Applicability of light-emitting diode on agricultural production processes from viewpoint of photoperiod in plants.

The vernalization requirement has been found existed in plants through which plants acquire the competence to flower in the spring after experiencing a period of low temperature in winter. Photoperiodism (or photoperiodicity) occurs in plants, animals and even fungi, and is the physiological reaction for these organisms to changes of daylength, mostly the developmental responses. Plants may initiate or accelerate the flowering process after the vernalization and then produce seeds in better environmental conditions to complete their life cycle. The response to photoperiod has evolved because daylength is a reliable indicator of the time of the year that enables developmental events proceeding as scheduled to fulfill a generation. The lightemitting diode (LED) can be used as a substitute of solar radiation under structure or in field, providing radiation and energy for the growth, development and reproduction of a plant. Many studies have proved the feasibility and applicability of using LED to shorten growth duration, adjust production timing, increase yield and promote quality of harvested products. With such a multifunctional application advantages, researches on establishing systems incorporating LED as a light source are greatly encouraged.