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2017 - 201922020 - 20231
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Subject: Botany × Author: Mandeep Kaur ×
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Now showing 1 - 3 of 3
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    ThesisItemEmbargo
    Impact of heat stress on germination and growth in wheat (Triticum aestivum L.): Physiological and biochemical mechanisms
    (Punjab Agricultural University, 2023) Mandeep Kaur; Bedi, Seema
    The present study was conducted with the objectives to screen a diverse set of wheat genotypes for thermo-tolerance and to investigate morpho-physiological and biochemical basis of thermo-tolerance under early sown conditions in Punjab. 467 wheat genotypes (winter wheat x spring wheat) were screened for high temperature tolerance at three temperatures viz., 25oC, 30oC and 35oC under laboratory conditions. Sixty genotypes showing maximum coleoptile length at 30oC were selected and grown in the field at three dates of sowing viz., early (20th October), timely (14th November) and late (5th December) in the years 2019-20 and 2020-21 respectively. Under early sown conditions (ambient temperature ranging between 25 to 28oC), the selected genotypes showed higher percentage of emergence, early growth vigor, root length (at 25 DAS), plant biomass (at 25 DAS), leaf area (at 90 DAS), chlorophyll content in flag leaf (at 90 DAS), tiller numbers, number of spikelets per spike, spike length, 100 seed weight and grain yield per plot as compared to timely and late sown conditions. From these, ten high yielding and two low yielding genotypes were identified. Biochemical estimations and root architecture studies were performed on these ten high yielding genotypes (heat tolerant) and two low yielding genotypes (heat sensitive) at seedling stage. The heat tolerant genotypes showed higher sugar, protein, proline and α-tocopherol content. Higher activity of antioxidant enzymes was observed in heat tolerant genotypes as compared to heat sensitive genotypes. Also, the tolerant genotypes showed more number of seminal roots, nodal roots, root branches and root length as compared to heat sensitive genotypes.
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    ThesisItemOpen Access
    Physiological and biochemical changes associated with moisture stress tolerance in maize (Zea mays L.) genotypes
    (Punjab Agricultural University, Ludhiana, 2019) Mandeep Kaur; Ghai, Navita
    The present investigation was conducted to study “Physiological and biochemical changes associated with moisture stress tolerance in maize (Zea mays L.) genotypes”. Twenty genotypes (CML 32, CM 139, CM 140, CM 143, SE 503, SE 544, SE 547, SE 552, I 122, I 132, I 162, I 164, LM 5, LM 11, LM 13, LM 15, LM 16, LM 20, LM 23, LM 24) were screened on the basis of percent survival rate of seedlings under different levels of moisture stress created by withholding 40%, 50% and 60% irrigation. Percent survival of seedlings was noted at 10, 15, 20 and 25 days after sowing at 40%, 50% and 60% moisture stress level and four genotypes: CM 140, LM 16 as tolerant and LM 13, LM 20 as sensitive genotypes were selected out of twenty genotypes. Effects of moisture stress on morpho-physiological and biochemical parameters in tolerant and sensitive maize genotypes along with a check PMH 2 were studied at seedling stage. Morpho-physiological parameters viz. root length, shoot length, root fresh weight, shoot fresh weight, root density, root dry weight, shoot dry weight, root volume, root:shoot ratio, membrane stability, relative leaf water content, chlorophyll content, vigour index I and vigour index II decreased with the moisture stress. However, carotenoid content was found to increase with increasing stress level. The various biochemical parameters viz. proline content, activities of superoxide dismutase, catalase and peroxidase were recorded higher in check PMH 2 and in tolerant genotypes as compared to sensitive genotypes. Also, accumulation of hydrogen peroxide content was lower in CM 140 and LM 16 than LM 13 and LM 20. Under moisture stress, root anatomy showed variations in all the maize genotypes. Density of metaxylem elements increased in all the genotypes as well as in check PMH 2 and more number of root hairs were also in LM 16 and PMH 2. In tolerant genotype CM 140, the diameter of metaxylem also decreased with the drought stress which helped in retention of water in roots under stress conditions. Higher levels of antioxidant enzymes, proline, carotenoid content and decreased hydrogen peroxide might have helped in imparting moisture stress tolerance to CM 140 and LM 16 genotypes. These genotypes can be used by the breeders in further breeding programs.
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    ThesisItemOpen Access
    Alteration of plant architecture and reproductive efficiency of pigeonpea (Cajanus cajan L.) genotypes through growth retardants
    (Punjab Agricultural University, Ludhiana, 2017) Mandeep Kaur; Jagmeet Kaur
    Field experiment was conducted at Punjab Agricultural University, Ludhiana during kharif season in the year 2016-17 with an objective to investigate the effect of ethrel (@ 200 ppm), stance (@ 200 ml/ac) and mepiquat chloride (@ 200 ml/ac) on the growth, flower retention and yield of pigeonpea genotypes PAU 881 and AL 201. The biochemical changes associated with the use of growth substances were also studied. Foliar spray of growth substances were done at 60, 68 and 75 days after sowing. Various morpho-physiological, biochemical and yield characteristics were analyzed at different developmental stages. The plant height reduced effectively with the foliar applications of growth substances. The leaves of treated plants exhibited increased level of chlorophyll, which provided better conditions for higher production of photosynthates to be utilized for grain yield. The parameters determining reproductive efficiency and yield were significantly improved due to reduction in flower abscission, improved flower retention, pod formation, and seed weight. The treatments also affected the various biochemical constituents viz. total soluble sugars, total starch content (leaves and stem), total soluble proteins and amino acids (pod wall and developing seed). The activity of enzymes viz., invertase (stem, leaves, pod wall and developing seed) and sucrose synthase (leaves and stem) also increased in response to growth substances. Ethrel (@ 200 ppm) 60+75 DAS showed the best result among all the treatments.