Photosystem II efficiency and mechanisms of energy dissipation in iron-deficient, field-grown pear trees (Pyrus communis L.)
Photosystem II efficiency and mechanisms of energy dissipation in iron-deficient, field-grown pear trees (Pyrus communis L.)
复制标题
缺铁条件下田间种植梨树（西洋梨）光系统II的效率及能量耗散机制
DOI：
10.1023/a:1006389915424
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发表时间：
2004
影响因子：
3.7
通讯作者：
F. Morales;R. Belkhodja;A. Abadı́a;J. Abadía
中科院分区：
文献类型：
--
作者：
F. Morales;R. Belkhodja;A. Abadı́a;J. Abadía
田间梨树叶片的暗适应光系统II效率由可变到最大的叶绿素荧光比率估算，受中度和重度缺铁的影响很小。只有极度缺铁的叶片在暗适应后表现出光系统II效率的降低。缺铁叶片在短期暗适应后，光系统II效率午间仍有下降，说明当叶片受到过量光照时，光系统II发生了下调。由于光系统II反应中心的关闭和固有的光系统II效率的降低，稳态光合作用的实际光系统II效率因清晨和中午的缺铁而降低。缺铁不仅通过降低吸收系数，而且通过增加光系统II天线的热耗散光的相对量，减少了超过光合作用所能使用的光量。与对照相比，在清晨和中午，缺铁的梨叶对光系统II吸收的光的热消散要高出20%。在弱光缺铁条件下，紫黄质循环色素/叶绿素比值高的叶片，色素脱环氧化、非光化学猝灭和热耗散增加。我们的数据表明，Δ的pH可能是控制热能耗散的主要因素，缺铁引起的玉米黄质和黄质与叶绿素摩尔比的较大变化(超过10倍)仅与光保护程度的适度增加有关。
The dark-adapted Photosystem II efficiency of field-grown pear leaves, estimated by the variable to maximum chlorophyll fluorescence ratio, was little affected by moderate and severe iron deficiency. Only extremely iron-deficient leaves showed a decreased Photosystem II efficiency after dark adaptation. Midday depressions in Photosystem II efficiency were still found after short-term dark-adaptation in iron-deficient leaves, indicating that Photosystem II down-regulation occurred when the leaves were illuminated by excessive irradiance. The actual Photosystem II efficiency at steady-state photosynthesis was decreased by iron deficiency both early in the morning and at midday, due to closure of Photosystem II reaction centers and decreases of the intrinsic Photosystem II efficiency. Iron deficiency decreased the amount of light in excess of that which can be used in photosynthesis not only by decreasing absorptance, but also by increasing the relative amount of light dissipated thermally by the Photosystem II antenna. When compared to the controls, iron-deficient pear leaves dissipated thermally up to 20% more of the light absorbed by the Photosystem II, both early in the morning and at midday. At low light iron-deficient leaves with high violaxanthin cycle pigments to chlorophyll ratios had increases in pigment de-epoxidation, non-photochemical quenching and thermal dissipation. Our data suggest that ΔpH could be the major factor controlling thermal energy dissipation, and that large (more than 10-fold) changes in the zeaxanthin plus antheraxanthin to chlorophyll molar ratio caused by iron deficiency were associated only to moderate increases in the extent of photoprotection.