What type of lighting is often used to extend photoperiod in greenhouses?

Using LED or fluorescent grow lights to extend photoperiod in greenhouses is highly effective due to several reasons related to their light spectrum and energy efficiency. These types of lighting are specifically designed to emit wavelengths that promote plant growth, particularly during critical growth stages such as germination and flowering.

LED lights are particularly advantageous because they can be customized to emit specific colors of light, which can be tailored to the needs of various plants. This flexibility allows for optimizing growth conditions and maximizing photosynthesis. Fluorescent lights, while less efficient than LEDs, still provide a suitable spectral output and are widely used for seedlings and young plants.

These lighting options produce less heat compared to incandescent or halogen bulbs, reducing the risk of burning plants and allowing for closer placement of lights to the plants. Additionally, they consume less energy, making them more sustainable for long-term use in greenhouse facilities.

In contrast, incandescent bulbs produce a lot of heat and have a relatively poor light spectrum for plant growth, making them less suitable for extending photoperiods. Halogen lights also generate significant heat and aren't designed for plant growth. Candlelight does not provide enough light intensity or the appropriate spectrum for photosynthesis, making it ineffective for extending photoperiods.