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.
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• 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.