Phototolerance of lichens, mosses and higher plants in an alpine environment: analysis of photoreactions
Phototolerance of lichens, mosses and higher plants in an alpine environment: analysis of photoreactions
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DOI：
10.1007/s004250000356
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发表时间：
2000-11-01
期刊：
影响因子：
4.3
通讯作者：
Lange, OL
中科院分区：
文献类型：
--
作者：
Heber, U;Bilger, W;Lange, OL
适应过度的光是在高山环境中生存的要求之一，特别是对于与高等植物的叶子相比耐受完全脱水的多水生物。在地衣Xanthoria elegans（Link）Th。Fr.和Rumbercarpon geographicum（L.）DC，在苔藓Grimmia alpestris Limpr。以及高等植物Geum montanum L.，黄花龙胆和豌豆，所有这些都是在海拔2000米以上的高度采集的。在脱水状态下，地衣和苔藓中的叶绿素荧光非常低，但高等植物中的叶绿素荧光很高。它增加了复水的地衣和苔藓，但在高等植物减少。光诱导的电荷分离光系统II的脉冲诱导的荧光增加，仅在干叶片，而不是在干苔藓和干地衣。强光照引起光损伤的干叶片，但不是在干苔藓和干地衣。在820-nm吸收光依赖性的增加揭示形成潜在的猝灭剂的叶绿素荧光在所有脱水植物，但能量转移到猝灭剂降低叶绿素荧光只有在苔藓和地衣，而不是在高等植物。在水合系统中，耦合的循环电子传输被认为是同时发生的线性电子传输下，强烈的光化照明，特别是在地衣，因为更多的电子成为光化照明后，光氧化的P700的还原比可在光系统II和I之间的电子载体池。在苔藓Grimmia，但不是在地衣或叶片中，光依赖的叶绿素荧光淬灭是广泛的，即使在氮，表明厌氧类囊体酸化持续循环电子传递。在没有光化照射的情况下，通过ca. 8%CO_2对苔藓和地衣的初始荧光强度F_0有猝灭作用，而对高等植物的叶片无猝灭作用。在相同条件下，8%CO_2使多水生物的最大荧光产额F-m显著降低，而对叶片的影响很小或完全不降低。这些数据表明，存在的失活途径，使polykilohydric生物体，以避免光损伤，不仅在水合，而且在脱水状态。在水合状态下，强烈的非光化学猝灭叶绿素荧光表示高度敏感的反应，过量的光，促进无害的耗散吸收的激发能量转化为热量。质子依赖的荧光猝灭的循环电子传递，P700氧化，并可能，激发光系统之间的转移相结合，产生光耐受性。
Adaptation to excessive light is one of the requirements of survival in an alpine environment particularly for poikilohydric organisms which in contrast to the leaves of higher plants tolerate full dehydration. Changes in modulated chlorophyll fluorescence and 820-nm absorption were investigated in the lichens Xanthoria elegans (Link) Th. Fr. and Rhizocarpon geographicum (L.) DC, in the moss Grimmia alpestris Limpr. and the higher plants Geum montanum L., Gentiana lutea L. and Pisum sativum L., all collected at altitudes higher than 2000 m above sea level. In the dehydrated state, chlorophyll fluorescence was very low in the lichens and the moss, but high in the higher plants. It increased on rehydration in the lichens and the moss, but decreased in the higher plants. Light-induced charge separation in photosystem II was indicated by pulse-induced fluorescence increases only in dried leaves, not in the dry moss and dry lichens. Strong illumination caused photodamage in the dried leaves, but not in the dry moss and dry lichens. Light-dependent increases in 820-nm absorption revealed formation of potential quenchers of chlorophyll fluorescence in all dehydrated plants, but energy transfer to quenchers decreased chlorophyll fluorescence only in the moss and the lichens, not in the higher plants. In hydrated systems, coupled cyclic electron transport is suggested to occur concurrently with linear electron transport under strong actinic illumination particularly in the lichens because far more electrons became available after actinic illumination for the reduction of photo-oxidized P700 than were available in the pool of electron carriers between photosystems II and I. In the moss Grimmia, but not in the lichens or in leaves, light-dependent quenching of chlorophyll fluorescence was extensive even under nitrogen, indicating anaerobic thylakoid acidification by persistent cyclic electron transport. In the absence of actinic illumination, acidification by ca. 8% CO2 in air quenched the initial chlorophyll fluorescence yield F-o only in the hydrated moss and the lichens, not in leaves of the higher plants. Under the same conditions, 8% CO2 reduced the maximal fluorescence yield F-m strongly in the poikilohydric organisms, but only weakly or not at all in leaves. The data indicate the existence of deactivation pathways which enable poikilohydric organisms to avoid photodamage not only in the hydrated but also in the dehydrated state. In the hydrated state, strong nonphotochemical quenching of chlorophyll fluorescence indicated highly sensitive responses to excess light which facilitated the harmless dissipation of absorbed excitation energy into heat. Protonation-dependent fluorescence quenching by cyclic electron transport, P700 oxidation and, possibly, excitation transfer between the photosystems were combined to produce phototolerance.