Let us know about Underground Stem. Underground stem are modified plants that emerge from the stem tissue but are present below the surface of the soil .  They act as storage tissue for food and nutrients, propagation of new clones, and perennials (surviving from one growing season to another).  Its types include bulb , corm , rhizome , stolon , spindle-shaped and tuber .
Plants have two axes of growth, which can be best visualized by seed germination and growth. Seedlings develop two structures or axes of growth, one that develops upward from the soil, called the stem, and structures that develop downward called the root . The roots are modified so that the root hairs and branches are indistinguishable with cells that carry water and nutrients, while the stems are modified to transfer water and nutrients to and from the leaves and flowers. Stems have knots with buds where leaves and flowers grow in specific places, while roots do not. plantsuse underground stems to multiply their numbers by asexual reproductionand to survive from one year to the next, usually in a period of inactivity.  Some plants produce modified stems to store energy and preserve the potential growth space to survive cold or dry periods that are normally periods of dormant growth, and when that period dies, the plants resume new growth from underground stems.  Being underground protects the stems from the elements during dormant periods, such as freezing and thawing in winter or drought in extreme heat and heat or fire. They can also protect plants from the pressure of heavy grazing by animals , the plant can be eaten on the ground but new growth can grow from under the ground that cannot be reached by herbivores .Many plants, including weed species, use underground stems to spread and colonize large areas, as the stems do not need to be supported or strong, requiring less energy and resources to produce these stems and often these plants have more mass. ground above ground.
Types of underground stems
Various forms of underground stems include:
- Bulb – Small, straight limb leaves modified into coarse fleshy scales. Tulips, daffodils  and lilies.
- Corms – short, straight, tough or fleshy stems covered with thin, dry papaya leaves.
- Rhizome – with less scale like leaves. The top can produce leafy stems while the bottom can produce roots. Eyeball.
- Stolons – horizontal stems that run at or just below the soil surface, with nodes that form the root and long internodes, the ends producing new plants. They are called “runners” when they are above ground.
- Tuber – An elongated fleshy end of a stem, usually from a rhizome, but often also refers to thick roots.
Many underground stems are consumed by people, including; Onion , Potato , Ginger , Yam and Taro .
A geophyte (earth + plant) is a plant with an underground storage organ consisting of true bulbs, corms, tubers, tuberous roots, elongated hypocotyl and rhizome. Most plants with underground stems are geophytes but not all plants that are geophytes have underground stems. Geophytes are often physically active even when there is a lack of leaves. They are able to survive during unfavorable environmental conditions by going into a state of silence and subsequently resuming growth from their storage organs, which contain carbohydrate and water stores when environmental conditions are again favorable.