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- Title
- Female inflorescence of <em>Garrya fremontii</em> Torrey, Fremont's silk tassel
- Author
- Dylan O. Burge Duke University Biology Biology Durham North Carolina 27708 USA dob7@duke.edu (919) 323-5447
- Description
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- Scientific Description/Explanation: The genus Garrya
Dougl. ex Lindl. [See "Terms From Scientific Description,"
below, for explanations of terms in italics] (Garryaceae) contains
15 species of winter-blooming, wind-pollinated, dioecious evergreen
trees and shrubs distributed in North America (including Mexico), Central
America, and the Caribbean Islands. The genus Garrya is found only
in the New World, but is closely related to the genus Aucuba, which
is native to China and Japan. The genus Garrya is thought to represent
a relatively recent introduction to the New World, which probably migrated
from Asia over a high-latitude land-bridge sometime during the last twenty
million years. Garrya fremontii is a widespread species that occurs
from central California to Washington State. It is most abundant at middle
and high elevations (1000-3000 meters) in parts of the Sierra Nevada Mountains,
the Pacific Coast Ranges, and the Cascade Range. It occupies a diversity
of habitats, from chaparral and oak woodland to coniferous forests. The
plant in the photograph is part of a population of Garrya fremontii
growing on Doe Mill Ridge in Butte County, California, about 15 kilometers
north-northeast of the town of Chico. These plants are part of a dense chaparral
community composed mainly of species of Arctostaphylos (manzanita)
and Ceanothus. This community is strongly fire regulated, with
fires occurring about every seven to ten years. Garrya fremontii,
along with many other members of this chaparral community, survives fire
by re-sprouting from a buried root-crown, or lignotuber. It also regenerates
from seeds deposited in the soil seed-bank. Garrya fremontii is
part of a complex of species from western North America, within which the
species are very difficult to differentiate. Garrya fremontii intergrades
morphologically with Garrya flavescens in the coast ranges of California,
which may indicate that these two taxa are not distinct. In addition, preliminary
results using DNA sequence data (see URL below) suggest that there
is very little genetic variation among species of Garrya in California.
Like all species in the genus, Garrya fremontii flowers during
the late winter, long before most plants have begun their growing season.
The flowers are born in pendulous inflorescences, as shown in the
image, and have a unique, highly reduced structure. In female inflorescences
the flowers are arranged in successive groups that are each partially surrounded
by a bract. In the photograph, these bracts are obvious as the
greenish, triangular flaps that cover the bases of the silky, developing
ovaries. Opposite bracts sometimes fuse, forming a cup that surrounds
multiple groups of flowers. Individual female flowers lack almost all vestiges
of a corolla or calyx, although minute remnants of these
structures are sometimes present near the base of the styles. The
presence of these perianth remnants is usually taken as evidence
that the ovaries of Garrya fremontii are inferior. The
ovaries of all Garrya species are composed of two carpels,
and thus produce two seeds. The styles of Garrya fremontii are
characteristically elongated and thin, often recurving toward the inflorescence
axis, which gives the appearance of a "handle-bar mustache." This
character is clearly visible in the image, although some of the styles have
dried up and broken off, as the inflorescence in the image is several weeks
old and past the fertilization stage. Male inflorescences are not shown
in the image, but male plants were present in the vicinity of the pictured
plant. Male inflorescences are also morphologically reduced, and specialized
for wind pollination. These adaptations include a special chamber formed
from the distally fused perianth members that is thought to aid
in preventing desiccation of the pollen. The male inflorescence is also
less rigid than the female inflorescence, which enables it to flex with
the wind currents. Most species of Garrya flower well before the
time when potential pollinators are active, sometimes while snow is still
on the ground, so scientists have inferred that they are wind pollinated.
The fruits of Garrya fremontii mature in the fall, and are dark
blue in color. It is not certain what the primary dispersal agent of this
plant may be, but species of Neotoma (wood rats) are known to collect
them. Overall, Garrya fremontii, and the genus Garrya
in general, present an intriguing combination of highly derived
morphological traits, unusual ecology, and potentially complex genealogical
and geographical patterns going back to the Old World. Garrya also
takes readily to cultivation, and several species and hybrids are popular
landscape plants in the Western United States.
TERMS FROM THE EXPLANATION
<font color="#666666">Garrya</font> - The scientific name of any
organism should always be underlined or printed in italics. The scientific
name of an organism always has two parts, the genus name (Garrya,
for instance), and the species name (fremontii, for instance).
Because of the parts of speech corresponding to these two words, and convention,
the first is always capitalized, while the latter is never capitalized.
<font color="#666666">Dougl. ex Lindl</font> - In plant
taxonomic treatments, papers, floras, labels, etc., the name of a plant
taxon is often given along with the name of the authority for that taxon
(the author of the taxon name). In the case of the genus Garrya,
the authority is Lindley, who was the first to validly publish (sanction)
the name Garrya, which had been proposed, but not validly published,
by Douglas.
