Graves J D, Taylor K
Department of Biology, Darwin Building, University College London, Gower Street, London WCI 6BT, U.K.
New Phytol. 1988 Mar;108(3):297-304. doi: 10.1111/j.1469-8137.1988.tb04166.x.
Geum urbanum and G. rivale are a sympatric interfertile pair of species with contrasting distributions. Geum rivale occurs at higher altitudes and more northerly latitudes than G. urbanum. As part of a study to determine the factors responsible for this difference in distribution, a comparison of the carbon economy of the two species was made. The light and temperature dependence of photosynthesis was assessed for plants of both species grown in contrasting light and temperature regimes. Acclimation to the prevailing environmental conditions was more pronounced in G. urbanum. Amongst populations of the two species originating from different altitudes the temperature optimum for photosynthesis was similar. When grown at 25/16 °C, higher rates of respiration were measured he roots of G. rivale at all temperatures, when pretreated at 8/5 °C there was a smaller increase in the rate of respiration in the roots of G. rivale. It is proposed that these differences in root respiration account for observed higher root growth rates at low temperatures in G. rivale. It is concluded that whilst carbon assimilation is not a critical factor determining the upper altitudinal limit of G. urbanum, the pattern of carbon utilization may be important. The greater phenotypic plasticity observed in G. urbanum, may be of value for survival in the herb layer of deciduous woodland where it is most commonly found.
城水杨梅和沼生水杨梅是一对同域分布且可杂交的物种，分布情况形成对比。沼生水杨梅比城水杨梅生长在更高海拔和更靠北的纬度地区。作为确定造成这种分布差异因素研究的一部分，对这两个物种的碳经济进行了比较。在不同光照和温度条件下生长的两个物种的植株，评估了光合作用对光照和温度的依赖性。城水杨梅对当前环境条件的适应性更为明显。在来自不同海拔的两个物种的种群中，光合作用的最适温度相似。当在25/16°C下生长时，在所有温度下沼生水杨梅根部的呼吸速率都更高，当在8/5°C预处理时，沼生水杨梅根部呼吸速率的增加较小。有人提出，根部呼吸的这些差异解释了沼生水杨梅在低温下观察到的较高根生长速率。得出的结论是，虽然碳同化不是决定城水杨梅海拔上限的关键因素，但碳利用模式可能很重要。在城水杨梅中观察到的更大表型可塑性，可能对其最常见的落叶林草本层中的生存具有价值。
