Journal of Experimental Botany, Vol 49, 1945-1952, Copyright © 1998 by Oxford University Press
Z Lu and P Neumann
The possible occurrence of species diversity in mechanisms underlying
leaf-growth inhibition by water stress, was investigated in related cereal
plants. Water stress was generated by additions of the osmoticum
polyethylene glycol 6000 to the root medium. Effects of external water
potentials ranging from 0 to -0.6MPa, on early growth parameters of
emerging leaves were measured under controlled environment conditions,
using pairs of maize, barley or rice genotypes with differing resistance to
water stress under field conditions. Water potentials of -0.4 MPa for 24 h,
similarly reduced leaf growth, comparative production rates of leaf
epidermal cells and cell size in all genotypes. These reductions did not
appear to be caused by reductions in the osmotic potential gradients
between the expanding leaf cells and their external water source. However,
growth inhibition in maize and barley, was accompanied by significant
reductions in comparative leaf and cell wall extensibility. Moreover,
regression plots revealed good linear correlations (r=0.83** for maize and
r=0.77** for barley) between the reductions in leaf growth induced by a
series of water potentials and associated reductions in leaf extensibility.
In contrast, the reduction in growth of rice leaves, was not accompanied by
any significant changes in leaf or cell wall extensibility. Similarly,
regression plots revealed poor correlations between leaf growth and leaf
extensibility in both paddy and upland rice (r=0.17 and r=0.07,
respectively). Thus, despite numerous inter-species similarities,
biophysical changes associated with stress-induced leaf growth inhibition
in maize and barley, differed from those in rice.Key
words: Cell walls, extensibility, water stress, cereal
diversity, leaf growth.
ARTICLES
Water-stressed maize, barley and rice seedlings show species diversity in mechanisms of leaf growth inhibition
Plant Physiology Laboratory, Lowdermilk Faculty of Agricultural Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel; Corresponding author e-mail: agpetern@tx.technion.ac.il
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