<font color="#666666">Dioecious</font> - Most plants have bisexual
flowers, with male and female parts combined within the same structure.
However, some taxa have the male and female parts separated into different
flowers. If both female and male flowers occur on the same plant, then the
species is known as monoecious. If the flowers are born on separate plants,
analogous to the two-sex system of many animals, then the plant is known
as dioecious.
<font color="#666666">DNA sequence</font> - DNA (Deoxyribonucleic
acid) is the information-carrying molecule of living things. DNA, which
encodes information for building proteins, is the basis for almost all of
the characteristics of a given organism, as expressed during development.
Scientists use DNA to gain insight into the history of life on earth, and
the dynamics of living systems. This is possible because of the unique hereditary
role of DNA, which accumulates errors in living organisms, some of which
are passed on to subsequent generations. DNA can be extracted from living
organisms and its code, or sequence, can be read using specialized techniques.
This information may be used in a statistical fashion to infer the genealogy
of a group of organisms, such as a genus or species of plant.
<font color="#666666">Inflorescence</font> - The reproductive part
of a plant, including all flowers and the stems on which they are born,
is called an inflorescence. There is considerable diversity in
inflorescence structure among flowering plants. A daisy "flower,"
for instance, is really an inflorescence containing several hundred individual
flowers.
<font color="#666666">Bract, carpel, ovary, corolla, calyx, perianth,
style</font> - Most flowers are composed of four "whorls"
of parts. (1) The female parts, or carpels, which each have an
ovary as well as a stigma (the receptive surface for pollen)
that is born on the end of a style. (2) The male parts, or stamens,
which are made up of pollen-bearing anthers on the end of filaments. (3)
The petals, which together are known as the corolla. (4) The sepals,
which are typically green and collectively called the calyx. The
calyx and corolla are together known as the perianth. All of these
flower parts are attached to a receptacle, which is often born on the end
of a stalk called the pedicel. This pedicel is often subtended by (found
immediately above) a leaf-like organ called a bract. All of the
amazing and beautiful diversity of flower morphology is simply variation
on this theme of four whorls and subtending elements.
<font color="#666666">Inferior</font> - When the corolla and calyx
become fused to the walls of the carpels so that the stamens, anthers, and
stigmas appear anatomically above the ovary, rather than below it, then
the ovaries of that flower are termed inferior. Normal ovaries
are termed superior. An apple, for example, is derived from a fertilized
flower with inferior ovaries. The perianth, stamens, and styles are often
visible in the depression on the distal end of the apple (opposite the stem,
or pedicel).
<font color="#666666">Distally</font> - In anatomical terms, an
organ that is far from a point of reference is distal, while an
organ that is near is proximal. Your hand, for instance, is on the distal
end of your arm. These terms are used universally in discussions of both
animal and plant anatomy.
<font color="#666666">Derived</font> - Genealogies of organisms
are also known as phylogenies. Humans, apes, and monkeys, for instance,
are all related, and the specific genealogical relationships between them,
as inferred from morphological traits or DNA sequence variation, can be
expressed as a branching, tree-like phylogeny, in which the earliest-branching
lineages (those appearing lowest on the tree) are considered as ancestral,
and the most recent, latest branching lineages are considered as derived.
REFERENCE
MATERIAL
Bremer, B., Bremer, K., Heidari, N., Erixon, P., Olmstead, R.G., Anderberg,
A.A., Källersjö, M., & Barkhordarian, E. 2002. Phylogenetics
of asterids based on 3 coding and 3 non-coding chloroplast DNA markers and
the utility of non-coding DNA at higher taxonomic levels. Molecular
Phylogenetics and Evolution 24: 274-301.
Dahling, G.V. 1978. Systematics and evolution of Garrya. Contributions
from the Gray Herbarium of Harvard University 209: 1-104.
Eyde, R.H. 1964. Inferior ovary and generic affinities of Garrya.
American Journal of Botany 51: 1083-1092.
Graham, A. 1999. The tertiary history of the northern temperate element
in the northern Latin American biota. American Journal of Botany 86:
32-38.
Hileman, L.C., Vasey, M.C., & Parker, V.T. 2001. Phylogeny and biogeography
of the Arbutoideae (Ericaceae): implications for the Madrean-Tethyan hypothesis.
Systematic Botany 26: 131-143.
Liston, A. 2003. A new interpretation of floral morphology in Garrya
(Garryaceae). Taxon 52: 271 276.
Oxelman, B., Yoshikawa, N., McConaughy, B.L., Luo, J., Denton, A.L., &
Hall, B.D. 2004. RPB2 gene phylogeny in flowering plants, with particular
emphasis on asterids. Molecular Phylogenetics and Evolution 32: 462-479.
- Additional data
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copyright:
license:
- Collection
-
Vascular plant systematics
- Botanical Name
- Garrya fremontii
- Common Name
- Fremont's silk tassel
- Location Area
- Doe Mill Ridge, Butte County
- Location State
- California
- Location Country
- USA
- Categories
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