HEAT-PRODUCTION BY SACRED LOTUS FLOWERS DEPENDS ON AMBIENT-TEMPERATURE, NOT LIGHT CYCLE

Flowers of the sacred lotus, Nelumbo nucifera, maintain receptacle tem perature (T-r) between about 30 degrees C and 36 degrees C during thei r 2-4 d sequence of anthesis by increasing the rate of heat production , measured as oxygen consumption ((V) over dot o(2)), at low ambient t emperature (T-a) at night and reducing it at high T-a during the day. The effects of T-a and photoperiod on (V) over dot o(2) were separated by manipulating T-a around outdoor flowers under natural photoperiod or constant darkness. There was no effect of time of day on either T-r or (V) over dot o(2), but both depended on T-a. Rising T-a resulted i n an increase in T-r, a brief upward spike in (V) over dot o(2), follo wed by a long-term decrease in (V) over dot o(2) Decreasing T-a had th e opposite effects: a decrease in T-r and a brief depression, followed by a slow rise, in (V) over dot o(2) The two-phase responses to sudde n T-a change indicate a rapid, mass-action effect and a slower, regula tory adjustment. Temperature regulation continued in constant darkness for over 3 d.