Browsing by Author "Nayanakantha, N.M.C."

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    Effect of Hydro and Chemical Priming on Seed Germination and Seedling Growth of Rubber (Hevea brasiliensis)
    (Uva Wellassa University of Sri Lanka, 2020) Jayangani, P.H.D.N.; Nayanakantha, N.M.C.; Senevirathne, A.M.W.K.
    Rubber (Hevea brasiliensis) is propagated through grafting buds of selected clones onto vigorous seedling rootstocks using a green budding technique. Both rootstock and budwood should be of high quality for producing high quality budded rubber plants. Seeds are used in raising rootstock plants of rubber. Being recalcitrant, rubber seeds deteriorate within a few days after falling from trees. The use of old seeds has resulted in low germination and extended germination period in commercial rubber nurseries. The main objective of this study was to investigate the effects of hydro- and chemical-priming on seed germination and seedling growth of Hevea. The experiment was conducted in a nursery at the Rubber Research Institute of Sri Lanka, Dartonfield, Agalawatta. Seeds were soaked in solutions of ZnSO4 (1% & 2%) Urea (0.05%, 0.10%, & 0.15%) and in water (mock treatment) for 24 hours followed by sown in a germination bed according to a randomized complete block design. Un-primed seeds were used as control. Germination percentage was recorded at 7, 9, 11, 13, and 17 days after sowing. Growth parameters of seedlings were recorded at monthly intervals for up to three months after transplanting in polybags. Significantly higher germination percentages were recorded in seeds primed with water (hydro priming), urea, and ZnSO4 after 17 days of sowing when compared to control. However, the highest germination percentage was recorded from the seeds primed with water (mock treatment). No significant differences were recorded in growth parameters of seedlings raised from seeds primed with chemicals or water when compared to those derived from un-primed seeds (control). Therefore, hydro priming may be the simplest and cost-effective priming treatment to improve the germination of rubber seeds. Keywords: Germination, Growth, Seed Priming, Urea, Zinc Sulphate
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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.
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    Study on Effectiveness of Ascorbic Acid, DRC+3 and Sodium Nitroprusside (SNP) on Recovery of Tapping Panel Dryness (TPD) of Rubber Trees
    (Uva Wellassa University of Sri Lanka, 2016) Watawala, W.K.S.W.; Senevirathna, A.M.W.K.; Arachchi, M.P.M.; Gunadasa, H.K.S.G.; Nayanakantha, N.M.C.; Samarasekara, R.K.
    Tapping panel dryness (TPD) of rubber is known as a physiological disorder (oxidative stress), which occurs in all rubber clones growing everywhere in the world resulting in severe loss of yield. At present, TPD affected trees are rested for about six months period to reduce stress to the trees in order to minimize TPD. There is no any effective treatment has been found to prevent or cure TPD. Therefore, rubber growers face serious problems due to high economic losses caused by TPD. This experiment was conducted to find the effectiveness of some chemical treatments for trees affected with TPD. Ninety TPD affected trees and 30 healthy trees of clone RRIC 121 that were planted in 1996 were selected. All the trees were being tapped at half spiral, every other day (S/2 d2), downward (J.) tapping system in the first renewed panel (C=BI- 1 panel). A commercial chemical named, DRC+3, Ascorbic acid (AA) and Sodium Nitroprusside (SNP) as a NO (nitric oxide) donor were used for the experiment, which are said to having antioxidant properties. DRC+3 (1g per tree with 6 days intervals), Ascorbic acid (1mM & 0.5mM with 6 days intervals) and Sodium Nitroprusside (100pM & 50 p..M with 2 weeks intervals) were applied on affected TPD trees with an untreated control. In another experiment, DRC+3(ig per tree with 10 days intervals) was applied for healthy trees with untreated control. Although data were not statically significant, there is a trend in increasing the yield per tree per tapping (g/t/t/) in TPD affected trees treated with DRC+3 and, Ascorbic acid, more prominently with 1 mM AA. Higher concentrations of Sodium Nitroprusside might be preferred as there was a positive effect on increasing yield of TPD affected trees with 100 11M SNP compared to 501.IM concentration, though the yield increase was not statistically significant. When compared to the pretreatment data and yield increase during the short period of the experiment, further continuation of this experiment is needed to arrive at firm conclusions. Key words: Ascorbic acid, DRC+3, Physiological disorder, Sodium Nitroprusside, Tapping panel dryness