BISC208 Lecture Notes - Lecture 4: Venus Flytrap, Thigmotropism, Gravitropism
16 May 2016
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Tropism: direction, growth responses: gravitropism, thigmotropism, chemotropism. Nastic: non-directional, typically does not involve growth, happens rapidly. Thigmonasty: a plant responding to mechanical pressure by non-directional movement: carnivorous plants (venus fly trap, sensitive plant leaves (mimosa) Long term: growth of roots & altered leaf/stem morphology: temperature. High temp: plants rapidly produce heat-shock proteins. Low temp: some plants change molecular structure of the membrane. Pollination: larger animals such as birds, small mammals. In return the animals feed on sweet nectar. Plants are not the defenseless organisms we imagine. Plants display a great variety of defense mechanisms. Chemical compounds that cause potent effects on animal physiological processes. Mechanical barriers: non-specific defense mechanisms: structural defenses, spines, thorns, hard or hairy fruits, sticky substances secreted, trichomes: leaf hairs that are needle-like barbs. Stinging nettles: bristles in plants are typified by nettles which possess sharp-pointed hollow bristles seated on a gland which secretes an acrid fluid.
