Forseth I N, Ehleringer J R
Department of Biology, University of Utah, 84112, Salt Lake City, Utah, USA.
Oecologia. 1982 Jan;54(1):41-49. doi: 10.1007/BF00541105.
The seasonal course of water relations in field populations of two leaf solar tracking desert winter annuals was examined. Measurements were made of leaf movements in relation to leaf conductance and water potential. Malvastrum rotundifolium maintained solar tracking movements up to the wilting point of the plant (-4 MPa). Lupinus arizonicus altered its morphology through paraheliotropic leaf movements as leaf water potentials declined to-1.8 MPa. Diurnal patterns of leaf conductance showed marked seasonal trends, with gas exchange activity being restricted to early morning hours as water availability declined. Studies of potted plants showed that L. arizonicus was not able to alter its osmotic potential in response to drought, while M. rotundifolium underwent a 1.86 MPa reduction in osmotic potential. The significance of the two contrasting patterns is discussed in terms of observed plant distribution and origin.
研究了两种叶片进行太阳追踪的沙漠冬季一年生植物田间种群水分关系的季节性变化过程。测量了与叶片导度和水势相关的叶片运动。圆叶赛葵在植株萎蔫点（-4兆帕）之前一直保持太阳追踪运动。随着叶片水势降至-1.8兆帕，亚利桑那羽扇豆通过避日性叶片运动改变其形态。叶片导度的日变化模式呈现出明显的季节性趋势，随着水分可利用性下降，气体交换活动仅限于清晨时段。盆栽植物研究表明，亚利桑那羽扇豆无法响应干旱改变其渗透势，而圆叶赛葵的渗透势降低了1.86兆帕。根据观察到的植物分布和起源，讨论了这两种截然不同模式的意义。
