Morphology of Flowering Plant: The Stem

  • The body of a typical flowering plant can be divided into the underground root system and aerial shoot system. The shoot system is heterogeneous. Shoot system (stem) is an aerial and erect part of plant body which grows upwards. It is usually above the soil and develops from plumule of the embryo of a germinating seed. It consists of stem, branches, leaves, flowers, fruits and seeds.
  • The stem is negatively geotropic (moves above the soil), negatively hydrotropic (moves away from the water) and positively phototropic (moves towards the light). 
  • Branches arise from axillary buds present in the axil of leaves. Each axillary bud is a small, compact, underdeveloped shoot covered with a large number of overlapping leaf primordia. Internodes of this bud enlarge and develop into a branch. Therefore the development of branches is exogenous (exo = outside).

Characteristics of Stem:

  • The shoot system is heterogeneous and consists of stem, branches, leaves and flowers.
  • The stem is negatively geotropic (moves above the soil), negatively hydrotropic (moves away from the water) and positively phototropic (moves towards the light). 
  • The stem bears nodes and internodes. The regions of the stem where leaves are born are called nodes while internodes are the portions between two nodes.
  • The stem bears buds, which may be terminal or axillary. The stem is generally green when young and later often become woody and dark brown.
  • Stem arises as a prolongation of plumule (one end of an embryo).
  • Stem bears vegetative buds which could be terminal (apical bud) for the plant to grow upwards or axillary (bud in the axil of leaf) which give rise to lateral branches. Stem bears floral buds (terminal or axillary) that grow into flowers

Functions of the Stem:

Primary Functions:

  • To support and orient the leaves in a manner that they are exposed to maximum sunlight and for efficient gaseous exchange during photosynthesis and respiration.
  • To conduct water and minerals from roots to leaves and manufactured food from leaves to different parts of the plant.
  • To bear flowers and fruits

Secondary Functions:

  • Some stems perform the function of storage of food, support, protection and of vegetative propagation.
  • Storage:  Stems store food and water in some plants e.g. potato
  • Perennation: The underground stems help tide over the unfavourable growing periods e.g. ginger.
  • Vegetative propagation: e.g. rose, and sugarcane th stem can be used for vegetative propagation.
  • Photosynthesis: In xerophytes (desert plants) the leaves are reduced to thorn, the stem possessing chlorophyll takes up the function of photosynthesis. e.g.Opuntia
  • Protection: In some plants, the axillary bud modifies into thorn and protects the plants from grazing animals e.g. citrus, Duranta.
  • Climbing and Clinging: Tendrils or hooks are modified branches or buds. They coil around
    the support and help the plant to climb e.g. grapevine..

Types of Stem: 

  • The stem may be
    • aerial (erect, rigid, strong and upright as in herbs, shrubs and trees)
    • subaerial (weak, unable to stay upright and trail on the ground as creepers or climb up as climbers) or
    • underground (buried in soil and produces aerial branches under favourable conditions only

Underground Modifications of the Stem:

  • Since underground, they may seem like roots but they have characteristics of the stem, like the presence of nodes and internodes, scaly non-green leaves and buds. This modification serves two functions it acts as perennating structures by remaining leafless and dormant in winter but giving off aerial shoots under favourable conditions (next season) and Store food and become thick and fleshy.


  • It is prostrate, dorsoventrally thickened brownish stem, which grows horizontally under the surface of the soil. It shows distinct nodes and internodes. It shows distinct nodes and internodes. It bears scale leaves on nodes, It possesses terminal bud and axillary buds in the axil of each scale-leaf present at the node. Adventitious roots are present.
  • e.g. Ginger (अद्रक), Turmeric (हलदी).

Stem 01

Stem Tuber:

  • Tubers are actually the swollen tips of ends of special underground branches swollen due to storage of food as starch. The tubers show nodes and internodes. Nodes bear scale leaves with axillary buds, commonly called eyes. Under favourable conditions eyes sprout and produce aerial roots. Thus tubers help in vegetative propagation. They do not produce adventitious roots.
  • e.g. Potato (आलू).

