Plant Response to Saline Substrates VIII. Regulation of Ion Concentrations in Salt-Sensitive and Halophytic Species

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Abstract
Concurrent uptake and export of ions were measured in a very salt-sensitive species, Phaseolus vulgaris, and in a halophyte, Atrlplex. Li plants with high chloride and sodium concentrations, whole plants, shoots, and older leaves exported only a small percentage of previously absorbed ions. However, chloride retranslocation from older leaves was appreciable in plants of low chloride concentrations. Similar results were obtained previously for a salt-tolerant non-halophyte (Hordeum vulgare). Thus these halophytes and non-halophytes do not differ in the characteristics measured. Halophytes like Atrlplex have a better regulation of their ion concentrations, for example, in the older leaves; this is not due to export but seems primarily related to continued growth and increased succulence. In Phaseolus vulgarls, chloride taken up during the first 4 days of treatment with sodium chloride was released more rapidly from roots than from stems and petioles. Stems and petioles retained a large proportion of the previously absorbed chloride during the subsequent 19 days of treatment.