Dual Control of Flower Initiation and Development by Temperature and Photoperiod in Hardenbergia violacea

Abstract

Exposure to both short-day photoperiods (< 12.5 h daily) and cool temperatures (15–18°C) is optimal for inflorescence initiation and development in the woody perennial Hardenbergia violacea (Scheeve) Stearn, an Australian leguminous plant species. After 9–12 weeks exposure to inductive conditions the inflorescences were 1–2 cm long and floral organ primordia were evident. At this stage of development, transferring plants to warmer conditions (e.g. 22°C) and/or long days led to flower bud abortion, abscission of the inflorescence and a resumption of vegetative growth within 30 days. Conversely, flowers opened with continued exposure to short days. Flower initiation and development of this Hardenbergia selection (cultivar Mini haha) is thus restricted to a narrow temperature range (15–18°C) in combination with a requirement for exposure to short days. Such complexity must be important in adaptation of Hardenbergia to its environment.