Temperature and Photosynthetic Photon Flux Influence Chrysanthemum Shoot Development and Flower Initiation under Short-day Conditions

Abstract

The effects of photosynthetic photon flux (PPF), day temperature (DT) and night temperature (NT) on leaf number, leaf unfolding rate and shoot length were determined for chrysanthemum ( Dendranthema grandiflora Tzvelev. ‘Bright Golden Anne’) grown under short day (SD) conditions. A functional relationship was first developed to predict if flower bud appearance would occur within 100 SD under a given set of environmental conditions. All combinations of DT and NT in the range from 10° to 30°C were predicted to result in flower bud appearance at higher PPF than 10.8 mol·day −1 ·m −2 . The number of leaves formed below the flower increased quadratically as DT and/or NT increased from 10° to 30°. As PPF increased from 1.8 to 21.6 mol·day −1 ·m −2 , one to two fewer leaves were formed per shoot. Rate of leaf unfolding increased linearly with increasing average daily temperature from 0.2 leaves/day at 10° to 0.5 leaves/day at 30°. Internode length was highly correlated with the difference between DT and NT (DIF = DT – NT) such that increasing DIF from –12° to 12° resulted in progressively longer internodes.