VIEWPOINT Plants and Altitude — Revisited J. GALE* Department of Plant Sciences, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel Received: 24 November 2003 Returned for revision: 3 March 2004 Accepted: 28 April 2004 Published electronically: 30 June 2004 The importance of modelling and the integration of all environmental factors as they change with time is emphasized in relation to the evaluation of plant response to altitude. ª 2004 Annals of Botany Company Key words: Altitude, carbon dioxide, oxygen, photosynthesis, transpiration. The physiological ecology, and particularly the leaf gas exchange (mainly CO 2 and O 2 ) of plants growing at high altitude, has been receiving renewed attention (e.g. Smith and Donahue, 1991; Terashima et al ., 1995; Sakata and Yokoi, 2002). In considering the effect of altitude on whole plant physio-logy andecologyallfactorsofthe environment must be taken intoaccount,notonlyleafgasexchangeundersaturatinglight and otherwise optimal conditions. For example, shortwave solar radiation increases with altitude while air temperatures usually, but not always, fall (Gale, 1972 a , b ). For many hours of the day at high elevation the maximum solar radiation may indeed be well above the saturation levels for photosynthesis of C 3 plants. Even so, on clear sky summer days, plants are
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