Mechanical forces active on steep slopes tend to overturn plants, which respond by developing a specific asymmetrical architecture in the root system. This asymmetric architecture is the consequence of preferential lateral root emergence and elongation in the up-slope and down-slope directions. Root systems show a normal symmetrical architecture when the same species is grown on plane soil. The asymmetrical root architecture on steep slopes seems to increase the plant’s stability by modifying the distribution of mechanical forces into the soil. This hypothesis is supported by the observation that lateral roots developing in the up-slope or down-slope directions present considerable anatomical modifications in shape and tissue-organization compared with lateral roots from plants growing on plane soil.