DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY
A growing shoot on a potato tuber, Solanum tuberosum. A potato is a storage organ containing starch, that is produced by an underground stem called a rhizome.Growth buds form on the surface of the potato.These are the "eyes" on a stored tuber. Initially these are dormant, but dormancy is broken after about two months in dry storage. If the potato is then brought into the light, the buds develop into shoots. The procedure is called chitting. It is used by growers to enable faster establishment after planting and an earlier crop. The picture shows a chitted potato, variety "Charlotte". The shoot has small root primordia ( pale cream growths ) and side-shoots ( light green ). When planted, the main stem ( purple, hairy ) will grow upwards, showing negative geotropism. The side-shoots show positive geotropism and grow downwards into the soil as rhizomes, eventually producing new tubers.
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