Simon Jean-Pierre, Potvin Catherine, Strain Boyd R
Départment de Sciences Biologiques, Université de Montréal, 90 Vincent D'Indy, H3C 3J7, Montréal, Québec, Canada.
Department of Botany, Duke University, 27706, Durham, North Carolina, USA.
Oecologia. 1984 Aug;63(2):145-152. doi: 10.1007/BF00379870.
Two populations of Echinochloa crus-galli (Québec, Mississippi) were grown at the Duke University Phytotron under 2 thermoperiods (28°/22°C, 21°/15°C day/night) and 2 CO regimes (350 and 675 μl l). Thermostability, energy of activation (E ),K (PEP), K (Mg), and specific activity of phospho-enol-pyruvate carboxylase (PEP) were analyzed in partially purified enzyme preparations of plants grown for 5 weeks. Thermostability of PEP from extracts (in vitro) and leaves (in situ) was significantly higher in Mississippi plants. In vitro denaturation was not appreciably modified by thermal acclimation but CO enrichment elicited higher thermostability of PEP. In situ thermostability was significantly higher than that of in vitro assays and was higher in Mississippi plants acclimated at 28°/22°C and in plants of the two ecotypes grown at 675 μl l CO. E (Q 30°/20°C) for PEP was significantly lower in Québec plants as compared to Mississippi and no acclimatory shifts were observed. Significantly higher K 's (PEP) in 20°C assays were obtained for Mississippi as compared to Québec plants but values were similar at 30°C and 40°C assays. K (Mg) decreased at higher assay temperatures and were significantly lower for PEP of the Québec ecotype. No significant changes in K (Mg) values were associated with modifications in temperature on CO regimes. PEP activity measured at 30°C was significantly higher for Québec plants when measured on a leaf fresh weight, leaf area or protein basis but not on a chlorophyll basis. Significantly higher PEP activity for both genotypes was observed for plants acclimated at 21°/15°C or grown at 675 μl l CO. Net photosynthesis (Ps) and net assimilation rates (NAR) were higher in Québec plants and were enhanced by CO enrichment. NAR was higher in plants acclimated at low temperature, while an opposite trend was observed for Ps. PEP activities were always in excess of the amounts required to support observed rates of CO assimilation.
将两种稗草种群（魁北克种群、密西西比种群）在杜克大学人工气候室中，于两种温度周期（28°/22°C、21°/15°C昼/夜）和两种二氧化碳浓度条件（350和675 μl l）下培养。对生长5周的植株部分纯化酶制剂中的热稳定性、活化能（E ）、K （磷酸烯醇丙酮酸）、K （镁）以及磷酸烯醇丙酮酸羧化酶（PEP）的比活性进行了分析。密西西比种群植株提取物（体外）和叶片（原位）中PEP的热稳定性显著更高。体外变性并未因热驯化而有明显改变，但二氧化碳浓度升高使PEP的热稳定性更高。原位热稳定性显著高于体外测定值，且在适应28°/22°C的密西西比种群植株以及在675 μl l二氧化碳浓度下生长的两种生态型植株中更高。与密西西比种群相比，魁北克种群植株中PEP的E （Q 30°/20°C）显著更低，且未观察到驯化转变。与魁北克种群植株相比，密西西比种群植株在20°C测定时K '（磷酸烯醇丙酮酸）显著更高，但在30°C和40°C测定时数值相似。K （镁）在较高测定温度下降低，魁北克生态型PEP的K （镁）显著更低。K （镁）值的变化与温度或二氧化碳浓度条件的改变无关。以叶片鲜重、叶面积或蛋白质为基础测定时，魁北克种群植株在30°C下测得的PEP活性显著更高，但以叶绿素为基础测定时并非如此。对于适应21°/15°C或在675 μl l二氧化碳浓度下生长的植株，两种基因型的PEP活性均显著更高。魁北克种群植株的净光合速率（Ps）和净同化率（NAR）更高，且二氧化碳浓度升高使其增强。低温适应植株的NAR更高，而Ps则呈现相反趋势。PEP活性始终超过支持观察到的二氧化碳同化速率所需的量。
