Effect of far-red light, temperature, and plant age on morphological changes and induction of flowering of a ‘June-bearing’ strawberry

Abstract

The main purpose of this study was to investigate the effects of supplementary far-red light on floral induction in the strawberry (Fragaria × ananassa Duch.). The plants were grown in summer conditions with natural daylight and an end-of-day far-red (EOD FR; 735 nm) light treatment. In experiments 1 and 2, the plants were exposed to EOD FR for 0, 2, 4, and 6 h daily for 8, 16, 24, and 32 days in July and August. In experiment 3, plants aged 8-, 10-, and 12-weeks old were treated with 32 daily cycles of EOD FR for 6 h. The plants exposed to high temperatures in July did not flower, although their morphological traits were altered by EOD FR. In the cooler temperatures of August, besides significant morphological changes, plants exposed to 6 h of EOD FR for 32 daily cycles produced flowers. The last experiment revealed a significant induction of flowering in the 12-week-old runner plants, which was absent in the younger plants. These results clearly demonstrate the effect of EOD FR treatment duration, temperature, and plant age on morphological traits and flowering. It can be concluded that flowering in 12-week old and older ‘Paros’ strawberries can be induced by 32 daily cycles of 735 nm far-red light in August and September.