BIOL 1902 Lecture Notes - Onopordum Acanthium, Verbascum, Automimicry
21 Mar 2014
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Plants face all of the same problems that animals encounter including the risk of being eaten. All parts of plants are eaten by animals. When you see a plant defoliated you see seige lost. When you see a plant untouched, you see a battle won. Milkweed; terpenoids are a major group of chemical toxins; cardiac glycosides = terpenoids; but monarchs have evolved a solution! Trees and other woody plants have external armour = bark. Water smartweed; no trichomes on leaves in water; if water goes away, trichomes appear on. Structural elements such as cellulose, hemicellulose, and pectin make plant tissues hard to digest. Lignin gives leaves stiffness, nuts and cherry pits their hardness; often housed in structures called sclereids. Silica found in horsetails (equisetum); housed in phytoliths. Calcium can also be used ; arum plants have calcium oxalate crystals in their leaves (skunk cabbage)
