journal of the Botanical Research Institute of Texas
Volume 8, Issue 1, 2014, Pages 87-126
Botanical Research Institute of Texas, 1700 University Drive, Fort Worth, TX 76107, United States
Abstract
The genus Echinacea
(Asteraceae) has importance economically, medicinally, and ornamentally.
Endemic to North America, distribution is centered in the states of
Arkansas, Kansas, Missouri, and Oklahoma. Native Americans of the
central Great Plains used Echinacea as a highly prized medicinal plant
panacea. This anatomical study is based on R.L. McGregor's taxonomic
treatment of the genus Echinacea that included 11 taxa: E. angustifolia
var. angustifolia, E. angustifolia var. strigosa, E. atrorubens, E.
laevigata, E. pallida, E. paradoxa var. neglecta, E. paradoxa var.
paradoxa, E. purpurea, E. sanguinea, E simulata, and E. tennesseensis.
Anatomy of Echinacea tennesseensis was not included because live plants were not available. Plants
were collected at the height of anthesis from the experimental gardens
at the University of Kansas. Samples were prepared for microtome and
free-hand sectioning and staining. Macromorphology and microanatomy are
described here, and photomicrographs illustrate the adaxial epidermal
cells of ray ligules. Tissue map line drawings illustrate the pattern
and distribution of stem trichomes, epidermal cells, cortex, vascular
bundles, and pith. Measurements were included for stem diameters,
epidermis, collenchyma, parenchyma, xylem vessels, sclerenchyma fibers,
xylem and phloem vascularization, protoxylem points, and location and
number of secretory canals for each Echinacea taxon. Sclerenchyma fibers
(sclerotic cells with a black phytomelanin substance) are located in
the pith tissue of all the varieties of E. angustifolia. Tissue maps and
photomicrographs illustrate petiole transections and the presence of
brachysclerids (stone cells) in E. paradoxa var. neglecta which were
found nowhere else in this study. Plants
resulting from crossings and introgression between E. atrorubens and E.
angustifolia had many intermediate characteristics and were called
"race intermedia." This name has no nomenclatural standing but the plants
were found to have unique ray ligule adaxial epidermal cells. These
multicelluar structures consist of an enlarged basal cell with a neck
and a catenuliform series of one, two, or three discrete pyramidal cells
that have not been described for any member of the Asteraceae or other
flowering plant. A key to
Echinacea taxa that includes the distinctive micromorphology of ray
ligule adaxial epidermal cells is presented. A discussion of the
structure and function of ray ligule microanatomy is included as this
relates to insect pollinators. Questions still remain concerning the
constancy of anatomical characters over a broad range of habitats based
on statistically sampled populations.
Author keywords
Dichotomous key; Echinacea (coneflower); Endangered
species; Ligule adaxial epidermal cells; Macro-and microanatomy;
Sclerotic and stone cells
ISSN: 19345259Source Type: Journal
Original language: English
Document Type: Article
Publisher: Botanical Research Institute of Texas Inc.
