Browsing by Author "Panditharathna, B.M.S.S."

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    Effect of Polybag Size on Growth and Physiological Attributes of Rubber (Hevea brasiliensis) Seedlings
    (Uva Wellassa University of Sri Lanka, 2018) Gayashan, N.D.K.; Nayanakantha, N.M.C.; Seneviratne, P.; Senavirathna, A.M.W.K.; Jayasinghe, H.A.S.L.; Panditharathna, B.M.S.S.
    The annual requirement of budded rubber plants [Hevea brasiliensis (Willd. Ex A. Juss.) Mull. Arg.] has increased. Currently, finding top soil for filling polybags has become an issue in raising rubber plants. Therefore, it is essential to find ways to minimize the amount of soil usage. The present study examined the effect of the size of polybag on growth attributes of rubber seedlings for an eight-week period. The experiments were conducted in the government rubber nurseries at Egaloya (Wet Zone, LW) and Monaragala (Intermediate Zone, IL). Six bag sizes with reduced volume (3" x 15",4" x 15", 5" x 15", 4" x 13", 5" x 13" and 6" x 13") as compared to the standard size (6" x 15"-control) were used for LW whereas five bag sizes (6" x 15", 6" x 16", 6" x 17", 7" x 16" and7" x 17") as compared to control (7" x 18") were used for IL. Germinated seeds were transplanted into each polybag filled with top soil and arranged in a nursery according to a randomized complete block design (RCBD). There were 60 replicate plants for each treatment. Growth and physiological attributes of seedling viz., stem height (cm), stem diameter(mm), number of leaves, chlorophyll content (SPAD value), leaf area (cm2), stomatal conductance (gs), tap root length (cm), tap root dry weight (g), total root dry weight (g) and shoot dry weight (g)were recorded after 8 weeks from transplanting. There was no significant (P > 0.05) difference in growth and physiological attributes of seedlings raised in reduced sizes of polybags when compared to those raised in the standard sized polybags in both agro-climatic zones during the experimental period. Therefore, there is a potential to use reduced sizes of polybags to raise rootstocks of rubber while reducing the amount of soil usage.
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    Priming with Nitric Oxide Donor Sodium Nitroprusside Enhances Germination and Storage Life of Recalcitrant Rubber (Ilevea brasiliensis) Seeds
    (Uva Wellassa University of Sri Lanka, 2018) Nayanakantha, N.M.C.; Madushani, K.A.U.; Karunarathna, B.; Seneviratne, P.; Panditharathna, B.M.S.S.
    Rubber (Hevea brasiliensis) seeds lose their viability within a few days after falling from the tree. Use of old seeds has resulted in low germination percentage and extended germination time in commercial rubber nurseries. Nitric oxide (NO) is a signaling molecule involved in biological processes from seed germination up to senescence. The present study explored the effect of NO donor sodium nitroprusside (SNP), as a chemical priming agent, on germination and storage life of rubber seeds and subsequent growth of seedlings. Fresh rubber seeds were soaked in SNP solutions at different concentrations viz., 50, 100 and 150 1.1M for 24 hours and were sown in a germination bed after storing at different time intervals viz., 0, 7, 14, 21 and 28 days, respectively. 140 seeds were used for each treatment at each storage time interval. No germination was recorded after 28 days of storage irrespective of priming treatments. At zero day of storage, there was no significant difference in germination percentage. However, after the 7th day of storage, a significantly (p<0.05) higher germination percentage was recorded with SNP at 50 iliS4 ( 80. 7% and 99.2% after 7 and 14 days of sowing respectively) as compared to control (60% and 75.7% after 7 and 14 days of sowing respectively). At the 14th day and 2151 day of storage, a significantly (p<0.05) higher germination percentage was recorded with SNP at 50 and 100 pM when compared to control and mock treatment (hydropriming) after 21 days of sowing. There was no significant difference in growth attributes viz, stem diameter, shoot height, number of leaves, leaf area, internodal length, chlorophyll content, dry weight of roots and shoots of seedlings raised from seeds imposed with different treatments after two months from planting. Therefore, NO treatment at 50 and 100 p.M concentrations could effectively be utilized to improve the germination and short-term storage life of rubber seeds.