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2010 - 20142
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Subject: Botany × Author: Radhika × Type: Thesis ×
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    Photosynthetic efficiency of wheat genotypes in relation to yield under terminal heat stress
    (PAU, 2014) Radhika; Thind, S.K.
    To evaluate the sensitivity or tolerance level of 40 wheat genotypes (assembled by CIMMYT and some Punjab cultivars as checks) a laboratory experiment, the two periodic field experiments (2011-12 and 2012 -13) with normal sowing (November 30) and late sowing (December 30) and a pot experiment (2013-14) were conducted. The cell membrane thermo stability supported lesser lipid peroxidation (MDA) and minimal changes in mitochondrial activity (TTC) of heat tolerant genotypes which ultimately increased the survival potential under laboratory conditions after long term (24 hrs) heat shock treatment (40±2°C). Delay in planting under the field conditions caused significant decrease in the source sink activity, photosynthetic efficiency and grain growth parameters besides negative effects of terminal heat stress. The impact of this adversity could be clearly seen in the late maturing genotypes as they were prone to the leaf senescence under the late sown conditions. The studied correlation suggested that net assimilation rate, leaf area index, total chlorophyll, starch, pre-stem reserve mobilization, canopy temperature depression, net photosynthetic rate and transpiration rate were found to be effective traits defining wheat genotypes adapted to production systems prone to high temperature stress at 10 DAA. Early maturing genotypes were less affected while late maturing genotypes were found sensitive and were affected up to much more extent as these were highly dependent upon the reserves for the grain filling with the onset of the terminal heat stress. A significant difference was recorded among the genotypes for various quantity and quality contributing traits. An increase in seed protein content, wet gluten, dry gluten, gluten index and sedimentation value and the decrease in number of grains/ spike, seed weight/spike,1000 grains weight, grain hardness and moisture content was recorded under the late planting conditions. Under the pot conditions the tolerant genotypes had relatively higher and wider growth ratios, photosynthetic efficiency (net photosynthetic rate, stomatal conductance and Rubisco enzyme activity) and grain yield when these were subjected to the heat stress (40±2°C) for 8hrs at anthesis.
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    ThesisItemOpen Access
    INFLUENCE OF BENZYLAMINOPURINE AND SALICYLIC ACID ON MORPHO-PHYSIOLOGICAL AND SOME BIOCHEMICAL PARAMETERS OF WHEAT (Triticum aestivum L.) UNDER WATER STRESS
    (Punjab Agricultural University, Ludhiana, 2010) Radhika
    The influence of Benzylaminopurine (BAP) and Salicylic acid (SA) on morphophysiological and some biochemical parameters of wheat (Triticum aestivum L.) genotypes (PBW 343 and PBW 527) under water deficit conditions was studied. The PEG (6000) induced water stress (-.2MPa, -.4MPa and -.6MPa) had markedly reduced the root and shoot traits (coleoptile length, seminal root number, seminal root length, number of leaves, total leaf area, seedling fresh weight and seedling dry weight) at 10 DAS under laboratory conditions. Foliar application of BAP and SA given at the 7 DAS had partially ameliorate the PEG induced water stress. Water stress given at the tillering stage and the boot leaf stage had significantly reduced the plant height, hill reaction activity, photosynthetic pigments, starch, proteins and significantly induced the sugars, free amino acids, proline, water saturation deficit, relative saturation deficit, acid invertase activity and membrane permeability in the leaves of the studied genotypes at both 70 DAS and 100 DAS. Water stress imposed at the tillering stage resulted in more yield loss as compared to the stress given at the boot leaf stage. Foliar application of BAP @100 μg ml-1 given at the vegetative stage under water deficit conditions had showed the stress ameliorative effect and foliar application of SA @ 30 μg ml- 1 given at the vegetative stage had more growth promotary effect as compared to the application given at the anthesis stage under water deficit conditions, whether the stress was given at the tillering stage or the boot leaf stage.