Plants require sunlight, water, oxygen, and minerals to grow and flourish. These are the extrinsic factors. Apart from this, plants' growth and development are governed by various intrinsic factors. Plant hormones, also known as phytohormones, are a type of hormone produced by plants. These are chemical substances found in plants at extremely low concentrations. They are derivatives of terpenes (Gibberellins), adenine (Cytokinins), indole (auxins), gases (Ethylene) and carotenoids (Abscisic acid). They can independent or synergistic. Different hormones can have either complementary or antagonistic roles. Hormones, together with extrinsic factors, play an essential part in processes such as vernalisation, phototropism, seed germination, and dormancy.
• Phytohormones
• Plant Growth Inhibitors
• Plant Growth Promoters