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Titre :
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Spatial distribution of solutes, K, Na, Ca and their deposition rates in the growth zone of primary cotton roots: Effects of Na Cl and Ca Cl2
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Auteurs :
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H. Zhong ;
A. Lauchli
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Type de document :
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article/chapitre/communication
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Année de publication :
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1994
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Format :
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34-41
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Langues:
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= Anglais
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Mots-clés:
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calcium
;
Gossypium
;
root
;
solutes
;
salinity
;
stress
;
solute
;
deposition
;
Croissance
;
Cinematique
;
Vitesse de depot
;
Stress
;
Element mineral
;
Gossypium hirsutum
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Résumé :
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Cotton (Gossypium hirsutum L. cv. Acala SJ-2) seedlings were grown in modified Hoagland nutrient solution with or without 150 m M Na Cl and supplemental 10 m M Ca Cl2. The spatial distribution of bulk-tissue osmotic potential (Psi(s)) and total osmotica, K, Na and Ca contents were determined in the growth zone of the primary root. This information was combined with the growth-velocity data from an earlier study (Zhong and Lauchli 1993) to estimate net deposition rates of osmoticum, water, K, Na and Ca by using the continuity equation. The Psi(s) was essentially uniform along the growth region for all treatments and considerably lowered by 150 m M Na Cl in the medium. Total osmotica deposition was well synchronized with growth and deposition rates were enhanced by 150 m M Na Cl. Osmoregulation in the treatments with 150 m M Na Cl was indicated by an apparent solute accumulation which appeared to be due to the enhancement of osmoticum deposition rates. The presence of 150 m M Na Cl greatly reduced the deposition rates of K and Ca throughout the growth zone; 10 m M Ca mitigated this effect only on K deposition in the apical 2.5-mm region. The deposition rate of Na was increased greatly by 150 m M Na Cl; the increase was reduced by 10 m M Ca. At 150 m M Na Cl, selectivity of K versus Na of the root was enhanced greatly in the apical 2 mm region by the presence of 10 m M Ca; this mitigating effect by Ca declined rapidly with distance from the root tip. We conclude that one possible mechanism by which supplemental Ca alleviates the inhibitory effects of Na Cl on cotton root growth is by maintaining plasma-membrane selectivity of K over Na.
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Source :
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Planta - 0032-0935, vol. 194, n° 1
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