Tuesday, January 6, 2009

Understanding of Translocation in Plants

The transport of sap containing dissolved products of photosynthesis through phloem is called translocation. Translocation is the transport of the products of photosynthesis by phloem to the rest of the plant. In angiosperms, sieve-tube members are the specialized cells of phloem that function in translocation. Sieve-tube members are arranged end-to-end forming long sieve tubes. Porous cross walls called sieve plates in between the members allow phloem to move the solution freely along the sieve tubes.

Phloem sap contains primarily sucrose, but also minerals, amino acids, and hormones. Phloem sap movement is not unidirectional; it moves through the sieve tubes from source to the sink. Source is the organ where sugar is produced by photosynthesis or by the breakdown of starch (usually leaves) and sink is the organ that consumes or stores sugar (growing parts of plant, fruits, non-green stems and trunks, and others). Sugar flows from source to sink. Source and sink depend on season. A tuber is a sink when stockpiling in the summer, but it is a source in the spring. The sink is usually supplied by the closest source. Direction of flow in phloem can change, depending on locations of source and sink.

Key words: Bio Genetics, Bio Technology

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