EFFECT OF TEMPERATURE ON THE SIZE OF STRAWBERRY FRUIT

Strawberry, Fragaria Xananassa Duch. cv. Toyonoka, plants were grown f rom October onward in two glasshouses where the air temperature was co ntrolled at either 15-degrees or 19-degrees-C night and day. Several d ays after pollination, the diameter of all the fruits in the first inf lorescence (truss) was measured at approximately two-day intervals, an d fully red ripe fruits were sampled. The growth of the fruits showed a double sigmoidal curve in all ranks of the inflorescence at both tem peratures. The growth was faster in the higher rank fruits that develo ped earlier and at 19-degrees-C than in the lower rank fruits and at 1 5-degrees-C. Fresh and dry weight per fruit was larger in the higher r ank fruits and at 15-degrees-C (mean of all fruits; 0.879 g DW) than i n the lower rank fruits and at 19-degrees-C (mean of all fruits; 0.774 g DW). The total numbers of ripe fruits per inflorescence (plant) wer e slightly smaller at 19-degrees-C. The values of the total fruit fres h and dry weight per inflorescence (plant) were much lower at 19-degre es-C. The bearing fruit period from the flowering of the first flower to the ripening of the last fruit in the inflorescence was 88 days at 15-degrees-C and 69 days at 19-degrees-C, respectively. The daily dry weight increments of total fruit in the inflorescence (per plant) were 0.170 g at 15-degrees-C and 0.151 g at 19-degrees-C. It was considere d that the small size of the fruits at a high temperature like 19-degr ees-C was not caused by the increase in the number of fruits, but by t he low rate of dry matter accumulation in fruit.