Effects of floral thermogenesis on pollen function in Asian skunk cabbage Symplocarpus renifolius

The effects of temperature on pollen germination and pollen tube growth rate were measured in vitro in thermogenic skunk cabbage, Symplocarpus renifolius Schott ex Tzvelev, and related to floral temperatures in the field. This species has physiologically thermoregulatory spadices that maintain temperatures near 23 degrees C, even in sub-freezing air. Tests at 8, 13, 18, 23, 28 and 33 degrees C showed sharp optima at 23 degrees C for both variables, and practically no development at 8 degrees C. Thermogenesis is therefore a requirement for fertilization in early spring. The narrow temperature tolerance is probably related to a long period of evolution in flowers that thermoregulate within a narrow range.