FOLIAR HETEROMORPHISM IN POPULUS (SALICACEAE), A SOURCE OF CONFUSION IN THE TAXONOMY OF TERTIARY LEAF REMAINS
FOLIAR HETEROMORPHISM IN POPULUS (SALICACEAE), A SOURCE OF CONFUSION IN THE TAXONOMY OF TERTIARY LEAF REMAINS
复制标题
DOI：
10.2307/2418518
复制
发表时间：
1980-01-01
影响因子：
1
通讯作者：
ECKENWALDER, JE
中科院分区：
文献类型：
--
作者：
ECKENWALDER, JE
一些现存的杨树物种的异母细胞叶发育和季节性异源性导致单个个体的个体发育过程中形成不同的成熟叶形态。异母细胞杨树（例如 P. mexicana Wesmael 和 P. monticola T. Brandegee）的幼叶比同种的成年叶窄，叶脉也有相应的差异。在具有季节性异源性的物种中，成年个体的早期叶子在叶子扩展之前的季节形成并在芽中越冬，而晚叶在它们开始的同一季节扩展。在 P. monticola 中，同一枝条的晚叶比早叶具有更细、更规则的锯齿，但其他物种在两种叶形之间表现出其他差异。虽然它们的叶子化石被发现是单个分离的器官，但与现存异叶物种有关的几种第三纪杨属物种，例如 P. cinnamomoides (Lesquereux) MacGinitie、P. adamantea H. Becker 和 P. cedrusensis J. Wolfe，也可能具有异形叶类型。这些物种的不同叶子类型已被古植物学家分为两到三个物种。有些被认为是不同属的代表。第三纪和近代胡杨中发现的叶异形性可能是化石植物区系分类混乱的一个比迄今为止所认识到的更普遍的来源。
Heteroblastic leaf development and seasonal heterophylly in some extant species of Populus result in diverse mature leaf forms during ontogeny of a single individual. juvenile leaves of heteroblastic poplars, such as P. mexicana Wesmael and P. monticola T. Brandegee, are narrower than adult leaves of the same species and share corresponding differences in foliar venation. In species with seasonal heterophylly, early leaves of adult individuals are formed in the season preceding leaf expansion and overwinter in buds, while late leaves expand in the same season in which they are initiated. In P. monticola, late leaves have finer, more regular serrations than early leaves of the same shoots, but other species show other differences between the two leaf forms. Although their fossilized leaves are found as single detached organs, several Tertiary species of Populus that are related to extant heterophyllous species, exemplified by P. cinnamomoides (Lesquereux) MacGinitie, P. adamantea H. Becker, and P. cedrusensis J. Wolfe, probably possessed heteromorphic leaf types as well. Diverse leaf types of each of these species have been divided among two or three species apiece by paleobotanists. Some have been considered representatives of different genera. Foliar heteromorphism of the kinds found in Tertiary and Recent Popolus may be a more prevalent source of taxonomic confusion in fossil floras than has heretofore been recognized.