Analysis of fast chlorophyll fluorescence rise (O-K-J-I-P) curves in green fruits indicates electron flow limitations at the donor side of PSII and the acceptor sides of both photosystems
Analysis of fast chlorophyll fluorescence rise (O-K-J-I-P) curves in green fruits indicates electron flow limitations at the donor side of PSII and the acceptor sides of both photosystems
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DOI：
10.1111/j.1399-3054.2010.01362.x
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发表时间：
2010-07-01
影响因子：
6.4
通讯作者：
Manetas, Yiannis
中科院分区：
文献类型：
--
作者：
Kalachanis, Dimitrios;Manetas, Yiannis
到目前为止，有限的证据表明，低线性光合电子流和CO2同化率在非叶叶绿体。在这项调查中，我们使用叶绿素荧光技术来定位可能的限制步骤，在暴露的，非胁迫绿色水果（果皮和种子）的三个物种，而相应的叶子作为对照。与叶片相比，果实光合作用的特点是少的光子捕获和电子流的量子产率，而非光化学猝灭较高，并可能与增强类胡萝卜素/叶绿素的比例。快速叶绿素荧光上升曲线的分析揭示了光系统II（PSII）的供体（释氧复合物）和受体（Q（A）-->中间载体）侧可能存在的限制，表明PSII的光化学活性天生较低。另一方面，PSI的特点是其最终电子受体的还原速度更快，其池尺寸小。我们认为，最终PSI电子受体的快速还原饱和可能会转移电子回到中间载体，促进PSI周围的循环流动，而线性流动的部分失活排除了质体醌的强还原。因此，果实叶绿体的光合作用属性可以起到补充由于缺氧而损失的ATP的作用，缺氧通常发生在对气体交换具有高扩散阻力的库器官中。
Limited evidence up to now indicates low linear photosynthetic electron flow and CO2 assimilation rates in non-foliar chloroplasts. In this investigation, we used chlorophyll fluorescence techniques to locate possible limiting steps in photosystem function in exposed, non-stressed green fruits (both pericarps and seeds) of three species, while corresponding leaves served as controls. Compared with leaves, fruit photosynthesis was characterized by less photon trapping and less quantum yields of electron flow, while the non-photochemical quenching was higher and potentially linked to enhanced carotenoid/chlorophyll ratios. Analysis of fast chlorophyll fluorescence rise curves revealed possible limitations both in the donor (oxygen evolving complex) and the acceptor (Q(A)--> intermediate carriers) sides of photosystem II (PSII) indicating innately low PSII photochemical activity. On the other hand, PSI was characterized by faster reduction of its final electron acceptors and their small pool sizes. We argue that the fast reductive saturation of final PSI electron acceptors may divert electrons back to intermediate carriers facilitating a cyclic flow around PSI, while the partial inactivation of linear flow precludes strong reduction of plastoquinone. As such, the photosynthetic attributes of fruit chloroplasts may act to replenish the ATP lost because of hypoxia usually encountered in sink organs with high diffusive resistance to gas exchange.