Underground stems have presence of nodes and internodes, scale leaves and adventitious roots arising from the nodes and presence of axillary and terminal buds. Functions: store reserve food, and are adapted for perennation and during favorable conditions underground stems give rise to aerial shoots, with the onset of unfavourable conditions the aerial shoots die.
Types | Characters | Examples |
Rhizome | Thick, fleshy, prostrate, flattened horizontally growing stem near the soil surface. Bears scale leaves and branches on nodes, terminal and axillary buds, adventitious roots | Ginger (Adrak), Turmeric (Haldi) |
Corn | Small, rhizome like, scale leaves bears, nodes and internodes, buds and adventitious roots | Saffron (kesar), Yam (jimikand), Gladiolus |
Bulb | Reduced stem, flattened discoid stem with crowded nodes bearing overlapping fleshy (inner) and dry (outer) scale leaves. Terminal bud forms foliage leaves. Adventitious roots grow from discoid base | Onion (Allium cepa) |
Tuber | Swollen tip of the underground branch, stores large amount of reserve materials primarily starch, bear ‘eyes’. Each eye is a node which bears bud and scar of scale leaves | Potato |
In sub-aerial modifications some parts of the stem lives underground whereas remaining part of stem is aerial, herbaceous plants with a thin, delicate and weak stem. Plants bear adventitious roots and aerial branches at their nodes function as vegetative propagation.
Type | Characters | Examples |
Runner | Slender stem, weak, slender, branch with long, thin internodes, runs horizontally on soil surface giving off adventitious roots at nodes | Grass, Oxalis |
Stolon | Slender lateral branch that arises from the base of the main axis, branch arches downwards to touch the ground, where its terminal bud gives rise to a new shoot and roots | Jasmine, Mint (Pudina) |
Offset | Stout and short runner like branch, which bands at the tip and gives rise to a rosette of leaves above and roots below | Water hyacinth, water lettuce |
Sucker | Originates from the basal and underground portion of the main stem, shorter and stouter than runner, grow horizontally for a distance partly below the ground | Chrysanthemum |