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Asterids: Asteraceae. Asterids Very large, diverse group 10 orders, many families Apomorphies: –iridoid compounds –sympetalous corolla –ovules: one.

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Presentation on theme: "Asterids: Asteraceae. Asterids Very large, diverse group 10 orders, many families Apomorphies: –iridoid compounds –sympetalous corolla –ovules: one."— Presentation transcript:

1 Asterids: Asteraceae

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3 Asterids Very large, diverse group 10 orders, many families Apomorphies: –iridoid compounds –sympetalous corolla –ovules: one integument and the megasporangium is generally one cell thick

4 Asteraceae Probably the most evolved of the families Two types of flowers –Ray –Disk Herbs in our area, but can be trees in tropics Very diverse: 19,000 species world-wide Many flowers on the head inflorescence Old name is compositae – b/c a composite of flowers

5 Asteraceae 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. Fruit an achene.

6 Floral Formula

7 Asteraceae – World-wide

8 Typical Asteraceae Flower

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10 Cross-section of Asteraceae Flower

11 More detail on disk flower

12 Note the chaff – bracts below each individual flower

13 Fruits are achenes

14 Sunflower seeds = achenes

15 Echinacea sp. – praire cone flower

16 Liatris flowers

17 Close-up of achene fruit with pappus

18 Taraxacum officinale

19 Close-up of Taraxacum head

20 Taraxacum fruits

21 Close-up of Taraxacum flower

22 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.

23 Bilabiate flower Acourtia microcephalaTrixis californica posterior lip anterior lip

24 Ray flowers ( heads ligulate = all rays) Rafinesquia neomexicanaMalacothrix californica ligulate corolla

25 Disk flower: heads discoid Palafoxia arida Psathyrotes ramosissima disk corolla Chaenactis gabriuscula

26 Disk flowers: heads disciform (2 types of disk fls., same or different heads) male heads Ambrosia chamissonis female heads

27 Xylorhiza orcuttiiEncelia farinosa Heads radiate: inner disk & outer ray fls. ray flowersdisk flowers

28 Encelia californica ovary Some heads are "chaffy" chaff : bracts subtending flowers disk flower

29 Involucre morphology one whorltwo whorlsmany whorls Senecio vulgarisCoreopsis maritimaEncelia californica

30 Circium vulgareSilybum marianum Phyllaries spiny Involucre morphology Phyllaries spiny & squarrose

31 Pappus: modified calyx

32 capillary bristles: barbellate capillary bristles: plumose beak capillary bristles, borne atop "beak"

33 Asteraceae Because the family is so large, it is divided into two Subfamilies which are then divided into tribes: 12 to 17 in the whole family Aster = Subfamily Asteroideae –Six tribes well see Dandelion = Subfamily Cichorioideae –One tribe

34 Tribes of the Aster Subfamily Heliantheae Asterae Anthemideae Senecioneae Gnaphalieae Eupatorieae Cynareae

35 Tribe Heliantheae – Sunflower tribe Opposite leaves Very resinous Bracts attached to individual flowers (chaffy receptacle) Both types of flowers Sunflower (Helianthus) and Echinacea

36 Heliantheae

37 Tribe Asterae – Aster Tribe No bracts at the bottom of individual flowers Example is genus Aster, generally fewer than 20 petals or ligulate flowers Similar to above tribe, but without resin Chrysothamnus (Rabbitbrush or chico) Another important genus is Erigeron aka fleabane daisy

38 Chyrsothamnus sp. rabbitbrush

39 Erigeron elatior

40 Tribe Anthemideae – Chamomile Tribe Multiple layers of phyllaries of different lengths Richly aromatic Thin, dry, and translucent (i.e. scarious) bracts surrounding the flower base Artemisia (sagebrush is in this tribe) Achillea, Chrysanthemum

41 Involucre morphology one whorltwo whorlsmany whorls Senecio vulgarisCoreopsis maritimaEncelia californica

42 Chrysanthemum

43 Achillea millefolium - yarrow

44 Tribe Senecioneae – Senecio or Groundsel Tribe –Silky pappus around each flower Pappus is usually pure white and very abundant Usually naked receptacle Senecio

45 Senecio triangularis

46 Tribe Gnaphalieae – Everlasting Tribe Also has scarious bracts around flower base No ligulate flowers, only tubular flowers Example is cudweed or everlasting (Gnaphalium)

47 Pussytoes in Gnaphalieae

48 Tribe Eupatorieae – Boneset Tribe Baseball bat stigmas No ligulate flowers Usually naked receptacle Snakeweed, Gutierrezia Liatris, common ornamental

49 Gutierrezia sarothrae – broom snakeweed

50 Liatris punctata

51 Dandelion Subfamily - Cichorioideae The Dandelion Subfamily Strap shaped ligulate petals No tubular flowers Dandelions (Taraxacum) Lettuce (Lactuca) Includes Cardueae Tribe

52 Lactuca serriola – prickly lettuce

53 Tribe Cynareae or Cardueae (in your book) – Artichoke Tribe Head inside a cluster of tightly compressed bracts Like an artichoke, which is in this tribe, we eat the bracts! No ligulate flowers Many bristles on receptacle (spines inside artichoke) Many thistles are in this tribe, Cirsium and also knapweeds, Centaurea Cynara is artichoke Name for genus Carduus

54 Artichoke - Cynara scolymus

55 Cirsium scariosum

56 Cirsium arvense

57 Argyroxiphium sandwicense, Silversword endemic toMaui

58 Argyroxiphium sandwicense, Silversword Maui


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