Plant Response to Saline Substrates V. Chloride Regulation in the Individual Organs of Hordeum Vulgare During Treatment with Sodium Chloride

Abstract

This is a study on the regulation of chloride concentrations in H. vulgare at the early tillering stage, when grown on media of high sodium chloride concentration. C136 was used during certain periods to determine retranslocation. Chloride, which had been absorbed either during the first 5 days, or between the fifth and tenth day of sodium chloride treatment, was not lost from the whole plant during subsequent periods, and this chloride moved to the shoot. Over the same period there was further chloride uptake from the medium. Developed leaves lost only small amounts of chloride by retranslocation and the concurrent intake far exceeded this loss. Evidence is presented that low concentrations in younger leaves are due to low morality of chloride already taken up by older organs of the shoot, and not to a chloride exclusion by younger organs. It is concluded that chloride contents within the shoot of H. vulgare are regulated at two locations: (1) During transfer from the root to the shoot. (2) During translocation from older to younger organs. In growing organs, ion concentrations depend not only on the rates of ion uptake but also on relative growth rates, i.e. ion concentrations at any one time are higher at low than at high relative growth rates. This interaction between growth and ion concentration is discussed in relation to ion imbalance, osmotic adjustments, and salt tolerance.