Induction of Reproductive Growth of Everbearing Strawberry Plants in Dormant Condition by Controlled Temperature and Photoperiod

Abstract

Effects of temperature and photoperiod on vegetative and reproductive growth were investigated in everbearing strawberry (Fragaria×ananassa Duch. cv. 'Summerberry') plants. Runner plants grown in a nursery field until November were transplanted to clay pots, and were grown in growth chambers at a 12-hr day/night setting of 20/15°, 25/20°, and 30/25°C, under either constant light (24-hr, long-day) or an 8-hr (short-day) photoperiod. The treatments were started on December 1. 1. At 30/25°C, the appearance of an inflorescence was inhibited under short-day. By contrast the number of inflorescences was remarkably increased until 10 weeks after the start of the long-day treatment. The production rate of axillary inflorescences which developed from subtended axillary bud without a foliage leaf was increased remarkably under long-day. These results were similar to those of non-dormant plants. 2. At 20/15°C and 25/20°C, more inflorescences were initiated under the long-day than under the short-day treatment. At 20/15°C, the photoperiod was not effective on the development of inflorescences. 3. Under the 8-hr photoperiod, the petioles grew longer at 25/20° and 30/25° than those on plants kept at 20/15°C ; conversely, under the 24-hr photoperiod, the average length of the petioles became shorter at the higher temperatures with time compared to that of plants kept at 20/15°C.