1)Department of Biology, Aichi University of Education, Kariya, Aichi-ken, 484 Japan
2) Faculty of Agriculture, Nagoya University, Chikusa-ku, Nagoya, 464 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.
References
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.