Chemistry

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    Effect of coconut (Cocos nucifera) water extract on the development of adventitious roots in Polyscias fillicifolia stem cuttings
    (The Journal of Agricultural Sciences - Sri Lanka, 2021) Jayawardena, B.M.; Agampodi, V.A.; Abeywickrama, K.P.
    Purpose Vegetative propagation continues to be a popular method to propagate ornamental plant species. Coconut water (CW) can be considered as an abundant source of hormones and other plant growth regulators (PGRs). In this study, vegetative propagation of Polyscias fillicifolia was attempted using PGRs isolated from CW. Research method Stem cuttings were treated with varying concentrations (5, 10, 25, 50,100 μg mL-1) of PGR isolated from CW. The results were compared with a control set (treated with distilled water) and with those treated with solutions of pure synthetic indole acetic acid (IAA). Findings P. fillicifolia canes treated with a 25 μg mL-1 concentration of IAA, isolated from CW, showed the highest levels of root induction and development. Root development was more rapid (5 weeks) in the samples treated with PGRs isolated from CW compared to the canes propagated in the field by placing the canes on coir beds in plant nurseries. (6 weeks). Originality This is the first study to use PGRs isolated from CW extracts to improve lateral root proliferation, induce shoot development and leaf emergence in P. fillicifolia.
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    Repellency and toxicity of four essential oils to Sitophilus oryzae L. (Coleoptera: Curculionidae)
    (2004) Paranagama, P.A.; Abeysekera, K.H.T.; Nugaliyadde, L.; Abeywickrama, K.P.
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    Foliage preservatives for vase life extension of two dieffenbachia species
    (2010) Thambugala, S.; Abeywickrama, K.P.; Karunarathna, S.
    Cut foliage of Dieffenbachia maculata and Dieffenbachia amoena were subjected to continuous treatment with several foliage preservatives and export simulation. The preservatives used were 1.75% of sodium hypochlorite, 5% vinegar and VimTM dish washing detergent. Tap water without any added chemicals was used as the control. The highest vase life of 45.1 days was observed in D. maculata cut foliage when subjected to continuous treatment with tap water. Cut foliage of D. maculata subjected to continuous treatment with 0.016% (v/v) dish washing detergent (Vim™) solution and 0.016% (v/v) sodium hypochlorite (NaOCl) and subjected to export simulation for two days at 12-140 C and 85-90% relative humidity (RH), had relatively longer vase life of 38.9 days and 37 days respectively. Cut foliage of D. amoena had the longest vase life of 21 days when subjected to 0.016% NaOCl treatment and export simulation. NaOCl which is considered as a biocide and mild vinegar solution which is acidic inhibited the bacterial growth in vase solutions increasing the vase life of cut foliage. A Bacillus sp. and a Staphylococcus sp. were associated with vase solutions of D. maculata and D. amoena cut foliage. Treatment with NaOCl and VimTM satisfactorily extended the vase life of cut foliage of D. amoena and D. maculata respectively and could be recommended as preservatives for use during export.
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    Effect of Chemical Pretreatments on the Quality of Minimally Processed Pineapple Stored in Polystyrene Packages
    (2012) Ediriweera, S.; Abeywickrama, K.P.; Latifah, M.
    Minimally processed pineapple (Ananas comosus L.) cv. Mauritius stored at cold temperature for seven days were evaluated for physicochemical, sensory and microbiological qualities. Pineapple pieces were treated with 1% sodium chloride, 1% calcium chloride, a combination of 1% sodium chloride and calcium chloride, 1% ascorbic acid, 1% citric acid, 0.1% chitosan and distilled water (control) and packed in polystyrene packages before storage. Pretreatments did not significantly affect the physicochemical properties studied. Many sensory attributes in minimally processed pineapple decreased after seven days of storage. However, sodium chloride (1%) and a combination of 1% sodium chloride and calcium chloride pretreatments resulted in maintaining a better flavour in pineapple after a seven day storage period than the rest of the treatments. Microbial counts for all treatments and the control were within safe-to-consume limits while Salmonella was not detected in any sample.
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    Wheat crown rot pathogens Fusarium graminearum and F. pseudograminearum lack specialization
    (2010) Chakraborty, S.; Obanor, F.; Westecott, R.; Abeywickrama, K.P.
    This article reports a lack of pathogenic specialization among Australian Fusarium graminearum and F. pseudograminearum causing crown rot (CR) of wheat using analysis of variance (ANOVA), principal component and biplot analysis, Kendall’s coefficient of concordance (W), and κ statistics. Overall, F. pseudograminearum was more aggressive than F. graminearum, supporting earlier delineation of the crowninfecting group as a new species. Although significant wheat line– pathogen isolate interaction in ANOVA suggested putative specialization when seedlings of 60 wheat lines were inoculated with 4 pathogen isolates or 26 wheat lines were inoculated with 10 isolates, significant W and κ showed agreement in rank order of wheat lines, indicating a lack of specialization. The first principal component representing nondifferential aggressiveness explained a large part (up to 65%) of the variation in CR severity. The differential components were small and more pronounced in seedlings than in adult plants. By maximizing variance on the first two principal components, biplots were useful for highlighting the association between isolates and wheat lines. A key finding of this work is that a range of analytical tools are needed to explore pathogenic specialization, and a statistically significant interaction in an ANOVA cannot be taken as conclusive evidence of specialization. With no highly resistant wheat cultivars, Fusarium isolates mostly differ in aggressiveness; however, specialization may appear as more resistant cultivars become widespread.
