Question

Mark the correct sequence of steps for the development of root nodules in legumes
A. Formation of infection thread.
B. Division of cortical and pericyclic cells.
C. Curling of root hairs.
D. Leghaemoglobin synthesis.

• A. B, D, A, C
• B. C, B, A, D
• C. C, A, B, D
• D. A, C, B, D

Answer 1

The correct option is C C, A, B, D

Development of root nodules in soybean:
(a) Rhizobium bacteria contact a susceptible root hair, divide near it
(b) Successful infection of the root hair causes it to curl
(c) Infected thread carries the bacteria to the inner cortex. The bacteria get modified into rod-shaped bacteroids and cause inner cortical and pericycle cells to divide. Division and growth of cortical and pericycle cells lead to nodule formation
(d) A mature nodule is complete with vascular tissues continuous with those of the root