42. Character expression of a root-growth inhibiting mutant in rice

1)Department of Biology, Aichi University of Education, Kariya, Aichi-ken, 484 Japan

As previously reported, a root-growth inhibiting mutant carries a single recessive gene, rt (Futsuhara and Kitano 1985). It was found that the radicle length in dormant seeds of this mutant is not much different from that of the original line, Fukei 71, suggesting that the effect of rt gene is not yet expressed in the process of embryonic growth. However, the seminal root of the mutant was significantly shorter than that of Fukei 71 after 24 hours of incubation of the sprouting seeds in a growth cabinet maintained at 30 degrees C. These results indicate that the gene acts on root growth and development immediately after seed germination.

Fig. 1. Longitudinal sections of crown root in a rt mutant (B) and its original line, Fukei 71 (A)

The crown roots of the mutants showed some morphological abnormalities which were similar to the so-called 'stunted root', described by Kawata et al. (1978). Cytohistological observation demonstrated that, although cell division and differentiation of the apical meristem occurred normally in both the mutant and its original line, remarkable inhibiion of cell elongation and excessive cell expansion occurred simultaneously in the protoderm derived from the mutant root apex, as show in Fig. 1. It was also observed that, during root elongation and maturity, the epidermis became stripped from the cortes. From these observations, it was concluded that the gene causes a inhibition of root elongation by inducing the formation of an abnormal root epidermal system.

Futsuhara, Y. and H. Kitano, 1985. Inheritance of a root-growth inhibiting mutant in rice. RGN 2: 70-71.

Kawata, S., S.E.M. El-Aishy, nd K. Yamaki, 1978. Morphology and anatomy of "stunted" roots in rice plants. Japan. J. Crop Sci. 47: 286-292.