Pattern of respiration by intact inflorescences of the thermogenic arum lily Philodendron selloum |
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Authors: | Seymour R |
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Institution: | Department of Environmental Biology, University of Adelaide, Adelaide, SA 5005, Australia; Fax: +61 8 8303 4364; E-mail: rseymour@zoology.adelaide.edu.au |
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Abstract: | Inflorescences of the neotropical arum lily, Philodendron
selloum, are strongly thermogenic for 2 d during anthesis.
Continuous measurements of spadix temperature (Ts) and
rate of oxygen consumption (VO2) were made outdoors in
whole inflorescences attached to the plants. Some inflorescences were
exposed to uncontrolled ambient temperature (Ta) while
others were enclosed in clear water-jackets that produced nearly constant
ambient conditions. A repeatable, diphasic pattern of heat production
appeared, most clearly in water-jacketed inflorescences, and it comprised a
short peak phase at sunset followed by a plateau phase that lasted until
the following sunset. Regulation of Ta occurred in
both phases, but at different levels. Peak phase Ta
was regulated in the region of 38-42 C, but
plateau phase Ta was usually in the range of
25-36 C. Both VO2 and
total heat produced throughout anthesis increased at lower
Ta. The data imply that the short peak phase is
related to the enhancement of odour production that attracts a single
species of large scarabaeid beetle in its native Brazil, and regulation of
maximum Ta may prevent overheating. Thermoregulation
in the long plateau phase produces equable temperatures inside the
inflorescence that may facilitate the resident beetles' activities as a
direct energetic reward. |
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