Secondary growth

Definition

Secondary growth refers to the increase in girth or thickness of a plant stem or root, primarily due to the activity of the lateral meristems, specifically the vascular cambium and cork cambium. This process allows plants to become woody and strengthens their structure, enabling them to support larger sizes and withstand environmental pressures. The formation of secondary tissues, including secondary xylem and phloem, is crucial for transporting water and nutrients as well as providing structural support.

5 Must Know Facts For Your Next Test

1. Secondary growth is mainly found in dicots and gymnosperms, while most monocots do not exhibit significant secondary growth.
2. The vascular cambium produces secondary xylem towards the inside and secondary phloem towards the outside, resulting in annual rings in tree trunks.
3. Cork cambium generates cork cells, which are important for protecting against water loss and pathogens.
4. The process of secondary growth can also lead to the formation of heartwood and sapwood within trees, affecting their strength and functionality.
5. Factors such as environmental conditions, age of the plant, and availability of resources can influence the rate and extent of secondary growth.

Review Questions

• How does secondary growth contribute to a plant's ability to thrive in its environment?
  • Secondary growth enhances a plant's structural integrity by increasing its girth, which allows it to support larger branches and leaves. This is vital for capturing more sunlight and accessing resources. By forming strong woody tissues through secondary xylem, plants can withstand strong winds and heavy snow loads, promoting their survival in various environments.
• Compare and contrast the roles of vascular cambium and cork cambium during secondary growth in plants.
  • Vascular cambium is responsible for producing secondary xylem and phloem, facilitating transport of water, nutrients, and sugars as the plant increases in diameter. In contrast, cork cambium generates protective cork cells that form a barrier against environmental threats like pathogens and moisture loss. Both are essential for maintaining plant health during secondary growth but serve different functions—structural support versus protection.
• Evaluate how variations in secondary growth can affect the overall ecology of forest ecosystems.
  • Variations in secondary growth influence forest structure and biodiversity by determining tree size, density, and competition among species. Trees with rapid secondary growth may dominate an area, outcompeting slower-growing species for light and resources. This can lead to monocultures or changes in species composition over time. Additionally, differences in wood density affect nutrient cycling and habitat availability for various organisms within the ecosystem.

Related terms

lateral meristem: Meristematic tissue that contributes to secondary growth, located between the xylem and phloem, responsible for increasing the thickness of stems and roots.

vascular cambium: A type of lateral meristem that produces secondary xylem (wood) and secondary phloem, contributing to the plant's growth in diameter.

cork cambium: Another lateral meristem that produces cork cells, which form the outer protective layer of stems and roots during secondary growth.