Frankiewicz K E, Chau J H, Baczyński J, Wdowiak A, Oskolski A
Institute of Evolutionary Biology, Faculty of Biology, Biological and Chemical Research Centre, University of Warsaw, Żwirki i Wigury 101, 02-089 Warsaw, Poland.
Centre for Ecological Genomics and Wildlife Conservation, Department of Zoology, University of Johannesburg, PO Box 524, Auckland Park 2006, Johannesburg, South Africa.
AoB Plants. 2023 Jan 24;15(2):plad003. doi: 10.1093/aobpla/plad003. eCollection 2023 Feb.
Bark (all tissues outside of the vascular cambium) has been extensively studied in recent years, especially its anatomy and physiology. Macromorphological bark characters can be important taxonomically for many plant groups, including the genus (Scrophulariaceae). However, the relationship between macroscopic bark appearance and its microscopic structure remains obscure, hampering the use and interpretation of bark traits in plant taxonomy and phylogenetics as well as in other fields of botany. We studied micro- and macrostructure of bark in the species of representing wide taxonomic and geographic diversity to identify general relationships between bark anatomy and morphology. We also examined xylem and discussed the importance of anatomical traits for understanding the relationships between clades in this genus. The smooth bark surface in sect. and the outgroup ( spp.) relates to the small number of periderms of superficial origin and limited sclerification. This allows for the retention of visible lenticels. In the rest of , bark sloughs off and division of labour is present: collapsed phloem undergoes sclerification and acts as a protective layer, while thin-walled phellem forms the separation layers. A similar pattern is found in some groups (e.g. ), but in others (e.g. and the species of with stringy bark), the pattern is inversed. Wood and bark anatomy supports a sister relationship between the southern African section and the rest of but is taxonomically uninformative among remaining clades. Limited development of periderms and sclerification allows for the retention of a smooth bark surface and conspicuous lenticels. Sloughing off of bark requires division of labour into a lignified protective layer and a thin-walled separation layer. These two functions are never served by a single tissue but are rather divided between phloem and periderm. How more subtle features (e.g. size and shape of fissures) are determined requires further study. Simultaneously, bark anatomy could be a useful source of data to complement molecular phylogenetic studies in a total evidence approach for systematics.
近年来，树皮（维管形成层以外的所有组织）受到了广泛研究，尤其是其解剖学和生理学。对于许多植物类群，包括玄参科（Scrophulariaceae）的某些属而言，宏观形态学的树皮特征在分类学上可能具有重要意义。然而，宏观树皮外观与其微观结构之间的关系仍不明确，这阻碍了树皮特征在植物分类学、系统发育学以及植物学其他领域中的应用和解读。我们研究了玄参科代表广泛分类和地理多样性的物种的树皮微观和宏观结构，以确定树皮解剖结构与形态之间的一般关系。我们还研究了木质部，并讨论了解剖特征对于理解该属各分支之间关系的重要性。玄参科中某组以及外类群（某些物种）的树皮表面光滑，这与起源于表层的周皮数量少和硬化程度有限有关。这使得可见的皮孔得以保留。在玄参科的其他部分，树皮会脱落且存在分工：塌陷的韧皮部发生硬化并起到保护层的作用，而薄壁的木栓形成分离层。在一些类群（如某些物种）中也发现了类似模式，但在其他类群（如某些具有丝状树皮的物种）中，模式则相反。木材和树皮解剖结构支持了南部非洲的某组与玄参科其他部分之间的姐妹关系，但在其余分支之间的分类学上并无信息价值。周皮和硬化的有限发育使得树皮表面保持光滑且皮孔明显。树皮脱落需要分工形成木质化的保护层和薄壁的分离层。这两种功能从未由单一组织承担，而是在韧皮部和周皮之间划分。更细微的特征（如裂缝的大小和形状）是如何确定的还需要进一步研究。同时，树皮解剖结构可能是一个有用的数据来源，可在系统发育学的全证据方法中补充分子系统发育研究。
