Rathnayake, R.M.C.G.2021-05-182021-05-182015UWU/PLT/11/0005http://www.erepo.lib.uwu.ac.lk/handle/123456789/6773Rubber 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.enPalm and Latex Technology and Value Addition Degree Programme ( PLT)Thesis