Journal of the Rubber Research Institute of Sri Lanka
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Item Effect of incubation time on acetylene reduction activity of common cover crops of Sri Lankan rubber plantation(Rubber Research Institute. Agalawatta, 1989) Jayasinghe, C.K.; Parker, C.A.; Kulasooriya, S.A.A wide range of incubation time from a few minutes to severl hours have been used with defferent plant systems in investigations on acetylene reduction assays. However, the duration of incubation period is of utmost importance in obtaining nitrogen fixation estimates using this technology. Time course experiment showed that acwtylene reduction by nodules of P. phaseoloides and D. ovalifolium started without a lag but rate of the nitrogenasse activity was reduced 4 hours after incubation while M. invisa showed a considerable activity even at the 8th hour of incubation. In the second experiment which was conducted to observe the relationship between acetylene reduction activity and incubation time upto one our, there was a linear relationship for both P. phaseoloides (r = +0.9832) and D. ovalifolium (r = + 0.99961)Item Diurnal variation in nitrogenase activity of common cover crops in rubber plantations of Sri Lanka(Rubber Research Institute. Agalawatta, 1989) Jayasinghe, C.K.; Parker, C.A.; Kulasooriya, S.A.Diurnal fluctuations in nitrogenase activity (acetylene reducing activity) have been observed in several nitrogen fixing systems. All experimental plants viz. P. phasides D. ovalifolium and M. invisa demonstrated diuanal rhythm withlight intensity. The lowest acetylene reduction activiteswere detected around midnight and they were activelyu fixing nitrogen by 8.00 am. M. invisa responded to high soil temperature in addition to light intensity. A marked drop in acetylene reduction activity was observed by about 4.00pm when the soil temperature was around 38ºCItem Nodulation nitrogenase activity and major nutrient constituents of common cover crop legumes during early growth(Rubber Research Institute. Agalawatta, 1989) Jayasinghe, C.K.; Parker, C.A.; Kulasooriya, S.A.