Starting an indoor garden could be a fun and sustainable method to grow those fresh vegetables you need during summer months when there is an insufficiency of sunlight. And just as every farmer knows (sure you’re one) – plants need sunlight, in fact, plenty of light to grow, bud, flower, and to yield bountiful produce.

Figuring out how to supply crops with sufficient light for their metabolism is a significant challenge faced by indoor growers – and this is where the understanding of what photosynthetically active radiation (PAR) is and its role in plant growth becomes crucial for the success of your indoor farm.

What is photosynthetically active radiation?

PAR is the amount of useful light available to crops for photosynthesis. The PAR for plants falls within the spectral range of 400 to 700 nanometer which is also the waveband for visible light.

The amount of photosynthetically active radiation available at a given location fluctuates all year round – this is due in part to some factors like the season of the year, cloud covers, latitude and longitude of the site. Air pollution and foggy air also block out the PAR reaching the plants.

But these conditions are not your concern since you’d be growing your crops indoor; however, you will have to choose the right light source with an adequate PAR emission.

Photosynthetically active radiation and Plants

You might be wondering, why is photosynthetically active radiation essential for plants’ growth?

The sunlight is composed of several wavelengths with varying energy levels. Bands of longer wavelengths tend to be less energetic and hence unable to stimulate photosynthetic processes in the plant while shorter wavelengths carry more energy that causes damage to the plant cells.

The photosynthetically active radiation is the wavelength with the right amount of energy to trigger photosynthesis in the plants. So, you now see why they are required by plants? – Most useful wavelengths fall within this range.

 

How do plants absorb PAR?

When photons (energy from the sun) hits plants the chlorophyll, carotene, and xanthophyll – that is the pigments that give color to plants – capture the light and pass it on to photosynthetic process.

The thing is plants need different light wavelength at various stage of growth. Take, for instance, the blue light or light with wavelength closer to the 400-nanometer spectrum promotes stem and leaf growth hence preventing leggy plants while a combination of the blue and red lights stimulate bud development and flowering.

Hence it is vital that while deciding what source of light to go for your indoor growing, to ensure choosing those that emit light within the useful wavelength to encourage photosynthesis and healthy crops.

 

Daily Light Integral, why you need to understand this too

As you embark on setting up your indoor farm, you may have an idea of the amount of energy at a particular wavelength hitting your plants per square meter but what you also should know about is the amount of this energy the plants may need per second.

This is what Daily Light Integral seeks to answer and is measured in moles of light (PAR light range) per square meter per day. This is important as it allows you to set up a system that is energy efficient thereby keeping your energy bills as low as possible.

 

Different types of grow light for your indoor farm

There are several lighting sources you can choose from for but, you should bear in mind that some of them might not provide the best lighting your plants require – note that different crops have varying light needs – So it becomes necessary to match the needs of your crops appropriately with the right light source.

High-intensity emission lighting provides a good spectrum light for the crops, but they are known to produce excessive heat which can burn the plants when close. Example of this lighting source is the high-pressure sodium and metal halide lights.

  • Metal halide lights – they produce mainly blue light and are not durable – that is they have a short lifespan. Most MH lights have high energy consumption and delicate.
  • High-pressure sodium lights – gives off light in the useful wavelength however due to they emit a lot of heat that shot up the cost of running them.

Fluorescent lights this is suitable for homeowners and small-scale indoor farm operators. Relatively low priced when compared to the HID lights and a longer lifespan of over twenty thousand hours have made indoor growers choose this light source over the HID. However, its non-specific spectrum has limited its use.

Full-spectrum fluorescent lights – this offers the same features as the regular fluorescent light in addition to providing full-spectrum light including the red light as well to stimulate blooming.

LED light – more and more farmers are switching over to LEDs due to its low operating cost, efficiency, extended lifespan and spectrum specificity making it possible to light the farms more efficiently without worrying about rising energy costs. According to NASA, LED lights seem to provide the optimum light wavelengths for plant growth.

Final Thoughts

Deciding to start an indoor grow is an exciting journey that has several benefits ranging from providing you with the lush green scenery that is lost during the winter periods to being a source of organic home-grown fruits and vegetables for a healthy meal.

However, this presents its own challenge, chief which is lighting. Securing a lighting source that provides active photosynthetic radiation – that is the useful light range used by plants to make their food is a task you must accomplish to run a successful indoor farm.

Photosynthetically Active Radiation: What It Is and Why You Need It for Your Indoor Gardening
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