Author: Joshua Lee
Date: 08:01:15 10/09/01
Go up one level in this thread
On October 08, 2001 at 15:34:05, Roy Eassa wrote: >On October 08, 2001 at 15:31:06, Joshua Lee wrote: > >>Can you use that in a sentence like : I went to the Store yesterday to find some >>tropism for my Piece's but they were sold out. > > >Involuntary response of an organism, or part of an organism, involving >orientation toward (positive tropism) or away from (negative tropism) one or >more external stimuli. > >The term tropism is usually applied to growth and turgor movements in plants; an >involuntary orientation of a microorganism toward or away from an external >stimulus is commonly called a taxic movement, or taxis-e.g., the negative >phototaxis of certain protozoans that move away from light. Tropistic stimuli >include light, heat, moisture, gravity, electricity, and chemical agents. Plant >stems are positively phototropic and negatively geotropic, i.e., they grow >toward light and against gravity; roots are the reverse, as well as positively >hydrotropic (moisture-seeking). Tropistic growth in plants is believed to be >triggered by the presence of plant hormones (see auxin) that promote cell >growth. Auxin action is apparently inhibited by light; hence, if a plant is >placed in a position of unequal lighting, the cells on the shadier side elongate >faster than those on the illuminated side, and the plant bends toward the light. >There is also evidence that auxins are affected by gravity, i.e., they >accumulate in the lower portions of the plant organs. Since an overconcentration >of these hormones inhibits growth, the cells on the underside of a root elongate >more slowly than those on the upper side, resulting in the root's downward >growth. Generalized plant responses to a stimulus are called nastic movements, >or nasties. These include the opening of bud scales and of flower petals, growth >movements that occur in response to stimuli such as light and heat without >regard for the direction of the stimulus. Some spring flowers exhibit >thermonasties, i.e., their flowers open in response to warmth rather than the >amount of light. Turgor movements are effected by changes in the water content >of cells and are often quite rapid. Examples are the "sleep movements of clover, >the sudden drooping of the leaves of the sensitive plant (mimosa) when touched >(thigmotropism), and the reactions of insectivorous plants to the presence of >their prey. The exact mechanism controlling the sudden loss of water pressure in >certain cells, producing turgor movements, is not clearly understood. Sounds like Conditioned Response was the first thing that poped into my mind but it isn't exactly. Are you a Biology Teacher you sound really good at this, I could've used you I'm sure i would've gotten an A.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.