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Write an account of the transport of organic substances in the plant.
Member rating: No Rating | Words: | Submitted: Wed Mar 24 2004
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Write an account of the transport of organic substances in the plant. Phloem tissue is made up of four main elements Sieve tubes are living, tubular cells that disintegrate during development. They are connected end to end, up and down the entire plant. The end cell walls have perforations in them to make sieve plates. The cytoplasm is present but in small amounts and in a layer next to the cell wall. It lacks a nucleus and most organelles so there is more space for solutes to move. The cell walls are made of cellulose so solutes can move laterally a well as vertically. Since the sieve tube element lacks organelles, the companion cell with its nucleus, mitochondria, ribosomes, enzymes etc., controls the movement of solutes and provides ATP for active transport in the sieve tube element. Strands of cytoplasm called plasmodesmata connect the sieve tube element and companion cell. Also, fibres...
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