Question

Coralloid roots help the plant
A. Absorb water more efficiently
B. Absorb and fix nitrogen better
C. Anchorage to the soil
D. Respiration

Answer 1

Hint: Coralloid roots are specialized roots associated with nitrogen-fixing cyanobacteria found in Cycas. The cyanobacterial zone, which is populated by cyanobacteria, is found within the coralloid root. This has special properties that make a close association between cycad and cyanobacteria possible. Symbiotic Cyanobacteria (blue-green algae) live in the coralloid roots, fixing nitrogen and producing helpful amino acids such asparagine and citrulline in conjunction with root tissues.

Complete answer:
Option A Absorb water more efficiently: Plants use their roots to absorb water from the soil. It also obtains nutrients in organic form through root hairs. The xylem vessels help in transporting both water and minerals. Coralloid roots, on the other hand, contain cyanobacteria (blue-green algae) that fix nitrogen in conjunction with root tissues. Hence option A is not correct.
Option B Absorb and fix nitrogen better: Coralloid roots are nitrogen-fixing cyanobacteria-related roots found in Cycas. Cyanobacteria, a blue-green bacteria that fixes nitrogen, is found in the coralloid roots. So, coralloid roots absorb and fix nitrogen better. Hence option B is the correct answer.
Option C Anchorage to the soil: Anchorage is provided by the root system, which securely keeps soil particles together and upholds a plant on the ground. But coralloid roots have other specialized function of nitrogen fixing other than providing anchorage. Hence option C is not correct.
Option D Respiration: Plants generally respire through stomata, which are specialized structures found beneath the plant leaves. Roots also assist in respiration. With the help of root hair on the roots, oxygen is then taken into the roots. But coralloid roots have other specialized functions of fixing and absorbing nitrogen. Hence option D is not correct.

Hence, option B. Absorb and fix nitrogen better is the correct answer.

Note:
The pericycle of apogeotropic secondary roots or adventitious roots that have become exposed or almost exposed to the soil surface was discovered to originate endogenously from the pericycle of coralloid roots of cycads. Algal endophytes, which appear to enter from the soil through a crack in the dermal layers, infect all mature coralloid roots.