• Volume 69, Issue 6

      June 1969,   pages  295-348

    • The fungicide Kitazin and the mycoflora of rice

      Shanker Bhat Sullia

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      The effect of foliar spray of Kitazin (0, 0-Diethyl-S-benzyl thiophosphate) on the rhizosphere, rhizoplane and phyllosphere mycofloras of rice (Oryza sativa L.) var. Co. 18 was studied. There was significant lowering of the number of fungal propagules per gram of dry soil in the rhizosphere following spray. Where soil was not covered while spraying, there was greater reduction in the number of fungal propagules in the rhizosphere than in the covered plots. Between three dilutions of the fungicide used, however, there was no significant difference in the effect on the mycoflora. In the rhizoplane lesser number of species were isolated from the sprayed plants as compared to controls. In the phyllosphere, where there was direct contact of the chemical, there was much more inhibition of fungi. However, comparing the total number of fungal species in the rhizosphere, rhizoplane and phyllosphere, there is dimunition in number with increasing concentration of the chemical in the rhizoplane and phyllosphere but this is not so in the rhizosphere. From the data presented, the fungicide appears to be toxic to many saprophytic fungi in the rhizosphere, rhizoplane and phyllosphere of rice under tropical field conditions.

    • Granophyre dykes from Hunsur area, Mysore district, Mysore state

      M G Tadkod M S Sadashivaiah

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      Four granophyre dykes occur in the Hunsur area cutting the foliation of the Peninsular gneiss. Petrology, mineralogy and petrochemistry have revealed that these dykes are formed from the crystallization and cooling of an acid residuum of a basic magma.

    • Evolution of new races of univoltine silkworm by physiological genetics

      E S Narayanan B L Tikoo

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      1. With a view to fix improved pure strains of silkwormBombyx mori Linn. suitable for the univoltine regions of India, two breeding plans were drawn up.

      2. Out of eighty sublines isolated only five,viz., S18, S21, S36, S58 and S79 were finally selected on the basis of their peak performances.

      These have been christened as Mandakini, Shivalika maid, Himalayan nymph, Doon Crescent and Yamuna respectively.

      3. Field trials both at Dehra Dun and Kashmir under village conditions have given encouraging results.

    • Tidal cycle and the environmental features of Cochin Backwater (a tropical estuary)

      S Z Qasim C K Gopinathan

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      In the Cochin Backwater the tides are of a mixed, semidiurnal type with a maximum range of about 1 m. Two high and two low water-marks occur each day, with an appreciable difference in range and time. The various environmental features such as temperature, salinity, dissolved oxygen, pH, seston, nutrients, alkalinity and chlorophyll are greatly influenced by the tidal rhythm. The differences in almost all these parameters are more marked at the surface than at the bottom. The magnitudes of variation are not consistent and largely depend upon the time of the year.

      Diurnal changes in dissolved oxygen followed the course of daily sunlight intensity. Gross primary production gave a similar day and night cycle. Because of high turbidity in the estuary, the primary production was much higher at the surface than at 1 m.

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