$A$ hormone delaying senescence is

Delay of senescence or Richmond-Lang effect is a physiological effect of:

Which one of the following phytohormones promotes nutrient mobilization which helps in the delay of leaf senescence in plants?

The word "cytokinin", which induces cell division, was given by

Study the following statements:
$I.$ Cytokinins are formed primarily in roots.
$II.$ Auxin and cytokinin are antagonistic in apical dominance.
$III.$ Kinetin (a modified $DNA$ purine) was discovered from herring sperm.
$IV.$ Zeatin is auxin.
$V.$ Zeatin was firstly extracted from herring.
Choose the incorrect one.

From your knowledge of physiology,can you think of some methods to increase the life span of cut plants in a vase?