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