Circadian Rhythm of Carbon Dioxide Production by Anthurium Flowers

A circadian rhythm in CO2 production was observed in three cultivars of Anthurium andraeanum Andre (‘Jaya’, ‘Fla-range’, ‘Leonette’) flowers. The rhythmicity was not affected by light, darkness, and detachment. However, the amplitude was dampened in darkness and after detachment. Spadix respiration accounted for 90% of the total flower respiration. Rhythmicity in CO2 production continued after spathe removal. Less pronounced rhythmicity was observed following spadix removal. Anthurium is widely cultivated for its attractive and long-lasting flowers. Research on anthurium physiology has focused mainly on its nutrition (Joiner et al., 1983), tissue culture (George and Sherrington, 1984), and postharvest handling (Pritchard et al., 1991; Shirakawa et al., 1964). Few studies have been done on anthurium respiration (Paull et al., 1985; Pritchard et al., 1991; Salisbury and Ross, 1992), particularly in relation to growth, development, and postharvest behavior, which is surprising in view of the uniqueness of aroid respiration (Meeuse, 1966, 1975). Interest in aroid respiration began following the pioneering work of Van Herk in 1937 (Beevers, 1961). Aroid respiration is remarkable because of its high rate and resistance to cyanide (Beevers, 1961; Meeuse, 1966, 1975). We report here the effects of light, dark, and detachment on the rhythmic CO2 production of three cultivars of Anthurium andraeanum flowers. Materials and Methods Anthurium ‘Jaya’ was grown under partial shade in the garden of the Botany Dept., National Univ. of Singapore. Two other anthurium cultivars, ‘Fla-range’ and ‘Loenette’, were obtained from Multico Orchids Pte, Singapore. The plants were transported in an airconditioned van to the laboratory on the day of the experiment and kept under a 12-h photoperiod. Light was supplied by a Philip mercury lamp (HPLR-N 700 W; Philip, Holland) The light intensity measured at plant height was 300 μmol•m•s, and the room temperature was at 22 ± 1C. Unless otherwise stated, respiration of mature, intact (attached) flowers was studied. The CO2 production of intact anthurium flowers was continuously measured with an open gas-flow system (Hew et al., 1978). The CO2 concentration in the gas stream was meaHORTSCIENCE, VOL. 29(9), SEPTEMBER 1994 Received for publication 10 Sept. 1993. Accepted for publication 5 Mar. 1994. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact. sured with an infrared CO2 analyzer (Analytical Development Co., Herts, U.K.). The respiration chamber was made of plexiglass with a removable top to allow the introduction of the flower, and a small groove was cut in one of the side walls to hold the peduncle. The air temperature around the flower was controlled by continuous circulation of water into a water Fig. 1. Diurnal rhythmicity of CO2 production by intact (A) ‘Jaya’ and (B) ‘Loenette’ and ‘Fla-range’. No and three cycles, respectively. jacket surrounding the chamber, while the water temperature was kept constant using a temperature-controlled water circulator (Thermomix, Braun, Melsungen AG, Germany). The leaf temperature was measured by pressing a thermocouple (module 80TK; John Fluke Manufacturing Co., Everett, Wash.) close to the lower surface of the leaf. The difference in leaf temperature during light and dark exposure was <1C. For removal of either spadix or spathe from intact flowers, the top of the respiration chamber was opened after one cycle of respiration measurement, and the spadix or spathe was carefully removed without disturbing the remaining flower parts. In the experiment with detached flowers, respiration of the intact flower was measured for one cycle. At the end of the first cycle, the flower was excised, immediately recut under water, and placed in a plastic tube containing water. Carbon dioxide production was measured mainly with ‘Jaya’. All determinations were carried out with at least three flowers. As the pattern of rhythmic CO2 production in each of the three determinations was the same, data of only one are presented. 1025 flowers of three cultivars of Anthurium andraeanum te that time scale differs for A and B; they have four