Exogenous induction of thermogenesis in Arum concinnatum by salicylic acid

Arum concinnatum Schott is a highly thermogenic species, with the temperature of the appendix exceeding ~10.9°C above the ambient temperature during thermogenesis, whereas the rates of respiration of the male florets in intact inflorescences peak at 0.92μmol s-1 g-1, which is the highest rate so far measured among the plants. Here, we attempt the ex situ exogenous induction of thermogenesis in whole inflorescences and in separate appendices of the spadix, and explore the thermogenic patterns under controlled laboratory conditions of light and temperature. Mature but unopened inflorescences and appendices showed thermogenic responses when treated with salicylic acid (SA), but not when treated with distilled water (control). With regard to light conditions, the responses revealed only one significant difference for inflorescences, which concerns the higher maximum temperature in the continuous light treatment compared with continuous dark. Along the ambient temperature gradient, at the lowest temperature edge individuals remained stable close to ambient temperature and to control. These findings suggest that, in general, ex situ exogenous induction of thermogenesis can be achieved in whole inflorescences and in separate appendices of spadix of A. concinnatum using SA. This study also indicates that SA acts independently of light conditions, while exogenous induction of thermogenesis takes place within an ambient temperature range.