AOBPreview originally published online on February 14, 2006
Annals of Botany 2006 97(5):831-835; doi:10.1093/aob/mcl031
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Stomatal Oscillations in Orange Trees under Natural Climatic Conditions
1 Faculty of Bioscience Engineering, Laboratory of Plant Ecology, Ghent University, Coupure links 653, B-9000 Ghent, Belgium and 2 Agricultural Meteorology Group, Physics Department, University of Zimbabwe, PO Box MP167, Mt Pleasant, Harare, Zimbabwe
* For correspondence. E-mail kathy.steppe{at}UGent.be
Received: 6 October 2005 Returned for revision: 2 November 2005 Accepted: 5 January 2006 Published electronically: 14 February 2006
Background and Aims Stomatal oscillations have been reported in many plant species, but they are usually induced by sudden step changes in the environment when plants are grown under constant conditions. This study shows that in navel orange trees (Citrus sinensis) pronounced stomatal oscillations occur and persist under natural climatic conditions.
Methods Oscillations in stomatal conductance were measured, and related to simultaneous measurements of leaf water potential, and flow rate of sap in the stems of young, potted plants. Cycling was also observed in soil-grown, mature orchard trees, as indicated by sap flow in stem and branches.
Key Results Oscillations in stomatal conductance were caused by the rapid propagation and synchronization of changes in xylem water potential throughout the tree, without rapid changes in atmospheric conditions.
Conclusions The results show marked stomatal oscillations persisting under natural climatic conditions and underscore the need to discover why this phenomenon is so pronounced in orange trees.
Key words: Citrus sinensis, orange tree, sap flow, transpiration, leaf water potential, stomatal conductance, stomatal oscillation, natural climatic conditions