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All living organisms need to distribute raw materials and remove waste. To do this they need a transport system. Transport within small organisms can be adequately handled through processes such as diffusion, active transport, osmosis, endocytosis and exocytosis (Roberts, 1993). In larger multi-cellular organisms, such as plants and mammals, a transport system is required to move particles around.
The transport systems of both plants and mammals consist of specialised tubes. In mammals these tubes are called arteries, capillaries and veins. This series of tubes is collectively known as a cardiovascular system. The cardiovascular system consists of a series of vessels with a pump – the heart – to move blood, the method of transport within this closed circulatory system (Fullick, 2000). The transport system within a flowering plant also consists of a closed system of tubes but it is not a circulatory system. Transport within a flowering plant takes place in xylem and phloem.
In the mammalian cardiovascular system the heart pumps blood into a system of arteries (vessels that carry blood away from the heart) which in turn branch into arterioles (smaller blood vessels which branch into capillaries). The capillaries are tiny blood vessels within tissues where there is an exchange of materials between the blood and the cells. From the capillaries blood is carried back towards the heart via a series of tiny venules which merge into larger vessels to form veins (Roberts, 1993). All mammalian transport system cells and tissues are living – unlike those in the flowering plant. Phloem tubes in the flowering plant are living but xylem are made up from dead, lignified cells. Xylem vessels are hollow tubes that transport water and mineral ions and also provide structural support to the plant (Fullick, 2000). Phloem is a compound tissue which contains sieve tubes along with companion cells. The sieve tubes are the site of transport for sucrose from the leaves to...