Which rooting hormone is commonly used to promote root initiation on cuttings, and name one alternative?

• A. Indole-3-butyric acid (IBA); alternative: Ethylene.
• B. Indole-3-butyric acid (IBA); alternative: Gibberellic acid.
• C. Indole-3-butyric acid (IBA); alternative: Naphthaleneacetic acid (NAA).
• D. Indole-3-butyric acid (IBA); alternative: Abscisic acid.

Answer: (C)

Root initiation in cuttings is driven by auxin hormones that stimulate the formation of adventitious roots. Indole-3-butyric acid (IBA) is a widely used synthetic auxin because it is stable and effective at low concentrations, making it a standard rooting hormone for many plant species. An alternative rooting hormone with similar activity is Naphthaleneacetic acid (NAA), another synthetic auxin that can promote root initiation in cuttings when used alone or with IBA. Ethylene influences various growth processes but is not used as the primary rooting stimulant for initiation. Gibberellic acid mainly promotes shoot elongation and seed germination rather than rooting. Abscisic acid tends to inhibit rooting by promoting dormancy or stress responses.