Eickmeier William G
Department of General Biology, Vanderbilt University, 37235, Nashville, Tennessee, USA.
Oecologia. 1979 Jan;39(1):93-106. doi: 10.1007/BF00346000.
Photosynthetic recovery (PR) in a southwest Texas, USA population of Selaginella lepidophylla (Hook and Grev.) (Selaginellaceae), a poikilohydric spikemoss, was examined in the laboratory. Infrared CO gas analysis and ribulose 1,5-bisphosphate (RuBP) carboxylase activity measurements indicated that optimal temperature for PR was near 25°C in terms of: (1) rapidity of net CO uptake after hydration (5.4 h), (2) maximum net photosynthetic rate at 2000 μE·m·s (2.44 mg CO·g(DWT)·h), and (3) maximum net CO assimilation per 30 h hydration event (43.8 mg CO·g(DWT)·30 h). The PR was much slower at both 15° and 35° C, with lower photosynthetic rates and net carbon gains per hydration event. High respiratory costs were incurred at 45°C and no net photosynthesis was observed. Increases in RuBP carboxylase activity and chlorophyll content during 24 h hydration were also greatest near 25°C. Dry plants had 60% of the enzyme activity of fully recovered (24 h hydration) plants, indicating enzyme conservation. Actinomycin D and cycloheximide did not appear to inhibit PR, but chloramphenicol appeared to totally inhibit RuBP carboxylase activity increases over levels conserved in dry plants. Therefore, rapid PR in S. lepidophylla was achieved by both rapid increase in RuBP carboxylase activity, possibly via de novo synthesis, and conservation of the photosynthetic enzyme. Both mechanisms are essential to maximize assimilation in S. lepidophylla in an environment where hydrated periods are rare and of short duration.
在美国得克萨斯州西南部的卷柏（卷柏科）种群中，对变水型卷柏的光合恢复（PR）进行了实验室研究。红外CO₂气体分析和1,5-二磷酸核酮糖（RuBP）羧化酶活性测量表明，PR的最适温度接近25°C，依据如下：（1）水化后（5.4小时）净CO₂吸收的速度；（2）在2000μE·m⁻²·s⁻¹光照强度下的最大净光合速率（2.44mg CO₂·g（干重）⁻¹·h⁻¹）；（3）每30小时水化事件的最大净CO₂同化量（43.8mg CO₂·g（干重）⁻¹·30 h⁻¹）。在15°C和35°C时，PR都要慢得多，每次水化事件的光合速率和净碳增益都较低。在45°C时呼吸成本很高，未观察到净光合作用。在24小时水化过程中，RuBP羧化酶活性和叶绿素含量的增加在25°C附近也最大。干燥植株的酶活性是完全恢复（水化24小时）植株的60%，表明酶得以保存。放线菌素D和环己酰亚胺似乎不抑制PR，但氯霉素似乎完全抑制RuBP羧化酶活性超过干燥植株中保存的水平的增加。因此，卷柏的快速PR是通过RuBP羧化酶活性的快速增加（可能是通过从头合成）和光合酶的保存来实现的。在水化期稀少且持续时间短的环境中，这两种机制对于卷柏最大限度地进行同化都是必不可少的。
