If a plant is deficient in the element $Zinc$,which plant hormone's biosynthesis will be affected in that plant?

Which phenomenon describes how apical buds inhibit the growth of lateral buds? How can this be overcome?

Levitt performed experiments. He observed that auxin-treated cells were able to absorb water even when kept in a hypertonic solution. Which explains this observation best?

Who isolated auxin from tips of coleoptiles of oat seedling?

The chemical formula of auxin $a$ is:

Assertion : Auxins help to prevent fruit and leaf drop at early stages.
Reason : Auxins promote the abscission of older mature leaves and fruits.