Abstract
The duration of pistil differentiation and enlargement on the receptacle of primary flower buds of five strawberry cultivars were investigated to clarify the cause of malformation in 'Ai-Berry'. This clone produces fruits with immature achenes on the distal region of receptacle.
1. 'Ai-Berry' had the largest number of rows of pistils between the base and apex of receptacles. The time interval between the onset of differentiation of the basal to the apical pistils was the longest compared to the other four cultivars. Except for the 'Hokowase', the rate of individual pistil differentiation was more rapid than it was in the other three cultivars. Hence, the duration for the complete differentiation of all pistils was the consequence of the large number of rows.
2. Basal pistils of 'Ai-Berry' grew more rapidly than did those on the apex so that there was a large difference in ovary diameter and stage of development between them at anthesis. Moreover, the number of days from the end of pistil differentiaiton to anthesis was fewer than were those of the four other cultivars. Accordingly, fruit malformaiton in 'Ai-Berry' is a consequence of the pistils on the distal region of receptacle not being mature at anthesis so that they were probably not pollinated and did not set seeds.
3. In 'Hokowase', the duration of pistil differentiation was shortest and the basal pistils compared to the distal ones grew most rapidly among the cultivars examined. Except for the 'Ai-Berry', the difference in ovary diameters between basal and distal pistils was greater in 'Hokowase' than in the other three cultivars.
4. In contrast to 'Ai-Berry' and 'Hokowase', the apical pistils of 'Reiko', 'Toyonoka' and 'Nyoho' grew faster than did those on the base of receptacle. Hence, the difference in ovary diameters between them was not large at anthesis.
