Question

The major site of uptake for soil applied herbicides are:
A) Root
B) Shoot
C) Seed
D) Leaves

• A. A, B, C and D.
• B. A and C only
• C. B and C only
• D. A, B and C only

Hint:

Pre-emergence (soil-applied) herbicides must be absorbed by subterranean organs (seed, germinating shoot, or root) because the weed has not yet developed emerged leaves.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Soil-applied (pre-emergence) herbicides are positioned in the top soil layer to control germinating weed seedlings before they emerge above ground.

Step 3: Detailed Explanation:
The target weed absorbs soil-applied herbicides during the germination process through underground structures:
- Roots (A): Active and passive absorption occurs through young, growing root tissues.
- Shoots (B): The emerging shoot (coleoptile in grasses, hypocotyl/epicotyl in broadleaves) is a highly active site of absorption as it pushes upward through the treated soil layer.
- Seeds (C): Imbibition of soil water allows the herbicide to enter the seed coat and access the embryo directly.
- Leaves (D): Since pre-emergence herbicides are applied before foliage is present, leaves do not act as a major uptake site. Leaf uptake is restricted to post-emergence foliar sprays.

Step 4: Final Answer:
The major sites of uptake are the root, shoot, and seed. This corresponds to (A), (B), and (C) only, which is option (D).