A seedling was made to stand in a solution of red ink for three hours and a transverse section of the stem was…

Step 1: Analyze the question A seedling is placed in red ink for a few hours. A transverse (cross) section of the stem is then viewed under the microscope. We need to identify the process being investigated.

Step 2: The concept Plants absorb water through their roots, and it travels upward through the xylem vessels. If the water contains a dye (red ink or eosin), the dye is carried up with it. The xylem tissue becomes stained, so you can see exactly where the water travels. This is a classic experiment on the ascent of sap / transport of water in plants.

Step 3: Working through the options

• A. Importance of micro elements: This would need nutrient solutions with and without specific minerals, and you would observe growth or deficiency symptoms. Red ink does not test this.
• B. Ascent of water through the xylem: Red ink travels up with the water and stains the xylem. The transverse section shows red-stained xylem vessels. This fits.
• C. Diffusion of colored substances: The experiment is about transport in a specific tissue, not simple diffusion. Diffusion would be shown with something like potassium permanganate in water or agar.
• D. Distribution of food in plants: Food moves through the phloem. This is usually investigated by ringing (girdling) experiments or by radioactive tracers, not by dye uptake.

Step 4: Answer The red stain appears in the xylem, showing the pathway of water upward through the stem.

Exam tip: If you see dye, eosin, or red ink plus a cross-section, think xylem and water transport. If you see ringing of the bark, think phloem and food transport.