Photothermal effects on corm and flower development in Anemone coronaria L.

The effect of photoperiod, thermoperiod and corm characteristics on corm and flower development in Anemone coronaria L. were studied under controlled conditions using a hybrid cultivar ('Hollandia' × Israeli wild type) possessing summer dormancy inducible by long days (LD) and/or high temperatures. Corm differentiation did not require photothermal induction and occurred very early in seedling development. The size of the corm at the end of the growth cycle (dormancy onset) was the net result of the differential effects of day length and temperature on its growth rate and growth period. LD of 16 h promoted corm growth rate compared with short days (SD) of 8 h, but high temperature and LD reduced its final size owing to the earlier induction of dormancy. A direct relationship existed between the phenological state that the plants attained in the field at the time of corm harvest and the responsiveness to subsequent dormancy induction by LD. The later the corms became dormant in the field and the larger their size, the less responsive were the plants to subsequent dormancy induction. However, the phenological state and the weight of the corms did not affect the time to flowering or the proportion of the plants that reached flowering under LD (77%) or SD (95%) conditions. Larger corms produced more shoots and flowers per corm, but the number of flowers produced per shoot was unaffected by initial corm weight. Flower size (scape length and perianth diameter) was reduced by high temperature under both LD and SD, but flowers were larger under LD. Smaller corms tended to produce large flowers.