Stem

Stem:

Stem is a part of plant which lies above from surface of soil i.e. it shows negative geotrophic growth. It has nodes and internodes. Branches, leaf, flower bud and bract are developed from nodes. Stem arises from plumule.

It normally has leaves, branches and flowers. Young stem is green in colour and performs Photosynthesis. The growing apex of the stem bears number of tiny leaves which protect them. The branches and leaves develop exogenously on stem, which develops into nodes and internodes

Node and Internode: The swalen part place of stem or branch from where leaves arise is known as node, and the space between two successive nodes is called internode. Leaf and branches develop from the node. Node may be easily distinguished in some plants eg. sugarcane, bamboo or may not have clear marks.

Bud: Bud can be defined as “young underdeveloped shoot consisting of a short stem number of tender leaves arching over the growing apex. In buds the internodes are not developed and the leaves cover the apex forming a compact structure. Leaves at the lower side of the buds are larger and at the upper side are small. (acropetal succession)

Buds are of two types i.e. floral buds from which flower develops and vegetative buds from which stem and leaves develops. When the stem or branch ends with vegetative bud it continues to grow. If floral bud is at the end of the stem the growth of stem ceases.

On the basses of the position buds can be classified into four categories

(a) Terminal bud : it grow the terminal position on the apex of the stem or branch which continuos to grow in upward direction.

(c) Accessory bud (6usest): It grows on the node but slightly away from the axil of the stem giving rise to the lateral branches

(d) adventitious buds

Buds arising on stem, leaf on roots are adventitious buds

Function of stem :

Bearing leaves and flower: Flowers and leaves are on branches and stem. Stem spreads them in all direction so that leaf gets enough sunlight and flowers can attract the insects for pollination and reproduction.

Conduction (Transportation): The stem transports water and minerals from the root to all parts of the plant and transport nutrition from leaf to all parts of the plant, especially to storage organ and growing region.

Support: The main stem acts as a supporting pillar for branches, which spreads in all direction.

Storage: Stem also acts as a storehouse of food material, especially in case of ginger, potato onion etc.

Food manufacture: Young stems, green in colour contains chlorophyll which manufactures food in the presence of sunlight.