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Subject: Plant Physiology × End date: 2014 × Start date: 2014 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Morpho-physiological changes in rice due to application of selected post emergent herbicides
    (Department of Plant Physiology, College of Horticulture, Vellanikara, 2014) Ramanarayana, C V; KAU; Girija, T
    The study on “Morpho-physiological changes in rice due to application of selected post emergent herbicides” was conducted during 2013-2014 at Alappad kole lands in farmer’s field. The objective of the experiment was to study the morphological, physiological and biochemical changes in rice due to application of Acetyl CoA carboxylase and Acetolactate synthase enzyme inhibitors and their effect on growth and yield of rice. The experiment was laid out in RBD with four replications and there were seven treatments comprising of three Acetyl CoA carboxylase enzyme inhibitors viz., Cyhalofop butyl, Fenoxaprop -p- ethyl and Metamifop and three Acetolactate synthase enzyme inhibitors viz., Bispyribac sodium, Azimsulfuron and Almix with Hand weeded as control. Herbicides were sprayed on 15 DAS. Observations on morphological, physiological, biochemical, yield attributes and yield of rice were recorded. Biochemical estimations were done on 7 days after herbicide application and at the time of flowering. Morphological characters were studied at 15 days interval. Herbicide application resulted in a two to four percent reduction in height and one to six percent reduction in tiller number of rice plant at harvest as compared to plants in the Hand weeded plot. Effect of herbicides on growth attributes viz., RGR, CGR and NAR indicated that at the initial and final stages of growth there was no significant difference between the treatments. However during the critical stages of growth i.e., 45-75 DAS significant variation was seen. Among the herbicide treatments, Bispyribac sodium.followed by Cyhalofob butyl applied plots had higher values as compared to the other herbicides. Azimsulfuron applied plots had the lowest value for these parameters. Among the growth indices LAI showed significant reduction irrespective of the herbicide throughout the growth stages as compared to Hand weeded control. The biochemical parameters such as nitrate reductase enzyme activity, phenol content, total soluble protein content and total amino acid content showed an initial decline when estimated one week after application of herbicide but by the time of flowering all the herbicide treated plants showed recovery. However the recovery was higher for Bispyribac sodium in the ALS inhibiting group and Cyhalofop in the ACCase inhibiting group. Proline content and catalase enzyme activity showed increase with herbicide application as compared to Hand weeded control indicating that application of these chemicals may be imparting stress to the plant, however by flowering time in most of the treatments there was recovery. Among the treatments, plants in the Almix and Azimsulfuron applied plots showed less recovery. The physiological parameters such as chlorophyll content, photosynthetic rate, stomatal conductance and IAA content showed decline when estimated one week after herbicide application. . In the case of chlorophyll content the recovery of the plant was comparatively less as compared to all other chemical constituents. Azimsufuron and Almix application contributed to maximum reduction in these constituents. Weed count and weed dry weight was taken on 60 DAS. The lowest values were recorded in Bispyribac sodium treatment. Azimsulfuron also a broad spectrum herbicide, was found less effective in the present study compared to Bispyribac sodium. In the present study, 5 to 17 percent reduction in grain yield and 6 to 17 percent reduction in straw yield of rice was observed by herbicide application. Among the ALS enzyme inhibitors, the lowest reduction in grain and straw yield was observed in Bispyribac sodium treatment and maximum reduction was in Azimsulfuron treatment. Among the ACCase enzyme inhibitors, Cyhalofop butyl showed least reduction in grain and straw yield of rice while fenoxaprop showed maximum reduction.
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    ThesisItemOpen Access
    Physiological, phytochemical and molecular studies on abiotic stress mediated antioxidant accumulation in Amaranthus spinosus Linn.
    (Department of Plant Physiology, College of Agriculture, Vellayani, 2014) Garggi, G; KAU; Roy, Stephen
    The study entitled “Physiological, phytochemical and molecular studies on abiotic stress mediated antioxidant accumulation in Amaranthus spinosus Linn.” was conducted during the period 2012-14 in the Department of Plant Physiology, College of Agriculture, Vellayani, Thiruvananthapuram. The objective of the study was to elicit information on the physiological, biochemical and molecular attributes associated to the antioxidant accumulation due to abiotic stress factors viz. light stress and water deficit stress and CO2 enrichment in Amaranthus spinosus Linn. The study was conducted as two separate experiments. One experiment was laid out in pot culture at Instructional Farm Vellayani, in Completely Random Design (CRD) with nine treatments which included combinations of three levels of water deficit stress and three levels of shade stress in three replications. The second experiment was laid out in Open Top Chamber (OTC) in CRD with six treatments which included combinations of CO2 enrichment and two levels of water deficit stress in four replications. The observations on growth parameters revealed a general increase in plant height under shaded condition. Leaf area was maximum for plants under 50% FC and 25% shade, T6 (42.663 cm2) and plants under 50% FC and 50% shade, T3 (40.567 cm2). The results of physiological observation showed maximum concentration for total chlorophyll for plants under 50% FC and 25% shade, T6 (1.947 mg/g of leaf tissue). The analysis of biochemical parameters showed the plants under 25% shade + 100% FC (T4) and plants under open condition + 50% FC (T9) had maximum starch content of 8.963 mg/g and 8.49 mg/g respectively. The results of enzymatic antioxidant assays showed Superoxide dismutase activity was higher for plants under treatments T9 (Open + 50% FC) and T3 (50% shade + 50% FC); 0.032 Units. The non-enzymatic antioxidant assays showed the maximum Ascorbic acid content of 3.6mg/g for treatment T1 (50% shade +100% FC) and Vitamin A content was maximum for T3 (50% shade +50% FC). Total flavonoids recorded highest in plant under treatment T2 (50% shade+75 % FC) whereas total phenol was maximum for the treatment T7 (Open + 100% FC).CO2 enrichment has no significant effect on plant height. Stomatal conductivity was significantly low for CO2 enriched plant under 100% FC (25.35 m moles s-1 for OT1) and 50% FC (21.8 m moles s-1 for OT2). Plants under CO2 enrichment and 50% FC showed maximum Catalase activity (0.169 Units).CO2 treatment did not show a significant variation with respect to antioxidants. Expression level study of the gene CHS (Chalcone synthase) revealed overexpression of the gene under abiotic stress, especially under moderate shade stress. Hence the plant can be exploited for its therapeutic value and can be cultivated as an intercrop in plantations.