Home | | Introduction to Botany | Compositae, or Asteraceae - aster family

Chapter: Introduction to Botany: The Origin of Flowering

| Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail |

Compositae, or Asteraceae - aster family

Compositae, or Asteraceae - aster family
Belong to asterids (Asteridae). More than 20,000 species—second place in flow-ering plants. Cosmopolitan, but better represented in temperate and subtropical regions.

Compositae, or Asteraceae - aster family

 

Belong to asterids (Asteridae). More than 20,000 species—second place in flow-ering plants. Cosmopolitan, but better represented in temperate and subtropical regions. Prefer open spaces. Herbs, rarely woody plants; store carbohydrates as inulin (not starch), sometimes have resin or laticifers (subfamily Cichorioideae). Leaves are alternate or opposite, without stipules, with pterodromous venation.

 

Flowers in involucrate heads which mimic one flower (Fig. 8.20). Calyx reduced to hairs or bristles (pappus), petals fused in tube or ligula (with 5 or 3 teeth). Stamens 5, fused by anthers. Pistil has 2 carpels, ovary inferior. Fruit is ach-ene, mature seed has almost no endosperm. Flower formula of the tubular (disk) flower is


Ligulate (ray) flower typically has formula like


 

Fruit of aster family is one-seeded achene (it is a frequent mistake to call it “seed”). In achene, walls of inferior ovary are tightly fused with seed coat. Ach-enes frequently bear diverse dispersal structures: trichomes, teeth, hooks etcetera.


 

Oil plants, vegetables, ornamentals and medicinal plants distributed in multiple subfamilies, most important are three:

 

                  Carduoideae: mostly tubular flowers

 

Centaurea—knapweed

 

Cynara—artichoke

 

Carthamus–safflower

 

                  Cichorioideae: mostly 5-toothed ligulate flowers + lacticifers with latex

 

Taraxacum—dandelion

 

Lactuca—lettuce

 

                  Asteroideae: tubular + 3-toothed ligulate flowers

 

Helianthus—sunflower (BTW, “canola”, or Brassica napus from Cru-ciferae is the second main source of vegetable oil)

 

Artemisia—sagebrush

 

Tagetes—marigold and lots of other ornamentals


Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail


Copyright © 2018-2020 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.