In vascular plants, the xylem tissue is primarily responsible for which one of the following transport functions?

Introduction / Context:
In higher plants, transport of materials is carried out by specialised vascular tissues known as xylem and phloem. Each tissue has a distinct role and structure. Understanding the primary function of xylem is a basic requirement in botany and general science examinations. This question asks you to select the correct transport function performed mainly by xylem in vascular plants.

Given Data / Assumptions:
• The subject is xylem, one of the two main vascular tissues.• The options mention transport of water, food, amino acids, oxygen, and hormones.• We assume a typical flowering plant with roots, stem, and leaves.• We focus on the primary role, not minor or indirect functions.

Concept / Approach:
Xylem is specialised for the conduction of water and dissolved mineral salts, mainly from roots to stems and leaves. It consists of tracheids, vessel elements, xylem fibres, and xylem parenchyma. Water and minerals absorbed from the soil move upward through xylem vessels driven by root pressure, capillary action, and transpiration pull. In contrast, phloem is responsible for transporting organic food, primarily sucrose, from leaves to other parts of the plant. Oxygen transport in animals is done by blood, not xylem. Therefore, the correct answer must emphasize transport of water and dissolved minerals from roots to aerial parts.

Step-by-Step Solution:
Step 1: Recall that there are two main types of vascular tissue in plants: xylem and phloem.Step 2: Remember that xylem transports water and mineral nutrients absorbed by roots.Step 3: Note that the direction of this transport is largely upward, from roots to stems and leaves.Step 4: Contrast this with phloem, which translocates food such as sugars from leaves to storage organs and growing regions.Step 5: Recognise that transport of oxygen and amino acids as described in the other options is not the primary role of xylem.Step 6: Choose the option that mentions transport of water and dissolved mineral salts from roots to other parts.

Verification / Alternative check:
Experimental evidence such as girdling experiments and dye tracing supports the role of xylem in water transport. When coloured dyes are taken up by roots, they are observed moving upward in the xylem vessels of stems and leaves. When xylem is blocked or damaged, plants wilt due to lack of water supply to leaves. Phloem transport, on the other hand, is demonstrated by tracing movement of labelled sugars from leaves to roots. These experiments clearly separate the functions of xylem and phloem and confirm that xylem is the water conducting tissue.

Why Other Options Are Wrong:
Transport of prepared food such as sugars from leaves to other parts is primarily the function of phloem, not xylem. Transport of amino acids only between storage organs is too narrow and does not describe the main role of any vascular tissue in standard textbooks. Transport of oxygen from lungs to tissues in animals is carried out by haemoglobin in red blood cells within blood vessels, and plants do not have lungs. Transport of plant hormones exclusively from roots to fruits is not a major defined role of xylem; hormones can move through both xylem and phloem depending on the hormone and situation. None of these descriptions match the primary function of xylem.

Common Pitfalls:
Students sometimes confuse xylem and phloem because both are part of vascular bundles. A common memory aid is to associate xylem with x for x upward water, and phloem with food flow. Another pitfall is to think that any substance moving in a plant is carried by xylem, but in reality transport is divided between xylem and phloem. Keeping these distinctions clear and linking xylem specifically with water and mineral transport will help answer similar questions accurately.

Final Answer:
The xylem tissue in plants is primarily responsible for Transport of water and dissolved mineral salts from roots to other parts.