Browsing by Author "Rathnayake, R.M.C.G."

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    Effect of Exogenous Nitric Oxide on Growth and Physiological Parameters of Rubber Clone PB 260 Subjected to Drought
    (Uva Wellassa University of Sri Lanka, 2016) Rathnayake, R.M.C.G.; Kaliyadasa', P.E.; Jayasinhe, H.A.S.L.; Nayanakantha, N.M.O.
    Rubber cultivation is being expanded into non-traditional areas of Sri Lanka where drought stress is one of the major abiotic stresses that limits growth and development. Nitric oxide (NO) is a bioactive molecule involved in diverse biological pathways that proved to be protective against damages under abiotic stress. Therefore, this study was carried out to investigate the effect of sodium nitroprusside (SNP) as an exogenous NO donor on physiological parameters and growth attributes in the rubber clone PB 260 under drought. Six treatments were imposed for polybagged rubber plants namely control (normal watering), Ti (drought stress, no watering), T2 (50 [IM SNP + normal watering), T3 (50 p,M SNP + drought stress), T4 (100 !AM SNP + normal watering) and T5 (100 pM SNP + drought stress) that grown under glass house condition. Photosynthesis rate (Pr) and Stomatal conductance (gs) were recorded at 0, 2, 4, 7 and 14 day's intervals. Chlorophyll content (Cc) was recorded at 0, 7, and 14 days and also two weeks after treatments. Growth parameters were recorded after maturing of the new shoot during post treatment period. Although there was no significant difference among different treatments initially, a significant increase in Pr and Cc were observed in drought stressed plants in T5 compared to T1 where no SNP treatments. Stomatal conductance was significantly decreased with increase in water stress irrespective of SNP treatments. Interestingly, significant increase in Cc was recorded in both concentrations of SNP in drought compared to drought stressed plants with no SNP in two weeks after recovering. There was a slight increase in dry weight of the new shoots in plants in T3 and T5 compared to the plants subjected to Ti. Results revealed that single application of SNP as a NO donor at the beginning of drought stress proved to be beneficial in alleviating the negative effects of drought stress on physiological and growth attributes of rubber plants. Key words: PB 260, Drought, Chlorophyll content, Stomata conductance, Dry weight,
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    Effect of Exogenous Nitric Oxide on Growth and Physiological Parameters of the Rubber Clone PB 260 Subjected to Drought
    (Uva Wellassa University of Sri Lanka, 2015) Rathnayake, R.M.C.G.
    Rubber cultivation is being expanded into non-traditional areas of Sri Lanka where drought stress is one of the major abiotic stresses limiting growth and development of rubber plants. Therefore, it is imperative to find ways to improve growth, development and abiotic stress tolerance in rubber plants grown in non-traditional areas. Nitric oxide. NO is a bioactive molecule involved in diverse biological pathways from seed germination up to senescence and proved to be protective against damages provoked by abiotic stress conditions. This study was carried out to investigate the effect of sodium nitroprusside (SNP) as an exogenous NO donor on physiological parameters (chlorophyll content, photosynthesis rate and stomatal conductance) and growth attributes viz., dry weight of shoots, leaf area, number of leaves and internodel length in the rubber (Hevea brasiliensis) clone PB 260 under drought stress condition. Six treatments were imposed for polybagged rubber plants namely control (normal watering), Ti (drought stress, no watering), T2 (50 p.M SNP + normal watering), T3 (50 [11\4 SNP + drought stress), T4 (100 µM SNP + normal watering) and T5 (100 [tM SNP + drought stress) grown under glass house condition. Photosynthesis rate (A) and Stomatal conductance (gs) were recorded at 0, 2, 4, 7 and 14 day's intervals. Chlorophyll content was recorded at 0, 7, and 14 days and also two weeks after the post treatments. Growth parameters were recorded after maturing of the new shoot during post treatment period. Drought stress negatively affected the growth and physiological parameters of rubber plants. Although there was no significant difference in net photosynthesis rate among drought stressed plants and also among irrigated plants since 4 days onwards from drought treatment, a significant increase in photosynthesis rate was observed in drought stressed plants treated with 100 RM of SNP compared to drought stressed plants devoid of SNP treatments. Stomatal conductance was significantly decreased with increase in water stress duration irrespective of SNP treatments since 4 days onwards. A significantly higher chlorophyll content was observed in drought stressed plants coupled with SNP treatment at 100 [1.N4 as compared to drought stressed plants devoid of SNP treatments. Interestingly, SNP treatment at both concentrations (50 and 100 1.1M) was resulted in significant increase in the chlorophyll content in drought stressed plants as compared to drought stressed plants devoid of SNP treatments two weeks after stopping the drought treatments. The overall growth of rubber plants increased with SNP treatment as compared to control under normal irrigation.