Harley P C, Tenhunen J D, Beyschlag W, Lange O L
Systems Ecology Research Group, San Diego State University, 92182, San Diego, CA, USA.
Lehrstuhl für Botanik II, Universität Würzburg, Mittlerer Dallenbergweg 64, D-8700, Würzburg, Federal Republic of Germany.
Oecologia. 1987 Dec;74(3):380-388. doi: 10.1007/BF00378934.
During five different periods between Nov. 1982 and Aug. 1983, the diurnal patterns exhibited in photosynthetic CO uptake and stomatal conductance were observed under natural conditions on twigs of Cistus salvifolius, a Mediterranean semi-deciduous shrub which retains a significant proportion of its leaves through the summer drought. During the same periods, net photosynthesis at saturating CO partial pressure was measured on the same twigs as a function of irradiance at different temperatures. From these data, photosynthetic capacity, defined here as the CO- and light-saturated net photosynthesis rate, was obtained as a function of leaf temperature. C. salvifolius is a winter growing species, shoot growth being initiated in Nov. and continuing through May. Photosynthetic capacity was quite high in Nov., March and June, exceeding 40 μmol m s at optimum temperature. In Dec., photosynthetic capacity was somewhat reduced, perhaps due to low night-time temperatures (<5°C) during the measurement period. In Aug., capacity in oversummering shoots at optimum temperature fell to less than 8 μmol m s, due to water trees and perhaps leaf aging. Seasonal changes in maximal photosynthetic rates under ambient conditions were similar, and like those found in co-occurring evergreen sclerophylls. Like the evergreens, Cistus demonstrated considerable stomatal control of transpirational water loss, particularly in oversummering leaves. During each measurement period except Aug. when capacity was quite low, the maximum rates of net photosynthesis measured under ambient conditions were less than half the measured photosynthetic capacities at comparable temperatures, suggesting an apparent excess nitrogen investment in the photosynthetic apparatus.
在1982年11月至1983年8月的五个不同时期，在自然条件下观察了地中海半落叶灌木岩蔷薇（Cistus salvifolius）嫩枝上光合二氧化碳吸收和气孔导度的日变化模式，该灌木在夏季干旱期间保留了相当比例的叶片。在同一时期，在不同温度下，对同一嫩枝在饱和二氧化碳分压下的净光合作用作为光照强度的函数进行了测量。根据这些数据，获得了光合能力，这里定义为二氧化碳和光饱和净光合速率，作为叶片温度的函数。岩蔷薇是一种冬季生长的物种，新梢生长始于11月并持续至5月。11月、3月和6月的光合能力相当高，在最适温度下超过40μmol m⁻² s⁻¹。12月，光合能力有所下降，可能是由于测量期间夜间温度较低（<5°C）。8月，由于水分胁迫和可能的叶片衰老，越夏新梢在最适温度下的光合能力降至低于8μmol m⁻² s⁻¹。环境条件下最大光合速率的季节变化相似，与同时出现的常绿硬叶植物中的情况类似。与常绿植物一样，岩蔷薇对蒸腾失水表现出相当程度的气孔控制，特别是在越夏叶片中。在除8月（此时光合能力很低）之外的每个测量期间，环境条件下测得的净光合最大速率均小于在可比温度下测得的光合能力的一半，这表明光合器官中存在明显的过量氮投资。
