

Key Metrics to look out for
Photosynthetically Active Radiation (PAR) – available light required for the photosynthetic process to take place. Refers to how efficient a lighting system is at converting electrical energy into photons of PAR. This is an essential component for the survival of a plant and will increase the speed at which a plant will grow. The photosynthetic range is found between 400nm – 700nm, which is also known as the visible light spectrum.
Photosynthetic Photon Flux (PPF) – the PAR (how much light/energy) that is emitted from a light source. This value is expressed as micromoles per second, µmol/s. In traditional lighting terms it is the equivalent to lumens – total amount of light a light source will give off
Photosynthetic Photon Flux Density (PPFD) – acutally amount of PAR (light/energy) that reaches the surface of the plant. This value is express as micromole per square meter per second, µmol/m2/s. In traditional lighting terms it is the equivalent to lux level on the surface at a particular distance – total amount of light that reaches the given task area at a particular distance from the light source
Uniformity – distribution of the light/energy that reaches the plant surface. Vital to look at the minimum, maximum and average amounts of PAR that reaches the plants surface
Efficiency – efficiency of the light source, micromoles per second µmol/s vs wattage. At a certain wattage a light source will give off a certain amount of light/energy.
Size – physical size of the space that requires illuminations and the size of the actually luminaire is important factor to take into consideration. Space is generally limited in indoor growing
Proximity – how close the light source can get to the plant, ideally it should not get closer than 12cm. Generally, the plant needs much light/energy as possible, so the closer the better while maintaining uniformity.

Photosynthesis
Primary metabolism which a chemical reaction that takes place within a plants leaves, assist in producing the nutrients for a plant to survive. Carbon dioxide, water and light are key requirements for this process to take occur. During this process by which plants originate and mature, develop leaves, stems, flowers and fruits. Three growth phases that occur:
Establishment growth
Occurs after seed germination or while rooting and establishing vegetative cuttings. Requires low light intensity
Vegetative growth
Occurs when leaves and stems are rapidly growing. Requires an increase in light intensity
Reproductive growth
Occurs when the plants transition to start producing flowers and/or fruit. Requires high light intensity
Photomorphogenesis
Secondary metabolism which is the process in which a plant develops form and structure, and this process is caused by light. It will assist the plants in developing colour, taste and smell
Photoperiodism
Plants response to the changes in the day’s length, so affectively the plants circadian rhythms. This is vital in plants the flower and fruit. Short day plants require long periods of darkness for flowering to occur, while long day plants require short periods for flowering to occur

