The effect of Ca 2÷ level in the growth medium on the response of germination and early seedling growth of Phaseolus vulgaris to NaC1 salinity was investigated. When NaC1 concentration was increased germination and early seedling growth was decreased. The addition of Ca 2+ to the media increased both germination percentage and seedling growth. Chloride concentrations were not affected by the level of Ca 2+. Potassium and Ca 2+ concentrations and transport from roots to shoots were decreased by NaCl, but were restored by increasing Ca 2+ in the medium. The opposite was true for Na +. Leakage of NO~ and H2PO 4 was increased by salinity and reduced by high Ca 2+ in the medium. The results are discussed in terms of the beneficial effects of calcium for plant growth under saline conditions.

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Abstract. The exogenous application of abscisic acid (ABA) to well-watered plants may be of interest in imitating the effects of salinity on shoot growth. In this paper we have determined the time course of ABA accumulation in control and saltstressed Phaseolus vulgaris plants and its possible relation to the accumulation of solutes and other physiologic conditions. The effect on shoot parameters of the application of exogenous ABA to the root system has also been checked. The addition of exogenous ABA to control plants caused a retardation of growth. The amount of ABA applied to the growth medium caused tissue ABA concentrations to become close to those of salinized plants. The addition of exogenous ABA to plants under control conditions resulted in a profile of proline and total sugar accumulation very similar to that observed in salinized plants. It was also found that NaCl treatment decreased the stomatal conductance and transpiration rate of leaves as well as the osmotic and turgor potentials. The addition of exogenous ABA also mimicked these responses, resulting in qualitatively and quantitatively similar results. These results, particularly those showing that the early transient rise in ABA upon exposure to NaCl coincides with the period of proline and total sugar accumulation, and that treatment of plants with exogenous ABA mimics these effects, are discussed around the idea that ABA stimulates the cellular processes of osmotic adjustment in P. vulgaris.Abscisic acid (ABA) is a ubiquitous molecule in higher plants. It was originally described as a dorAbbreviations: ABA, abscisic acid; HPLC, high performance liquid chromatography; DW, dry weight; FW, fresh weight.

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