Secondary growth

Definition

Secondary growth refers to the increase in thickness or girth of a plant, primarily through the activity of lateral meristems such as the vascular cambium and cork cambium. This process allows for the formation of additional vascular tissue, which enhances the plant's ability to transport water and nutrients, and contributes to the overall structural support of woody plants.

5 Must Know Facts For Your Next Test

1. Secondary growth primarily occurs in dicots and gymnosperms, allowing these plants to become larger and stronger over time.
2. The vascular cambium is crucial for secondary growth, as it generates new layers of xylem and phloem each year, leading to annual growth rings in trees.
3. Secondary growth leads to increased bark formation, which serves as protection against physical damage and pathogen invasion.
4. Unlike primary growth, which increases length, secondary growth increases a plant's girth, allowing for a more robust structure to support larger leaves and reproductive structures.
5. In some plants, such as trees, secondary growth can significantly enhance their ability to transport water and nutrients over long distances due to increased vascular tissue.

Review Questions

• How does secondary growth differ from primary growth in plants, and what are the implications of these differences?
  • Secondary growth differs from primary growth in that it increases the thickness or girth of a plant rather than its length. Primary growth occurs at the tips of roots and shoots through apical meristems, leading to an increase in height. In contrast, secondary growth involves lateral meristems like the vascular cambium, which produces additional layers of vascular tissue. This thickening is crucial for supporting larger plant structures and improving water and nutrient transport within more massive plants.
• Discuss the roles of vascular cambium and cork cambium in secondary growth and how they contribute to a plant's overall structure.
  • The vascular cambium plays a central role in secondary growth by producing secondary xylem (wood) towards the inside and secondary phloem towards the outside. This adds layers each growing season, increasing the plant's diameter. The cork cambium complements this by generating protective cork cells that form the outer bark. Together, these meristems enhance a plant's structural integrity and resilience against environmental challenges.
• Evaluate how secondary growth can impact a plant's ecology and interactions with its environment over time.
  • Secondary growth significantly impacts a plant's ecology by enabling it to reach greater heights and develop thicker trunks, which can influence local ecosystems. Taller trees can outcompete smaller plants for sunlight, impacting biodiversity in forested areas. Additionally, thicker bark protects against pests and diseases while providing habitats for various organisms. As these changes occur over time, they reshape interactions within ecosystems, including competition for resources, habitat availability, and overall forest dynamics.

Related terms

lateral meristem: A type of meristem that is responsible for secondary growth, producing new cells that contribute to the thickness of stems and roots.

vascular cambium: A layer of lateral meristematic tissue that produces secondary xylem (wood) and secondary phloem, increasing the plant's diameter.

cork cambium: A lateral meristem that produces cork cells, contributing to the protective outer layer of bark in woody plants.