Diffusion

(1) Diffusion [ Ecology - Biology ]
Synonym: Dissemination, Dispersal, Spreading


	*The property of being diffused or dispersed*

Especially used in botany and ecology to indicate plant, seed or pollen dissemination or dispersal.

In ecology a diffuse distribution indicate plants widely spread or scattered over an area, not concentrated in a definite and delimited place.

In cell biology, diffusion is described as a form of "passive transport", by which substances cross throughout membranes.

(2) Diffusion [ Chemistry - Physics]


	CHEMISTRY: Diffusion is movement of molecules, atoms or ions of liquids and gases from their region of higher concentration to their region of lower concentration until it is same throughout the given space. In general the diffusion is the passage of particles through a material from an area of high concentration to a region of low concentration resulting in an even distribution particles. The phenomenon is readily observed when a drop of coloured water is added to clear water, or when smoke from a chimney dissipates into the air. In these cases, diffusion is the result of turbulent fluid motion rather than chemical reactions or the application of external force. For example: When perfume is spilt in one corner of a room its fragrance spreads all over the room. PHYSICS: Diffusion is the spreading of radiation, heat, or sound across a fluid or solid medium in a direction tending to equalize concentrations in all parts of the system. For example: Scattering of light rays trough a frosted glass or a translucent body or membrane.

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Holdfast roots [ Botany ]
Dictionary of botanic terminology - index of names

Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.

Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans), develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994