Question

The activity of lateral meristems older roots and stems. a. lengthens b. thickens c. both a and b

Short answer

Lateral meristems thicken older roots and stems.

Step-by-step solution

Understanding Meristem Function

Meristems are regions in plants where active cell division occurs. Lateral meristems are responsible for the growth that increases the diameter or girth of a plant, rather than its length.

Identifying Lateral Meristems

There are two main types of lateral meristems: the vascular cambium and the cork cambium. These tissues are involved in the secondary growth of plants, which increases the thickness of stems and roots.

Analyzing Plant Growth Types

Primary growth in plants is associated with lengthening, which is mainly a function of apical meristems. Secondary growth, facilitated by lateral meristems, results in the thickening of older roots and stems.

Connecting Concepts to Options

Since lateral meristems are responsible for secondary growth, they specifically thicken the older roots and stems. Therefore, they do not contribute to lengthening.

Key concepts

Secondary Growth

Secondary growth is an essential process in plants that contributes to an increase in thickness or girth. Unlike primary growth, which elongates plants, secondary growth is all about making them bigger around. This type of growth is typically found in woody plants, such as trees and shrubs. It is facilitated by lateral meristems and plays a critical role in supporting the plant, allowing it to withstand external forces like wind and cover more canopy area, thus enhancing photosynthesis.

Through secondary growth, plants develop a stronger and more robust structure. This process is crucial for older stems and roots, helping them maintain stability and transport nutrients effectively. It's like equipping the plant with a stronger backbone, enabling it to thrive in various environmental conditions.

Vascular Cambium

The vascular cambium is a type of lateral meristem that plays a pivotal role in secondary growth. Positioned between the xylem and phloem tissues in stems and roots, it generates new layers of these tissues every year.

Functions of Vascular Cambium

• Xylem and Phloem Production: The vascular cambium produces new xylem (wood) cells on the inside and phloem (bark) cells on the outside, contributing to the thickening of stems and roots.
• Increased Transport: By continuously producing these vascular tissues, the plant enhances its ability to transport water, nutrients, and sugars effectively throughout its structure.
• Support and Stability: The thickening from the xylem layers provides structural support, crucial for larger plants like trees to endure environmental stressors.

This continuous growth cycle ensures that plants can not only grow taller and cover more ground but also maintain an efficient internal transport system.

Cork Cambium

The cork cambium is another type of lateral meristem vital for the secondary growth process. Found in the outer layers of stems and roots, it is responsible for producing the protective outer covering known as the bark.

Importance of Cork Cambium

• Protection: By generating cork cells, the cork cambium forms a protective layer over older stems and roots, shielding them from physical damage and pathogens.
• Water Loss Prevention: This protective layer also prevents excessive water loss, which is crucial for plant survival, especially in drier climates.
• Insulation: The cork helps insulate the plant, aiding in temperature regulation, which is essential for maintaining internal processes.

In essence, the cork cambium equips the plant with a natural protective armor. It allows the plant to adapt to various environmental challenges, reinforcing the integrity and longevity of the plant’s structure.