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Subject: Crop Physiology × End date: 2016 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Carbon sequestration through bamboo plantation
    (AAU, Jorhat, 2015) Choudhury, Hemendra; Kalita, P.
    A study was conducted during 2011-13 in i) inside open top chambers (OTC) with four CO2 concentrations (control, 380, 550 and 750 ppm), ii) in the experimental bamboo field of B N College of Agriculture, AAU Biswanth Chariali (OST) and iii) in farmer’s field of Biswanath Chariali (OFT) to assess the carbon sequestration potential of four bamboo species viz. S1: Bambusa tulda, S2: B. nutans, S3: B. balcooa and S4: Dendrocalamus hamiltonii. The result revealed that with the increase in CO2 concentration from 380 ppm to 750 ppm the seedling height, seedling girth, number of shoot/seedling, phyllochron, leaf number and leaf area/seedling, weight of leaf, branch, main stem, rhizome and whole seedling, specific leaf weight, relative leaf water content, stomatal frequency, stomatal index, stomatal pore area, chlorophyll content, chlorophyll stability index, carotenoid content, Rubisco activity, photosynthetic rate, content of starch, reducing and nonreducing sugar total sugar, non structural carbohydrate and soluble protein of bamboo seedlings showed better results in all four bamboo species tested. Being C3 plant the bamboo seedlings increase the rate of photosynthesis at elevated CO2 concentration and thereby register the higher values of growth parameters. At OST and OFT the S4 maintained the highest average culm height, DBH of culm, cum thickness, RLWC, stomatal frequency, stomatal index, percent pore area of leaf, LAI, Rubisco activity, rate of photosynthesis, content of chlorophyll, carotenoid, soluble protein, starch, total sugar in leaf and content of C, N, P, K in leaf branch, culm and in rhizome. In contrast the S1 registered the poorest performances among all four bamboo species. The S4 produced the highest (260.25 ton/ha) total dry biomass with the highest leaf (7.16 ton/ha), branch (24.83 ton/ha), culm (207.64 ton/ha) and rhizome (10.98 ton/ha) biomass while S1 produced the lowest (212.10 ton/ha) total dry biomass with lowest leaf (3.88 ton/ha), branch (20.36 ton/ha), culm (171.84 ton/ha) and rhizome (8.86 ton/ha) biomass. S4 sequestered the highest total carbon (118.72 ton/ha) followed by S3 (110.00 ton/ha) and S1 sequestered the lowest total carbon (93.52 ton/ha) at 5th year of plantation. The S4 also produced the highest average leaf (1.35 kg), sheath (0.90 kg) and branch (0.12 kg) litter per clump. The bamboo plantation also enriched the soil with organic carbon, available N, P, and K up to 50 cm soil depth. The present study therefore, concludes that bamboo being an efficient carbon sequesterer could contribute tremendously to mitigate the climate change, besides providing other economic and social contributions.
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    ThesisItemOpen Access
    Interactive effect of elevated carbondioxide and temperature on physiological characterisation of bhoot jolokia (Capsicum chinense Jacq.)
    (AAU, Jorhat, 2015) Das, Sangita; Das, Ranjan
    A study was conducted during 2012-2014 in Carbondioxide Temperature Gradient Tunnels (CTGTs) and in ambient condition to assess the interaction effect of elevated carbondioxide and temperature in two cultivars of Capsicum chinense Jacq. The treatments consisted of field (ambient CO2 and ambient temperature), CTGT I (380 ppm CO2 and ambient temperature), CTGT II (550 ppm CO2 with ambient temp. + 20 C elevation) and CTGT III (750 ppm CO2 with ambient temp. + 40C elevation). The elevation of temperature as compared to ambient was maintained from flower bud initiation to maturity stage. The results revealed that CTGT II had a greater impact on the various morpho physiological parameters viz. plant height, leaf number, branch number, plant spread, leaf area index, leaf area duration, specific leaf weight, root: shoot ratio, relative leaf water content, water potential, osmotic potential, C: N ratio, photosynthesis and chlorophyll stability index. However, at a higher CO2 and temperature in CTGT III, most of the above parameters showed a declining trend indicating the deleterious effect of high temperature. But, some parameters viz. senescence index, stomatal conductance and transpiration rate were significantly reduced at CTGT II. The phyllochron index was significantly reduced in both the elevated CO2 and temperature treatments. Similarly in biochemical parameters viz. accumulation of sugars, starch, total non structural carbohydrate, proline, antioxidant enzymes, capsaicin content showed a significantly higher value in both CTGTs as compared to ambient condition. A decline in pigments content of leaves such as chlorophyll and carotenoid were observed under both the CTGTs. A better status of membrane was recorded at CTGT