For the first time, a cutin-like, highly chemically resistant macropolymer has been isolated from rachises of sp. (lyginopteridalean pteridosperm, Middle Pennsylvanian). Samples are obtained from a cuticular or “paper” coal-shale, i.e., an organic-rich and highly clastic rock associated with the Upper Block Coal Member of the Brazil Formation, Parke County, west-central Indiana, U.S.A. specimens are preserved as naturally oxidized compressions, termed “fossilized cuticles”, and possibly represent vegetation of mineral substrate environments. Employing laboratory oxidation reactions, the fossilized cuticle of rachises is used to obtain the cuticle. After additional and long-term oxidation treatment, the cuticle yields the cutin-like macropolymer, here referred to as “cutin” for simplicity. The fossilized cuticle, cuticle, and cutin samples of sp. are chemically analyzed using semi-quantitative Fourier transform infrared (FTIR) spectroscopy. Cutin IR spectra of rachises are characterized by (a) a predominantly aliphatic composition as indicated by intense aliphatic (CH) CH stretching peaks at 3000–2700 cm, which are assigned to methylene (CH) and methyl (CH) groups; (b) carbonyl (C=O) groups at 1730–1640 cm, and aromatic carbon (C=C) absorption bands at 1600–1500 cm. A comparison with the cuticle, the cutin stands out due to relatively higher values of CH/CH and C=O/C=C, while displaying notably low values of CH/C=O and CC contribution. Specifically, the relatively low value of CH/C=O ratio obtained for the cutin of rachises is consistent with those found in the cutin of extant and fossil leaves. This lower CH/C=O ratio indicates the important role likely played by CO groups in creating a deformable and flexible structure in both the cutin and the cuticle. Such a reduced rigidity suggests a high level of rachis flexibility of the once-living plant, supporting the interpretation of a climbing or liana habit. Cutin isolation and its chemical characterization shed light on the probable biomechanical (flexibility) properties of rachises, thereby enhancing our understanding of the plant growth habit.

中文翻译：

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来自美国印第安纳州“纸”煤的 Karinopteris（宾夕法尼亚中部蕨类植物）的角质化石

首次从 sp. 的轴中分离出一种类角质、高度耐化学性的大分子聚合物。（lyginopteridalean 蕨类植物，中宾夕法尼亚州）。样品取自角质层或“纸质”煤页岩，即与美国印第安纳州中西部帕克县巴西组上区块煤层相关的富含有机物且高度碎屑的岩石，标本以自然状态保存氧化压缩，称为“化石角质层”，可能代表矿物基质环境的植被。采用实验室氧化反应，利用轴的化石角质层来获得角质层。经过额外的长期氧化处理后，角质层产生角质状大分子聚合物，为简单起见，这里称为“角质”。sp. 的角质层化石、角质层和角质样本。使用半定量傅立叶变换红外 (FTIR) 光谱进行化学分析。轴的角质红外光谱的特征在于 (a) 主要为脂肪族成分，如 3000-2700 cm 处强烈的脂肪族 (CH) CH 拉伸峰所示，这些峰属于亚甲基 (CH) 和甲基 (CH) 基团；（b）1730-1640 cm-1 处的羰基（C=O）吸收带，1600-1500 cm-1 处的芳香碳（C=C）吸收带。与角质层相比，角质层由于 CH/CH 和 C=O/C=C 值相对较高而脱颖而出，而 CH/C=O 和 CC 贡献值明显较低。具体而言，在轴的角质中获得的相对较低的CH/C=O比值与在现存和化石叶的角质中发现的值一致。这种较低的 CH/C=O 比率表明 CO 基团可能在角质和角质层中创建可变形且灵活的结构中发挥重要作用。这种刚性的降低表明曾经有生命的植物的轴灵活性很高，支持对攀缘或藤本植物习性的解释。角质分离及其化学表征揭示了轴可能的生物力学（灵活性）特性，从而增强了我们对植物生长习性的了解。