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    Quality of minimally processed modified atmosphere sorted bell pepper, as affected by pre treatments
    (2015) Ediriweera, S.; Abeywickrama, K.P.; Latifah, M.; Othaman, F.; Hussin, R.; Tham, S.
    Minimally processed bell pepper strips stored at 8-100C for seven days were evaluated for variation in color, in package gases, firmness, physicochemical sensory and microbiological quality. Bell pepper strips were treated with sodium chloride, calcium chloride, sodium chloride+calcium chloride or distilled water (control) and packed in polystyrene packages before storage. Pretreatments did not drastically affect the physicochemical properties (titratable acidity (TA), total soluble solids (TSS) and pH) when compared to the control. A slight discoloration of bell pepper was evident, indicated by decreasing L*, a* and b* values. Variations in firmness were observed. Fair-ly high level of CO2 accumulation was evident inside packages where O2 concentration displayed a declining trend. Sensory attributes generally declined with time but were within acceptable limits. Microbial counts were within safe-to-consume limits for all samples within the storage period. All pretreatments tested had no drastic effect on sensory properties and maintained low microbial counts, however 1% sodium chloride pretreatment was more successful in retaining higher sensory properties and maintaining lower microbial counts by the end of stor-age period than the other pretreatments.
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    Root growth promotion of Ficus species during air-layering
    (2010) Gamlath, M.; Abeywickrama, K.P.; Wickramarachchi, S.
    Three chitosan concentrations (1%, 3%, 5% w/v) were tested for their root growth promotion properties in air-layering of three popular ornamental Ficus species namely Ficus triangularis, Ficus microcarpa and Ficus benjamina. Subsequently, these treatment responses were compared with a rooting hormone (naphthalic acetic acid) and an organic root promoting extract (Root Most) available in the local market. Tap water was used as the control. Air-layered plants were further subjected to export simulation for 14 days at 12-14 0C and 90% relative humidity (RH) with the aim of lengthening the storage period. 3% (w/v) chitosan treatment concentration was shown to promote the root growth significantly. 3% (w/v) chitosan treatment resulted in the highest mean root length of (15.3 cm) in F. triangularis compared to the 10.3 cm of tap water control. Similarly, highest mean root length of 38.8 cm was recorded for F. microcarpa for 3% (w/v) chitosan treated layers compared to 14.8 cm of tap water treated layers. Further, the highest mean root density of 3.17 was recorded for 3% (w/v) chitosan treated layers of F. triangularis. A cost effective packaging system was developed during this research which could be utilized in cold storage of air-layers during air or sea freight.
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    Deterrent effects of some Sri Lankan essential oils on oviposition and progeny production of the cowpea bruchid, Callosobruchus maculatus (F.)(Coleoptera; Bruchidae)
    (2003) Paranagama, P.; Adhikari, C.; Abeywickrama, K.P.; Bandara, P.
    Essential oils extracted from five plant materials were tested on oviposition and progeny production of F1 adult of cowpea bruchid, Callosobruchus maculatus on cowpea seeds. All oils tested showed a significant inhibition of oviposition and F1 adult emergence compared to the control during no-choice tests. Cymbopogon citratus and C. nardus showed higher effect on oviposition and F1 adult emergence than the essential oils of Alpinia calcarata, Cinnamomum zeylanicum and Murraya koinigii. In the choice test, the percentage ovipositions in all oils treated samples (except 10 mg of M. koinigii) were significantly lower than that of the control and ethanol treated samples. The percentage eggs deposited decreased with increasing doses of the oils ranging from 10 to 160 mg. The percentage of eggs laid was zero in samples treated with 40 mg of C. nardus or A. calcarata, 80 mg of C. citratus and 160 mg of C. zeylanicum. The essential oils of M. koinigii showed the lowest effect on oviposition when compared to other four essential oils.
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    Cymbopogon citratus (lemongrass) and citral a+ b spray treatments alone or in combination with sodium bicarbonate in controlling crown rot in Embul banana (Musa acuminata AAB)
    (2004) Abeywickrama, K.P.; Kularathna, L.; Sarananda, K.; Abeygunawardena, D.
    The mounting pressure against synthetic fungicidal dips and sprays, restrict their use in controlling crown rot, a major post-harvest disease in banana. Generally regarded as safe (GRAS) compounds have a great potential to be used as alternatives to fungicides. Identification of chemical constituents of Cymbopogon citratus oil revealed the presence of citral as the main component. Cymbopogon citratus and citral with sodium bicarbonate (SBC) was fungicidal against the 3 banana fungal pathogens at 0.10-0.20 % v/v and 0.07-0.08 % v/v respectively. Embul banana sprayed with C. citratus alone or in combination with SBC after induced ripening, indicated a crown rot severity of 25 - 5 0% whereas, citral treatment resulted in a slightly lower disease severity. The physico-chemical parameters tested were not affected by the treatments. Oil/citral, SBC treated bananas and control were ranked good to excellent with respect to odour, flavour, taste and overall acceptability. The low disease severity of crown rot due to spray treatment of citral and SBC highlights the importance in adapting this simple, alternate treatment strategy for quality maintenance.