Dear Aspirant,

Calyx is the outermost whorlpf the flower.Excluding the petals doen below the petals there is a peetal like part which surrounds the lowermost part of the flower which is known as sepals or calyx.It protects the petal as it develops.

Receptacle is the part of the flower where other parts like calyx petals are attached.It is a part of the flower stalk and gives support to the growing flower.In simpler words the long part present below sepals to support the flower is receptacle.

Hope it helps!!

REGARDS!!