Grow Lights and Indoor Agriculture

A burgeoning industry with potential impact for our future

Indoor agriculture is a promising alternative for food supply at a time of global environmental crisis.  One important component is the use of grow lights to complement or substitute sunlight.  Here we discuss how grow lights and PAR measuring devices are important in this industry.

PG200N Spectral PAR Meter

Image courtesy of Taiwan Highpoint Corporation

▸Download Grow Light Handbook

▸PG200N Spectral PAR Meter

▸MK350S Premium

Grow Lights – Unravelling the secrets of sunlight

As we know, plants need soil, water and sunlight.  But there are vast regions of the planet that don’t get any sunlight during the winter months, and other places that are simply too inhospitable for any sort of agriculture.

Recently, a new generation of farmers have emerged, who are moving indoors for agriculture.  Indoor farming has allowed all kinds of fruits, vegetables and ornamentals to be produced locally anywhere, in plant factories or abandoned warehouses, for year-round production.

The big challenge was and is unlocking the secrets of sunlight so we can substitute or complement with indoor lighting.  And thus a new era of lighting focused on indoor farming has emerged – they are called Grow Lights. 


 Science of Grow Lights

The strategies behind Grow Lights are essentially about biology, chemistry and physics. Ultimately, the goal is to understand the secrets of sunlight to use to our advantage.

Grow Lights with the right colors

How do plants use light?  Most plants appear green because they are reflecting the green light from the Sun – in effect, they don’t use green light.  The Red and Blue light, however, are absorbed by the plant and is used to start a chemical and electrical process called photosynthesis, a vital bio-mechanism that produces sugar.  Sugar is used to power the growth of the plant (stems, leaves, flowers and fruit).  The main pigment molecules (light absorptive molecules) in a plant that can receive and process light are called Chorophyll and Carotenoids. As you see below, the light absorbed by these pigments are mostly  in the realms of blue and red light.  Your grow lights need to amply supply light in those colors.

This graph show the color peaks where different Chlorphyll absorbs the most light (blues and reds).

How much light do you need?

Aside from color you have to know how much light to give.  Giving too much light has adverse affects on some plants, and indiscriminately showering your plants with light is energy wasteful.  But, too little light means your plants are not nourished properly.  But how do you measure light quantity?

If you remember from your Physics class, light is both wave and particle – it is the particle aspect of light that we are measuring. PPFD or Photosynthetically Photon Flux Density is the quantitative measure of photons or particles of light falling on an area.


So how do measure the Colors and Quanitity of light?

It’s called a PAR meter. PAR stands for Photosynthetically Active Radiation and it refers to the wavelengths that plants react to.  A PAR meter can measure quantities of light (in PPFD) as well as the colors that the light is providing (spectrum).

PAR meters with detachable heads are important to measure with precise, consistent angle and distance.

UPRtek PG200N displays PPFD as well as grow light spectrum with Chlorophyll color sensitivity range superimposed over it.

All plants are not created equal – Plant Recipes

Different plants have evolved to respond to different lighting conditions.  They have what are called “recipes” or plant formulas, which are used as guidelines for lighting conditions.

A Recipe for Lettuce for a plant factory with vertical shelving with LED lights underneath.

  • LED distance from plant 30-50 cm
  • Light Quantity: PPFD 120-140
  • 18 hours Light / 6 hours dark
  • Sowing to nursery 10-14 days
  • Plant to harvest 28 days


Climate and Seasons

There’s more to growing plants than sun, soil and water.  Plants are sensitive to humidity and temperature, which are important factors to be considered.  PAR meters like the PG200N can be equipped with a temperature and humidity sensor (Thermo-Hygro-cable).

The Phytochrome PSS (Photostationary State) metric also assists growers using LED lights to simulate seasonal sunlight to control sprouting and flowering activities.

▸Read on about PSS


Oregon State University Hydroponics CC-By-SA-2.0

PG200N with Thermo-Hygro Cable Accessory

Indoor Agriculture and data analytics

As you might have guessed, grow lights and indoor agriculture is about collecting information to ensure efficient, productive plant growth and conservation of energy.  Data about PPFD, temperature, humidity need to be collected, saved and analyzed.  Indoor agriculture is more than ever about the numbers.

Download handbook all about Grow Lights and PAR meters (here)

Indoor Agriculture future impact

The growing concern for environmental crisis is at hand.  Indoor Agriculture is a burgeoning but still developing strategy for year-round food production, water reclamation-conservation and food safety (less pesticides).  Energy efficient LED Grow Lights are front-and-center as a complement to sunlight. With developing technologies and collection of data, it could be a promising piece to help improve the human condition.

Handbook Series

The Flicker Handbook

Everything thing you need to know about Flicker, an insidious, potentially serious lighting artifact impacting visual safety for public places like hospitals, offices, libraries, and more...

▸ Get it!

About UPRtek

United Power Research and Technology

UPRtek (est. 2010) is a manufacturer of portable, high-precision light measurement instruments; Handheld Spectrometers, PAR meters, Spectroradiometers, Light Calibration Solutions.

UPRtek HQ, R&D and manufacturing are all based out of Taiwan, with Worldwide representation through our certified Global Resellers.

▸ Read on


Medical Setting using LED or Fluorescent Lights

What is a Spectrometer, Spectrophotometer, Spectroradiometer?

In the realm of spectral devices, three devices stand out: a Spectrometer, a Spectrophotometer, and a Spectroradiometer. However, these terms have been so interchangeably used that we felt obligated to clarify their differences in one short article.

  ▸ Spectrometer v Spectrophotometer v Spectroradiometer