Three issues were investigated; first, the influence of virus on pigment production in diseased plants; second, the increase of virus as indicated by a resulting change in carotene concentration; third, the function of pigments other than chlorophyll in photosynthesis in young potato leaves. Results on the first issue demonstrated an increase in carotene and xanthophyll concentration, and a decrease in chlorophyll concentration in diseased relative to normal plants. Evidence on the second issue suggested a close relationship between virus increase and carotene concentration. Data on the third issue indicated a soil and possibly significant photosynthesis due to leaf carotenoids / Thesis / Master of Science (MS)