Temperature and growth regulator effects on growth and development of strawberry (Fragaria x ananassa Duch.)

Abstract

Changes in concentration/composition of carbohydrate and hormones in different plant parts have been related with photoperiod and temperature, which are considered major factors regulating growth and development in strawberry (Fragaria x ananassa Duch.). The major objectives of this research were to determine how the exposure of detached and attached strawberry plants to differential temperatures may affect carbohydrate concentration/composition, and plant growth and development, and to examine flower and runner production patterns in plants exposed to growth regulators. In growth chamber experiments, under floral inductive conditions growth regulators either had no affect or decreased floral initiation, compared to the control. Under non-inductive conditions for flowering, growth regulators either decreased leaf number or increased runner length and daughter plant number. In field experiments, most growth regulator treatments did not increase total flower number. No consistent early flowering or fruit production was obtained by using growth regulators in the conditions of these experiments. Northern (Canada) grown ‘Sweet Charlie’ transplants had greater initial soluble carbohydrate concentration in the crown and roots, greater root starch concentration, and increased early and total marketable yields, fruit number, and average fruit weight compared with southern (Florida) grown transplants. Hence, better yielding performance of northern grown transplants might be related to a greater carbohydrate concentration, especially in the roots. In experiments where mother/daughter plants were grown at the same temperature, attachment and high temperature decreased root soluble carbohydrate concentration and promoted runner formation in mother and daughter plants, suggesting that changes in carbohydrate concentration in the roots may be correlated with changes in vegetative growth. In experiments where attached mother/daughter plants were grown in differential temperature regimes, daughter plants affected flowering in mother plants, and mother plants affected vegetative growth in daughter plants. High temperatures enhanced vegetative growth while lower temperatures enhanced flowering. These results suggest that growth and development in attached strawberry plants are affected by the growth conditions of both the older and the younger plant, that temperature is as important as photoperiod and that carbohydrate concentration in the roots is sensitive to temperature. Further research needs to be done in order to clarify the relationship between hormones, temperature, carbohydrates and plant growth and development in strawberry.