Abstract
Excised rice seminal roots with scutella were cultured aseptically in vitro by means of "bi-media culture" method. The morphogenetic responses of roots to the changes of the concentration of sugar supplied as glucose solution through the basal parts of the roots were studied. The sugar concentration of the media was changed after the roots were pre-cultured for 7 days and then cultured for succeeding 7 days. When the concentration of glucose was changed from 0.5% to 7%, the elongation rate of primary roots and lateral roots increased immediately after the treatment. The increase in diameter of primary roots which owed to the expansion of individual cortical cells was also observed. On the other hand, when the concentration of glucose was changed from 7% to 0.5%, the elongation rate of primary roots and the thicker laterals did not decrease, but the elongation of the thinner laterals was restricted. The addition of 0.5% of mannose to 6.5% of glucose following the pre-culture with 7% of glucose strictly restricted the elongation of pimary roots and laterals. The results indicate the important role of sugar provision from shoot to root in determining the length, diameter and branching patterns of crown roots of rice plants.
