Changes in Vegetative Growth and Stored Carbohydrate Contents in Roots as Influenced by Winter Chilling under Light or Shade of June-bearing Strawberry Plants

Abstract

June-bearing strawberry plants (Fragaria × ananassa, cv. Hokowase) were exposed to winter chilling for 47 days under light or shade and then forced at 25°/20 °C (day/night) under a 15-hr photoperiod. The plants were harvested at 14-day intervals and changes in the vegetative growth and stored carbohydrate contents in the roots were noted.
Petiole lengths and areas of new leaves of chilled plants which unfolded under forcing conditions were larger than those of the unchilled control plants, especially at higher leaf positions. Winter chilling did not precondition root growth to increase under forcing conditions.
Under the light treatment, reducing sugar and sucrose levels (mg•g^-1 dry wt) of roots increased during winter chilling, while the starch level remained unchanged. Under the shade treatment, the sucrose level in the roots significantly increased during winter chilling, with a concomitant decrease of the starch level. Although all inflorescences were removed as they emerged, the amount of stored carbohydrates in roots (mg per roots) decreased rapidly during the first 14 days of forcing, irrespective of the treatments except for starch in shade treatment.
In the roots of shaded plants, the sucrose level at the onset of forcing was only 40% of roots of exposed plants. However, reduction of the sucrose during the first 14 days of forcing was insignificant between the treatments.