm B), emergence of tassels and anthesis was suppressed and delayed. In a large percentage of boron deficient plants the stamens lacked sporogenous tissue and appeared as staminodes or floral appendages that either lacked or had branched vascular supply. The apparently normal stamens of these plants also failed to dehisce and showed a marked decrease in pollen producing capacity, pollen size and pollen germination. Even in plants that were only marginally deficient in boron (0.066 ppm B), without any foliar symptoms of boron deficiency, pollen grains showed poor germination and changes in enzyme activities. Pollen grains of such plants had low activities of catalase, acid phosphatase, starch phosphorylase and invertase and high activities of ribonuclease and amylase.

Enzymic changes in response to zinc nutrition

Summary With a view to evaluating the suitability of Zn induced changes in enzyme activities and for assessing Zn nutrient status, black gram ( Vigna mungo L. cv. IPU 94) was grown under controlled sand culture at five levels of Zn supply ranging from 0.01 to 10 μmol/L. Leaves of 60 d old plants were examined for Zn concentration and activities of fructose 1,6 biphosphate aldolase, carbonic anhydrase, total superoxide dismutase, Cu-Zn SOD, acid phosphatase and ribonuclease, which have been shown to be activated/inhibited by Zn deficiency. Sub-optimal supply of Zn decreased the activities of FBPAse, CA, total SOD and Cu-Zn SOD and increased the activities of APase and RNAse. Activities of the Zn enzymes CA and Cu-Zn SOD, are highly correlated with Zn supply, and suitable as indicators of Zn nutrient status of plants. Activation of APase and RNAse by other micronutrient deficiencies and stress conditions does not favour their use as indicators of Zn nutrient stress.

Manganese deficiency in maize affects pollen viability

Maize (Zea mays L. cv. G2) was grown with 0.55 mg L−1 (sufficient), or 0.0055 mg L−1 (deficient) manganese in sand. Manganese-deficient plants developed visible deficiency symptoms and showed poor tasseling and delayed anther development. Compared to Mn-sufficient plants, Mn-deficient plants produced fewer and smaller pollen grains with reduced cytoplasmic contents. Manganese deficiency reduced in vitro germination of pollen grains significantly. Ovule fertility was not significantly affected by Mn. But in Mn-deficient plants seed-setting and development was reduced significantly.

Mineral nutrient deficiencies affect plant water relations

Sand culture studies using cauliflower as the test plant revealed changes in water relations of plants subjected to deficiencies of Fe, Cu, Zn and B. While deficiencies of Zn and B caused a decrease in water potential, transpiration rate and water loss, deficiencies of Fe and Cu caused an increase in each of these. Observed changes in water relations have been examined in terms of changes in leaf morphology and metabolism.

Copper stress affects grain filling in rice

Abstract Rice (Oryza sattva L.) cv. Jaya was grown in refined sand at graded levels of copper (Cu) viz. 0.00065, 0.0065, 0.013, 0.065, 0.13, 0.65, and 6.5 mg L‐1. In acute Cu deficiency (0.0065, 0.00065 mg L‐1), the visible foliar symptoms appeared on young leaves as chlorosis changing to necrosis, later affected leaves appeared papery and withered. The biomass and grain yield were highest at 0.065 mg L‐1 and compared to this, the decrease in both parameters was significant at low and high Cu supply. The concentration of Cu in grains increased from 0.4 in acute deficiency to 47.4 ppm at excess Cu. In rice leaves, concentration of sugars and activities of polyphenol oxidase and ascorbic acid oxidase were decreased both by low and excess Cu. Both low and high Cu also retarded the grain formation as well as their quality by decreasing the grain yield and the concentration of starch, sugars and proteins in grains and activities of amylase, invertase and starch phosphorylase at the time of grain filling in see...

Metabolic changes associated with boron-calcium interaction in maize

Maize (Zea mays L.) cv. T42 was grown in refined sand at low (0.1 μM) and normal (30 μu) concentrations of boron each under low (1 mM), normal (4 mM), and excess (8 mM) supply of calcium. Visible symptoms of boron deficiency which appeared first, were accentuated by calcium deficiency and were least evident when calcium was added in excess. The yield was maximum at normal levels of boron and calcium and was the lowest under boron and calcium deficiency. In maize leaves when both calcium and boron were deficient together the activity of starch phosphorylase increased markedly and that of ribonuclease and polyphenol oxidase also increased. The increase in the calcium content inhibited the starch phosphorylase activity when boron was deficient. The activity of peroxidase was stimulated under boron deficiency at all levels of calcium and that of ATPase was depressed significantly when calcium was deficient alone. A decrease in the tissue boron (except in old leaves) and tissue calcium content as well as sugar...