18. Water absorbing capacity of a root-growth inhibiting mutant in rice

Yuzo FUTSUHARA1, Kazumi HATTORI1 and Hidemi KITAN02

1) Faculty of Agriculture, Nagoya University, Chikusa-ku, Nagoya, 464 Japan

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

The root-growth inhibiting mutant with recessive gene rt, induced from a dwarf line Fukei 71, showed remarkable inhibition of root elongation although its shoot-growth was nearly normal (Futsuhara and Kitano 1985). Its shoot and root characters and water-absorbing capacity of the roots in the seedling stage, as compared with those of the original line, are given in Table 1. The rt mutant showed a water-absorbing capacity equivalent to that of the original line although its roots were exceedingly short. When water uptake only by the longest root was measured, the mutant had somewhat lower water-absorbing ability than the control, but the mutant had somewhat larger root number than the control. Perhaps, a short piece of root has a high ability of water uptake. Water supply may not be a limiting factor for shoot growth of the mutant when grown in a water-saturated soil. Its smaller plant height may be attributed to a pleiotropic effect of the rt gene.

Table 1. Characteristics and water absorbing ability of the rt 
mutant and its original line (Fukei 71) in the seedling stage
Character                    Mutant rt        Normal (Fukei 71)
Plant height (cm)            10.04±2.05      13.25±2.23
No. of leaves                 3.32±0.48       3.08±0.28
No. of roots                  7.81±1.45       5.07±9.04
Length of longest root (cm)   0.78±0.23      15.02±2.39
Water uptake, by total roots (g),
6  hrs.                       0.135±0.021     0.133±0.027
16  hrs.                      0.366±0.049     0.374±0.031
Water uptake, by longest root (g),
6  hrs.                       0.098±0.019     0.116±0.015
16  hrs.                      0.320±0.060     0.384±0.045


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