GLYCOALKALOID CONCENTRATION OF POTATO-TUBERS FOLLOWING CONTINUOUS ILLUMINATION

The total glycoalkaloid concentration of dormant (non-sprouted) and sp routed potato tubers cv Pentland Hawk was measured following 13 days c ontinous illumination (250 mu mol m(-2) s(-2) photosynthetically activ e radiation) using high-performance liquid chromatography. Comparisons were made of the influence of three sources of illumination: high-pre ssure mercury, high-pressure sodium and fluorescent tube type warm whi te. Glycoalkaloid concentrations in both dormant and sprouted tubers i ncreased over 13 days illumination regardless of the form of illuminat ion used. Glycoalkaloid concentrations accumulated with time in dorman t and sprouted tubers exposed to mercury light. Dormant tubers were mo re sensitive to illumination than sprouted tubers regardless of light source. Fluorescent light was associated with maximum glycoalkaloid sy nthesis in dormant tubers; while sodium light enhanced glycoalkaloid s ynthesis in sprouted tubers to the greatest extent. Mercury light weak ly elicited glycoalkaloid synthesis in both sets of tubers. Exposure o f dormant tubers to continous light altered the ratio of alpha-chaconi ne to alpha-solanine irrespective of illumination source.