Growth of strawberry fruit and sugar uptake of fruit discs at different inflorescence positions

Abstract

The growth of fruit from greenhouse-grown ‘Brighton’ strawberry plants (Fragaria × ananassa Duch.) was analyzed from anthesis to ripening, Absolute growth rates neared a maximum at the onset of ripening when the rates for primary, secondary, tertiary and quaternary fruit were 106, 53, 22 and 3 mg dry weight day−1, respectively. Length, diameter, fresh weight and dry weight were greatest in primary fruit throughout development, and were progressively smaller in fruit at lower rankings. At 15 days after anthesis, fresh weight of secondary, tertiary and quaternary fruit were, respectively, 55, 13 and 3% of primary fruit weight. The amount and rate of fruit expansion, estimated from achene separation, was highest in primary fruit, the maximum rate being over twice that of secondary fruit. Relative growth rate was also highest in primary fruit from anthesis to red-ripe. To relate fruit growth to rates of sucrose uptake, discs of fruit cortex tissue were incubated in 10 mM 14C-sucrose solutions. The rate of sucrose uptake by tissue discs from primary fruit was greater than uptake by secondary or tertiary fruit tissue and similar to the rate of dry matter accumulation in intact fruit. In primary fruit, sucrose uptake reflected dry matter accumulation at increasing ages, the rate of both activities decreasing 60% from 9 to 17 days after anthesis. Results suggest that sucrose uptake may relate to rates of strawberry fruit growth.