CO_2 assimilation-governing mechanisms based on the balance in chemical energy produced and consumed in the photosynthetic process.

本研究通过将叶片CO_2交换速率与光合系统与CO_2同化之间的化学能生产-消耗平衡联系起来，了解CO_2同化调控机制。(1)测定了不同CO_2、O_2浓度和光照强度组合下，绿豆叶片在间隔20 s开/关的间歇光照条件下的CER的时间过程。通过计算点亮（20s）时刻产生的能量和熄灭（20s）时刻吸收的co2质量，估计了间歇光照对Rubisco （RuBP羧化酶/加氧酶）活性的影响。在高光强的间歇照明下，由于CO_2可以利用光照时刻积累的能量在熄灯时刻被吸收，从而提高了光利用率。CO_2和O_2浓度不同，Rubisco的光活化水平也不同。不同环境条件下羧化酶和加氧酶的相对活性不同，影响了间歇光照下植物的CER和光能利用效率。(2)为了更清楚地解释光系统与CO_2同化系统之间的作用平衡，研究了CER与叶绿素荧光猝灭的关系。改进的测量工具巧妙地组合在一起，使两个因素同时测定。在绿豆叶片中，光呼吸的能量消耗明显影响光合作用的CER和潜在能量利用效率。

This study was conducted to understand the CO_2 assimilation-governing mechanism by relating the leaf CER (CO_2 exchange rate) with the chemical energy production-consumption balance between photosystem and CO_2 assimilation. (1) CER of mungbean leaves were determined as a time course under the intermittent illumination with 20 second-intervals of light on/off in the different combinations of CO_2 and O_2 concentrations and light intensities. Based on the calculation of the energy produced at the light-on (20s) moments and the weight of CO_2 assimilated at the light-off (20s) moments, the effect of the intermittent illumination on the Rubisco (RuBP Carboxylase/Oxygenase) activity was estimated. CER or light utilization efficiency was increased at the intermittent illumination in high light intensities, because CO_2 was possible to be assimilated at the light-off moments by using the accumulated energy at the light-on moments. Light activation level of Rubisco varied with CO_2 and O_2 concentrations. The relative activity between carboxylase and oxygenase differed depending on the environmental conditions, affecting the CER and light utilization efficiency at the intermittent illumination. (2) Then, to get more clear explain for the action balance between photosystem and CO_2 assimilation system, the relationships between CER and chlorophyll fluorescence quenching were studied. The improved measurement tools were skillfully assembled to make a simultaneous determination of both factors. It was evident in mungbean leaves that the energy consumption by photorespiration significantly affected, in relation to environmental factors, both CER and the potimal energy utilization efficiency in photosynthesis.