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Item Cell wall degrading enzyme secretion by Cylindrocladium quinqueseptatum(Rubber Research Institute. Agalawatta, 1999) Jayasinghe, C.K.; Wijesundera, R.L.C.Cylindrocladium quinqueseptatum causes leaf fall of clove in Sri Lanka and is responsible for the leaf spots of rubber in Malaysia.only one isolate (KP)from four pathogenic isolates examined secreted polygalacturanase(PG) when grown in liquid media.None ofthe isolates secreted pectin lyase(PL).The extracts of clove and rubber leaf tissues,inoculated with the KP isolate did not show any PG and PL activity .The leaf tissue did not have the ability to ingibit c.quinqueseptatum PG produced in culture.All isolates of C.quinquesepltatum secreted cellulases viz.cellobiase and b-glucosidase in culture.cellobiase was detected in the inoculated rubber leaves,The levels of B-glucosidase,an ingerent enzyme of Hevea leaves,also increased rapidly following infection.The results indicate that pectic enxymes play a minimal or no role in disease developmet of C.quinqueseptatum infecton in cloves and Hevea.Thus cellulolyic enzyme probably play a nutritive role.Item Effects of combined nitrogen on nodule function of leguminous crops with special reference to tropical soils(Rubber Research Institute. Agalawatta, 1991) Jayasinghe, C.K.The effect of combined nitrogen on nitrogen fixation has been discussed by several investigators from their findings it could be concluded that inorganic nitrogen may have either stimulatory, neutral or negative effect on nitrogen fixation depending on the type of legume soil condition. It was reported in some instances that low levels of combined nitrogen especially when applied as a "Starter" fertilizer at germination, stimulates plant growth enhances nodule mass nitrogen fixation. On the other hand when most of the legumes are grown in soil high in available nitrogen, the nitrogen fixation rate is severely affected. This phenomenon may become more critical when legumes are grown as cover crops where non legume counterpart is fertilized with nitrogenous fertilizer. The degree of inhibition appears to vary with several factors viz. concentration of combined nitrogen, host species, cultivar, strain of of root nodule bacteria, rate of inoculation, light intensity temperature. However, the most critical factor is the concentration of combined nitrogen it has been shown that very low concentrations such as 240 ppm N reduced the nitrogen fixation of bradyrhizobia - legume symbioses whereas 80-100 Kg of N ha-1 inhibited the nodulation nitrogen fixation of Vigna spp. totally. It was further pointed out that extra caution should be taken when recommending nitrogenous fertilizer to mixed cropping systems in tropical soils as nodulation nitrogen fixation of legume counter parts such as Pueraria, Desmodium Mimosa were reduced to neglegible levels when 140 ppm N was added to Sri Lankan rubber soils.