Attractants and rewards are required for :
Pollination through insects -
To sustain animal visits, the flowers have to provide rewards to the animals. Nectar and pollen grains are the usual floral rewards. For harvesting the rewards from the flower, the animal visitor comes in contact with the anthers and the stigma. The body of the animal gets a coating of pollen grains, which are generally sticky in animal-pollinated flowers. When the animal carrying pollen on its body comes in contact with the stigma, it brings about pollination.
In some species, floral rewards are in providing safe places to lay eggs; an example is that of the tallest flower of Amorphophallus.
one biotic agent for pollination is in sheets which transfer pollen gramme to a stigma of a flower. this is known as entomophily and plants are characterised by attractive and brightly coloured flowers.