Aims of this investigation were to determine whether chlorophyll fluorescence values obtained from excised leaves of woody perennials subjected to salinity stress under laboratory conditions provided a measurable indicator of whole plant salinity tolerance. Laboratory tests consisted of measurements of the ratio of variable to maximal chlorophyll fluorescence (Fv/Fm) performed on excised leaves taken from thirty woody perennials following immersion in salt solutions ranging from concentrations of 2% to 7%. Based on reductions in Fv/Fm of excised leaves following salinity treatments plants were ranked in order of tolerance. Whole plants of six of the thirty species tested were then subjected to a foliar applied salt at a concentration of 7% and placed under glass for 14 weeks. Damage to, and recovery of whole plants from salt damage as measured by chlorophyll fluorescence, leaf necrosis and chlorophyll content mirrored tolerance ranking of excised leaves under laboratory conditions. In addition, based on reductions in plant growth at the cessation of the experiment, salt tolerance followed a similar order as that obtained from Fv/Fm values of excised leaves. Results indicate that testing of excised leaf material of woody perennials under laboratory conditions using chlorophyll fluorescence offers a potentially quick, reliable and inexpensive procedure that can provide a useful means of estimating whole plant salt tolerance.

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The total glycoalkaloid concentration of dormant (non-sprouted) and sprouted potato tubers cv Pentland Hawk was measured following 13 days continuous illumination (250 pmol m -' s-photosynthetically active radiation) using high-performance liquid chromatography. Comparisons were made of the influence of three sources of illumination : high-pressure mercury, high-pressure sodium and fluorescent tube type warm white. Glycoalkaloid concentrations in both dormant and sprouted tubers increased over 13 days illumination regardless of the form of illumination used. Glycoalkaloid concentrations accumulated with time in dormant and sprouted tubers exposed to sodium and fluorescent light but fluctuated in those exposed to mercury light. Dormant tubers were more sensitive to illumination than sprouted tubers regardless of light souce. Fluorescent light was associated with maximum glycoalkaloid synthesis in dormant tubers; while sodium light enhanced glycoalkaloid synthesis in sprouted tubers to the greatest extent. Mercury light weakly elicited glycoalkaloid synthesis in both sets of tubers. Exposure of dormant tubers to continuous light altered the ratio of a-chaconine to a-solanine irrespective of illumination source.

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