Forms of Stem:

  1. Strong Stem:

The following terms are important in relation to strong stems.

  • Excurrent:- The main axis shows continues growth and the lateral branches develop regularly giving a conical appearance to the trees; Pinus.
  • Deliquescent:- The growth of lateral branch is more vigorous than that of main axis. The tree has a rounded or spreading appearance; e.g. Mangifera, Ficus.
  • Caudex:-  It is unbranched, stout, cylindrical stem, marked with scars of fallen leaves; e.g. Cocos, Date-palm.
  • Clum:- Erect stems with distinct nodes and internodes. Stem shows jointed appearance. e.g. Bambusa arundinacea.

Branching of stem

Stem branching is of three types:

  1. Dichotomous: Pandanus, Asclepias.
  2. Racemose (Monopodial): Pinus, Eucalyptus.
  3. Cymose: a) Sympodial or uniparous cyme. e.g., Saraca (Helicoid), Grape (Scorpoid).

b) Dichasial cyme: e.g. Viscum, Datura.

c) Polychasial cyme : e.g., Euphorbia, Croton.

Types of stem

Weak Stem:

Theses stems cannot maintain an upright position. Weak stems can be divided into following categories:

Trailing:

It is a weak stem that spreads over the surface of the ground without rooting at the nodes. These fall into three categories:

  • Prostrate (procumbent): A stem that lies flat on the ground.

Creeping:

The plant grows horizontally on the ground and gives off roots at each node; e.g. grasses, strawberry, Oxalis. Runners, stolons, offset and suchers.

 

 

  • Climbing:

This week stem climbs a support by means of some special structure or organ for attachment. These are divided into following types.

  • Twiners : It is week, long and slender stem that climbs by twining is body around the support.
  • Tendril Climbers : It is a week stem climbing by its slender, leafless, spirally coiled structures, known as tendrils.
  • Leaf tendril : The whole leaf is modified into a tendril.
  • Leaflet tendril : Some upper leaflets of a leaf are modified into a tendril.
  • Petiole tendril :  Petiole is modified into a tendril e.g., Clematis.
  • Leaf apex tendril :  Apex of a leaf is modified into a tendril e.g. , Gloriosa.
  • Stipule tendril : Stipule is modified into a tendril e.g., Smilax.
  • Apical bub tendril :  Apical bub is modified into a tendril e.g. , Vitis.
  • Axillary bub tendril :  Axillary bub is modified into a tendril e.g., Passiflora (Passion flower).
  • Extra axillary bub terndril : e.g. cucurbits.
  • Inflorescence axis tendril : Inflorescence axis is modified into a tendril e.g., Antionan.
  • Root climbers : Such climbers give out adventitious roots at each node which stick to the support; e.g. Pothos scandens (money plant).
  • Hook climbers (Scramblers) : In Bougainvillea.
  • Lathyrus  - Whole leaf modified into tendril
  • Pisum sativum – Upper leaflet modified into tendril,
  • Clematis – Petiole modified into tendril,
  • Gloriosa – Leaf apex modified into tendril,
  • Smilax – Stipule modified into tendril.

 

Sucker :- Arising from the basal underground portion of the main. Initially it grows horizontally below the surface of the earth but soon grows obliquely upward forming a leafy shoot e.g. Chrysanthemum.

 

Stolen:

It is subterranean long lateral branch arising from base of the stem. It first grows obliquely upward and then bends down to touch the ground surface. e.g., Colocasia.

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