Introduction to Secondary Growth in Plants

Introduction to Secondary Growth

• Secondary growth is an increase in the girth of a plant, primarily in woody plants.
• It is a result of the activity of lateral meristems.

Lateral Meristems

• Lateral meristems are responsible for secondary growth in plants.
• Two main types of lateral meristems are the vascular cambium and the cork cambium.

Vascular Cambium

• The vascular cambium is a cylinder of meristematic cells that produces secondary xylem (wood) and secondary phloem (inner bark).
• It is located between the primary xylem and primary phloem.
• Cells in the vascular cambium divide to create new cells.
• The division of cells causes the girth of the plant to increase.
• Formation of new xylem cells on the inside and phloem cells on the outside increases the girth of the stem.
• The vascular cambium is initiated from the procambium of the primary vascular tissues.

Cork Cambium

• The cork cambium is a lateral meristem that replaces the epidermis with periderm, a protective layer in outer bark.
• It forms to the exterior of the vascular cambium.
• The cork cambium is responsible for producing cork cells, which are dead cells that provide protection and strength to the plant.
• Cork cells mature to form the cork, composed of suberized cell walls for water-proofing.
• Cork cambium aids in the protection against damage, pathogens, and water loss.

Secondary Xylem

• Secondary xylem is the wood produced by the vascular cambium.
• It is responsible for water transport in the plant.

Secondary Phloem

• Secondary phloem is the inner bark produced by the vascular cambium.
• It participates in the transport of photosynthates produced by the leaves.

Importance of Secondary Growth

• Secondary growth is crucial for the survival and growth of woody plants.
• It provides support and strength to the plant.
• It enables larger plants to withstand external stresses like wind and harsh weather.
• It allows for the transport of water, minerals, and nutrients throughout the plant body.

Factors Influencing Secondary Growth

• Factors such as light, temperature, water, and nutrients influence the activity of lateral meristems.
• Water availability is essential for the functioning of the xylem and phloem.
• Appropriate levels of light are important for photosynthesis, which contributes to the energy needed for growth processes.

Secondary Growth in Different Plant Parts

• Secondary growth occurs primarily in stems and roots, though some plants also display it in leaves.
• Roots typically have a stronger secondary thickening compared to stems.
• The process varies somewhat in stems and roots in terms of the initiation of secondary growth.

Conclusion

• The vascular cambium and cork cambium are collectively responsible for secondary growth in plants.
• The functions of these meristems are vital to the structure and survival of woody plants.

This quiz covers the concept of secondary growth and its processes in woody plants, focusing on lateral meristems like vascular and cork cambium. Understand how these meristems contribute to the increase in girth of the plant. Test your knowledge on the structure and function of these important tissues.