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The model proposes that auxin, a plant growth hormone, is synthesized in the coleoptile tip, which senses light or gravity and will send the auxin down the appropriate side of the shoot. This causes asymmetric growth of one side of the plant. As a result, the plant shoot will begin to bend toward a light source or toward the surface. [3]
The light from the lamp (1.) functions as a detectable change in the plant's environment. As a result, the plant exhibits a reaction of phototropism--directional growth (2.) toward the light stimulus. Auxin distribution controls phototropism. 1. Sunlight strikes the plant from directly above. Auxin (pink dots) encourages growth straight up. 2 ...
It proposes that auxin, a plant growth hormone, is synthesized in the coleoptile tip, which senses light or gravity and will send the auxin down the appropriate side of the shoot. This causes asymmetric growth of one side of the plant. As a result, the plant shoot will begin to bend toward a light source or toward the surface. [citation needed]
The Dutch biologist Frits Warmolt Went first described auxins and their role in plant growth in the 1920s. [4] Kenneth V. Thimann became the first to isolate one of these phytohormones and to determine its chemical structure as indole-3-acetic acid (IAA). Went and Thimann co-authored a book on plant hormones, Phytohormones, in 1937.
Indole-3-acetic acid (IAA, 3-IAA) is the most common naturally occurring plant hormone of the auxin class. It is the best known of the auxins, and has been the subject of extensive studies by plant physiologists. [1] IAA is a derivative of indole, containing a carboxymethyl substituent. It is a colorless solid that is soluble in polar organic ...
The theory was widely accepted when first proposed, but began to receive serious criticism in the mid-1980s. [6] Arguments against the model have included views that growth regulators other than auxin may be involved, and that there is no difference in the concentration of auxin on the light and shady sides, or not enough difference to explain the difference in growth rates. [7]
Indole-3-butyric acid (1H-indole-3-butanoic acid, IBA) is a white to light-yellow crystalline solid, with the molecular formula C 12 H 13 NO 2. It melts at 125°C in atmospheric pressure and decomposes before boiling. IBA is a plant hormone in the auxin family and is an ingredient in many commercial horticultural plant rooting products.
The acid-growth hypothesis is a theory that explains the expansion dynamics of cells and organs in plants. It was originally proposed by Achim Hager and Robert Cleland in 1971. [1] [2] They hypothesized that the naturally occurring plant hormone, auxin (indole-3-acetic acid, IAA), induces H + proton extrusion into the apoplast.