Stem 02


  • It is condensed disc like an underground stem.
  • The upper surface of the disc-like stem, is conical and bears centrally placed apical bud and many concentrically arranged overlapping scale leaves. Scale leaves store food.  When the scale leaves surround the apical bud in the form of concentric rings, it is called tunicated bulb. e.g. onion (प्याज).

Stem 05

  • When the scale leaves partially surround the apical bud by overlapping each other, it is called scaly bulb. e.g. garlic (लहसुन).

Stem 04

  • The lower surface of stem produces adventitious roots.


  • It is condensed disc like underground, fleshy, spherical stem with flattened base, It grows vertically, bears many scale leaves, distinct nodes and internodes, buds and adventitious roots. e.g.  Saffron (केसर), yam (जिमीकंद), gladiolus.

    Stem 03

Sub Aerial Modifications Of Stem:

  • Stems are weak, therefore lie prostrate on the ground or may get partially buried in the upper layer of soil. The plants bearing such stems are called creepers. Their stems serve the function of vegetative propagation.


  • The basal internodes of the bud elongate horizontally and trail along the soil carrying the bud to a distance from the mother plant where it gets fixed to the soil by means of adventitious roots and develops a new daughter plant. This branch carrying the bud is called a runner.  It grows in all the direction and a single plant soon covers a large area by its pro­geny. e.g. Grass, Oxalis, Centella asiatica, strawberry, etc.

Stem 06


  • When a weak lateral branch which grows upwards then arches down to meet the soil, strike roots and produce daughter plants. The difference between the runner and stolon is, runner grows horizontally, while stolen grows obliquely upward and then arches to the ground.
  • e.g. Mint (‘Pudina’), Jasmine.

Stem 07

  • Like runner but thicker and shorter, grow for a short distance then produce cluster (rosette) of leaves above and adventitious roots below; generally in aquatic plants. It is just like the runner, only it is shorter and thicker.
  • e.g. water hyacinth (Eichhornia crassipes), pistia (Pistia stratiotes), water lettuce

Stem 08


  • Underground runner which grows horizontally for a distance under soil then emerges obliquely upwards, strikes roots and forms daughter plants.
  • e.g. Chrysanthemum, Mentha arvensis, banana, pineapple etc.

Stem 09

Aerial stem modifications:

  • Whole stem or its part (axillary or terminal bud) gets modified to perform definite functions. It is a stem because they show characteristics like a) Arise in the axil of leaf b) Bear nodes and internodes c) may bear leaves, buds, flowers.

Stem Tendrils:

  • Stem or its branches get modified into a green threadlike, spirally coiled leafless structures called tendrils which are meant for climbing. They twine around neighbouring objects and help weak plants to climb. These may be branched or unbranched. A scale leaf is always present at the point of branching of the tendril.
  • e.g. Grapevine, cucumber, pumpkins, watermelon, etc.

Stem 10


  • These are straight, pointed, hard or woody structures sometimes they bear leaves, flowers or may be branched. Axillary buds of stems get modified into thorns (e.g. Citrus, Duranta, and Aegel). In Carrissa, terminal buds get modified into thorns.
  • Thorns are used as organs of defence against grazing animals or climbing (e.g. Bougainvillea) and to check transpiration.

Stem 11


  • These are fleshy, green flattened or cylindrical branches of unlimited growth with nodes and internodes. The leaves are modified into spines or scales to check transpiration. This modification of stem is observed in plants growing in dry regions. The stem takes part in photosynthesis and stores water. e.g. Opuntia, Euphorbia, Casuarina, Cocoloba etc.

Stem 12

Cladode or Cladophylls:

  • It is a phylloclade with limited growth i.e. with only one or two internodes; help in photosynthesis. These are green cylindrical or flattened leaf-like branch. In Asparagus, the cladodes are one internode long and in Ruscus, the cladodes are two internodes long. They help in photosynthesis.

Stem 13


  • These are modified vegetative or floral buds with stored food and meant for vegetative propagation.
  • In Dioscorea, bulbils are condensed axillary buds while in Agava and lily the floral buds develop into bulbil. They detach to develop into a new plant.

Stem 14

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