THE EFFECT OF DAYTIME, NIGHTTIME, AND MEA N DIURNAL TEMPERATURES ON THE GROWTH OF MORIOKA-16 STRAWBERRY FRUIT AND PLANTS

Strawberry plants of 'Morioka 16' were grown in growth environments in which the daytime and nighttime temperatures were such that the mean temperatures were : 15-degrees (A), 20-degrees (B) and 25-degrees-C (C ). The diurnal subset temperatures for sets (A), (B), and (C) were : 1 5-degrees/15-degrees-C, 20-degrees/10-degrees-C, and 25-degrees/5-degr ees-C ; 20-degrees/20-degrees-C, 25-degrees/15-degrees-C, and 30-degre es/10-degrees-C; 25-degrees/25-degrees-C, 30-degrees/20-degrees-C, and 35-degrees/15-degrees-C, respectively. The photoperiod for all chambe rs were day (12 hr) and night (12 hr). 1. Fruits from (A) required the most days from anthesis of the primary flower to harvest; but they we re largest, had the highest Brix values, and Brix/acidity ratio, compa red to fruits from sets (B) and (C). Within a set in which the mean di urnal temperature was constant, fruits on plants exposed to warmest da ytime temperatures were the first to ripe even though the night temper atures were the lowest. In sets (B) and (C), the time required from an thesis to harvest became shorter, but the daytime temperatures had les s influence on fruit size. 2. Comparisons among plants in sets (A) 15- degrees/15-degrees-C, (B) 20-degrees/20-degrees-C, and (C) 25-degrees/ 25-degrees-C revealed that the whole plant, terminal inflorescence, an d roots in (A) accumulated the most dry matter; those from (B) were in termediate; whereas the plant and its parts from set (C) accumulated t he least assimilates. 3. Within any set, the position of the flowers o n the terminal inflorescence had a significant effect on the final siz e of the fruit and the number of days from anthesis to harvest. Among the subset, the day- and nighttime temperatures had the greatest effec t. Fruits, resulting from the primary flowers, especially those expose d to the coolest daytime temperature, were always the largest and requ ired the most days from anthesis to harvest.