11th Class Biology Morphology of Flowering Plants (Root, Stem And Leaf) Stem Branching

Stem Branching

Category : 11th Class

In angiosperms, always the branches are produced by the growth of axillary buds or lateral buds. This type of branching is known as lateral branching. The lateral branching is classified into two kinds racemose and cymose.

(1) Racemose branching : In this type of branching, the terminal (or apical) bud of the main stem grows indefinitely and the axillary buds grow out into lateral branches in acropetal succession.

This type branching is also called monopodial branching. Due to monopodial branching the shoot system of plant appears conical e.g., Eucalyptus, Polyalthia (Ashoka tree).

(2) Cymose branching : In cymose branching the terminal bud is active for a short period and becomes modified into some permanent structures like tendrils, thorns of flowers etc. Due to the terminal bud modification the growth of the main stem is definite. This is also called sympodial branching. Further growth in the plant is carried by one or more axillary buds. Cymose branching may be of three types :

(i) Uniparous or Monochasial type : In uniparous type of branching only one lateral branch is produced at each time below the modified terminal bud. Here the successive lateral branches that are formed unite to form a stem. Such a stem is called false axis or sympodium. The uniparous branching is of two kinds, helicoid and scorpoid.

(a) Helicoid branching : If the successive lateral branches develop on one side it is called helicoid branching. e.g., Saraca, Canna and Terminalia.

(b) Scorpioid branching : If the successive lateral branches develop on either side alternately, it is called scorpioid branching, e.g., Cissus, Gossypium and Carissa.

 

 

(ii) Biparous or Dichasial type : When the activity of terminal bud stops, further growth of plant takes place by two lateral branches, e.g., Viscum (Mistletoe), Silene, Stellaria, Mirabilis jalapa (Four O’ clock), Dianthus (Pink), Carissa carandas (Karonda), etc.

(iii) Multiparous or Polychasial type : When the activity of terminal bud stops, further growth of plant takes place by a whorl of three or more axillary branches. The axis is said to be multipodial, e.g., Euphorbia tirucalli, Croton, Nerium odoratum (Oleander).

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