PURSE 2004

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    An Ecological Study of Grasslands at Hantana
    (University of Peradeniya, 2004-11-10) Niroshini, D. M. K. G.; Weerasinghe, H. M. S. P. Madawala
    Grasslands of Sri Lanka are ecologically fascinating for their wide floristic, physiological and environmental diversity. Grasslands at Hantana come under humid zone dry patanas. There are many floristic and edaphic variations within these grasslands due to altitude. microclimate, moisture regime, nutrient status. textural properties of soil, human interferences etc. During this study we tried to identify the ecology of grasslands at two different elevations at Hantana and the edaphic factors that may have contributed to this variation. Two grassland sites with an elevation difference of approximately 35 m were selected for this study. Floristic information such as the species composition, density and cover were investigated. Shannon Diversity Index and Evenness values were calculated. Biomass allocation pattern was determined using three 1m x 1m plots. For soil characters, 5 plots (10 m x 10 m each) were randomly selected at each elevation level. In each plot, 12 soil samples were collected randomly from a depth of 0-15 cm, Soil samples were then analyzed for chemical parameters using standard procedures. Panicum maximum (density, 10000 ha-1) is the dominant species at lower elevation grasslands (LoG) while Cymbopogon nardus (density, 8800 ha-1 ) is the dominant species at higher elevation grasslands (HiG). From the total of 18 plant species, 17 % were represented by grasses, 50 % represented by herbs, 22 % by shrubs and 11% represented by treelets in LoG. At HiG, 21 plant species were recorded, and out of that 24% were represented by grasses, 54% were represented by herbs, 19% by shrubs, and 5% by treelets. The Shannon Diversity Index showed that the species richness is higher at HiG than at LoG. The family Poaceae showed the highest cover values in both grasslands (LoG = 44%, HiG = 35%) whereas the family Fabaceae showed the second highest cover values in both grasslands, but it is relatively higher in RiG (33%) than in LoG (29%). The root: shoot ratio of Panicum maximum (0.9460) is higher at LoG than the root: shoot of Cymbopogon nardus (0.7633) at HiG Slightly higher soil pH (6.4) was recorded at LoG compared to HiG (6.0). The total nitrogen (0.2%) and magnesium contents (162 ppm) are significantly higher at HiG than in the LoG (0.15%, 25 ppm respectively) whereas the potassium content is higher at LoG (150 ppm), than HiG (50 ppm). Organic carbon (LoG = 5%, HiG = 5.4%), sodium (LiG = 35 ppm, HiG = 23 ppm) and calcium (LoG = 314 ppm, HiG = 288 ppm) contents are more or less similar in both grasslands. The C: N ratio is close to 30 in both elevations indicating a net immobilization. Results of the present study indicate that the floristic composition and diversity as well as some soil characters differ markedly in these grasslands within this small elevation gradient.
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    Canker Disease of Psidium Guajava L. Caused by Pestalotiopsis Psidii and Host Defencive Responses
    (University of Peradeniya, 2004-11-10) Bandaranayake, B. M. R. P.; Adikaram, N. K. B.
    Canker disease caused by Pestalotiopsis psidii in unripe guava is characterized by browning and cracking of outermost epicarp. Cracking exposes the internal tissues of fruits resulting secondary infections. Infection and development of limited symptoms occur in the field and may develop into progressive fruit rot during ripening. It does not penetrate deeply but reduces the market value. When fruits are severely infected, mummified fruits fall off resulting in yield losses. Causative agent was isolated from the infected areas as well as from healthy internal tissues where symptoms were not visible. The fungus may therefore exist as an endophyte. Healthy and canker infected epicarp tissues of mature and immature fruits were extracted in ethyl acetate for antifungal zones. Four pre-formed antifungal zones were detected on TLC bioassay in healthy tissues. Only two antifungal zones were present in TLC, which was extracted from infected tissues. No additional or larger antifungal zones were present in the extracts taken from infected tissues. Infected tissues observed were yellowish brown in colour and the cells had disintegrated. The infected necrotic tissues did not show deposition of lignin, suberin or tannins. Measurement of pH at the canker infected and healthy areas of the guava fruits, did not show a significant difference. These investigations have revealed that the primary defense response in guava fruit against the canker pathogen brings about rapid necrosis development in which no phytoalaexins were accumulated.
