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The rhizome also retains the ability to allow new shoots to grow upwards. [4] A rhizome is the main stem of the plant that runs typically underground and horizontally to the soil surface. [5] [6] Rhizomes have nodes and internodes and auxiliary buds. [7] Roots do not have nodes and internodes and have a root cap terminating their ends. [8]
A geophyte (earth+plant) is a plant with an underground storage organ including true bulbs, corms, tubers, tuberous roots, enlarged hypocotyls, and rhizomes.Most plants with underground stems are geophytes but not all plants that are geophytes have underground stems.
Stem tubers manifest as thickened rhizomes (underground stems) or stolons (horizontal connections between organisms); examples include the potato and yam. The term root tuber describes modified lateral roots, as in sweet potatoes, cassava, and dahlias.
Tubers develop from either the stem or the root. Stem tubers grow from rhizomes or runners that swell from storing nutrients while root tubers propagate from roots that are modified to store nutrients and get too large and produce a new plant. [22] Examples of stem tubers are potatoes and yams and examples of root tubers are sweet potatoes and ...
Since the hypocotyl is a region between the stem and the roots, such tubers are variable in their anatomy and growth habits. Thus the roots of Cyclamen graecum grow from the base of the tuber, suggesting it is a stem tuber, whereas those of Cyclamen hederifolium mostly grow from the upper surface of the tuber, suggesting it is a root tuber. [10]
A number of plants have soil-level or above-ground rhizomes, including Iris species and many orchid species. T. Holm (1929) restricted the term rhizome to a horizontal, usually subterranean, stem that produces roots from its lower surface and green leaves from its apex, developed directly from the plumule of the embryo.
In some species (e.g. Cyclamen coum) roots come from the bottom of the tuber, suggesting that it is a stem tuber; in others (e.g. Cyclamen hederifolium) roots come largely from the top of the tuber, suggesting that it is a root tuber. [6] As an example of a combination, juno irises have both bulbs and storage roots. [7]
Tuberous roots or root tubers – Narrow sense, those storage roots that do not conform to a specific shape, such as fasciculated, nodulose moniliform, annulated, etc.: e.g. sweet potato (Ipomoea batatas), whose edible part is a root of this type. Broader sense, adventitious roots swollen due to their storage function.