Effect of shading on growth, development and reproductive biology of major weed species of winter season
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Date
2018-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
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.
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