http://ir.lib.ruh.ac.lk/handle/iruor/7508 2026-04-06T12:55:21Z 2026-04-06T12:55:21Z Nayanakantha, N.M.C. Hettiarachchi, N.N. Seneviratne, P. Wathugala, D.L. http://ir.lib.ruh.ac.lk/handle/iruor/7918 2024-10-23T05:00:02Z 2016-11-30T00:00:00Z

EXOGENOUS NITRIC OXIDE DONOR SODIUM NITROPRUSSIDE ENHANCED GROWTH ATTRIBUTES OF POLYBAGGED RUBBER (Hevea brasiliensis ) SEEDLINGS Nayanakantha, N.M.C.; Hettiarachchi, N.N.; Seneviratne, P.; Wathugala, D.L. Shoot die-back condition has been observed in young-budded rubber plants especially under hot and dry weather conditions. This is partly attributed failure of the root system. Therefore, it is imperative to find ways to improve the root system while enhancing other growth attributes of polybagged rubber seedlings. Nitric oxide (NO) func tions as a signaling molecule as well as a phytohormone in numerous physiological processes in plants from seed germination up to senescence. In the present study, the effect of sodium nitroprusside (SNP) as a NO donor on the root architecture and growth characteristics of polybagged rubber seedlings were investigated. Seven days old rubber seedlings were soaked in 200 µM and 500 µM solutions of SNP for 6 hours and 24 hours respectively prior to transplanting in polybags. Mock treated seedlings were soaked in water. Pretreatment with SNP greatly im proved the root architecture of rubber seedlings by increasing the number and the length of lateral roots and the dry weight of roots while enhancing other growth parameters viz., stem diameter, shoot height and dry weight, leaf area and chlorophyll content in dose and time-dependant manner. Pretreatment with SNP at 500 μM for 6 hrs was found to be more effective for overall growth improvement in rubber seedlings. The improved growth characteristics of rubber seedlings could be attributed to the beneficial effect of SNP as a NO donor in modifying phytohormone signalling pathways, enhancing antioxidant enzyme activity, increase in nutrient uptake and effec tive allocation of photoassimilates.

2016-11-30T00:00:00Z Perera, A.G.W.U. Karunaratne, M.M.S.C. http://ir.lib.ruh.ac.lk/handle/iruor/7917 2024-10-24T06:26:31Z 2016-08-26T00:00:00Z

POTENTIAL OF Olax zeylanica LEAVES IN THE SUPPRESSION OF Sitophilus oryzae L. INFESTATIONS Perera, A.G.W.U.; Karunaratne, M.M.S.C. In spite of the growth of paddy production, significant losses occur globally during post harvest storage of rice, due to the rice weevil Sitophilus oryzae attack, which is considered the major insect pest of stored rice. In order to develop green alternative to synthetic insecticides, the repellent and toxic properties of Olax zeylanica leaf powder, solvent extracts and essential oil were tested against S. oryzae under laboratory conditions. Laboratory reared one week old adults were used to determine the efficacy of plant products. Repellent effect was evaluated within an hour of exposure using a contact-repellency chamber by admixing leaf powder with 30g of rice grains at 4 doses (1, 3, 5 and 7 g). Repellency of leaf-solvent extracts (methanol, ethyl acetate, hexane and water) was investigated at 10%, 50% and 100% (v/v) while the repellency of essential oil was assessed at same concentrations using area preference method and all the observations were recorded after 30 minutes. Observations on contact and fumiga tion toxicity of the essential oil were made 30 and 60 minutes after exposure to weevils. All tested plant products elicited significantly very high responses in S. oryzae when compared with the controls (0.00%). Leaf powder of O. zeylanica evoked 100% repellency at the highest dose (23.33% w/w) and the repellent rate increased with the in crease in dose. In repellency assays using leaf extracts, methanol extract was found to be the most effective causing 96% repellency in the weevils, followed by ethyl acetate (95%) and hexane (89%) whereas the aqueous extract was least effective (70%) indicating the lowest level of repellency. Furthermore, three concentrations of the essen tial oil evoked extremely high repellent action in weevils (94%, 99%, and 100% respectively) within 30 minutes. Both contact and fumigant toxicity effects with the essential oil were dose dependent and 100% adult mortalities were observed at the highest concentration after one hour of exposure. The overall results of the present study indicate that, O. zeylanica leaves could be utilized as a very successful candidate in the development of bio insecticides in controlling S. oryzae infestations.

