1. Which synthetic auxin is commonly used as a selective herbicide to control broad-leaved weeds?
A.
2,4-D
B.
Gibberellic acid
C.
Ethylene
D.
Cytokinin
Correct Answer:
2,4-D
Explanation:
2,4-D is a synthetic auxin used as a selective herbicide against many broad-leaved weeds.
2. Selective weed control means the removal of weeds without seriously damaging the:
A.
Crop plants
B.
Soil particles
C.
Rainwater
D.
Farm tools
Correct Answer:
Crop plants
Explanation:
A selective herbicide kills or suppresses weeds while allowing the cultivated crop to survive.
3. 2,4-D is especially effective in controlling which type of weeds?
A.
Broad-leaved weeds
B.
All crop plants
C.
Only mosses
D.
Only algae
Correct Answer:
Broad-leaved weeds
Explanation:
2,4-D selectively controls many broad-leaved weeds, particularly in cereal crops.
4. Which crop is commonly protected from broad-leaved weeds by using 2,4-D?
A.
Wheat
B.
Mango tree
C.
Rose plant
D.
Pea plant
Correct Answer:
Wheat
Explanation:
Wheat is a narrow-leaved cereal crop in which 2,4-D can be used to control many broad-leaved weeds.
5. The selective action of 2,4-D mainly depends on the different sensitivity of:
A.
Weeds and crop plants
B.
Roots and stones
C.
Seeds and water
D.
Flowers and fruits
Correct Answer:
Weeds and crop plants
Explanation:
Selective weed control occurs because weeds are more sensitive to the herbicide than the crop at the recommended dose.
6. At a suitable concentration, 2,4-D acts mainly as a:
A.
Selective herbicide
B.
Fertilizer
C.
Fungicide
D.
Plant pigment
Correct Answer:
Selective herbicide
Explanation:
2,4-D is an auxin-like chemical used as a selective herbicide to control certain weeds.
7. Why can 2,4-D control broad-leaved weeds in wheat fields?
A.
Broad-leaved weeds are more sensitive to it than wheat
B.
Wheat absorbs no water
C.
Weeds produce oxygen at night
D.
Wheat has no roots
Correct Answer:
Broad-leaved weeds are more sensitive to it than wheat
Explanation:
The herbicide can damage sensitive broad-leaved weeds while wheat remains comparatively less affected at the proper dose.
8. Which of the following is an example of selective weed control by an auxin-like compound?
A.
Killing broad-leaved weeds in a wheat field with 2,4-D
B.
Watering every plant in a garden
C.
Adding compost to the soil
D.
Removing insects from leaves
Correct Answer:
Killing broad-leaved weeds in a wheat field with 2,4-D
Explanation:
Applying 2,4-D to wheat fields to control broad-leaved weeds is a standard example of selective weed control.
9. What is the main purpose of using 2,4-D in cereal fields?
A.
To control broad-leaved weeds
B.
To increase flower colour
C.
To ripen fruits
D.
To prevent seed formation in cereals
Correct Answer:
To control broad-leaved weeds
Explanation:
In cereal fields, 2,4-D is applied mainly to suppress broad-leaved weeds that compete with the crop.
10. A chemical used to kill weeds while sparing the crop is called a:
A.
Selective herbicide
B.
Plant hormone receptor
C.
Pollinating agent
D.
Seed dispersal agent
Correct Answer:
Selective herbicide
Explanation:
A selective herbicide targets weeds but does not significantly harm the crop when used correctly.
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