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    Changes in pH Following Freckle Infection (Phyllosticta Musarum) as a Defense Response Against Anthracnose
    (University of Peradeniya, 2004-11-10) Weerakoon, A. U.; Adikaram, N. K. B.; Abeysekara, C. L.
    The host environment pH is found to be a regulatory factor in pathogenesis of certain fungi. Some fungi increase the host pH while others tend to reduce it. Certain ColLetotrichum spp. have the ability to modulate host pH by secreting ammonia locally into the host tissue, resulting in a pH increase which enables enzymatic secretion and enhance virulence. Colletotrichum musae causes quiescent infections in unripe green banana fruits which develop into anthracnose lesions during fruit ripening. Freckle disease in banana caused by Phyllosticta musarum is associated with a number of defence responses viz. accumulation of phytoalexin and PR proteins, and certain other changes such as lignification and suberization and accumulation of tannins, which in turn reduce the development of anthracnose disease. Six phytoalexins have been isolated from freckle infected banana peel, which contribute to defense against C. musae. The objective of this study was to determine whether P. musarum causes a pH alteration in the banana peel and if so whether this acts as an additional defence response by the fungus against anthracnose. Freckled and non freckled "Embul'' fruits at a similar stage of maturity were obtained from the same bunch. A set of freckled fruits and non freckled fruits were inoculated with 50 III of C. musae spore suspension (105 spores ml") per inoculation, while the control sets of freckled and non freckled fruits were treated with sterile distilled water. Lesion diameters and pH of the peel were measured daily for 7 days. There was a significantly higher anthracnose development in non freckled fruits compared to the freckled fruits. This was observed when fruits were artificially inoculated and also when natural quiescent infections of C. musae were allowed to develop. The freckle infected banana peel had a significantly (p=O.05 level) higher pH than the non freckled peel throughout the ripening process. This indicates that P. musarum infection increases host pH. In fruits inoculated with C. musae, the peel pH was significantly higher (p = 0.05 level) in the freckled peel compared to the non-freckled peel during initial necrosis. Furthermore, at the onset of tissue maceration pH of the freckled peel was higher than that of the non-freckled peel. However with the expansion of lesions the pH in the non-freckled peel was significantly higher at p=0.05 level, when compared to the freckled peel. The higher values of pH in the freckled peel during initial necrosis and the onset of tissue maceration could be a contributing factor in limiting anthracnose in bananas. The increase in pH at an advanced stage of lesion development, in non freckled peel, may be due to rapid tissue maceration caused by C. musae. These results indicate that pH increase following P. musarum infection may be an additional defense response in banana fruit.
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    Changes in Women's Role in Families in Mahaweli Resetlements of Sri Lanka: A Sociological Study of System 'C'
    (University of Peradeniya Sri Lanka, 2004-11-10) Manuratne, M. G.
    This study examines the change in the role of women within the context of families in Teldeniya, a Mahaweli resettlement unit in system 'C' of Sri Lanka. In this study, the role changes of women in the settlement have been examined in comparison to the original villages of the settlers. Intra-community variations of role changes within the settlement were examined in relation to the three family types (allottees, sub-families, and encroachers) and gender. The data were collected using standard anthropological and sociological methodologies involving case studies, observations, interviews and a survey. The study was conducted during the 'Maha' season of October, 1998 to March, 1999. The study found that the women have undergone tremendous change in their roles within the families in the areas of irrigated rice farming, highland cultivation, household chores, activities outside the house, and non-agricultural economic activities. In rice farming, the women work in different types of activities, which outnumbers the activities of the men. This has implications for traditional forms of division of labour. In highland farming, the work becomes the total responsibility of the women, who therefore perform almost all the activities. The women in the settlement perform those activities in addition to what they do at home (household chores), in a context of secluded family, which has tremendously expanded the work 'field' of women from what it has been in the original village. The role changes of women vary with family type, showing that the women in allottee families have undergone most of the changes described above. The study argues, using Bourdieu's concepts of 'field' and 'habitus' that the women in Mahaweli resettlements, although undergoing change in their role within the family, have been much more introvertly structured within the family 'field' than was in the original village. It also refutes the assumption that with the increase in the workload and responsibility, the women in Mahaweli resettlements have liberated themselves. The change in their role within the family has brought in new perspectives of gender relations, which have implications for the occurrence of family crises in Mahaweli settlements.