Primary and Secondary Growth

Growth is the process by which a plant increases in the number and size of leaves, roots, and stems. The growth in plants depends on the hormones which are produced in minute amounts and the physiological effect is shown at other site.

The growth in plants is studied at two different levels such as primary and secondary. The primary growth refers to increase in length of plant, number of leaves, and production of branches. Secondary growth refers to increase in girth and growth associated with girth.

Primary Growth

It refers to the growth taking place in apical surface where higher amount of cell division takes place in apical meristem. The high pace of cell division results in cell elongation and takes place in undifferentiated regions referred as meristems.

The primary growth in roots is concentrated at root tip and is covered by the presence of root cap. The root cap produces polysaccharide and help in rapid rate of growth. The growth at the apical meristem in roots takes place at rapid phase and results in replacement of cells at root cap. 

 

Secondary Growth

Secondary growth in plants takes place in vascular cambium and at a later stage it produces secondary xylem cells in the inside of the meristem and formation of secondary phloem cells on the outside of the meristem.

It is found that the secondary growth disturbs the epidermis in terms of rupture it results in formation of cork cambium which is in general dark and gives rise to thickened cork cells. The thickened cork cells are known for their role to protect. 

 

The Differences 

Primary Growth	Secondary Growth
Taking place at the tip of the plant (tip of shoot and tip of root)	Taking place in the stem
Occur in every plants	Occur only in woody plants
Increase in length of plant, number of leaves, and production of branches	Increase in girth or diameter
Occur by the activity of apical meristem	Occur by the activity of Cambium

 

SOURCE : http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect17.htm http://www.botany.hawaii.edu/faculty/webb/bot201/angiosperm/magnoliophytalab99/magnoliosidalab.htm

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