According to the textbook:

• Abscisic acid (ABA) stimulates the closure of stomata and acts as a stress hormone .
• Cytokinins have specific effects on cytokinesis, i.e., cell division .
• IAA (Auxin) is responsible for growth, which implies cell elongation and division .
• Gibberellic acid (GA) is known to delay senescence (aging), allowing fruits to remain on the tree longer. It does not promote leaf fall; rather, Ethylene and ABA are the hormones associated with promoting senescence and abscission (leaves falling) .