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Differentiate between primary and secondary growth of plants.

GeneralClass 12AllAnswered 27 Mar 2026
Answer

Aspect

Primary Growth

Secondary Growth

Definition

Increase in length of roots and stems

Increase in girth/diameter of roots and stems

Meristem Involved

Apical meristems (shoot apex, root apex)

Lateral meristems (vascular cambium, cork cambium)

Tissues Formed

Primary tissues: Primary xylem, primary phloem, epidermis, cortex, pith

Secondary tissues: Secondary xylem (wood), secondary phloem, cork, secondary cortex

Distribution

All flowering plants (monocots and dicots)

Most dicots and gymnosperms; absent in most monocots

Duration

Throughout life (continuous at apices)

After primary growth in mature regions

Axis Affected

Vertical axis (height/length)

Horizontal axis (thickness)

Economic Importance

Determines plant height, leaf production

Produces wood, cork (timber, cork industry)

Developmental Sequence:

  1. Primary Growth (all plants)
    • Apical meristem → Primary tissues → Elongation
  2. Secondary Growth (dicots/gymnosperms only)
    • Vascular cambium → Secondary vascular tissues
    • Cork cambium → Periderm (bark)

Evolutionary Perspective:

  • Secondary growth is an ancestral trait in vascular plants
  • Monocots lost this ability during evolution (adaptation for herbaceous habit)

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General · Class 12