Question

Roots and shoots lengthen through activity at a. apical meristems c. vascular cambium b. lateral meristems d. cork cambium

Short answer

Roots and shoots lengthen through activity at apical meristems (option a).

Step-by-step solution

Understand the Question

The question is asking where the primary growth in plants occurs, specifically referring to where roots and shoots increase in length.

Identify the Key Term: Apical Meristems

Apical meristems are tissues found at the tips of roots and shoots, responsible for primary growth, which is the increase in length of a plant.

Evaluate Other Options

Vascular cambium and cork cambium are involved in secondary growth, which increases the thickness of stems and roots, not their length. Meanwhile, lateral meristems also generally refer to secondary growth activities.

Make a Conclusion

Given that apical meristems are responsible for lengthening growth in roots and shoots through primary growth, option (a) is correct.

Key concepts

Apical Meristems

Apical meristems are essential regions of growth for plants. They are located at the very tip of roots and shoots. These specialized tissues are responsible for producing new cells, leading to the elongation of the plant.
Apical meristems are crucial for plants as they facilitate the process known as **primary growth**. This results in the increase of length in both roots and shoots, allowing the plant to extend upwards towards light and downwards into soil.
These meristems have actively dividing cells that continually contribute to the formation of new tissues, enabling plants to grow taller and roots to become deeper. This is important for plants to reach resources such as sunlight and water, which are vital for their survival.

Primary Growth

Primary growth in plants is the process through which a plant increases in height or length. This is a key function of the apical meristems.
During primary growth, cells at the apical meristems divide, elongate, and differentiate into various types of tissues. This growth is significant because it marks a plant's ability to grow upwards towards sunlight and downwards into deeper soil layers to access water and nutrients.
The tissues that result from primary growth include things like stems, leaves, and roots, which allow the plant to perform essential life processes such as photosynthesis, transpiration, and nutrient absorption.

Secondary Growth

Unlike primary growth, secondary growth leads to an increase in the thickness or girth of the plant. This process mainly occurs in woody plants.
Secondary growth is controlled by the **vascular cambium** and **lateral meristems**, not the apical meristems. This type of growth strengthens the plant, allowing stems and roots to support more leaves, branches, and fruits.
It occurs after primary growth and in regions like the trunk of a tree or the thickening of roots. This is essential for plants that grow tall, as it helps them to withstand strong winds and other environmental challenges.

Vascular Cambium

The vascular cambium is a type of lateral meristem that plays a crucial role in secondary growth. It is a continuous cylindrical layer of tissue that forms inside the stem and root.
Its primary role is to produce new vascular tissues, specifically xylem and phloem. These tissues are vital as they transport water, nutrients, and food throughout the plant.
As the vascular cambium generates new cells, it contributes to the thickening of the plant organ. This is why trees and shrubs, which undergo significant secondary growth, can become so wide and robust over time.

Lateral Meristems

Lateral meristems are responsible for the secondary growth in plants, increasing their diameter rather than their height. Plants have two main types of lateral meristems: the vascular cambium and the cork cambium.
These meristems allow plants to develop thicker tissues, which provide increased support and protection. This is particularly important for woody plants, giving them the ability to develop trunks and support more extensive root systems.
Lateral meristems contribute to the formation of wood and bark, enabling a plant to sustain itself over long periods and adapt to environmental changes.