Question

In paddy, the elongation of leaf sheath after the infestation of gall fly is due to

• A. Allethrin
• B. Ecdysone
• C. Cecidogen
• D. Allomone

Hint:

Always associate "cecidogen" with gall midges (Cecidomyiidae) and gall formation in plants, such as the silver shoot gall in rice.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Certain gall-inducing insects manipulate plant growth hormones by secreting chemical compounds that trigger abnormal cell division and elongation, forming a gall.
In rice (paddy), the gall midge (*Orseolia oryzae*) causes a classic symptom known as "silver shoot" or "onion shoot."

Step 2: Detailed Explanation:
When the newly hatched larva of the rice gall midge (*Orseolia oryzae*) migrates to the growing tip of the rice shoot, it begins feeding on the apical meristem.
During feeding, the larva secretes a specialized bioactive chemical compound called cecidogen (a gall-inducing substance).
Cecidogen acts as a plant growth regulator, stimulating hyperactive cell division (hyperplasia) and cell elongation (hypertrophy) in the surrounding leaf sheath tissues.
As a result of this localized tissue manipulation, the normal development of the leaf blade is suppressed, and the leaf sheath elongates rapidly into a hollow, light-green or silver-white tube.
This structure is called a "silver shoot" or "onion shoot."
Let us review the other terms:
1. Allethrin: A synthetic pyrethroid insecticide.
2. Ecdysone: An insect steroid hormone responsible for molting and metamorphosis.
3. Allomone: A chemical substance secreted by an individual of one species that affects the behavior of another species to the benefit of the emitter.

Step 3: Final Answer:
Therefore, the leaf sheath elongation is due to Cecidogen.