Thermogenesis and respiration of inflorescences of the dead horse arum Helicodiceros muscivorus, a pseudo-thermoregulatory aroid associated with fly pollination

Abstract

1. In central Corsica, Helicodiceros muscivorus (Schott ex. K. Koch) produces a protogynous inflorescence that resembles the anal area of a dead mammal and produces a foetid scent during the few hours after sunrise. Flies enter the floral chamber, pollinate the female florets and become trapped until the next morning, when pollen is shed from the male florets and the flies are released. 2. The exposed appendix exhibits a strong, unimodal episode of thermogenesis associated with scent production, reaching a maximum of 30 ° C at 15 ° C ambient temperature. The male florets in the floral chamber are highly thermogenic throughout the second night and generally maintain stable floret temperatures of about 24 ° C at ambient temperatures down to 13 ° C. 3. Maximum respiration rates of the appendix (0·45 μ mol CO 2 s − 1 g − 1 ) and the male florets (0·82 μ mol s − 1 g − 1 ) may be the highest recorded for plant tissue. 4. Thermogenesis of the appendix does not depend on ambient temperature, but that of the male florets increases with decreasing ambient temperature in most cases. However, the pattern of heat production by the males appears related more to time than to ambient temperature, hence the term ‘pseudo-thermoregulation’. 5 . The behaviour and thoracic temperatures of flies emerging from captivity suggests that male floral warming does not enhance their activity.