IN-VIVO PHOTOSYNTHETIC ELECTRON-TRANSPORT DOES NOT LIMIT PHOTOSYNTHETIC CAPACITY IN PHOSPHATE-DEFICIENT SUNFLOWER AND MAIZE LEAVES
IN-VIVO PHOTOSYNTHETIC ELECTRON-TRANSPORT DOES NOT LIMIT PHOTOSYNTHETIC CAPACITY IN PHOSPHATE-DEFICIENT SUNFLOWER AND MAIZE LEAVES
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DOI：
10.1111/j.1365-3040.1993.tb00500.x
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发表时间：
1993-09-01
影响因子：
7.3
通讯作者：
LAWLOR, DW
中科院分区：
文献类型：
--
作者：
JACOB, J;LAWLOR, DW
研究了在受控环境条件下生长的向日葵（Helianthus annuus）和玉米（Zea maays）叶片生长过程中极度缺磷（Pi）对腺苷酸和吡啶核苷酸含量以及光系统II （PSII）体内光化学活性的影响。缺磷降低了单位叶面积ATP和ADP的含量，降低了叶片腺苷酸能荷。单位叶面积氧化吡啶核苷酸的数量随着缺磷而减少，但还原吡啶核苷酸的数量没有减少。这导致pi缺乏叶片中还原与氧化吡啶核苷酸的比例增加。室温下叶绿素a荧光分析表明，缺乏Pi降低了开放PSII反应中心的激发捕获效率（phi(e)）、PSII光化学的体内量子产率（phi(PSII)）和光化学猝灭系数（q(P)），增加了非光化学猝灭系数（q(N)），表明PSII可能受到光抑制损伤。向缺乏Pi的向日葵叶片提供Pi可逆转Pi缺乏对PSII光化学的长期影响。用甘露糖或FCCP喂养富含pi的向日葵叶片，对叶绿素a荧光的影响与长期pi缺乏相似。我们的研究结果表明，在光合机制对π缺乏的长期和短期反应中，Pi和光磷酸化对PSII光化学的直接作用。在不同光强和环境空气中21 kPa O2和35 Pa CO2分压下测定的phi（PSII）与CO2同化表观量子产率的关系在pi充足和pi缺乏的向日葵和玉米叶片中呈线性关系。计算表明，缺乏pi的叶片每摩尔CO2吸收的PSII活性相对较高。这表明，在这些叶片中，通过PSII传输的光合电子中有更大比例用于除二氧化碳还原外的其他过程。因此，我们得出结论，通过PSII的体内光合电子传递并没有限制向日葵和玉米叶片的光合作用，二氧化碳同化的减少是由于ATP含量减少和能量电荷降低，从而限制了二氧化碳受体核酮糖1-5二磷酸的产生。
The effects of extreme phosphate (Pi) deficiency during growth on the contents of adenylates and pyridine nucleotides and the in vivo photochemical activity of photosystem II (PSII) were determined in leaves of Helianthus annuus and Zea mays grown under controlled environmental conditions. Phosphate deficiency decreased the amounts of ATP and ADP per unit leaf area and the adenylate energy charge of leaves. The amounts of oxidized pyridine nucleotides per unit leaf area decreased with Pi deficiency, but not those of reduced pyridine nucleotides. This resulted in an increase in the ratio of reduced to oxidized pyridine nucleotides in Pi-deficient leaves. Analysis of chlorophyll a fluorescence at room temperature showed that Pi deficiency decreased the efficiency of excitation capture by open PSII reaction centres (phi(e)), the in vivo quantum yield of PSII photochemistry (phi(PSII)) and the photochemical quenching co-efficient (q(P)), and increased the non-photochemical quenching co-efficient (q(N)) indicating possible photoinhibitory damage to PSII. Supplying Pi to Pi-deficient sunflower leaves reversed the long-term effects of Pi-deficiency on PSII photochemistry. Feeding Pi-sufficient sunflower leaves with mannose or FCCP rapidly produced effects on chlorophyll a fluorescence similar to long-term Pi-deficiency. Our results suggest a direct role of Pi and photophosphorylation on PSII photochemistry in both long- and short-term responses of photosynthetic machinery to Pi deficiency. The relationship between phi(PSII) and the apparent quantum yield of CO2 assimilation determined at varying light intensity and 21 kPa O2 and 35 Pa CO2 partial pressures in the ambient air was linear in Pi-sufficient and Pi-deficient leaves of sunflower and maize. Calculations show that there was relatively more PSII activity per mole of CO2 assimilated by the Pi-deficient leaves. This indicates that in these leaves a greater proportion of photosynthetic electrons transported across PSII was used for processes other than CO2 reduction. Therefore, we conclude that in vivo photosynthetic electron transport through PSII did not limit photosynthesis in Pi-deficient leaves of sunflower and maize and that the decreased CO2 assimilation was a consequence of a smaller ATP content and lower energy charge which restricted production of ribulose, 1-5, bisphosphate, the acceptor for CO2.