What does PAR mean in BOTANY

Photosynthetically Active Radiation (PAR) is the range of light frequencies necessary for photosynthesis in plants and other photosynthetic organisms. This light is generally considered to be in the 400-700 nanometer range of the electromagnetic spectrum.

The energy from PAR is critical for plant growth. It increases photosynthesis, which produces energy that helps drive processes such as respiration, transpiration, and germination of seeds. Additionally, it affects photomorphogenesis, the process by which a plant adjusts its shape and size to changes in light intensity and quality.

The ideal intensity of PAR for optimal plant growth will vary depending on the species or cultivar being grown. Generally speaking, a light intensity ranging from 500-800 µmol·m⁻²·s⁻¹ is suitable for most high-light crops like tomatoes or peppers. Low-light crops such as leafy greens require less intense levels of light (200-400 µmol·m⁻²·s⁻¹).

There are several ways to measure PAR, including using a quantum sensor, photodiode array spectrophotometer or integrating sphere spectrophotometer. Quantum sensors measure every photon individually while photodiode arrays measure an area all at once to create an average value. Integrating spheres provide more detailed information about individual wavelengths within a specific range.

Not all lightsources are appropriate for providing adequate PAR to plants. For example, common tungsten and fluorescent bulbs emit only small amounts ofPAR when compared with specialized horticultural grow lamps such as LED (Light Emitting Diode) fixtures or HIDs (High Intensity Discharge). These are specifically designed to output higher amounts of useful light frequencies needed for optimum yield production and quality in plants.

Yes, temperature can affect the accuracy of a PAR reading if not taken into account when measuring it. Higher temperatures will cause increased air movement which can scatter some wavelengths thereby reducing the amount detected by a meter or measuring device. That's why ambient temperature should always be taken into account when conducting measurements with a quantum sensor or other devices designed to measure PAR.

UV radiation falls within the spectrum between 400nm - 700 nm used to calculate Photosynthetically Active Radiation (PAR), however since UV can harm plants it's excluded from measurements because its presence varies greatly depending on factors like latitude and season.