Branching pattern : Monopodial and sympodial growth

  Stem is the main axis of shoot system of plants. stem can be defined as the ascending part of shoot apex which is negatively geotropic, positively phototropic and develops from plumule of embryo.

There are two chief functions of stem

1. The conduction of water, minerals, and food materials.

2. The production and support of leaves and reproductive structure.

A stem with its leaves is called shoot. A stem is differentiated into Nodes and Internodes.

Branching of the stem

1. Dichotomous branching

2. Lateral branching

a. Dichotomous branching- here the growing point gets divided into two in the region of branching eg. Dictyota, Marchantia etc.

This type of branching is very common in Bryophytes and rarely in Angiosperms.eg. Asclepias.

False Dichotomy may appear due to the appearance of two lateral branches due to damage of growing points.eg. False Dichotomy in Plumeria.

b. Lateral branching- In such case branches appear exogenously from the lateral vegetative buds.

Lateral branching further divided into two parts-

1. Racemose or Monopodial

2. Cymose or sympodial

A. In Racemose or Monopodial branching the axis of the plant grows indefinitely due to the continued activity of terminal or apical bud.

The lateral branches appear in acropetal succession i.e Older towards the base and younger towards the apex. The lateral branches do not compete with the growth of main stem.

Example- Pinus, Eucalyptus, Polyalthia etc. 

B. In cymose or sympodial branching the terminal or apical bud after forming a small portion of axis either stops it's activity or gets modified into flowers,thorn or tendrils etc.

The further growth of the axis is continued by one or more lateral axillary bud that become active.

Types- 

1. Uniparous/monochasial

a. Scropioid

b. Helicoid

2.  Biparous/ dichasial

3. Multiparous/ polychasial

a. Uniparous- In this type of branching when the terminal bud stops it's activity, further growth takes place by single axillary branch. Soon it's bud also stop it's growth and process is repeated.

The axis of the plant thus formed is false because it is formed by the fusion of basal part of successive lateral branches and called as Sympodial axis.

a. Uniparous scorpioid

b. Uniparous helicoid

In uniparous scorpioid successive lateral branches appear on alternate sides eg. Vistis vinifera (grapevine) and howthorn. Axis in such as is sympodial and bear leaves on alternate sides on successive nodes.

fig : uniparous scorpioid

   In uniparous helicoid type successive branches appears on one side only eg. Saraca indica ( Ashoka tree). Axis in this case is sympodial which bears leaves on one side only. 

fig : uniparous helicoid

b. Biparous or Dichasial sympodial branching- In this type after the stoppage of growth of terminal bud, growth of plant axis is continued by the activity of two lateral branches. The process is Repeated. The axis is said to be multipodial eg. Stellaria, Carissa, viscum, mirabilia jalapa etc.

fig : Biparous or Dichasial 

c. Multiparous or polychasial sympodial branching-  After the stoppage of growth of terminal or apical buds, growth of plant axis is continued by the activity of more than two lateral buds. eg. Euphoria helioscopia, E. Tirucalli. The axis in this case is multipodial. 

Here in cymose branching the lateral branches appears in Basipetalous succession.

fig : Multiparous or polychasial

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