Impact of Simulated Acid Rain on Growth and Yield of Two Cultivars of Wheat

The present study reports the results of a field-basedexperiment conducted to assess the effect of simulated acid rain(SAR) of different pH i.e. 5.6 (control), 5.0, 4.5, 4.0 and 3.0on two cultivars of wheat (Triticum aestivum, Malviya 213(M213) and Sonalika). Shoot and root lengths significantlydeclined at pH 3.0 in both varieties. Leaf area declined at pH4.0 and 3.0 in M213 at both ages and at 75 days in Sonalika.Total biomass of 75 days plants declined significantly at pH range4.5–3.0 in M213 and at pH 4.0 and 3.0 in Sonalika. Netassimilation rate (NAR) declined significantly at pH 3.0 inboth varieties. Compared to control, yield of M213 showedsignificant reductions at pH 4.0 and 3.0, whereas Sonalikaresponded negatively at pH 3.0. The study showed that acid rainhas a significant negative effect on wheat plant performance.     

Single and Combined Effects of Cadmium and Zinc on Carrots: Uptake and Bioaccumulation

ABSTRACT

The present study was conducted to evaluate the effects of different concentrations of cadmium (Cd) and zinc (Zn), singly and in combination, on uptake and bioaccumulation of Cd and Zn in Daucus carota L. (carrot) grown under natural field conditions. Carrot plants were treated with two Cd concentrations (10 and 100 μg mL^?1), two Zn concentrations (100 and 300 μg mL^?1), and two combined concentrations of Cd and Zn (10 + 100 and 100 + 300 μg mL^?1) 15 d after seed germination. Treatments were repeated at 10 d intervals up to 90 d of plant age. A control was also kept without a Cd or Zn treatment. Uptake, total accumulation rate (TAR), bioconcentration factor (BCF), primary transport index (PTI), secondary transport index (STI), and accumulation of Cd and Zn in root, stem, and leaf were quantified. The results show that uptake, TAR, and accumulation of Cd and Zn are concentration-dependent phenomena. Highest accumulation of Cd and Zn was found in the root, followed by the stem and then leaves. The results also showed that bioaccumulation of Cd in root, stem, and leaf was greater at the low metal-application rates of Cd and Zn in combination than at the higher rate. This study further showed that interactions of Zn and Cd are dependent on the concentrations of those metals in the soil.     

Effect of Industrial Emission on Atmospheric Wet Deposition

In order to quantify the role of industries on atmospheric depositions, wet depositions were collected at different sites in Singrauli area of Sonbhadra district, U.P., India. Rainwater samples were collected on event basis and were analyzed for pH and concentration of H+ ion, cations and anions. The monthly variations in rainwater pH clearly indicate that early rainfall is more alkaline and as rainy season proceeds rainwater showed lower pH. The pH of rain from June to September varied from 6.6 to 4.8 at most polluted locality. Among different cations, Ca²⁺ showed maximum concentration followed by NH₄ ⁺,Na⁺, Mg²⁺ and then K⁺, whereas among anions sulphate concentration was maximum followed by nitrate and then chloride. A significant positive correlation observed between sulphate and accumulated rainfall suggests that the source of sulphate is mainly the industrial activities. While the negative correlations of other cations with accumulated rain suggest their additional sources in the area. The study clearly indicates that the abundance of alkaline substances reduces the acidity of wet depositions.     

PHYSIOLOGICAL AND BIOCHEMICAL RESPONSES RESULTING FROM CADMIUM AND ZINC ACCUMULATION IN CARROT PLANTS

The interactive effect of cadmium (Cd) and zinc (Zn) bioaccumulation on physiological and biochemical characteristics of carrot (Daucus carota L. var Pusa Kesar) plants grown with different levels of Cd and Zn was examined. The combined application of Cd and Zn (Cd+Zn) had synergistic and antagonistic effects at low and high concentrations, respectively, on Cd accumulations in plants, chlorophyll b, and photosynthesis and transpiration rates. Whereas both low and high Cd+Zn concentrations had synergistic effects on Zn accumulation, ascorbic acid, protein content, total phenols, peroxidase activity, chlorophyll a, total, carotenoids and stomatal conductance. Bioaccumulation of Cd had strong and negative relationships with measured physiological and biochemical parameters. The study further showed that Cd and Zn in combination have more toxic effects on carrot plants as compared to their individual treatments. This study concludes that interactive effects of Cd and Zn on test plant depend on their ratios present in plants.     

