Tropism Tropism Chemotropism is movement caused by chemical stimulus in organisms such as bacteria and plants. An example of chemotropic movement can be seen during the growth of the pollen tube. ...more on Wikipedia about "Chemotropism"
Gravitropism (or geotropism) is a turning or growth movement by a plant or fungi in response to gravity. Charles Darwin was one of the first to document that roots show positive gravitropism and stems show negative gravitropism. That is, roots grow in the direction of gravitational pull (i.e., downward) and stems grow in the opposite direction (i.e., upwards). This behaviour can be easily demonstrated with a potted plant. When laid onto its side, the growing parts of the stem begin to display negative gravitropism, bending (biologists say, turning; see tropism) upwards. Herbaceous (non-woody) stems are capable of a small degree of actual bending, but most of the redirected movement occurs as a consequence of root or stem growth in a new direction. ...more on Wikipedia about "Gravitropism"
Hydrotropism is the tendency for an organism to grow towards (or away from) water. The most common example is that of plant roots preferentially growing in the direction of a source of water. In other cases a root might grow away from excess water, which would also be considered an instance of negative hydrotropism. Hydrotropism is a special case of tropism. ...more on Wikipedia about "Hydrotropism"
Phototropism or heliotropism are botanical terms for an organism's response to light (in the case of heliotropism, specifically the light from the Sun). These are one of the many plant tropisms or movements in response to external stimuli. Growth toward a light source is a positive phototropism, while the reverse is called negative phototropism (if growth or orientation is toward darkness). Leaves and other parts of the plant that require light for photosynthesis exhibit positive phototropism, while roots usually exhibit negative phototropism, although gravitropism may play a larger role in their behavior and growth. ...more on Wikipedia about "Phototropism"
(Thermotropism) A thermotropic response causes a plant to grow either away from or towards a source of heat. This is caused by an unbalance of plant hormones that manipulate growth. ...more on Wikipedia about "Thermotropism"
Thigmotropism is a tropism in which an organism moves or grows in response to touch or contact stimuli. The prefix thigomo comes from the Greek for "touch." Usually thigmotropism occurs when plants grow around a surface, such as a wall, pot, or trellis. Climbing plants, such as vines, contain tendrils that coil around supporting objects. Touched cells produce auxin and transport it to untouched cells. Untouched cell then elongate faster so growth bends around the object. ...more on Wikipedia about "Thigmotropism"
A tropism is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus. The word tropism comes from the Greek tropos ("to turn"). Tropisms are usually named for the stimulus involved (for example, a phototropism is a reaction to light) and may be either positive (towards the stimulus) or negative (away from the stimulus). ...more on Wikipedia about "Tropism"
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