A horticulturist wants to achieve three specific goals in a commercial nursery: (i) Initiate rooting in stem cuttings to quickly propagate a desired plant. (ii) Cause apples to elongate and improve their shape. (iii) Delay the senescence of harvested leaves. Which of the following sequences of plant growth regulators should be applied to achieve these goals respectively?

Step-by-step solution

Goal (i): Auxins (such as IBA and NAA) are widely used to initiate rooting in stem cuttings, which is a common application for vegetative plant propagation. Goal (ii): Gibberellins (GAs) are specifically used to cause fruits like apples to elongate and improve their shape. Goal (iii): Cytokinins help delay leaf senescence by promoting nutrient mobilisation. Thus, the correct sequence of plant growth regulators is Auxin, Gibberellin, and Cytokinin. Answer: Auxin, Gibberellin, Cytokinin