Browsing by Author "Jayawardana, N.U."

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    Amelioration of Cadmium (Cd) Stress in Rice (Oryza sativa L.) by using Selected Soil Amendments and Aquatic Plants
    (Uva Wellassa University of Sri Lanka, 2020) Weerakkodi, W.A.G.I.S.; Ranawana, S.R.W.M.C.J.K.; Jayawardana, N.U.
    Heavy metal contamination in paddy soil, particularly Cadmium (Cd) has become a serious issue with the potential risk of transferring Cd to the human food chain. Rice plants exposed to high Cd, encounter deleterious effects on growth and yield. This necessitates the need to identify effective and feasible remediation measures to ameliorate Cd stress in rice. Therefore, the efficacy of using selected soil amendments and floating aquatic plants to ameliorate Cd stress in rice was evaluated in this study under controlled environmental conditions using rice variety Bg 250. The experiment was laid out in a Complete Randomized Design with six treatments replicated thrice. Water lettuce (Pistia stratiotes), duckweed (Lemna minor), partially burnt rice husk (RH), and rice straw (RS) were evaluated as the amelioration treatments under two soil Cd contamination levels (5 and 8 ppm). The control was maintained with the only Cd without any amelioration. RH and RS were separately incorporated to Cd treated soil and mixed well at two levels (soil: RH or soil: RS, 1:1 and 2:1 v/v). Upon transplanting of rice, the aquatic plants were introduced to Cd treated pots. Growth and yield parameters were measured at 45 and 75 days after transplanting. Rice grown in the soil medium amended with RH (1:1 v/v) showed significantly higher values for plant height (43±0.2 cm), the number of tillers (3.67±0.03), root length (24.33±1.2 cm), root volume (13.33±0.7 cm3 ), root dry weight (3.17±0.2 g plant-1 ), shoot dry weight (7.44±0.07 g plant-1 ) and seed dry weight (3.12±0.15 g plant-1 ) compared to the control under 5 ppm Cd level. A similar pattern was observed in the other Cd level as well. Interestingly, the aquatic plants reduced the growth and yield of rice possibly due to competition for resources. In conclusion, RH has the potential to be used as an effective soil amendment to ameliorate Cd stress in rice. Field investigations are suggested for making a general recommendation. Keywords: Aquatic plants, Cd stress, Growth and yield, Rice, Soil amendments
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    Effect of Lead (Pb) on Germination and Early Vegetative Development of Selected Traditional and Improved Rice Varieties in Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2020) Ranasinghe, R.H.T.D.; Bandara, R.M.G.A.; Kumari, S.M.N.B.; Jayawardana, N.U.
    Contamination of soil by heavy metals is a worldwide phenomenon, which has dire consequences on human health, agriculture, and the environment. Among heavy metals, Lead (Pb) is one of the most abundant environmental pollutants. Being readily absorbed by plants, it exerts toxic effects causing altered plant morpho-physiological and biochemical attributes. There is a dearth of research studies in Sri Lanka to elucidate the effect of Pb on rice. Thus, the current study was conducted to assess the effect of Pb on germination and early vegetative development of selected five traditional (Kuruluthuda, Pachchaperumal, Godaheenati, Suwandel, and Sudurusamba) and two newly improved (Bg 352 and Bg 360) rice varieties. The plants were exposed to 0, 10, 50, and 100 µM of Pb concentrations in a completely randomized design, with four replicates. Germination energy, speed of germination, and final germination percentage were taken 7 days after sowing. The average root length and average shoot length were taken 7th day after transplanting (14 days after sowing). The data were analysed using SAS 9.1 statistical software and mean separation was done using Duncan’s Multiple Range Test at p <0.05. The results revealed that the germination of each tested variety was not significantly (p <0.05) affected even at the highest Pb concentration (100 µM). However, even at the least Pb concentration (10 µM), variety Kuruluthuda, Pachchaperumal, Godaheenati, Bg 352 and Bg 360 showed a significant (p <0.05) reduction in shoot length (10.92±0.76, 14.77±0.43, 9.98±0.69, 8.43±0.48 and 8.95±0.63 cm respectively) and Variety Pachchaperumal, Bg 352 and Bg 360 showed a significant (p <0.05) reduction in root length (12.08±0.70, 14.74±0.92 and 13.3±0.70 cm respectively) compared to the control. As per the preliminary results, Suwandel and Sudurusamba were least affected in the parameters tested. Thus, these two varieties have the potential to tolerate Pb toxicity in the early vegetative stages of development. Keywords: Lead toxicity, Traditional rice, Improved rice, Germination, Early vegetative growth