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20182
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Subject: Botany × Author: Avneet Kaur × End date: 2022 × Type: Thesis ×
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    ThesisItemOpen Access
    Hormetic studies of 2,4-D in wheat (Triticum aestivum L.) and associated dicotyledonous weeds - Medicago denticulata Willd. and Rumex dentatus L.
    (Punjab Agricultural University, Ludhiana, 2018) Avneet Kaur; Navjyot Kaur
    The present study entitled, “Hormetic studies of 2,4-D in wheat (Triticum aestivum L.) and associated dicotyledonous weeds - Medicago denticulata Willd. and Rumex dentatus L..” was conducted to test the effect of low doses of 2,4-D on wheat and associated dicotyledonous weeds. Low concentrations of 2,4-D failed to accelerate either germination or seedling growth of Triticum aestivum and tested four weed species – Phalaris minor, Avena ludoviciana, Medicago denticulata and Rumex dentatus. The application of 2,4-D herbicide inhibited the seed germination and seedling growth of these weeds in a dose dependent manner with higher concentrations being more inhibitory. Foliar applied 2,4-D in range of 5-20 g ha-1 increased the chlorophyll content index (CCI) and chlorophyll fluorescence (Fv/Fm) values in wheat as compared to control and maximum value of CCI and Fv/Fm was recorded at 20 g/ha 2,4-D showing hormetic effect of 2,4-D at low doses upto flag-leaf stage of crop. Wheat yield and yield attributing parameters were not boosted significantly by low doses of 2,4-D ranging from 5 to 50 g ha-1. No significant difference between control and treated plants at harvest indicates that growth stimulation by low doses of 2,4-D was not sustained over time. The foliar application of 2,4-D at low concentrations ranging from 5-50 g ha-1 did not exert hormetic effects in R. dentatus and M. denticulata as application of different doses of 2,4-D led to a reduction in seed production potential of these weeds.
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    Partitioning of zinc and its associated metabolites in diverse rice (Oryza sativa L.) genotypes
    (Punjab Agricultural University, Ludhiana, 2018) Avneet Kaur; Nirmaljit Kaur
    The present investigation entitled “Partitioning of zinc and its associated metabolites in diverse rice (Oryza sativa L.) genotypes” was undertaken in the Department of Botany, Punjab Agricultural University, Ludhiana during 2016-17. Seeds of sixteen genotypes with diverse zinc content were procured from the Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana. The studies were conducted in two experiments, in the first experiment sixteen rice genotypes were raised in the nursery and; physiological and biochemical parameters of rice genotypes were quantified from 35-days old seedlings. The chlorophyll pigments, hill activity, total soluble sugars, total soluble proteins, free amino acids, starch and superoxide dismutase (SOD) activity were recorded higher in PR113 and PR121, whereas these were lower in RYT Biofort1 and RYT 3403 as compared to the rest of the genotypes. Grain weight, grain yield and grain zinc uptake also followed similar trend. Hence, PR113 and PR121 were characterized as zinc efficient, whereas, RYT Biofort1 and RYT 3403 as zinc inefficient. These zinc efficient and zinc inefficient genotypes were put to further experimentation. The zinc content and zinc associated traits were quantified during three stages of development: maximum tillering, anthesis (50% flowering) and maturity. The chlorophyll content, hill activity and SOD activity increased significantly from maximum tillering to anthesis stage and these parameters were also higher in zinc efficient genotypes as compared to zinc inefficient genotypes. The total soluble sugars, total soluble proteins, free amino acids and starch increased significantly from maximum tillering to anthesis stage, whereas decreased from anthesis to maturity. These metabolic reserves were higher in zinc efficient genotypes as compared to the zinc inefficient genotypes. The plant height, leaf area, flag leaf area, leaf weight, number of tillers and internodal length was also higher in zinc efficient genotypes as compared to the zinc inefficient genotypes. The leaf, tiller, spike and grain were separated at each representative stage of growth for quantifying weight, zinc content and zinc uptake. A higher dry matter accumulation as well as zinc remobilization from the vegetative to reproductive parts of the plant was observed in the zinc efficient genotypes as compared to the inefficient ones.Panicle characteristics, viz., panicle length, panicle number per m2, filled spikelet percentage and percent grain filling were high in zinc efficient genotypes, whereas low in zinc inefficient genotypes. On the contrary, panicle sterility was high in the zinc inefficient genotypes. Yield and yield contributing traits, viz., test weight, grain weight per plant, grain yield and harvest index were high in the zinc efficient genotypes as compared to the zinc inefficient genotypes. Based on the present investigation, PR113 and PR121 have been characterized as zinc efficient and RYT Biofort1 and RYT 3403 as zinc inefficient genotypes.