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ThesisItem Open Access Physiological aspects of enhancing grain zinc content and its bioavailability in winter wheat (Triticum aestivum L.) through foliar application of zinc(G. B. Pant University of Agriculture and Technology, Pantnagar, 2022-06) Mishra, Sudershan; Guru, S.K.Zinc deficiency stems from dietary malnutrition. Wheat grains are inherently low in zinc concentration as well as bioavailability primarily on account of being cultivated in soils with poor zinc phyto-availability. Wheat-based products account for provisioning of 50% daily dietary zinc intake. Therefore, there is a need to biofortify the wheat grains with Zn. The present investigation was carried out to study the physiological aspects of enhancing grain zinc content and its bioavailability in wheat cultivar PBW 343. The field investigation was carried out in two successive winter seasons (2018-19 and 2019-20) at the Dr N. E. Borlaug Crop Research Center, Pantnagar, India. A pot culture experiment was also carried out to study the effect of chelators on grain zinc and its bioavailability. Five different concentrations of zinc 0, 567.5, 1135, 1702.5 and 2270 ppm zinc were used in the field study which were sprayed at three different stages viz. 30, 45 and 60DAE. Two different Zn concentrations 1135ppm Zn and 1702.5ppm Zn along with three chelators 0.025% Methionine, 0.02% Histidine and 0.1% Citric acid were used in the pot culture experiment. The results show that Zn application had promoting effect on growth, yield and yield related attributes. It also increased chlorophyll content as well as zinc associated enzyme activities in the flag leaf. The maximum increase in grain yield was recorded at 1702.5ppm of Zn. Under the field conditions, three sprays of 2270ppm Zn resulted in maximum grain zinc content of 24.1 mg/kg (28.19% increase over control). Use of chelators along with zinc in the pot culture experiment revealed that while addition of methionine further increased the grain yield, using histidine as a chelator increased the grain zinc content upto 27.71 mg/kg). Application of Zn increased total available zinc (TAZ; mmol/day) and maximum TAZ of 1.95mmol/day was observed with three sprays of 2270ppm of Zn. Addition of histidine as chelator further increased TAZ to a maximum of 3.7mmol/day.ThesisItem Open Access Effect of shading on growth, development and reproductive biology of major weed species of winter season(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2018-06) Mishra, Sudershan; Guru, S.K.Light plays a major role through its direct effects on morphology and biomass production by plants. Both crops and weeds compete for light by shading each other. Therefore the effects of shading on growth and development of both crops and weeds will determine their competitive ability.To analyse the implications of shade on weed biology, an experiment was conducted in winter season 2017 to evaluate the effects of shading on growth, development and reproductive biology of seven major weed species of winter season viz. Phalaris minor,Polypogon monspeliensis, Melilotus indica, Medicago denticulata, Lathyrus aphaca, Vicia sativa, and Solanum nigrum. The treatments included full sunlight, 55% shade and 75% shade. Data on phenology, biomass partitioning and reproductive biology was recorded for all the species. The total duration was delayed by more than two weeks under 55% shading and by three four weeks under 75% shading for all the weeds, as a result of cumulative increase in vegetative, reproductive as well as time taken from flowering to maturity. Plant height was doubled within two weeks after shading and was enhanced by more than 30cm and 38cm under 55% and 75% shading, respectively. Total aboveground dry matter accumulation decreased by more than 80% under shading and almost two-three fold proportion of dry matter was partitioned towards leaves. Concomitant variation in SLA, RGR, NAR and LAR indicated adaption to shade at whole plant level. The lowest decrease in maximum NAR and RGR was observed in Polypogonand Solanum, expressing their high competitive ability over other weeds under study Number of seeds per plant was reduced by 67% under shading as a consequence of proportional reduction in number of fruits/inflorescences. However the number of seeds per fruit remained fairly constant. Chlorophyll a/b ratio was also found to be reduced under shading.