PLANT PHYSIOLOGY , Vol 113, Issue 3 881-893, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Growth, Water Relations, and Accumulation of Organic and Inorganic Solutes in Roots of Maize Seedlings during Salt Stress
H. G. Rodriguez, JKM. Roberts, W. R. Jordan and M. C. Drew
Department of Soil and Crop Sciences (H.G.R., W.R.J.), and Department of Horticultural Sciences (M.C.D.), Texas A&M University, College Station, Texas 77843
Seedlings of maize (Zea mays L. cv Pioneer 3906), hydroponically grown in
the dark, were exposed to NaCl either gradually (salt acclimation) or in
one step (salt shock). In the salt-acclimation treatment, root extension
was indistinguishable from that of unsalinized controls for at least 6 d at
concentrations up to 100 mM NaCl. By contrast, salt shock rapidly inhibited
extension, followed by a gradual recovery, so that by 24 h extension rates
were the same as for controls, even at 150 mM NaCl. Salt shock caused a
rapid decrease in root water and solute potentials for the apical zones,
and the estimated turgor potential showed only a small decline; similar but
more gradual changes occurred with salt acclimation. The 5-bar decrease in
root solute potential with salt shock (150 mM NaCl) during the initial 10
min of exposure could not be accounted for by dehydration, indicating that
substantial osmotic adjustment occurred rapidly. Changes in concentration
of inorganic solutes (Na+, K+, and Cl-) and organic solutes (proline,
sucrose, fructose, and glucose) were measured during salt shock. The
contribution of these solutes to changes in root solute potential with
salinization was estimated.
