Which of the following plant hormones is responsible for delaying the senescence of plant organs?

Which hormone is helpful in the regulation of xylem differentiation and also in cell division?

Discovery of which one of the following is connected with the use of an old sample of $DNA$ in a culture medium?

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.

Which of the following exerts the Richmond-Lang effect,i.e.,prevents the loss of chlorophyll?

Which hormone is responsible for delaying leaf senescence by promoting chlorophyll retention?