Browsing by Author "Mmbaga, Margaret Thomas"

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    Studies on vesicular - arbuscular mycorrhiza in rice (Oryza - Sativa L.). Masters dissertation, University of Dar es Salaam. Available at(http://41.86.178.3/internetserver3.1.2/detail.aspx)
    (University of Dar es Salaam, 1975) Mmbaga, Margaret Thomas
    The morphology of V-A mycorrhiza was found to be similar in rice and species of Cerpus, Cyperus, Kyllinga, Digi taria, Eriochloa, Spilanthes and Commelina. Structures were similar to those described in the literature for Endone spp. on other plants. Extra-matrical vesicles on infected roots were ascribed to Gigaspora spp. Twelve different types of chlamydospore, azygospore and zygo spore extracted in soil sievings from nine collecting sites in Tanzania appeared to belong to the genera Gigaspora, Glomus and Acaulospora. Differences in intensity of infection and in spore numbers in the soil may be attributed to soil nutrients, soil moisture, pH or soil sand content. No correlation was established between spore numbers in the soil and infection intensity. Distribution of the different spore hypes did not appear to be associated with edaphic or host related factors. There was no evidence of host specificity; findings of a field survey and controlled experiments indicated that flooding reduced mycorrhizal infection but did not completely suppress it. Rate of mycorrhizal development was related to increase in root dry weight. Arbuscules were shown to be ephemeral structures whose disappearance coincided with maximum growth of the host. It is suggested that arbuscule degradation, however, may be a fungus rather than a host regulated phenomenon. The effect of mycorrhiza on rice plant growth was inconsistent increasing plant dry weight in some pot experiments but not in others. In two experiments it was shown that mycorrhiza increased phosphorus uptake by plants when soil phosphorus was low. The merits of different forms of inoculum and methods of application are discussed, spore-impregnated filter paper was satisfactory. Infected root pieces were more convenient but may have contained a mixture of fungi which could account some of the discrepancies in these results.