The removal of all the phloem tissues of the stem of a plant close to the root system for a long period of time is likely to

Analyze the question: All the phloem is removed from the stem near the base (a complete "girdling" or ringing). We must predict the long-term effect on the plant.

Concept:

• Phloem carries manufactured food (sucrose and amino acids) from the leaves down to the roots and other parts. This is called translocation.
• Xylem carries water and mineral salts up from the roots to the leaves.

Solution, step by step:

1. With the phloem removed, food made in the leaves can no longer travel down to the roots.
2. The xylem is still intact at first, so water continues to rise for a while. Food accumulates above the ring, which is why a swelling forms there.
3. The roots are starved of food. They cannot respire properly, so they lack the energy for active uptake of water and minerals.
4. Over a long period the roots die. Once they die, no water or minerals reach the leaves, so photosynthesis stops and the whole plant withers and dies.

Checking the options:

• A. Wrong. The roots would receive less food, so they get less energy, not more.
• B. Wrong. Starch accumulates above the ring, not in the roots, because food cannot get past the gap.
• C. Wrong. Buds would not develop on starved roots. If anything, buds may develop above the ring.
• D. Correct. Starved roots die, and then the whole plant withers and dies. (The option has a typo, "p ant", meaning "plant".)

Answer: D

Exam tip: Remember "Phloem = Food down; Xylem = Xtra water up." Whenever a question mentions ringing or girdling, think: swelling above the ring, starvation of the roots below it, and eventual death of the plant if it lasts a long time.