Problem 5 - Campbell Biology

Question

The vascular cambium gives rise to (A) all xylem. (B) all phloem. (C) primary xylem and phloem. (D) secondary xylem and phloem.

Step-by-Step Solution

Answer

(D) secondary xylem and phloem.

Step 1: Identify the Vascular Cambium's Function

Understand that the vascular cambium is a type of meristematic tissue in plants. It is responsible for the production of secondary vascular tissues.

Step 2: Differentiate Between Primary and Secondary Vascular Tissues

Primary xylem and phloem are produced by the primary meristems during the initial stages of growth. Secondary xylem and phloem are produced by the vascular cambium during the plant's secondary growth.

Step 3: Connect the Cambium to Secondary Growth

Recall that the cambium is involved in the increase in girth of the plant, which corresponds to secondary growth. Therefore, it contributes to the formation of secondary xylem and phloem.

Step 4: Identify the Correct Option

Evaluate the given options based on the previous steps: Option (D) is correct because the vascular cambium specifically gives rise to secondary xylem and phloem.

Key Concepts

Vascular Cambium

The vascular cambium is a layer of meristematic (actively dividing) tissue found in plants. It plays a crucial role in the plant's growth and development. This tissue is located between the xylem and phloem, and it is responsible for the production of secondary vascular tissues.
Secondary vascular tissues help in increasing the plant's diameter or girth. The vascular cambium produces new layers of cells internally to the xylem and externally to the phloem.
This process is essential for the plant to grow thicker and support its increasing height and the weight of its upper structures. Therefore, the vascular cambium is key to the plant's ability to strengthen and enlarge itself through secondary growth.

Secondary Growth

Secondary growth refers to the increase in the thickness or girth of plants, particularly in woody species. This growth occurs after the primary structure of the plant is established. Primary growth, governed by the apical meristems, elongates the plant. In contrast, secondary growth, driven by the vascular and cork cambium, thickens the plant.
The vascular cambium forms a ring around the stem and branches of the plant. As it produces new cells, it lays down secondary xylem (wood) towards the inside and secondary phloem towards the outside.
Secondary growth is essential for the plant's structural integrity. It allows trees and shrubs to become more robust, enabling them to transport water and nutrients more effectively throughout their larger structures.

Xylem and Phloem

Xylem and phloem are vital tissues in the vascular system of plants. They are responsible for the transport of water, nutrients, and food.

• Xylem: Xylem's primary function is to transport water and dissolved minerals from the roots to the rest of the plant. This tissue also provides structural support. Xylem vessels are made of dead cells that form long tubes.


• Phloem: Phloem is responsible for the transport of food produced during photosynthesis, from the leaves to other parts of the plant. Unlike xylem, phloem is made of living cells. These cells transport sugars and other metabolic products both upwards and downwards through the plant.

The vascular cambium produces the secondary xylem and phloem during secondary growth. This arrangement enhances the efficiency and capacity of nutrient and water transportation as the plant grows thicker and taller.