THE RESPONSE OF ACHILLEA MILLEFOLIUM L. (YARROW) TO SHADING

Abstract

Growth analysis was used to assess the response of vegetative rosettes of Achillea millefolium L. (yarrow) to shading in the range of full daylight irradiance to a relative level of irradiance (r.l.i.) of 0–064. As functions of time, SLA, LWR, NAR and RGR showed more or less pronounced ontogenetic drifts which interacted with r.l.i. As functions of total dry weight, these interactions were greatly diminished. At dry weights from 1.53 to 4.0 g, the response of RGR to shading was characterized by a plateau between full daylight and approx. 0.40 r.l.i. owing to increases in SLA and LWR compensating for a reduction in NAR. Relative growth rate then fell steeply to a compensation point of O.o37 r.l.i. It was concluded that A. millefolium is considerably tolerant of shading and an ecological interpretation is given. Copyright © 1984, Wiley Blackwell. All rights reserved