Question

site of synthesis of cytokinins and conditions for its synthesis

Answer 1

Cytikinins were discovered by Skoog and Miller 1957 ; while working on the callus under in vitro conditions. They found the callus that develops from the stem explants, containing both pith and vascular elements, develops well.  But the explants containing just pith cells produces callus, but further growth of its stops, even in the presence of optimal concentration of auxins.  This is because the cell in the callus somehow rendered incapable of cell division.  If such callus is supplanted with vascular tissues, extract of vascular tissues, coconut milk or malt extracts, the growth of the callus will be restored and the cells exhibit mitotic activity.  This effect has been attributed to the presence of some active principle in the supplanted coconut milk.  Cytokinins in coconut milk  have various functions in association with other hormones or its accessories.

Answer 2

synthesized in roots.
am not sure about the conditions