Abscission zone can be induced for formation by

The correct option is abscisic acid.

Plant senescence and abscission are complex physiological processes regulated by various plant hormones. Abscission refers to the natural shedding or separation of parts of a plant, such as leaves, flowers, fruits, or seeds, when they reach maturity or senescence.
To facilitate this shedding, a distinct layer of cells called the abscission zone forms at the base of the petiole, pedicel, or peduncle.

Among the phytohormones, abscisic acid (ABA) plays a vital role in promoting senescence and inducing the formation of the abscission zone. It stimulates the synthesis of hydrolytic enzymes like cellulase and pectinase in the cells of the abscission zone. These enzymes break down the cell walls and middle lamella between the cells, making the region structurally weak and facilitating the detachment of the plant organ.

While other hormones listed have different primary functions:
- Cytokinins delay senescence (the Richmond-Lang effect) and promote cell division.
- Gibberellins are involved in stem elongation, seed germination, and flowering.
- Auxins generally inhibit abscission when present in high concentrations in the organs, although their depletion or relative concentration gradient with ethylene can affect the process.
Therefore, the hormone primarily associated with inducing the formation of the abscission zone among the given options is abscisic acid.