Potato Seed-tuber Age Affects Mobilization of Carbohydrate Reserves During Plant Establishment

During the early stages of growth, developing sprouts rely heavilyupon tuber carbohydrate reserves. Strong sprouts are producedfrom young potato (Solaman tuberosum L.) seed-tubers, whereastubers of advanced physiological age produce sprouts with reducedvigour. Single-eye seedcores from 7- and 19-month-old seed-tuberswere sprouted in order to study the effect of tuber age on carbohydratereserve mobilization. Following 24 d of growth, the same amountof total shoot dry matter was produced from both ages of seedcores.However, d. wt of individual shoots from older seedcores was93 % lower than that from younger cores, reflecting a significantloss in apical dominance with age. Furthermore, core d. wt lossper unit gain in plant d. wt was greater from 19-month-old seedcores,indicating an age-related decrease in the efficiency of reservemobilization over the growth interval. During sprouting, ratesof starch hydrolysis and subsequent increases in total solublecarbohydrates were similar for both tuber ages. Reducing sugars(mg g d. wt^–1) accumulated faster in older than in youngercores; non-reducing sugars (mainly sucrose) decreased 53% inolder seedcores over the 24 d growth interval. Non-reducingsugar content (mg g d. wt^–1, mg core^–1) of youngercores remained constant. The results suggest that older coresare either less efficient at converting glucose to sucrose (themain translocatable carbohydrate in potatoes) or have higherrates of sucrose hydrolysis (e.g. increased invertase activity)compared with younger tuber tissues during sprouting Potatoes (Solanum tuberosum L.), seed-tuber age, carbohydrate mobilization, plant growth potential