CONCURRENT MEASUREMENTS OF OXYGEN AND CARBON-DIOXIDE EXCHANGE DURING LIGHTFLECKS IN MAIZE (ZEA-MAYS L)
CONCURRENT MEASUREMENTS OF OXYGEN AND CARBON-DIOXIDE EXCHANGE DURING LIGHTFLECKS IN MAIZE (ZEA-MAYS L)
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DOI：
10.1104/pp.103.3.823
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发表时间：
1993-11-01
期刊：
影响因子：
7.4
通讯作者：
PEARCY, RW
中科院分区：
文献类型：
--
作者：
KRALL, JP;PEARCY, RW
玉米（Zea mays L.）在35 Pa（350 μ bar）CO2和0.2 kPa（0.2%）O-2下，将其封闭在温控比色皿中，并暴露于短时间（1-30 s）的照明（光闪烁）。测定了CO_2同化速率和总同化量以及O-_2释放量。O-2释放速率被认为是光合非循环电子传递速率（NCET）的一个指标。在这个C-4物种，电子传递的响应在lightfecks定性模仿的C-3物种以前测试，而CO2同化的响应不同。在高光子通量密度（PFD）的短时光照条件下，由于光斑形成初期的O-2释放爆发，O-2释放的平均速率大于相同PFD条件下的稳态O-2释放速率.这种O-2爆发被认为表明高水平的NCET通过ATP、NADPH和还原或磷酸化代谢物参与同化电荷的积累。然而，随着光斑持续时间的减少，每单位时间光斑的CO2同化量（CO2同化的平均速率）下降。在低PFD光照开始时，叶片中也有CO2的爆发，这进一步降低了这些光照期间的同化作用。结果进行了讨论，在同化电荷的积累，通过合成的高能量代谢产物特定的C-4代谢。据推测，相对于C-3物种，C-4物种在短暂的光瞬变期间碳吸收的效率低下是由于C-4循环中间体的无效合成。
Leaves of maize (Zea mays L.) were enclosed in a temperature-controlled cuvette under 35 Pa (350 mu bars) CO2 and 0.2 kPa (0.2%) O-2 and exposed to short periods (1-30 s) of illumination (light-flecks). The rate and total amount of CO2 assimilated and O-2 evolved were measured. The O-2 evolution rate was taken as an indicator of the rate of photosynthetic noncyclic electron transport (NCET). In this C-4 species, the response of electron transport during the lightfecks qualitatively mimicked that of C-3 species previously tested, whereas the response of CO2 assimilation differed. Under short-duration lightflecks at high photon flux density (PFD), the mean rate of O-2 evolution was greater than the steady-state rate of O-2 evolution under the same PFD due to a burst of O-2 evolution at the beginning of the lightfleck. This O-2 burst was taken as indicating a high level of NCET involved in the buildup of assimilatory charge via ATP, NADPH, and reduced or phosphorylated metabolites. However, as lightfleck duration decreased, the amount of CO2 assimilated per unit time of the lightfleck (the mean rate of CO2 assimilation) decreased. There was also a burst of CO2 from the leaf at the beginning of low-PFD lightflecks that further reduced the assimilation during these lightflecks. The results are discussed in terms of the buildup of assimilatory charge through the synthesis of high-energy metabolites specific to C-4 metabolism. It is speculated that the inefficiency of carbon uptake during brief light transients in the C-4 species, relative to C-3 species, is due to the futile synthesis of C-4 cycle intermediates.