The plant growth is influenced by a variety of external and internal factors. The former include light, temperature, water, nutrients etc. while the latter includes genetic and hormonal factors.
Auxins are powerful plant growth hormones (or plant growth regulators) produced by plants. They are found in the shoot and root tips and promote cell division, stem and root growth. Auxins are involved in phototropism, geotropism, hydrotropism and various other developmental changes.