Question

What is the characteristic of haustorial roots of cuscuta?
A. Presence of both xylem and phloem
B. Presence of only xylem
C. Presence of phloem
D. Absence of both xylem and phloem

Answer 1

Hint: Xylem and phloem are the vascular tissues present in the vascular plants. Xylem transports water and minerals within the plants. The translocation of organic substances occurs through the phloem.

Complete answer:
Seed plants (spermatophytes) are vascular plants and produce seeds. Angiosperms and gymnosperms are collectively known as spermatophytes. They have vascular tissues called xylem and phloem which assist in the transport of substances within the plant body. Water and minerals absorbed by roots from the soil and xylem are transported to shoot through the xylem. Likewise, the organic substances such as sugars are delivered from the source to the sink organs through the phloem.

Cuscuta is an obligate parasite vine and belongs to the family Convolvulaceae of the angiosperms. It lacks chlorophyll in its leaves and therefore, cannot perform the process of photosynthesis. Cuscuta derives the organic nutrients and other substances from the host plant. Its leaves are reduced into scale-like structures. The plant has haustorial roots to withdraw the nutrition from the host plant. Haustorial roots have both xylem and phloem tissues. These slender roots penetrate the host plant and establish contact with its xylem and phloem to absorb water, minerals, and food.

Hence, the correct answer is option (A).

Note: Cuscuta is a stem parasite and is also called dodder or amarbel. It lacks roots and has a yellow coloured thin stem that wraps around the stem of the host plant. Haustorial roots of Cuscuta establish direct contact between the vascular tissues of the host and parasite plant.