Q.Which one is not an allelo chemical?

Allelochemicals and Allelopathy

Plants cannot move, so they cannot run from competitors or walk away from crowding. Instead, many of them fight a chemical battle. Allelopathy is the phenomenon in which one plant releases chemicals into its surroundings that inhibit or affect the growth, survival or reproduction of neighbouring plants or other organisms.

Allelochemicals — the weapons

The chemicals responsible are called allelochemicals, and they are secondary metabolites — substances the plant makes not for its own growth but for defence and competition. They can be released from roots, fallen leaves, bark, or by leaching from the plant's tissues into the soil. Well-known examples include:

• Juglone, released by walnut trees, which suppresses the growth of many plants beneath them.
• Sorgoleone, exuded by sorghum roots, which inhibits nearby weeds.
• Ailanthone, produced by the tree-of-heaven (Ailanthus), toxic to competing seedlings.

Why plants do this

The evolutionary logic is competition for limited resources — light, water, soil nutrients. By poisoning the soil around itself, an allelopathic plant reduces the germination or growth of rivals, effectively clearing space for its own roots. It is chemical warfare in place of physical competition.

Where it matters

Allelopathy is not just a curiosity: …