title: The dynamics of leaf extension in plants with diverse altitudinal ranges : I. Field observations on temperature responses at one altitude.
abstract: Rates of leaf extension have been studied with electronic auxanometers at mid-altitude in the Austrian Alps, where both low and high altitude species co-occur. The results demonstrate a clear differentiation in the temperature responses of extension between these two groups of species. For the low or mid-altitude species of Achillea millefolium, Agrostis stolonifera, Poa alpina and Rumex arifolius, the average rate of leaf extension increases from 0.1 to 0.4 mm h-1between 10 and 20° C. For the high-alpine species of Achillea erba-rotta ssp moschata, Poa alpina ssp vivipara and Polygonum viviparum the average rate of leaf extension was considerably lower from 0.016 to 0.064 mm h-1, between 10 and 20° C.Leaf extension in the lowland species was not observed below an average temperature of about 5° C, whilst no limit was observed for the upland species, down to a temperature of about 0° C.In the cases of the dicotyledons that were studied, leaf plus petiole shrinkage was observed to occur, for as much as 2 to 4 h, during periods of high water vapour pressure deficits. This response was not observed for the monocotyledons.The observations of leaf extension show that daily totals of extension in species from high altitudies will be much less sensitive to day, to day variations in local climate than will the species from low altitudes. The lowland species will have higher rates of extension during clear and warm weather conditions but lower rates in cold, cloudy weather.
authors.affiliation: Department of Botany, University of Cambridge, Downing Street, CB2 3EA, Cambridge, UK.
authors.forename: F I
authors.initials: FI
authors.lastname: Woodward
authors.affiliation: Institut für Botanik, Universität Innsbruck, Sternwartestrasse 15, A-6020, Innsbruck, Austria.
authors.forename: Ch
authors.initials: C
authors.lastname: Körner
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, 02138, Cambridge, MA, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Crabtree
keywords: Achillea millefolium; Agrostis stolonifera; Asteraceae; Leaf extension; Poaalpina; Poaceae; Polygonaceae; Rumex arifolius; Temperature-Altitude; alpine habitats