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| Plant growth regulation – an important new discovery | |
| Plant growth is controlled by molecular signals emanating from the epidermis. By controlling these growth signals, Prof. Joanne Chory and her team of researchers at the Salk Institute for Biological Studies in the USA have succeeded to manipulate plant growth. They discovered that plants of a very dwarf clone of Arabis thaliana were deficient in the plant growth hormone called brassinolide or defective in responding to it. The cells of the outer epidermis (leaf, shoot, root) are able to communicate with those of the inner layers stimulating them to grow or not to grow according to the changing environmental conditions of light, humidy, CO2 etc. Among the genes identified in Arabidopsis is the receptor, BRI1 that is activated by the brassinolide hormone. In dwarf Arabidopsis plants the BRI1 receptor does not express itself. In normal plants the BRI1 receptor expresses itself both on the outer epidermis and the inner epidermal layer which contains the chloroplasts. When the the hormone in the leaf epidermis was broken down with an enzyme the normal sized plant reduced into a dwarf. When the inner epidermis of the dwarf Arabidopsis plant is left as normal without BRI1 receptors and the expression of the BRI1 receptors is made to function in the outer epidermis, the dwarf plant grows into a full-sized plant. The findings effectively represent a new important instrument in the genetic expression of dwarfism that molecular geneticists and plant breeders can eventually utilize. Further developments should eventually lead to the manipulation of plant growth without artificial growth regulators. It could help to maximize productivity through increased plant density or size and angulation of leaf surfaces. Salk Institute for Biological Studies, San Diego, USA. Fax 001 8584538534. E-mail: communications@salk.edu www.salk.edu |
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