MICROFLORA OF THE RHIZOSPHERE OF THE PINEAPPLE PLANT

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Abstract
A method is presented for the quantitative-qualitative characterization of microbial rhizosphere populations by the calculation of ratios between the numbers of organisms developing on various media (nutritional groups). Such ratios are regarded as lacking all dimensions other than those assigned by the selection of the media used to obtain the counts. This allows for the comparison of the microflora of regions of different physical character and obviates the necessity of calculating counts on a wt. or vol. basis. Employing this method in the study of the rhizosphere of the pineapple, it was found that: 1) there was no observable difference between microbial populations of the inner and outer rhizosphere; 2) at any given time, there was no interaction between the ratios of the nutritional groups and plant age, but the over-all rhizosphere effect was influenced by the age of the plant; 3) the ratios of the nutritional groups changed with planting time, as did the rhizosphere effect; 4) no difference in the bacterial flora of plants grown in Wahiawa and Helemano was shown, although a suggestive difference in the fungus flora was noted. The 30 spp. of heterotrophic, aerobic bacteria and the 17 spp. of filamentous fungi most commonly found in the rhizosphere of plants of various ages grown under Standard Plantation Practices are listed.