A synthetic plant growth regulator 'X' is widely used by gardeners to prepare weed-free lawns. It achieves this by selectively killing 'Y' weeds. Identify 'X' and 'Y'.

Step-by-step solution

Auxins are classified into natural and synthetic types. IAA (Indole-3-acetic acid) and IBA are natural auxins, whereas NAA and 2,4 -D are synthetic auxins. The synthetic auxin 2,4 -D is extensively used by gardeners to prepare weed-free lawns. It acts as a selective weedicide that kills dicotyledonous weeds but does not affect mature monocotyledonous plants. Thus, X is 2,4 -D and Y is Dicotyledonous. Answer: X = 2,4 -D, Y = Dicotyledonous