Spatial distribution of solutes, K, Na, Ca and their deposition rates in the growth zone of primary cotton roots: Effects of NaCl and CaCl2

Abstract

Abstract.Cotton (Gossypium hirsutum L. cv. Acala S J-2) seedlings were grown in modified Hoagland nutrient solution with or without 150 mM NaC1 and supplemental 10 mM CaC12. The spatial distribution of bulk-tissue osmotic potential (U?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 L/iuchli 1993) to estimate net deposition rates of osmoticum, water, K, Na and Ca by using the continuity equation. The u?~ was essentially uniform along the growth region for all treatments and considerably lowered by 150 mM NaC1 in the medium. Total osmotica deposition was well synchronized with growth and deposition rates were enhanced by 150 mM NaC1. Osmoregulation in the treatments with 150 mM NaC1 was indicated by an apparent solute accumulation which appeared to be due to the enhancement of osmoticum deposition rates. The presence of 150 mM NaC1 greatly reduced the deposition rates of K and Ca throughout the growth zone; 10 mM 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 mM NaC1; the increase was reduced by 10 mM Ca. At 150 mM NaC1, selectivity of K versus Na of the root was enhanced greatly in the apical 2 mm region by the presence of 10 mM 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 NaC1 on cotton root growth is by maintaining plasma-membrane selectivity of K over Na. *Present address:Department of Integrative Biology, University of California, Berkeley, CA 94720, USA Abbreviations and symbol: HCa, LCa = high (10 mM) and low (1 mM) CaCI2; HNa, LNa = high (150 mM) and low (1 mM) NaC1; T~ = osmotic potential Correspondence to: H. Zhong; FAX: I (510) 643 6264;

Response of wheat plants to sodium and calcium ion interaction under saline environment

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Effects of Salinity on Initial Seedling Growth of Chickpea (Cicer Arietinum L.)

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Arabidopsis CALCINEURIN B-LIKE10 Functions Independently of the SOS Pathway during Reproductive Development in Saline Conditions

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