Browsing by Author "Perera, H.S.M."

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Analysis of Water and Sediment in Attanagalu Oya in Sri Lanka: Pollution Levels and Effects
(In: Proceedings of the International Postgraduate Research Conference 2017 (IPRC – 2017), Faculty of Graduate Studies, University of Kelaniya, Sri Lanka., 2017) Premaratne, W.A.P.J.; Perera, H.S.M.
The Attanagalu Oya plays a major role in national water supply since it contains four major national water supply and drainage board intakes. This study intends to investigate the water quality variation and pollution levelin Attanagalu Oya in Gampaha municipal council area.Sampling was conducted for a period of six months from November 2016 to April 2017 at nine locations situated between 7° 05' 33.8" to 7° 05' 53.1’’N latitude and 79° 58' 15.6"to 79° 59' 32.5"E longitude along the main river. Both water and sediment samples in the river were collected and tested for physical and chemical parameters. Electrical conductivity (EC), pH, titratable acidity, total hardness, chemical oxygen demand (COD), and metal ions content (Fe, Pb, Cd, Ni, Mn, Cu) were analyzed in water samples. EC, pH, organic matter content and soil texture were analyzed in sediment samples. Experimental results were ascertained to find out the quality and pollution level of water and sediment by comparing with the standards levels given by the Central Environmental Authority (CEA) in Sri Lanka and World Health Organization (WHO) guidelines. According to the experimental results, average pH values of water in the river was from 7.1 to 7.6 and did not exceed the proposed ambient water quality standards for fish and aquatic life. EC values ranged from 81.9 to 91.7 μS/cm and conductivity shows a drastic increment due to dry season. Titratable acidity, total hardness and metal ions content in water samples were not in the limits of CEA and WHO standards for drinking water parameters. COD values of water samples exceeded the maximum CEA standards during the sampling period. Sediment analysis indicated that physical and chemical parameters are not in the limits of CEA standards. Therefore, this study shows that the river is polluted and the effects being significant in the urban areas.
Comparative study on the effect of different substrate compositions on performance of tissue cultured Dendrobium bigibbum during the prehardening process
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Perera, H.S.M.; Rodrigo, W.U.M.; Perera, U.I.D.; Swarnathilaka, D.B.R.
Development of planting material using tissue culture is an established and widely used mass propagation method in the floriculture industry. However, considerable percentage of tissue culture raised plants may not survive during acclimatization process, due to inability to compete with soil microbes and adverse environmental conditions. The present study aimed to establish a successful pre-acclimatization procedure for in vitro produced Dendrobium bigibbum plants. Plants of 2.5 cm average height, with at least 3 leaves and 2-3 roots were selected for pre-acclimatization practices. Plants were planted in vessels with different compositions of substrates denoted as A and B series (A series-Sand:Compost:Charcoal Powder; A1-1:2:0.5, A2-2:2:0.5, A3-1:1:0.5, A4-1:2:1 and B series-Sand:Compost: Charcoal Chips (4-5 mm size); B1-1:2:0.5, B2-2:2:0.5, B3-1:1:0.5, B4-1:2:1) with Murashige and Skoog (MS) basal medium supplemented with benzylaminopurine (BAP) (0.1 mg/L) and naphthaleneacetic acid (NAA) (2 mg/L). Plants were grown under laboratory conditions at 22 ± 1 0C, and 16/8 hr photoperiod for three months before the acclimatization process. As the control, plants were grown in MS basal medium without any substrates. Oneway ANOVA was used to determine whether there is a significant difference between tested samples using Minitab 16. According to the results obtained, there was no significant difference (p>0.05) in the shoot lengths of “A series” compared to the control. However, “B series” has shown a significant difference in the shoot lengths compared to the control (p<0.05). The highest shoot length of 3.87 ± 0.25 was observed in B1 medium. When fresh weights were compared, in “A series”, only A1 showed a higher significant difference (1.30 ± 0.08) with the control while “B series” performed better compared to the control. Dry weight in both A and B series have shown a significant difference compared to the control. Plants grown in B1 medium has the highest number of roots (16.67 ± 1.53) compared to the other treatments. After acclimatization, the highest survival rate of plants were observed in “B series” (90%) whereas “A series” and control showed survival rates of 60% and 30% respectively. Hence, B series is suitable for shoot multiplication, root generation as well as pre-hardening to survive in vivo.
Effect of growth regulators on in vitro regeneration of Gerbera jamesonii.
(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Perera, H.S.M.; Swarnalatha, K.D.S.; Senanayake, S.P.
Gerbera jamesonii (Gerbera), belongs to the family Asteraceae, is considered as one of the important cut flowers in the global floriculture industry. The propagation process of Gerberas require improvements to fulfill the commercial demand and in vitro propagation was considered as a suitable solution to overcome this problem. The aim of the present study was to determine the effect of various concentrations of growth regulators on callus formation and shoot regeneration of Gerbera using leaves as explants. Healthy mature leaves were taken from Gerbera grown in the plant house, University of Kelaniya for obtaining suitable explants. Excised explants were washed with teepol (0.1%) solution for 06 mins followed by washings pre-treated with 10% (w/v) captan and sterilized distilled water (SDW). The explants were surface sterilized with Clorox solution (5%) with addition of Tween 20, followed by washing with SDW. Sterilized leaves were cut into 5-10 mm pieces. Callus induction, shoot proliferation and root regeneration were accomplished on Murashige and Skoog (MS) basal medium supplemented with different concentrations (0, 0.5, 1.0, 1.5 and 2.0mg/L) of 6-benzylaminopurine (BAP) and (0, 0.5 and 2mg/L) of naphthaleneacetic acid (NAA). For rooting, MS medium was supplemented with different concentrations of BAP (0, and 2.0 mg/L) and NAA (0, 2.0 mg/L). The highest callus initiation was observed in MS medium with 2 mg/L NAA and 1.0 mg/L BAP (60 days) while highest shoot initiation was obtained in MS medium with 2 mg/L BAP and 0.5mg/L NAA. Number of shoot formation per explant was 80% and shoots were visible after 26 days. When BAP was used as the sole growth regulator in the culture medium without NAA, limited shoot proliferations and translucent short shoots were observed (54%), whereas, NAA alone as the sole growth hormone did not initiate any shoot proliferation. With up to 2 mg/L NAA in the medium, BAP had a negative effect on shoot development, multiplication rate and the height of the shoots. MS medium supplemented with, 2 mg/L NAA, was identified as the best response for rooting initiation and number of roots per explant were 23.2±1.34. The first roots appeared after 1–2 weeks of culturing and a well developed root system was noted in 4–5 weeks. Subsequently, plants were removed from the medium and transferred to coir dust for acclimatization. The findings indicate that above three media compositions could be utilized for callus initiation, shoot proliferation and root formation from leaf explants of Gerbera jamesonii.