The correct option is D All of these
Plant growth regulators or PGRs are chemicals or signal molecules that act as regulators that promote growth. These signal molecules act like chemical messengers between different parts of the plant. PGRs determine the formation of flowers, stems, leaves, the shedding of leaves, and even the development and ripening of fruit. They affect tropism, which tissues should grow upward and which should grow downward, they also decide the longevity of of plants.