Secondary growth

Definition

Secondary growth is the process by which plants increase their thickness or girth through the division of vascular cambium and cork cambium, leading to the formation of new xylem and phloem tissues. This type of growth is essential for the development of woody plants, allowing them to support larger structures and transport nutrients and water more efficiently as they mature.

5 Must Know Facts For Your Next Test

1. Secondary growth primarily occurs in dicots and gymnosperms, while most monocots do not undergo significant secondary growth.
2. The process of secondary growth results in the formation of annual rings in trees, which can be used to determine the age of a tree.
3. Xylem produced during secondary growth is known as secondary xylem, which provides structural support and is often referred to as wood.
4. The increase in girth through secondary growth allows plants to access more light by growing taller and to enhance stability against environmental forces such as wind.
5. Secondary growth can also contribute to the storage of nutrients and water within woody plants, making them more resilient during periods of drought.

Review Questions

• How does secondary growth differ from primary growth in plants, particularly regarding tissue types and their functions?
  • Secondary growth differs from primary growth in that it increases a plant's thickness rather than its height. Primary growth occurs at the tips of roots and shoots, leading to the formation of primary tissues like parenchyma, while secondary growth involves lateral meristems, specifically vascular cambium and cork cambium. This allows for the production of secondary xylem and phloem, which are crucial for structural support and nutrient transport as the plant matures.
• Discuss the role of vascular cambium in secondary growth and how it contributes to the overall health of woody plants.
  • Vascular cambium is a key player in secondary growth as it produces new layers of xylem and phloem, allowing for an increase in the plant's diameter. This addition of new tissues not only strengthens the plant structurally but also enhances its ability to transport water and nutrients throughout a larger structure. As woody plants grow older, their vascular cambium becomes more active, contributing to a healthier plant capable of supporting larger foliage and resisting environmental stresses.
• Evaluate how environmental factors might influence the rate of secondary growth in trees and discuss potential ecological implications.
  • Environmental factors such as temperature, moisture availability, and soil nutrients significantly influence the rate of secondary growth in trees. For instance, warmer temperatures and adequate water supply generally promote faster growth rates, leading to thicker trunks and more substantial canopies. Conversely, stressors like drought or nutrient deficiency can slow down this growth process. Ecologically, variations in secondary growth rates can affect forest dynamics, biodiversity, and carbon storage capabilities, ultimately impacting local ecosystems and climate regulation.

Related terms

vascular cambium:

A layer of meristematic tissue in plants that produces secondary xylem (wood) on the inside and secondary phloem (bark) on the outside.

cork cambium:

A lateral meristem that produces cork cells, which replace the epidermis in older stems and roots, providing protection and reducing water loss.

lateral meristem: Tissues in plants that are responsible for secondary growth; they enable the increase in diameter of stems and roots.