PHYSIOLOGICAL TEMPERATURE REGULATION BY FLOWERS OF THE SACRED LOTUS

Flowers of the sacred lotus, Nelumbo nucifera Gaertn. (Nelumbonaceae) are thermogenic and physiologically thermoregulatory. The 42 g flowers remain between 30-36 degrees C during a 2-4-day period despite fluctu ations in environmental temperatures between about 10-45 degrees C. As the ambient temperature drops, the flowers increase heat production i n proportion. Temperature regulation apparently occurs at a cellular l evel, by a steep, reversible thermal inhibition of respiration at flow er temperatures above 30 degrees C. There was a marked time lag betwee n change in flower temperature and compensatory response, suggesting r egulation through a biochemical feedback mechanism rather than structu ral changes in enzymes or membranes. By oxidizing carbohydrate, the fl owers produce up to 1 W with about half of the heat coming from the 8. 5 g carpellary receptacle. The period of temperature regulation begins before petal opening and continues through the period of stigma recep tivity. Temperature regulation may reward insect pollinators with a wa rm, equable environment, or it possibly enhances and coordinates flowe r development.