Can the progressive increase of C4 bundle sheath leakiness at low PFD be explained by incomplete suppression of photorespiration?
Can the progressive increase of C4 bundle sheath leakiness at low PFD be explained by incomplete suppression of photorespiration?
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DOI：
10.1111/j.1365-3040.2010.02196.x
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发表时间：
2010-11-01
影响因子：
7.3
通讯作者：
Schepers, Hans E.
中科院分区：
文献类型：
--
作者：
Kromdijk, Johannes;Griffiths, Howard;Schepers, Hans E.
在Rubisco周围集中二氧化碳的能力使C-4作物能够抑制光呼吸。然而，由于磷酸烯醇式丙酮酸的再生需要ATP，在低光合通量密度(PFD)下C-4途径的能量效率成为叶肉(M)细胞的初级固定和CO2浓度与束鞘(BS)细胞的CO2减少之间的平衡。在低PFD时，相对于M细胞中重碳酸盐固定率(称为渗漏Phi)，BS细胞中二氧化碳的反向扩散被认为是增加的。在不完全抑制光呼吸的条件下，测定了250mmolm-2 S 1pfd(HL)和750mmolm-2 S 1pfd(HL)下生长的玉米幼苗在不同O-2分压下对phi的PFD响应。PHI在低PFD时升高，并与氧分压呈正相关。在生长过程中，低PFD导致与HL相比，LL植株的BS电导和脉间距离较低，这与较低的phi相关。模型分析表明，光呼吸的不完全抑制，特别是在HL植物中，以及低PFD时线粒体呼吸相对贡献的增加可以解释观察到的phi增加。
The ability to concentrate CO2 around Rubisco allows C-4 crops to suppress photorespiration. However, as phosphoenolpyruvate regeneration requires ATP, the energetic efficiency of the C-4 pathway at low photosynthetic flux densities (PFD) becomes a balancing act between primary fixation and concentration of CO2 in mesophyll (M) cells, and CO2 reduction in bundle sheath (BS) cells. At low PFD, retro-diffusion of CO2 from BS cells, relative to the rate of bicarbonate fixation in M cells (termed leakiness phi), is known to increase. This paper investigates whether this increase in phi could be explained by incomplete inhibition of photorespiration.The PFD response of phi was measured at various O-2 partial pressures in young Zea mays plants grown at 250 (LL) and 750 mu mol m-2 s-1 PFD (HL). phi increased at low PFD and was positively correlated with O-2 partial pressure. Low PFD during growth caused BS conductance and interveinal distance to be lower in the LL plants, compared to the HL plants, which correlated with lower phi. Model analysis showed that incomplete inhibition of photorespiration, especially in the HL plants, and an increase in the relative contribution of mitochondrial respiration at low PFD could explain the observed increases in phi.