Oskolski Alexei, Vuza Nathi, Shipunov Alexey
Department of Botany and Plant Biotechnology, University of Johannesburg, Auckland Park 2006, Johannesburg P.O. Box 524, South Africa.
Komarov Botanical Institute, Prof. Popov Str. 2, 197376 St. Petersburg, Russia.
Plants (Basel). 2021 Aug 26;10(9):1773. doi: 10.3390/plants10091773.
is a shrubby genus endemic to páramo in the northern Andes representing the sister group to and . Stem and leaf structure of were studied to clarify the evolutionary pathways and ecological significance of their anatomical traits. and share a non-fascicular primary vascular system, rayless wood and secondary phloem, and anomocytic stomata. is distinctive from most Plantaginaceae in the presence of cortical aerenchyma and of helical thickenings in vessels. Its procambium emerges in the primary meristem ring as a continuous cylinder. The view on the ring meristem and procambial strands as developmental stages in the formation of a primary vascular system is not relevant for , and probably for other Plantaginaceae. The raylessness is synapomorphic for the crown clade of Plantaginaceae comprising , , , , , , and . The loss of rays is thought to be predetermined by procambium rather than by the vascular cambium. The extremely narrow vessels with helical thickenings are presumably adaptive to hydric and thermic conditions of páramo. Cortical aerenchyma is thought to be a response to the local hypoxia caused by the water retained by ericoid leaves. Trichomes on juvenile leaves are expected to be the traits of considerable taxonomic importance.
是一个灌木属，特产于安第斯山脉北部的帕拉莫地区，是 和 的姐妹群。对 的茎和叶结构进行了研究，以阐明其解剖特征的进化途径和生态意义。 和 具有非束状的初生维管系统、无射线木材和次生韧皮部，以及不规则型气孔。 与大多数车前科植物不同，其具有皮层通气组织和导管中的螺旋状加厚。其原形成层在初生分生组织环中以连续的圆柱体形式出现。关于环分生组织和原形成层束作为初生维管系统形成中的发育阶段的观点与 无关，可能与其他车前科植物也无关。无射线是包括 、 、 、 、 、 和平车前在内的车前科冠群的共衍征。射线的丧失被认为是由原形成层而非维管形成层预先决定的。具有螺旋状加厚的极窄导管大概适应了帕拉莫地区的水分和热量条件。皮层通气组织被认为是对石南状叶保留的水分引起的局部缺氧的一种反应。幼叶上的毛状体有望成为具有重要分类学意义的特征。
