JXB Advance Access published online on November 23, 2007
Journal of Experimental Botany, doi:10.1093/jxb/erm247
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© 2007 The Author(s).
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RESEARCH PAPER |
Evidence for the presence of photorespiration in desiccation-sensitive leaves of the C4 ‘resurrection’ plant Sporobolus stapfianus during dehydration stress
1Dipartimento di Scienze Agronomiche e Gestione del Territorio Agroforestale, Facoltà di Agraria, Università degli Studi di Firenze, 50144 Firenze, Italy
2Unité de Nutrition Azotée des Plantes, INRA, Route de Saint Cyr, F-78000 Versailles, France
3Department of Molecular and Cell Biology, University of Cape Town, Private Bag Rondebosch 7700, South Africa
4Consiglio Nazionale delle Ricerche, Istituto di Biologia Agroambientale e Forestale, Monterotondo Scalo, 00015 Roma, Italy
* To whom correspondence should be addressed. E-mail: tommaso.martinelli{at}unifi.it
The possible role of photorespiration as a general stress protection mechanism, and in C4 plant metabolism, is controversial. In particular, the potential involvement of photorespiration in the acquisition of desiccation tolerance in ‘resurrection’ plants is unknown. An investigation was carried out into whether photorespiration is present in leaves of the C4 resurrection plant Sporobolus stapfianus Gandoger (Poaceae) and whether it functions as a mechanism of stress resistance in the desiccation-tolerant younger leaves (YL) of this plant. It is shown that the enzymes involved in the photorespiratory pathway maintain their activity until 88% relative water content (RWC) in both YL and desiccation-sensitive older leaves (OL). In subsequent stages of dehydration stress, the enzymatic activity declined similarly in both YL and OL. The content of the phorespiratory metabolite, serine, and ethanolamine, a direct product of serine decarboxylation, is higher in the early stages of dehydration (88% RWC) in OL, suggesting a transiently enhanced photorespiratory activity in these leaves. This was confirmed by simultaneous gas exchange and fluorescence measurements, showing suppression of the electron transport rate in OL exposed to non-photorespiratory conditions (2% O2) at 85% RWC. It is concluded that a higher photorespiratory electron transport occurs in desiccation-sensitive OL, and it is therefore proposed that the capacity to scavenge excess electrons through photorespiration does not contribute to protect leaves of the desiccation-tolerant YL of S. stapfianus during the stress.
Key words: Ethanolamine, glycine, photorespiratory enzymes, photosynthesis, poikilohydric plant, serine
Received 5 June 2007; Revised 3 September 2007 Accepted 17 September 2007