Calyx is the most essential part because it protect the flower
The essential parts of a flower are the reproductive structures, which include the carpels (female parts) and stamens (male parts). These structures are essential for the flower's reproduction, as they produce the ovules and pollen needed for fertilization to occur. The carpels contain the ovules, which develop into seeds after fertilization, while the stamens produce pollen, which contains the male gametes.
Accessory whorls are extra floral parts found in some plant species that are located outside of the typical floral organs like sepals, petals, stamens, and pistils. These additional whorls can include structures like bracts, bracteoles, or extra sepals. They are not essential for reproduction but can serve functions like attracting pollinators or providing protection for the flower.
In monocots, flowers are trimerous (number of flower parts in a whorl in threes). In dicots the flowers are tetramerous or pentamerous (flower parts are in fours or fives).
This process is called pollination. Bees transfer pollen from the male parts of one flower to the female parts of another flower, which is essential for fertilization and seed production in many plants.
Pistil and stamen .
The nonessential flower parts include the flower stalk, sepals and petals. The essential flower parts are those necessary for reproduction, the stamen and pistil.
The main function of flower is formation of seeds by sexual reproduction. Anthers and Carples are main parts for this purpose and sepals and petals being protective and attractive parts are called accessory parts.
The accessory parts are; 1. Petals 2. Sepals 3. Receptacles the essential parts are; 1. Stamen 2. Pistil
The female parts of a flower are called style, ovary, ovule and stigma. All of these parts together are called the pistil.
The collective term for the male parts of a flower is called the stamen. This comprise of the anthers and the filament.
the Gynoecium (meaning "womans house") and refers to all the ovule producing parts of the flower. See related link
No, a China rose (hibiscus) is not a complete flower as it lacks some essential parts like stamens and pistils. It is considered an incomplete flower because it is missing either male or female reproductive structures.