NCERT Based Test: The Stem

Hydrophytes are plants adapted for growing in waterlogged soil or on a substrate that becomes inundated on a regular basis. In hydrophytes, roots are of secondary importance so they are poorly developed.

Erect unbranched stems with distinct nodes and intermodes are called culms, nodes are swollen giving a jointed appearance e.g., Bamboo.

Cladodes (cladophylls) are green stems of limited growth (usually one internode long), which have taken over the function of photosynthesis from the leaves. It is an adaptation to reduce water loss. The true leaves are reduced to scales or spines e.g., Asparagus and Ruscus.

Phylloclades have unlimited (or indefinite) gworth whereas cladodes ahve a limited (or definite) growth. Opuntia and Euphorbia royleana are the examples of phyllodades whereas Ruscus aculeatus and Asparagus are the examples of dadodes.

Stem tuber is an oval or spherical underground swollen stem structure which does not bear adventitious roots, e.g., potato (Solanum tuberosum), Jerusalem artichoke (Helianthus tuberosus). Food reserve is starch in potato and inulin in artichoke.

Bougainvilea is one of many plants that fall into the scamblers category. These plants have long, fleible, curved stem thorns which help them in gripping neighbouring stems and clombing.

Offsets are one internode long, thick, small runner bearing a cluster of leaves in rosette manner at the water or ground level and adventitious roots beow the water or ground level arising from all nodes, e.g., Pistia (water letiuce), Eichhomia crassipes, etc.

Phyllodades of Opuntia represent flattened green fleshy stems of unlimited growth which have take over the function of photosynthesis. Each segment of phylloclade develops in the axil of caducous leaf which falls down and leaves behind a scar. The segment may possess flower fruits. It bears many raised areas caled areoles. An areole is actually a node. It has a leaf scar, one or two large spines and a number of stiff hair called bristles or glochidia. The spines are modified leaves of suppressed aillary branches. They protect the plant against animals.

Zingiber officinale(ginger) is a straggling sympodial rhizome, which is a perennial, fleshy, dorsiventral, horizontal, usually branched, underground stem growing beneath the surface of soil. It possesses nodes and internodes, scaly leaves, axillary buds and roots at their nodes.

In potato, the stem nature is evident by the presence of eyes on its brownishy corky surfaces. Each sye is a pit like structure and represents the node. At the rim of the eye, scale leaf scar is seen.Buds are situated in the pit of the eye.

• Thorns represent the modification of an axillary shoot system in which the leaves are reduced. Their main function is to protect the plant from herbivores, example are Citrus.
• Phylloclades are the flat photosynthetic shoots which are the modified branches.
• Vegetative propagation is a method of reproduction in plants by the fragments or cutting of parent plant which further produce the more plants or clones. Runner is also type of vegetative reproduction. Strawberry plant has a stolon, which is also called a runner.
• Stilt roots are the adventurous roots that help in supporting the plant body. They are also known as support roots. They develop from the base nodes of the main stem and they always grow obliquely., e.g, are Maize, sugarcane.
• Haustorium are the highly modified stem stem or root of a parasitic plant. It penetrates the host tissues and then absorbs nutrients and water.

Sucker is a special non-green slender stem  branch which arises from underground base of  an erect shoot or crown. It grows  horizontally in soil and ultimately comes out to  form a new aerial shoot or crown. The process  is repeated. Each sucker has one or more  nodes with scale leaves and axillary buds. e.g.  Chrysanthemum. Curcuma domestica and  Zingiber officinale both are the examples of  rhizomes.

In onion the fleshy scales represent leaf bases  in the outer part and scale leaves in the central  region. They occur in concentric  fashion. The bulb is covered by a whitish or  pinkish tunic. Fleshy scales enclose terminal  bud. Fleshy scales represent the edible part of  onions.

Onion (Allium cepa) is a bulb. It is a short, modified, underground stem surrounded by usually fleshy modified leaves that contain stored food for the shoot within. Therefore edible part of onion is fleshy leaves.