GLYCOALKALOID CONCENTRATION OF POTATO-TUBERS FOLLOWING CONTINUOUS ILLUMINATION

The total glycoalkaloid concentration of dormant (non-sprouted) and sprouted potato tubers cv Pentland Hawk was measured following 13 days continous illumination (250 mu mol m(-2) s(-2) 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 mercury light. Dormant tubers were more sensitive to illumination than sprouted tubers regardless of light source. 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 continous light altered the ratio of alpha-chaconine to alpha-solanine irrespective of illumination source.