Diversity And Classification of Flowering Plants:
Eudicots: Asterids
Michael G. Simpson
Asterids
• Very large, diverse group
• 10 orders, many families
• Putative apomorphies:– iridoid compounds– sympetalous corolla– ovules: unitegmic (one integument),
tenuinucellate (megasporangium 1-cell thick)
Ovules unitegmic, tenuinucellate
Apiaceae (=Umbelliferae) - Carrot family (Apium, used in Pliny for a celery-like plant). 446 genera / 3,540 spp.
The Apiaceae are distinctive in being herbs, with sheathing leaves, (compound or simple. often decompound), the inflorescence usually an involucrate compound umbel [rarely a head, simple umbel, or reduced] with actinomorphic flowers having a 2-carpellate and 2-loculate, inferior ovary, each carpel with one, axile-apical, pendulous ovule, the fruit a schizocarp of mericarps.
K 5 or 0 C 5 [0] A 5 G (2), inferior, hypanthium absent.
Economically important members include a
number of food, herb, and spice plants, such as
Anethum, dill; Apium, celery; Carum, caraway;
Coriandrum, coriander; Cuminum, cumin;
Daucus, carrot; Foeniculum, fennel; and
Petroselinum, parsely; some species are
poisonous, such as Conium maculatum, poison-
hemlock; others are used as ornamental cultivars.
Leaves sheathing
Inflorescence an umbel, compound umbel, or head
ovary inferior
placentationapical-axile
stylopodium
Fruit a schizocarp of mericarps
Araliaceae - Ginseng family
(possibly from French Canadian Aralie). 47 genera / 1,325 species.
The Araliaceae are distinctive in being mostly tropical trees, shrubs, lianas, or herbs with palmate or pinnate (rarely simple, then usually divided) leaves, an inflorescence of heads, umbels, or with umbel units, the flowers with often reduced calyx, apopetalous to sympetalous corolla, and a 1-∞-carpellate inferior ovary with usually apical-axile placentation, the fruit a berry, drupe, or schizocarp.
K 0-5 C 5 [3-12] A 5-10 [3-∞] G (2-5) [(-∞)], inferior, rarely superior.
Asteraceae (Compositae)
Characteristics:
Vegetatively variable.
Inflorescence a head (capitulum): (usu.) many flowers arising from a compound receptacle, subtended by inflorescence bracts: involucral bracts or phyllaries, collectively termed the involucre.
Calyx modified as pappus.
Stamens syngenesious.
K pappus C 5 A (5) G(2), inferior, 1 basal ovule
Fruit an achene.
Asteraceae (=Compositae) - Sunflower family
(after Aster, meaning star). 1,528 genera / 22,750 species.
The Asteraceae are distinctive in being herbs, shrubs, vines, or trees, the inflorescence a head (capitulum) subtended by an involucre of phyllaries, flowers either bilabiate, disk, or ray/ligulate, (heads of many taxa a mixture of central disk flowers and peripheral ray flowers), with the calyx, termed a pappus, modified as scales, awns, or capillary bristles (or absent), the androecium syngenesious, and with an inferior ovary with a single, basal ovule, the fruit a multiple of achenes.
Asteraceae (=Compositae) - Sunflower family
(after Aster, meaning star). 1,528 genera / 22,750 species.
Economic importance includes some food plants (e.g., Cynara scolymus, artichoke, and Helianthus annuus, sunflower), a number of ornamental cultivars, and various species used locally or industrially; the prickly fruits of Arctium lappa (burdock) are purported to have been the model for invention of velcro.
Argyroxiphium sandwicense, SilverswordMaui
Argyroxiphium sandwicense, SilverswordMaui
Asteraceae (=Compositae) - Sunflower family
(after Aster, meaning star). 1,528 genera / 22,750 species.
K 0-∞ (pappus)
C (5) [(4)] or (3) in some ray flowers
A (5) [(4)]
G (2), inferior, hypanthium absent.
Asteraceae: floral variationThree types of flowers:
1) Bilabiate: zygomorphic (bilateral) with 2 lips2) Ray (ligulate): zygomorphic (bilateral) with 1
lobe3) Disk: actinomorphic (radial), usu. 5-lobed
Five types of heads:
1) discoid, with only disk flowers;
2) disciform, with central disk flowers and marginal, eligulate female flowers;
3) radiate, with central (bisexual or male) disk flowers and peripheral (female or sterile) ray flowers;
4) ligulate, with all ray flowers (typically with 5-toothed corolla apices);
5) bilabiate, with all bilabiate flowers.
Bilabiate flower
Acourtia microcephala Trixis californica
posterior lip anterior lip
Ray flowers (heads ligulate = all rays)
Rafinesquia neomexicana Malacothrix californica
ligulate corolla
Disk flower: heads discoid
Palafoxia arida Psathyrotes ramosissima
disk corolla
Chaenactis gabriuscula
Disk flowers: heads disciform(2 types of disk fls.,
same or different heads)
male heads
Ambrosia chamissonis
female heads
Xylorhiza orcuttii Encelia farinosa
Heads radiate: inner disk & outer ray fls.
ray flowers disk flowers
Encelia californica
ovary
Some heads are "chaffy"
chaff : bracts subtending flowers
disk flower
Involucre morphology
one whorl two whorls many whorls
Senecio vulgaris Coreopsis maritima Encelia californica
Circium vulgare Silybum marianum
Phyllaries spiny
Involucre morphology
Phyllaries spiny & squarrose
Pappus: modified calyx
capillary bristles: barbellate
capillary bristles: plumose
beak
capillary bristles, borne atop "beak"
Pappus: modified calyx
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