Plant Biol (Stuttg) 2005; 7(2): 176-181
DOI: 10.1055/s-2005-837541
Research Paper

Georg Thieme Verlag Stuttgart KG · New York

Redundancy of Stomatal Control for the Circadian Photosynthetic Rhythm in Kalanchoë daigremontiana Hamet et Perrier

T. P. Wyka1 , H. M. Duarte2 , U. E. Lüttge2
  • 1Biology Department, General Botany Laboratory, Adam Mickiewicz University, ul. Umultowska 89, 61-614 Poland
  • 2Institut für Botanik, Fachbereich Biologie, Technische Universität-Darmstadt, Schnittspahnstraße 3 - 5, 64287 Darmstadt, Germany
Weitere Informationen

Publikationsverlauf

Received: August 23, 2004

Accepted: January 12, 2005

Publikationsdatum:
11. April 2005 (online)

Abstract

In continuous light, the Crassulacean acid metabolism plant Kalanchoë daigremontiana Hamet et Perrier has a circadian rhythm of gas exchange with peaks occurring during the subjective night. The rhythm of gas exchange is coupled to a weak, reverse phased rhythm of quantum yield of photosystem II (ΦPSII). To test if the rhythm of ΦPSII persists in the absence of stomatal control, leaves were coated with a thin layer of translucent silicone grease which prevented CO2 and H2O exchange. In spite of this treatment, the rhythm of ΦPSII occurred with close to normal phase timing and with a much larger amplitude than in uncoated leaves. The mechanism underlying the ΦPSII rhythm in coated leaves can be explained by a circadian activity of phosphoenolpyruvate carboxylase (PEPC). At peaks of PEPC activity, the small amount of CO2 contained in the coated leaf could have become depleted, preventing the carboxylase activity of Rubisco and causing decreases in electron transport rates (observed as deep troughs of ΦPSII at 23-h in LL and at ca. 24-h intervals afterwards). Peaks of ΦPSII would be caused by a downregulation of PEPC leading to improved supply of CO2 to Rubisco. Substrate limitation of photochemistry at 23 h (trough of ΦPSII) was also suggested by the weak response of ETR in coated leaves to stepwise light enhancement. These results show that photosynthetic rhythmicity in K. daigremontiana is independent of stomatal regulation and may originate in the mesophyll.

References

T. Wyka

Biology Department, General Botany Laboratory
Adam Mickiewicz University

ul. Umultowska 89

61-614 Poznań

Poland

eMail: twyka@amu.edu.pl

Editor: R. Monson

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