Physiological evaluation of source-sink relationships in soybean (Glycine max L. Merrill) genotypes under variable photoperiods
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Date
2014
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PAU
Abstract
Soybean is a short day plant. Both photoperiod and temperature control the duration of pre and post flowering phase and are expected to affect source-sink relationships. The present investigations were aimed at evaluating the relative performance of different maturing group of soybean genotypes with respect to different physiological and biochemical indices for higher productivity under variable photoperiods. To achieve the objectives, field experiments were conducted during kharif seasons of 2012 and 2013 at Punjab Agricultural University, Ludhiana. The experiment were laid out in randomised block design with three replications consisting of 15 genotypes to screen for various morpho – physiological traits, yield and yielding attributes in first year. On the basis of results obtained from the first year experimentation, two genotypes from early maturing genotypes and each of three from medium and late maturing genotypes were selected for biochemical analysis. Morpho-physiological parameters viz., leaf area, leaf area index, leaf and stem fresh and dry weight, net photosynthesis, growth efficiency, chlorophyll content, photochemical efficiency and transpiration rate were affected by photoperiods. Under both the photo-periodic conditions, the late maturing group genotypes maintained higher leaf area, biomass accumulation, leaf area index, photosynthetic rate and transpiration rate as compared to medium and early maturing genotypes leading to higher yield. Under longer photoperiod i.e. June sowing showed more metabolic status as compared to shorter photoperiod (July sowing). Nitrogen metabolizing enzymes viz., GOGAT, GS, GDH and NR activity showed varied response in leaf and stem. Highest activity of these enzymes was found in longer photoperiod as compared to shorter photoperiod. Carbon metabolizing enzyme- invertase also showed varied response in podwall and developing seeds. The activity of this enzyme increased in developing seeds and the highest activity was observed in late maturing genotypes. Finally, it can be concluded that for selection of better genotypes under variable photoperiods, the physiological parameters total dry matter, CGR, RGR, photosynthetic rate, chlorophyll content, LAI, SPLW, 100 seed weight, numbers of pods per plant and harvest index should be considered. These parameters were found to have significant positive correlation with seed yield. Of the evaluated 15 diverse maturing genotypes, the early maturing genotypes EC 457161, medium SL 983 and late SL 958 are superior in terms of yield as well as in other morpho-physiological traits. Of all genotype SL 958 performed the best.
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Keywords
developmental stages, sowing, soybeans, yields, genotypes, planting, photoperiodicity, biological development, crops, area