Several outside factors influence the way in which roots grow. They grow away from light and are pulled downwards by gravity, as you can see in simple experiments with large seeds such as beans or peas. This downward growth naturally takes the roots towards water in the soil. Some roots seek water more actively, for example trees such as willows. They send out roots that extend well beyond the spread of their branches; these roots may enter the joints of water pipes and sewers in search of water.
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