Variations in the stable carbon isotope compositions of individual lipids from the leaves of modern angiosperms: Implications for the study of higher land plant-derived sedimentary organic matter
Variations in the stable carbon isotope compositions of individual lipids from the leaves of modern angiosperms: Implications for the study of higher land plant-derived sedimentary organic matter
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DOI：
10.1016/s0146-6380(96)00135-0
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发表时间：
1997-01-01
影响因子：
3
通讯作者：
Evershed, RP
中科院分区：
文献类型：
--
作者：
Lockheart, MJ;VanBergen, PF;Evershed, RP
研究了几种树种叶子中各个脂质的 δ(13)C 值的季节性变化，以便为今后陆源沉积有机质同位素特征的研究提供必要的背景信息。桦木、栗叶栎和山毛榉的正构烷烃显示，与生长季节开始时取样的叶子相比，秋季叶子中的 δ(13)C 有所增加。每月从 Q.castaneifolia 和 F.sylvatica 采集的样品显示，在整个生长季节，大量组织中的 C-13 和正构烷烃逐渐减少。这可能是由于回收耗尽的内部碳以替换风化的蜡，或由于夏季气温升高而通过核酮糖 1,5-二磷酸羧化酶增加了对 C-13 的分馏的结果。谷甾醇在 F. sylvatica 中表现出与正构烷烃相似的同位素趋势，但在 Q. castaneifolia 中却表现出相反的行为。研究了阳光强度对 delta(13)C 的影响，在 Q. robur 和 F. sylvatica 两个脚趾周围的不同罗盘位置取样的叶子中进行了研究。内荫叶的大块组织和脂质的 C-13 含量始终比相应的阳叶的大块组织和脂质消耗更多。平均接受最高阳光辐照度的叶子，即南方叶子，在脂质和块体组织中表现出最低的δ(13)C。 δ(13)C 值随辐照度水平的变化可能是由于光合同化率的变化以及叶表皮和气孔对其光环境的适应的变化。研究发现，栎属植物叶子的脂质和大块组织的 δ(13)C 值略高于水青冈属植物，但种间变异性相当大。这项研究对于研究古代沉积物中保存的陆地来源的有机物具有重要意义。结果表明，在使用沉积物和化石脂质中的同位素变化作为古环境变化的指标之前，阐明影响现代叶子中单个脂质的 delta(13)C 值的环境因素的重要性。 (C) 1997 爱思唯尔科学有限公司。
Seasonal changes in delta(13)C values for individual lipids from the leaves of several species of tree have been studied in order to provide essential background information for use in future investigations of the isotopic signatures of terrigenous sedimentary organic matter. The n-alkanes of Betula ermanii, Quercus castaneifolia and Fagus japonica revealed increased delta(13)C in autumn leaves compared with leaves sampled at the start of the growing season. Samples taken from Q. castaneifolia and F. sylvatica at monthly intervals showed gradual depletion of C-13 in bulk tissues and n-alkanes through the growing season. This may be a consequence of either recycling of depleted internal carbon in order to replace weathered waxes, or increased fractionation against C-13 by the enzyme ribulose 1,5-bisphosphate carboxylase in response to increasing summer temperatures. Sitosterol exhibited similar isotopic trends as the n-alkanes in F. sylvatica, but shelved the opposite behaviour in Q. castaneifolia. The effect of sunlight intensity on delta(13)C was investigated in foliage sampled at different compass positions around two toes, Q. robur and F. sylvatica. Bulk tissue and lipids from inner shade leaves were consistently more depleted in C-13 than those from the corresponding sun leaf. The leaves receiving the highest sunlight irradiance on average, i.e. southern foliage, exhibited the lowest delta(13)C in lipids and bulk tissues. The variability of delta(13)C values with irradiance level may be due to changes in photosynthetic assimilation rates and the adaptation of the leaf epidermis and stomata in response to its light environment. Lipids and bulk tissues from leaves of Quercus species were found to possess slightly more depleted delta(13)C values than those in Fagus species, although interspecies variability was quite large. This study has important implications for the study of terrestrially derived organic matter preserved in ancient sediments. The results demonstrate the importance of elucidating the environmental factors that influence delta(13)C values of individual Lipids in modern leaves prior to using isotopic shifts in sedimentary and fossil lipids as indicators of palaeoenvironmental change. (C) 1997 Elsevier Science Ltd.