S02-induced enzymatic changes and ascorbic acid oxidation in Oryza sativa

Field grown rice (Oryza sativa L.) plants exposed separately to 0.25 or 0.5 ppm SO₂ for 1.5 hr daily for 40 days, showed significant decrease of catalase (p < 0.001) and increase of peroxidase (p < 0.001) activities as well as decreases of protein (p < 0.001) and ascorbic acid (p < 0.001) contents associated with leaf lesions, which were proportional to SO₂-dose. Catalase and peroxidase activity levels showed an inverse relationship. It is hypothesized from the molecular structure of both enzymes and from the in vitro relationship between catalase and peroxidase activity that the tetrameric molecules of catalase in vivo might disintegrate into monomeric units with peroxidase activity, which in turn oxidise ascorbic acid and may reduce tolerance of plants to SO₂.     

Effect of ozone and sulphur dioxide pollutants separately and in mixture on chlorophyll and carotenoid pigments ofOryza sativa

Exposure of rice plants to low concentrations of O₃ and SO₂ singly and in combination showed foliar injury of different levels. The maximum leaf injury was noted in case of O₃+SO₂ treated plants and the minimum in O₃ treated ones. Also the reductions in chlorophylla,b and total chlorophyll and carotenoid contents in leaves exposed to O₃+SO₂ mixtures were higher than the reduction noted in case of each individual pollutant. Thus the results suggest a synergism existing between O₃ and SO₂ regarding plant injury, especially with respect to chlorophyll and carotenoid contents of rice (Oryza sativa).     

Litter decomposition and nutrient release in relation to atmospheric deposition of S and N in a dry tropical region

Temporal and spatial variations in litterfall, leaf litter decomposition and nutrient release were quantified along an air pollution gradient around an industrial area in a dry tropical region of India. Significant differences were found in litterfall between the sites. Litter decomposition rates also significantly varied among the study sites. Litter decomposition was faster at sites away from the industrial region with coal-fired power plants. The concentrations of N and P increased, whereas that of Ca and SO₄-S decreased in decomposing litter over time. The nutrient release pattern was also modified by atmospheric deposition. Concentrations of SO₂ and NO₂ were negatively correlated with relative mass loss. Turnover time of nutrients, except SO₄-S in decomposing litter was maximal at the site receiving highest atmospheric depositions. The study documents that industrial emissions significantly modified nutrient cycling in adjacent terrestrial ecosystems.     

Effect of elevated O3 on rhizospheric enzymatic activities of ozone sensitive and tolerant wheat cultivars

Tropospheric ozone (O₃) is considered harmful to agriculture production and soil community. Wheat cultivars HD 2987 (O₃ sensitive) and Kharchiya 65 (O₃ tolerant) were grown under ambient and elevated (ambient + 30 ppb) levels of O₃ (EO) using open top chambers, and microbial biomass and enzymatic activities were investigated in soil rhizosphere. Elevated O₃ declined soil enzymatic activities related to carbon cycling viz. β-glucosidase, cellobiohydrolase, cellulase and amylase more in sensitive cultivar compared to tolerant. Enzymatic activities linked to nitrogen cycling like N-acetyl-glucosaminidase and urease decreased while protease and glycine aminopeptidase increased. Microbial biomass carbon and nitrogen declined more in sensitive cultivar by 11.1 and 21.2%, respectively. Root biomass reduced in wheat cultivars with an increase of their phenolics contents by 34.3 and 10.2% in HD 2987 and Kharchiya 65, respectively at 60 days after germination. Non-significant changes were observed in soil organic carbon and total nitrogen in both the cultivars. Redundancy analysis suggested that soil enzymatic activities were predominantly affected by O₃ induced changes in microbial biomass carbon and root biomass. Study also showed that rhizosphere of sensitive cultivar HD 2987 was affected more under EO as compared to tolerant Kharchiya 65.