Question

Differentiate between primary and secondary growth?

Answer 1

1. Primary growth of stems is a result of rapidly dividing cells in the apical meristems at the shoot tips.
   Subsequent cell elongation also contributes to primary growth.
2. The influence of the apical bud on overall plant growth is known as apical dominance, which diminishes the growth of axillary buds that form along the sides of branches and stems.
3. Most coniferous trees exhibit strong apical dominance, thus producing the typical conical Christmas tree shape.
4. If the apical bud is removed, then the axillary buds will start forming lateral branches.
5. Gardeners make use of this fact when they prune plants by cutting off the tops of branches, thus encouraging the axillary buds to grow out, giving the plant a bushy shape.
6. The growth of the lateral meristem, which includes the vascular cambium and the cork cambium (in woody plants), increases the thickness of the stem during

Secondary growth:

• Normally it occurs in dicotyledonous stem.
• However, a different kind of secondary growth occurs in some monocotyledonous stem (e.g., Dracaena, Aloe, Yucca, Agave, Kingia, San-sieviera, Xanthorrhoea and Lomandra), which is considered as abnormal or anamalous type.