Characteristics of the Uptake Mechanism of Chloride Ions in Excised Roots of a Woody Plant (Citrus)

A. ALTMAN*, K. MENDEL

*Corresponding author for this work

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12 Scopus citations

Abstract

The characteristics of the uptake mechanism of chloride ions in citrus (Citrus spp.) were studied in excised, high‐salt, roots as to the nature of the isotherm at a wide range of uptake durations and Cl concentrations. In addition, the effects of metabolic inhibitors, low temperature and various treatments were studied, and compared with Cl uptake in excised roots of wheat (Triticum vlgare) under the same conditions. It was found that the uptake mechanism in excised roots of citrus differs considerably from that in wheat: (1) the rate of active uptake from 10 mM NaCl in citrus is 2.0 to 4.3 umol Cl per g dry weight and h (vs. 35.5 umol in wheat); (2) there is no saturation of the system even at high external concentrations (up to 90 mM), and uptake is continuous; (3) uptake in citrus is less sensitive to KCN and dinitro‐phenol. In addition, it was noted that the age of citrus seedlings and the initial chloride content of both citrus and wheat roots markedly affected Cl uptake. The data were analyzed in the light of the dual mechanism hypothesis of ion uptake, and it was concluded that only system 2 (high Km), is operating in the excised citrus roots studied. This is in accordance with the conditions prevailing in the field (whence the plant material was collected): high concentration of the soil solution in contact with the roots, and high salt status of the tissue. It is further suggested that the uptake of ions in citrus (and presumably in other perennial woody plants), is related to its growth habits and to the size and morphology of the root systems.

Original languageEnglish
Pages (from-to)157-162
Number of pages6
JournalPhysiologia Plantarum
Volume29
Issue number2
DOIs
StatePublished - Oct 1973

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