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CO2交换速率(CER)与光系统和CO2同化之间的化学能生产-消耗平衡联系起来，来了解CO2同化的调控机制。(1)在不同CO_2、O_2浓度和光照强度组合下，间歇光照20秒，测定了绿豆叶片的CER。通过计算开灯时刻(20s)产生的能量和关灯时刻(20s)吸收的CO2质量，估计了间歇光照对Rubisco(RuBP羧基酶/加氧酶)活性的影响。在高光强下，间歇光照可提高CER或光能利用率，这是因为利用开灯时刻积累的能量，可以在关灯时刻吸收CO2。Rubisco的光激活程度随CO_2和O_2浓度的变化而变化。不同环境条件下，羧基酶和加氧酶的相对活性不同，影响间歇光照下的CER和光能利用效率。(2)为了更好地解释光系统与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。改进后的测量工具被巧妙地组装在一起，以同时测定这两个因素。在绿豆叶片中，光呼吸能量消耗显著影响光合作用的CER和光合作用的最大能量利用效率，与环境因子相关。

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.