Tag: parts of flower and its functions

Stamens or androecium are the male reproductive part and responsible for the production of pollen grains (male gamete). Pistil or gynoecium are the female reproductive part and produce ovum (female gamete). If both the organs are present it is called bisexual flower. If only one of them is present flower is referred to as unisexual.
So the correct option is 'Presence of stamen and pistil in the flower'.

1. Carpels, pistil or gynoecium are the female reproductive part of the flower that consists of a stigma that holds the pollen grains, the style that leads the path of pollen tube and ovary produce ovum (female gamete). 
   
2. Stamens or androecium are the male reproductive part contains filament which is slender stalk and anther is bilobed and responsible for the production of pollen grains (male gamete). 
   

Non-essential parts of the flowers are the accessory parts that are not directly involved with the gametes formation and sexual reproduction. The whorls of the calyx (individual unit - sepals) and corolla (individual unit - petals) are involved in the protection of flower and attraction of the pollinators, respectively. So, these are considered to be non-essential parts of flowers.