A Student Project: Light Color & Seedlings
One of the great things about LED lights is the ability to isolate very narrow color bands, without relying on filters. The diodes themselves can be customized to produce a variety of wavelengths. This enables some very interesting experimentation. Researchers can examine how plants respond to certain colors and combinations.
But such research is not limited to astronauts in space shuttles. These days, LEDs are available to the general public. Thus, "citizen scientists" can design their own LED experiments at home, sharing their results with the world. And students can also create science fair experiments for school projects.
Today, we're looking at one such student from The Netherlands, named Louise. Louise contacted me, wanting to interview me for a portion of her school project. The interview is below. But first, let's look at the experiment she set up using some DIY LEDs and some plant seedlings!
Experiment: Colored LEDs & Seedling Growth
At this point, why don't we have Louise tell us about some highlights from her experiment.
An Interview with a Student:
Louise: So first of all, Urban Gardening is your passion if I understand that correctly, and you have done quite some researches about plants. What made you do those home-made researches in the first place? And what prompted you to start a YouTube channel to share your researches?
AL: I started with home gardening as a hobby. To simplify the watering process, I learned about self-watering planters (sub-irrigated or wicking beds). I noticed that some of the information on the internet was not very clear or reliable. This prompted me to start a website about urban gardening and self-watering planters. Eventually, I decided to start a YouTube channel so that I could demonstrate how those systems work. My training as a graphic designer made all of this much easier for me.
I noticed that there were many popular videos on gardening that were not very in-depth - gardening for dummies. I've always loved sciences like chemistry, physics, biology and botany. I wanted to get into the more advanced aspects of how plants grow. So I began setting up small experiments to test different products and methods for growing plants. My goal has been to try to learn and also to teach others as I share my results.
I hope to someday support myself off of my YouTube channel. But I'm most concerned about motivating people. I try to inspire others to grow food in whatever ways they can. I also enjoy science and demonstrating scientific concepts through hands-on experimentation. Even if we don't specialize in a field of science at a university, we can still have a passion for learning and for the scientific method. In my channel, I hope to bridge gaps between the common person and the advanced fields of scientific study.
Getting Into LEDs
Louise: My topic are plants growing under LED lights. You have done some research for that too. What made you so curious for doing this specific research category (Plants growing under LED lights)? What was the first time you heard about the affect of growing plants under different colors of light?.
AL: After my first successful gardening season in 2010, I decided to try growing my own seedlings indoors. This prompted me to examine LED grow lights as an effective way to grow plants while saving money on electricity. When I researched LED plant grow lights, I found many multi-colored lights that combine red and blue diodes resulting in a pink or purple colored light. LED Manufacturers offer various explanations as to why plants only need red and blue wavelengths for effective growth.
Running my YouTube channel has resulted in many comments from people about LEDs. I came to realize that there are many misconceptions about how plants use and respond to light. For example, many people believe that plants do not use green light for photosynthesis. I too was misled by many LED manufacturers and their product claims. I can't accurately teach others if I have wrong ideas about plant lights. So I began researching and conducting experiments to verify my research.
Louise: This subject has rather some complicated maths and theory within it. On your site I've read that Urban Gardening is your passion and Graphic Designing is your profession. How have you learned about the theory (how the plant precisely reacts to the colored lights (the math behind it)) for all the researches you did? Did you read books, asked or asked the internet for help?
AL: I often wish I had taken courses in horticulture to get a better understanding of the mechanisms that fuel plant growth. However, even without that formal training, I've been able to learn more and more. The key is to pay attention to where your information is coming from. Sources like personal blogs, web forums, YouTube and retail sites can be deceptive or completely false. It requires critical thinking skills to examine what you read or hear and then look to see if there are sources to validate a claim.
I've been reading some botany books from university professors. I watch lectures from professors that teach at universities. I've also learned a lot from horticulture magazines designed for professional growers. Finally, I've looked up dozens of published scientific journals to see what scientists are discovering through official research. When I write articles or publish videos, I try to list scientific references to add authority to what I'm saying. Also, the materials I cite allow people to dig deeper, expanding their own knowledge.
How Plants Respond
Louise: You have seen how plants react to the colored LED lights. What was the most surprising result you ever received in one of those experiments?
