Environmental and physiological factors regulate eryngium planum flowering

Eryngium planum was introduced as a cut flower in Israel 20 years ago. So far, all efforts to hasten and synchronize flowering time have failed. In the present work we study the factors affecting eryngium flowering. We found that variation in flowering time is not caused by genetic variation but probably by physiological factors. Exposure of root cuttings to low temperature (2 °C for 2 months) enhanced the percentage of flowering plants but did not shorten time to flowering. High temperature during growth inhibited flowering in vernalized plants, probably via devernalization. Gibberellic acid (GA₃) had little, if any, effect on either flowering time or quantity. The size of the initiated bud on the root cuttings was related to flowering time and quantity. Plants from vernalized roots with large buds bloomed faster and at a higher percentage than those from roots with smaller buds. It is suggested that the ability to respond to inductive low temperatures is related to the size of the apical meristem, which is correlated to bud size.