Yoshida - 1981 - Fundamentals of Rice Crop Science

GROWTH AND DEVELOPMENT OF THE RICE PLANT 35
1.33. Diagram of a young root, showing relation between anatomy and
absorbing regions for water and salt (from Plant and Soil Water Relationships
by P. J. Kramer, Copyright © 1969 by McGraw-Hill. Inc. Used with
the permission of McGraw-Hill Book Company).
organic matter left in the soil and attributable to root growth should be much
higher.
1.7.3. Water and nutrient uptake by single roots
The tip of a single root is relatively impermeable to water and the region some
distance away from the tip toward the proximal end also has a low permeability to
water due to suberization. The entrance of water and salt is most rapid between the
above two low permeable regions of a root (Fig. 1.33).
Along the axis of a single rice root, the meristematic region is about 0.25 mm
from the tip; branched roots are recognizable at 30–40 mm; and considerable
suberization occurs at about 40–50 mm. Suberization is more intense in regions
further away from the tip (Kawata and Lai 1968). Water absorption is most active
between the root tip and the site of branched roots (Fig. 1.34).
1.7.4. Water and nutrient uptake by old and new roots
When half of the roots of a rice plant are cut at the base around panicle initiation
time and the plant is placed in nutrient solution for about 10 days, new roots will
emerge to replace those lost. The capacity of these new roots to absorb water and
nutrients can be examined if they are placed in separate nutrient containers
(Okajima 1960).