This is not the case with hybrid corn where different inbred lines are used as the maternal and paternal sources and pollination is controlled by removing the tassels of the female plants and seed is not harvested from the male plants. There are exceptions to these two methods of reproduction. In sexual reproduction by seeds - specialized reproductive cells called gametes are formed in a process known as gametogenesis. Fusion of the male and female gametes leads to the development of an embryo and eventually a seed. Flowering and seed production is energy intensive for the plant.
Most plants develop adequate vegetative structure before flowering can occur.
This is often referred to as the juvenile stage. Once sufficient vegetative structures are present, the plant generally receives an appropriate flowering stimuli such as light or temperature changes to induce the plant to change from vegetative to reproductive growth. Plants that fail to respond to light duration changes are classified as day-neutral plants. These species demonstrate both vegetative and reproductive growth concurrently and may be more difficult to harvest seed because ripening is not uniform. Neither petals or sepals are required for reproduction, only the stamens and the pistil.