In a vascular plant, which of the following tissues primarily transports water and dissolved mineral salts from the roots to the leaves?

Introduction / Context:
Plants have specialized vascular tissues that transport water, minerals, and food throughout the organism. Understanding which tissue performs which function is a key part of basic botany. This question asks specifically about the tissue that carries water from the roots upward to the leaves in a vascular plant.

Given Data / Assumptions:

• The plant described is a typical vascular plant with xylem and phloem.
• The focus is on the transport of water and mineral salts from roots to leaves.
• Options mention xylem, phloem, both together, and cortex.

Concept / Approach:
Xylem is the vascular tissue responsible for the unidirectional upward transport of water and dissolved minerals from the roots to the aerial parts, especially leaves. This movement is driven by root pressure, capillarity, and transpiration pull. Phloem, in contrast, transports organic food materials such as sugars from leaves (sources) to various parts of the plant (sinks) in a mostly bidirectional way. The cortex is a region of ground tissue and does not serve as the main long distance transport pathway. Therefore, the correct answer must be xylem.

Step-by-Step Solution:
Step 1: Examine option A, xylem. Standard textbook definitions state that xylem conducts water and mineral salts from the roots upward to the leaves.Step 2: Examine option B, phloem. Phloem conducts organic nutrients, primarily sucrose and other sugars, and does not serve as the main water transport tissue.Step 3: Examine option C, both xylem and phloem equally for water. While phloem sap contains some water, phloem is not the principal pathway for bulk water transport from roots to leaves.Step 4: Examine option D, cortex. The cortex is a supportive and storage tissue located between the epidermis and vascular bundles and does not conduct water over long distances.Step 5: Conclude that xylem is the correct tissue for this function.

Verification / Alternative check:
A simple check is to recall diagrams of plant stems and roots, where xylem vessels are often drawn as large, thick walled tubes forming a central core. Laboratory experiments that demonstrate water movement using colored dyes show the dye climbing mainly through xylem vessels. These consistent observations support the idea that xylem is the primary water conducting tissue.

Why Other Options Are Wrong:
Option B is wrong because phloem’s main job is to move food, not water and minerals. Option C is wrong because, although phloem carries some water in solution, it is not the main conduit of water from roots to leaves. Option D is wrong because the cortex stores food and provides support; it is not a specialized conducting tissue.

Common Pitfalls:
Students sometimes confuse xylem and phloem because both are vascular tissues and are often taught together. A helpful mnemonic is “Xylem up, Phloem around,” indicating that xylem carries water upward, while phloem distributes food in many directions. Remembering this distinction will help you answer many plant transport questions accurately.

Final Answer:
Xylem.