AL: With each experiment, I seem to learn more and more. It was interesting to see plants growing vegetative mass without any blue light. Pure red light can produce just as much plant mass. But the signals that plants receive from various colors are critical for healthy development. Plant morphology is very complex and different plants can respond differently to various color combinations. LED manufacturers might sell a custom grow light that uses a mixture of only red and blue, claiming that it will work for all plants and growth stages. But I've been running an experiment with lettuce that completely surprised me.
I selected a bib lettuce that I expected to exhibit short, compact growth. I grew the plants under custom LEDs that were marketed for vegetative growth phase. But the lettuces grew vertically, stretching upward. It appeared to be a shade avoidance response. I was growing 3 plants under increasing light intensities. Even under very intense light, the lettuce grew very tall as though it was going to flower. I contacted the LED manufacturer and they sent a full spectrum version of the LED. I've been running the exact same test using this white light LED and the lettuce is compact and extremely healthy. No stretching at all! The manufacturer did not expect their light to adversely affect plant development, but I was able to demonstrate what happened. Clearly, they did not select a suitable ratio of blue to red light. They were very interested in the details of my test.
Pros & Cons of LEDs
Louise: Do you think growing plants under LEDs or any other artificial light works better than normal sunlight? Do you LEDs could be useful for households to grow their own greens in efficient ways? What are the advantages and disadvantages?
AL: Full spectrum natural sunlight is the best, the gold standard for growing plants. Plants use all light from UV to far red in ways that researchers are still exploring. Sunlight is also free and 100% sustainable. It does not result in any CO2 emission. However, sunlight is highly variable. Photoperiods vary with latitude and time of year. Sunlight intensity changes depending on the time of day. Weather patterns, such as cloud coverage, can also greatly affect the amount of sunlight reaching the plant canopy.
That is what makes LED and other efficient lights so appealing. They can consistently emit light regardless of the weather or the time of year or time of day. As lights become more efficient, they become more sustainable and profitable for food production. Indoor growing with artificial lights makes a lot of sense with lettuce greens, microgreens and culinary herbs. The plants are clean and predictably healthy. They can be grown locally in urban areas. This is why there is a boom in vertical farms. LEDs enable such production systems.
Of course we don't always have to choose between one or the other. Many greenhouses are able to harness natural sunlight which is then supplemented with artificial light as needed.
I'm very interested in growing some greens for personal consumption in my home. I'm looking into white LEDs that will seamlessly integrate into my living space. Electricity is the greatest cost of food production. My goal is to analyze the cost per gram. I want to select the most efficient lettuce varieties and light configurations. It should be possible to grow lettuce for less than the cost of buying it at the grocery store.
Louise: If growing plants under colored LEDs is very efficient in contrary to other growing methods, should it then be used for farming of big amounts of crops? Do you think there is any future in manipulating plants by colored lights or do you think it's more probably that it'll be just used for research to gather some knowledge about the workings of a plant?
AL: When comparing LEDs to other technologies, a crucial parameter to look at is the PPF per joule. How much light is produced for each watt of electricity? Some LEDs are much more efficient than others. Similarly, some HID lights are still quite effective, such as double ended high pressure sodium and ceramic metal halide. Plasma (LEP) grow lights are also gaining popularity. But the key is to match the growing technology to the growth environment and crop type.
In vertical farms where you have multiple racks of lettuce squeezed into a tight space, LEDs are the clear winners. In general though, certain crops are more profitable for artificial lighting than others. For example, tomatoes require more energy per weight of harvestable crop than salad greens. Also, salad greens demand a higher market price per gram than tomatoes.
In regards to using colored LEDs for manipulating plant growth, LEDs are very useful for research purposes. Custom LED colors can be used to produce shorter, denser plants. Fruiting or flowering can be enhanced. Or plant pigments can be intensified. However, for general plant production, growers often look for full spectrum light. And LED companies have been adding more and more color bands to compete.
When selecting a versatile LED intended for multiple plant applications, I prefer broad spectrum white LEDs. If planning to use a red / blue LED, be aware that not all manufacturers have selected ratios that will produce proper growth. Also, bear in mind that some plants might do well, while others display abnormal morphologies.
Science is Not Just for Universities!
The scientific method enables any of us to carry on our own tests, regardless of our age or background. We can learn to conduct experiments at home, using the resources at our disposal. Often, such projects create excellent learning opportunities. But we can do even more in this modern age of interconnectivity. Through the internet and social media, citizen scientists can share their findings with the entire world! Your research could impact thousands or even millions of people!
Special thanks to Louise for her hard work on this project and for allowing me to share it on my site!