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Biology Question 101 – NEET-UG 2024

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Auxin is used by gardeners to prepare weed-free lawns. But no damage is caused to grass as auxin

Auxins are plant hormones with diverse roles, including growth regulation. Synthetic auxins are commonly used as selective herbicides.

Step 1: Understand the Application of Auxin as a Herbicide✦ Active

Auxins, particularly synthetic auxins like 2,4-D, are widely used as selective herbicides. They are effective in eliminating broad-leaved weeds (dicots) from monocotyledonous crops or lawns (like grass).

Step 2: Analyze the Differential Effect on Monocots vs. Dicots○ Expand

Synthetic auxins cause abnormal, uncontrolled growth in dicot weeds, leading to their death. However, monocotyledonous plants (like grasses) are generally resistant or less sensitive to these auxins at the concentrations used for weed control. This resistance is due to differences in absorption, translocation, or metabolism of the herbicide.

💡 Teacher's Secret Hint

Remember that 2,4-D is a common synthetic auxin used as a selective herbicide.

Step 3: Evaluate Options based on Grass Resistance○ Expand

The question asks why no damage is caused to grass. Option (2) states that auxin 'does not affect mature monocotyledonous plants.' Since grass is a monocot, this option directly explains its resistance to the herbicide. The other options describe general functions of auxin but do not specifically address the selective non-damaging effect on grass in the context of weed control.

💡 Teacher's Secret Hint

Focus on the 'no damage' aspect and the specific plant type (grass, which is a monocot).

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