II as compared to CTGT III and ambient condition in terms of lower activity of lipoxygenase, MDA (Lipid peroxidation) and H2O2 content and relative stress injury; hence a higher value of membrane stability index was recorded in CTGT-II. An enhancement in flowering was observed in both the elevated CO2 and temperature than ambient condition. Anatomical studies revealed better pollen characters; stem xylem and phloem status in CTGT II when compared to CTGT III. RT PCR data showed up-regulation of some genes viz. photosynthetic genes, antioxidant genes and capsaicin synthase gene under both the CTGTs. Better yield attributing parameters were recorded in CTGT II as compared to CTGT III and other treatments, which could be correlated to a higher percent of fruit dropping in CTGT III. Reduction due to high temperature in terms of above parameters was ameliorated under CTGT II. From the above experiment, it is evident that some degree of tolerance exhibited against high temperature stress which could be attributed to higher accumulation of carbohydrate, proline, adjustment of anatomical features, modification of antioxidant pool, better water status, lower fruit drop percent, in cv. Manipur as compared to cv. Assam under elevated carbondioxide and temperature condition. This indicates the differential responses of genotypes under future climate change conditions.
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    ThesisItemOpen Access
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    ThesisItemOpen Access
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    ThesisItemOpen Access
    PHYSIOLOGICAL PERFORMANCE OF SOME SALI RICE GENOTYPES UNDER DELAYED DATES OF SOWING
    (2015) Konwar, Priti Bandana
    A study was conducted during the sali seasons of 2012 and 2013 at the experimental field of Instructional cum Research (ICR) farm, and at the Department of Crop physiology, Assam Agricultural University, Jorhat to assess the physiological performance of seven selected sali rice genotypes namely, Satya (G1), Luit (G2), Monoharsali (G3), Jaya (G4), Bordhan (G5), Basundhara (G6) and Srimanta (G7) under delayed dates of sowing. All agricultural practices were followed as recommended while raising the crop in the field. The experiments in the field were laid out in split plot design with three replications where five sowing dates were allocated the main plots and seven genotypes were allocated sub-plots. Uptake kinetics studies were carried out in the laboratory using Hoagland solution. Results obtained during the investigation revealed that delayed dates of sowing had significant influence on various morpho-physiological, biochemical and yield attributes. As compared to timely sowing, delayed sowing resulted in progressive reduction in the values of parameters namely leaf area index, leaf area duration, in-vivo leaf nitrate reductase activity, total leaf chlorophyll content ,chlorophyll stability index, starch content in culm, leaf soluble protein, rate of photosynthesis, plant biomass, accumulated nitrogen in above ground biomass , longest root length, root volume, days to panicle emergence and yield attributing traits. However, net assimilation rate showed an increase upto 27th July sowing and there after it decreased upto 10th August sowing. Root to shoot ratio, chlorophyll a to b ratio, proline content and chaffy grain percentage showed an increasing trend with deferred dates of sowing. While comparison was made between timely sowing and the deferred dates of sowing lowest reduction in the values of grain yield were recorded in genotype Manoharsali and Srimanta (G3 and G7) (35.66 % and 35.03 % under D2 ) , (42.89% and 58.57% under D3), (58.07% and 65.32 % under D4 ) and ( 78.07% and 77.73 % under D5). These two genotypes recorded better performance in terms of parameters like leaf area index, leaf area duration, total leaf chlorophyll content, proline content in leaf, starch content in culm, leaf soluble protein, photosynthetic rate, nitrogen accumulation in biomass and plant biomass etc. Uptake kinetic studies revealed that the genotype Basundhara (G6) and Srimanta (G7) showed lowest Km values and the latter genotype also showed highest accumulation of nitrogen in plant biomass. Plant biomass at physiological maturity stage and grain yield at harvest showed significant positive correlation with leaf area index, leaf area duration, starch content at dough stage and leaf soluble protein. The genotype Srimanta (G7) showed higher grain yield in timely sowing situation and its percent reduction with delayed dates of sowing was lowest. Therefore the genotype Srimanta (G7) can be regarded as better genotype for delayed sowing. The genotypes Satya (G1), Monoharsali (G3) and Srimanta (G7) were found to be superior in terms of nitrogen uptake efficiency; however, their physiological nitrogen utilization efficiency were lower as compared to other genotypes.