Underground stems are modified plant parts that derive from Plant stem tissue but exist under the soil surface. They function as storage tissues for food and nutrients, facilitate the propagation of new clones, and aid in perennation (survival from one growing season to the next). Types of underground stems include , , , , and .Figure 3 in
Plants have two structures or axes of growth, which can be best seen from seed germination and growth. Seedling develop two axes of growth: stems, which develop upward out of the soil, and Root, which develop downward. The roots are modified to have and branch indiscriminately with cells that take in water and nutrients, while the stems are modified to move water and nutrients to and from the Leaf and Flower. Table 1 in Stems have nodes with where leaves and flowers arise at specific locations, while roots do not. Plants use underground stems to multiply by asexual reproduction and to survive from one year to the next, usually through dormancy. Some plants produce stems modified to store energy and preserve a location of potential growth to survive a cold or dry period which normally is a period of inactive growth, and when that period is over the plants resume new growth from the underground stems.
Being underground protects the stems from the elements during the dormancy period, such as freezing and thawing in winter, extreme heat and drought in summer, or other potentially harmful elements such as fire. They can also protect plants from heavy grazing pressure from animals, the plant might be eaten to the ground but new growth can occur from below ground stem that can not be reached by the .
A number of underground stems are consumed by people including; onion, potato, ginger, yam and taro.Figure 3 in
The below-ground stems of grasses have scales, while roots are smooth without scales.
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