EFFECT OF SOIL-MICROORGANISMS ON THE GROWTH OF ROOTS IN RICE SEEDLINGS .1. MORPHOLOGICAL MODIFICATION IN ROOT DEVELOPMENT

Root system of rice seedlings grown on nutrient solution inoculated with soil microorganisms were examined morphologically in comparison with those obtained under sterile condition. In the presence of soil microorganisms, primary roots increased in their number and decreased in the total length. Inoculated plants had more secondary roots equipped with tertiary roots. In addition, longer root hairs developed densely on primary and secondary roots of the inoculated seedlings. Anatomical examination of the primary roots revealed that the number and width of cortical layers, as well as the length and width of the cortical cells, were increased by the effect of microorganisms. Microbial effect on outer morphology of rice roots, consequently, was estimated to have been induced from the alteration in histological and cytological activities including the activation of the periclinal divisions of the epidermal cells, the inactivation of the transverse divisions of the cortical cells and the activation of the elongation of cortical cells. © 1979 Taylor & Francis Group, LLC.