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ThesisItem Open Access Biogenesis of chloroplast and photosynthetic efficiency in mango (Mangifera indica L.) leaves(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2004-08) Sah, Chitra; Singh, M.Mango (Magnifera indica L.) is an important fruit crop of India. The fruit yield depends upon flowering and proper fruit set, which is largely influenced by the environmental variables. Vegetative growth in mango is periodic with major number of flushes occurring in the months of April-June when temperature is high coupled with strong irradiance and low humidity. The proposed study was undertaken to correlate the effect of environmental variables with biogenesis of chloroplast and acquisition of photosynthetic ability in expanding immature leaves. These leaf flushes were analysed morphologically, anatomically and bio-chemically. The growth stages classified as S1, S2 and S3 were studied for plastid/chloroplast development through transmission electron microscopy. The chlorophyll fluorescence variable yield (Fv/Fmax) was monitored to study the acquisition of photosynthetic efficiency. Immature and mature leaves differentially acquired photosynthetic ability. The young leaves were found susceptible towards mid-day depression of their Fv/Fmax compared to the mature leaves. The mature leaves were less affected under high temperature. Investigations related to PS II performance showed ca. 50 % less photosynthetic efficiency in young leaves as compared to the mature leaves. Thus, our findings suggest that acquisition of photosynthetic machinery in the form chloroplast biogenesis seems to be coupled with photosynthetic efficiency of the leaves.ThesisItem Open Access Studies on the growth, development and some physiological and biochemical parameters of problematic weed spp. of winter season(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2004-06) Bisht, Smita; Guru, S.K.The experiment was conducted in Plant Physiology Department of G. B. Pant University of Agriculture and Technology, Pantnagar, to study the growth, development and some physiological and biochemical parameters of ten problematic weed species, two monocot and eight dicot of winter season. Studies on germination and the effect of various chemicals and growth regulators on the process were carried out in petri dishes under laboratory conditions. Seed production potential was maximum in C. album, while its test weight (1000 seeds) was the lowest. All the chemicals such as potassium nitrate, H2O2 thiourea and the growth regulator GA3 promoted the germination of all the weed species, their concentration being specific for each species. Morphological parameters such as plant height, leaf number as well as leaf growth parameters; physiological growth parameter such as RGR and NAR, dry matter production, biochemical parameter such as chlorophyll and carotenoid content were estimated at different days after seedling emergence. Concentrations of N, P and K were determined at harvest. Chlorophyll fluorescence values (Fv/Fm) and SPAD meter reading were also recorded from time to time: Plant height of monocots weed were higher than dicots whereas the i,ea.f area was higher in dicot leaves. Shoot dry matter production was highest in I?. acelosella and lowest in L. aphaca. Total chlorophyll contents of weed species was positively correlated with their chlorophyll fluorescence values. But SPAD values could not be correlated with their chlorophyll contents. NR activity was higher during the initial growth stages (upto 45 to 60 DAE) and it correlated with the nitrogen-assimilating capacity of almost all the weed species. Contents of N, P and K were usually higher in the dicot weed species than in monocots. In all the weed species, N content was lower in the stem, whereas P and K contents were higher as compared to those of the leaves.