2016-08-26T00:00:00Z Leelamanie, D.A.L. Liyanage, T.D.P. Rajarathna, I.M.L.V. http://ir.lib.ruh.ac.lk/handle/iruor/7912 2024-10-24T08:52:53Z 2016-09-27T00:00:00Z

A COMPARISON OF WEIGHT LOSS AND C ANALYSIS METHODS IN DETERMINING ORGANIC MATTER CONTENT IN SRI LANKAN SOILS Leelamanie, D.A.L.; Liyanage, T.D.P.; Rajarathna, I.M.L.V. Determination of organic matter in soils and sediments is typically requested with contaminant analysis as a part of ecological risk assessments. However, reliable and sensitive methods are required to enable the research and extension work to substantiate the expected outcome. The purpose of this study is to provide a comparison be tween weight loss and carbon (C) analysis methods in determining soil organic matter (SOM) content considering their usability with potential merits and demerits. Soil samples were collected from 20 locations representing vari ous agro-ecological regions ranging from Jaffna to Matara, Sri Lanka. The samples were analyzed for the SOM content using the Walkley-Black (WB), hydrogen peroxide digestion (H2O2), and loss on ignition (LOI) methods. The SOM content by different methods were compared using C conversion factors of 1.724, 2.2, and 3.3 for the WB method. The SOM contents determined by H2O2 and the WB methods showed linear relationships (moderate correlation) with those determined by LOI method, where the coefficients of determination (R2 ) were 0.58 and 0.61, respectively. The LOI method provided the highest or comparably similar SOM content with the H2O2 and the WB methods except at very low SOM contents. Use of C conversion factors 2.2 and 3.3 made SOM content estimated by WB method closer to values obtained by H2O2 and LOI methods, respectively.

2016-09-27T00:00:00Z Balagalla, D.N. Wijesuriya, A. Ranathunge, N.P. Perera, A.M.M.S. http://ir.lib.ruh.ac.lk/handle/iruor/7911 2024-10-11T07:49:02Z 2016-09-01T00:00:00Z

NEAR-OPTIMAL LEVELS OF 2,4-DICHLOROPHENOXYACETIC ACID AND INDOLE ACETIC ACID FOR IN-VITRO DIRECT REGENERATION OF SHOOTS FROM SUGAR CANE (Saccharum spp. Hybrid) LEAF TISSU Balagalla, D.N.; Wijesuriya, A.; Ranathunge, N.P.; Perera, A.M.M.S. Four combinations with two levels of each 2,4-Dichlorophenoxyacetic Acid (2,4-D) (0.2mg/L, 0.5mg/L) and Indole Acetic Acid (IAA) (1mg/L, 4mg/L) together with 0.1 mg/L of Kinetin and 40mg/L of Cysteine Hydrochloride de termined by testing their 150 combinations for in-vitro direct shoot regeneration from sugarcane (Saccharum spp. Hybrid) leaf tissues were further evaluated using the variety SL 96 328 in a completely randomised layout with 30 replicates to find out their near-optimal levels. Leaf spindle slices of the sugarcane variety SL 96 328 was used as ex-plants for culture in the modified MS medium. After 3 weeks of culture, the survival of ex-plants and the num ber of shoots directly regenerated from ex-plants were recorded in one-week intervals. The concentration of 0.5mg/L of 2,4-D and 1mg/L of IAA together with 0.1mg/L of Kinetin and 40mg/L of Cysteine Hydrochloride re generated the highest number of viable shoots from leaf spindle discs after 4 weeks of culture. On average, 21 shoots were obtained from a leaf spindle disc of 2mm thickness and 3mm in diameter obtained from sugarcane plants of 5- to7- month old.

2016-09-01T00:00:00Z