EFFECTS OF THE PHYSIOLOGICAL AGE OF SEED POTATOES ON TUBER INITIATIONAND STARCH AND DRY-MATTER ACCUMULATION

The physiological age of seed potato tubers (Solanum tuberosum L.) mod ifies several morphological, physiological and agronomic characteristi cs of the crop, However, there is little evidence on the possible infl uence of physiological age upon the mechanism involved in tuber initia tion and starch accumulation. This study investigated the effects of t he physiological age of seed tubers on tuber initiation, starch syntha se activity and dry matter accumulation and distribution. Physiologica lly aged seed potatoes promoted an early tuber initiation in the follo wing crop. Early in the season the stolen tips of these plants showed an increase in starch synthase activity and an anticipated starch accu mulation. During the rest of the season the starch synthase activity i n the stolen tips of tubers grown from young seed was higher than thos e grown from the physiologically older ones, which decreased by day 70 after planting. Dry matter accumulation by leaves and stems did not d iffer between treatments, while tuber dry matter accumulation was high er in those plants originated from physiologically young tubers. These results confirmed that physiologically old seed anticipates tuber ini tiation and demonstrated that the pattern of starch synthase activity, starch accumulation and dry matter accumulation and distribution depe nds on the physiological age of seed tubers.