Photoperiod and temperature effect on growth of strawberry plant (Fragaria x ananassa Duch.): development of a morphological test to assess the dormancy induction
At the end of summer, the diminution of photoperiod and temperature cause a decrease in vegetative growth and the dormancy of strawberry plants. Although the decrease in vegetative growth can be measured morphologically, no test is able to evaluate the decrease in growth potential (during induction of dormancy) nor its possible influence on vegetative growth. Photoperiod and temperature decreases were monitored against the vegetative growth decrease of some cultivars observed in the field (southern France). Results confirmed the major role of photoperiod, temperature and the effect of growth potential decrease on vegetative growth. Moreover, the results showed that the decrease in vegetative growth was an early event at the end of summer which depended upon the cultivar. Petiole length was measured under standard climatic conditions in a growth chamber, after natural summer and autumnal exposures. Observations of strawberry plants under these conditions revealed a decrease in their growth potential which also depended upon cultivar. Results also confirmed the possible action of growth potential decrease on the vegetative growth at the end of the summer. The observation of strawberry plants under standard conditions can be used as a test to assess the exact moment of dormancy induction.