Relictual vegetative anatomical characters in Cactaceae: the genusPereskia |
| |
Authors: | James D Mauseth James V Landrum |
| |
Institution: | (1) Department of Botany, University of Texas, 78713 Austin, TX, USA |
| |
Abstract: | The genusPereskia, which contains numerous morphological features considered relictual in the Cactaceae, has numerous anatomical features that
we consider to be relictual also. These were studied to establish a basis for determining the ways that morphogenic mechanisms
and anatomical characters diversified as the family evolved. ThesePereskia features may be relictual in the family: epidermis predominantly unistratose and lacking crystals; hypodermis absent or of
about three layers of weakly collenchymatous cells with druses; cortex thin and predominantly parenchyma with druses and mucilage
cells but lacking cortical bundles; secondary phloem without early differentiation of sclerenchyma but with secondary sclereids
developing later, either idioblastically or in clusters; ergastic substances lacking from old secondary phloem; wood with
a matrix of libriform fibers (mostly septate and nucleate), scanty paratracheal parenchyma, vessels solitary or in small clusters,
perforations simple, pitting circular, oval or very broad; wide-band tracheids absent; ray cells slightly thick-walled, lignified,
upright, isodiametric or procumbent; all primary rays narrow; pith without medullary bundles; leaves lacking hypodermis, with
only weak development of palisade mesophyll; veins of four orders, strongly distinct in size, none with fibers; vessels in
leaves narrower than those in stems. |
| |
Keywords: | Anatomy Cactaceae Development Evolution Morphogenesis Pereskia |
本文献已被 SpringerLink 等数据库收录! |
|