Light, a basic need
All gardeners know that light is an element that is of capital importance for the growth of their plants. Some, like cacti and succulents, require intense direct light, while others, like the majority of tropical plants, prefer to avoid direct sunlight and thrive in indirect, rather moderate light. The effects of insufficient lighting are observed quite easily: wilting, plants without vigor, loss of color, etc.
In this article, we will see why light is so important for our plants and also how we can provide them with artificial lighting if our light conditions are insufficient.
Photosynthesis
It would be difficult to understand in depth the importance of light without first going through some notions of plant biology.
We know that plants need light. But do we really know and understand why? In fact, by capturing light, plants actually produce their fuel, their food! The equation is quite simple, lack of light = lack of food.
Let's look at this in more detail, but simply.
Plants are made up of plant cells in which various organelles (components) interact with each other. Among these organelles: chloroplasts. Chloroplasts, through their chlorophyll content, are responsible for the physiological process of photosynthesis by which plants use light energy and transform it into another energy, this time chemical. Indeed, with the process of photosynthesis, plants have the formidable capacity to take the energy given to them by light to transform water (H 2 O) and carbon dioxide (CO 2 ) (captured by the stomata of their leaves and by their roots) in sugars (carbohydrates) and oxygen (O 2 ).
The process of photosynthesis and cellular activity in plants could be explained in more detail, but for our purposes here we will limit ourselves to these explanations.
Let us add that photosynthesis takes place mainly in the leaves of plants which act as light sensors. The upper leaves, often more exposed to light, will have higher photosynthetic activity than the lower leaves, often less exposed to light.
Factors that affect photosynthesis
Photosynthesis is therefore a process which regulates the internal activity of plants and on which both their growth and their needs depend.
Certain external elements have a direct influence on the photosynthesis process, such as temperature, carbon dioxide content, quantity of water and nutrients, certain internal factors and illumination.
There is no perfect temperature suitable for all plants. It all depends on their origins, but generally speaking, we can say that the colder it is, the more the physiological activities of the plant are slowed down, and therefore the less photosynthesis there is. This is what happens, for example, when we induce a state of dormancy in certain plants. The opposite effect also exists: a warmer temperature (within the limits of what is possible for plants, do not try to put your plants in the oven!) will have the effect of increasing the internal activity of the plants.
Carbon dioxide content also affects photosynthesis. The more carbon dioxide there is in the ambient air, the more the photosynthesis process increases. Here too, there is a limit: when the plant is saturated, it closes its stomata and blocks the entry of carbon dioxide. The question of carbon dioxide is interesting for growing areas where ventilation is less or not active. For example, greenhouse operators in winter sometimes use carbon dioxide injectors to meet the needs of their crops.
Water and nutrients (mineral salts) are essential for photosynthesis. A plant with a water deficit will close its stomata and no longer photosynthesize, so as not to run the risk of dying from desiccation. Regarding nutrients, to be able to make chlorophyll and carry out photosynthesis, a plant needs elements such as nitrogen (N), phosphorus (P), magnesium (Mg), chlorine ( Cl), iron (Fe), manganese (Mn), boron (B), zinc (Zn). A deficiency in any one of these will affect the entire process.
The other factor that has a big impact on the photosynthesis process, and not the least, is illumination . Illuminance consists of both the quality of light and its quantity , and it is when the two come together that a plant can have efficient photosynthesis. Photosynthesis increases with illumination up to a saturation point (maximum photosynthesis) and drops sharply as light decreases. There is a critical light stage, however, below which the plant will remain in a vegetative state, showing no activity if light does not increase.
If this is you, you love plants, but don't have enough natural lighting in your home to keep them looking beautiful. Whether they wither, don't grow, experience so much stress that they end up having lots of parasites, or die... Well, it's time to see what artificial lighting can do for you.
What do we know about light?
When shopping for artificial lighting for our plants, we need to have some basic knowledge. We often see growth lamps that diffuse a purple light while others often diffuse a white… Which one to choose? How do we know what is appropriate for our plants?
Let's look at some concepts to better understand the rest of the article.
Light is made of photons (particles) which move in waves (wave movements). Each wavelength corresponds to a color of light (red has a fairly long wavelength (700 nm), while violet has a shorter wavelength (400 nm).
White light is in fact composed of a set of colors (therefore a set of waves of different lengths), as we can see when, for example, we pass light through a crystal prism (or observe a Rainbow).
Not all white lights are equal, because they do not contain the same proportions of each color. There are warm whites (which contain more yellow, orange and red) and cool whites (which contain more purple, green, blue). The color of light is measured in degrees kelvin: 1,000K represents a very warm white, 10,000K a very cold white. The light from a bright, cloudless sun is 6,500K.
The color or wavelength of the light corresponds to what is called the quality of light, which we talked about above. This little detour to explain that the plant reacts differently depending on the wavelength (or color of light) it receives. For example, blue-violet light is absorbed by chlorophyll during the plant's growth phase, it promotes more robust plants with a bushy habit, increases metabolism, growth and development. Red light is rather absorbed during the flowering phase. It will tend to influence the smell and flavor of plants by increasing their concentration of oils and sugars. It is also the red light that influences the photoperiod (the plant knows that it is daytime when it receives daylight and knows that it is dark when it does not receive any), which is useful for certain types of flower cultivation. And it can sometimes promote wasting, which we do not want.
Let us remember that the sun presents the full spectrum of light colors. We may wonder if lamps that provide only purple light meet all the needs of plants.
The other aspect of illuminance, the amount of light , is also very important. The best quality light available, if it is not present in sufficient quantity, will not meet the needs of our plants. Generally speaking, the more light plants receive, the more their metabolism is activated, and the more they grow. To this equation, we must naturally add water, relative humidity, nutrients and adequate temperature.
The unit of measurement for illuminance is lux * (international system). To give an idea, a sunny summer day has more than 50,000 lux of illumination while a well-lit room in the house varies from 100 to 500 lux. The interior of a house with a window in full sun this time gives around 60,000, while a cloudy day 2,000 lux. In addition, the further you move away from the light source, the more the amount of light received decreases. This goes without saying, one thinks, but what is surprising is in fact that if there is, say, twice as much distance, there will be four times less light! It's going down quickly.
It is estimated that full sun plants (cacti and succulents for example) need 20,000 to 30,000 lux to be able to photosynthesize efficiently, while shade plants (certain tropical plants such as Calathea or Sansevieria ) can be satisfied with 2,000 to 5,000 lux.
It should be added to this that the windows of modern houses are made up of more layers than before and that they often block certain types of rays. It is not uncommon to have plants well exposed, in a window, but which never seem to be satisfied, and which continue to grow in pride (to wither). Difficult to give them more without resorting to artificial lighting.
* On the packaging of lighting products, we will often see the unit of measurement of illuminance in lumen. The difference is that lux corresponds to the amount of light received while lumen corresponds to the amount of light diffused. To have an equivalence, we must consider that 1 lux = 1 lumen / m 2 .
Artificial lighting
To be able to optimize the growth of our plants indoors using artificial lighting, we must try to provide them with lighting that is as close as possible to sunlight, powerful (lux) and balanced (at the level of the color spectrum).
In some cases, the choice of lighting will depend on what we want to do with our plants. If we want to induce flowering in a certain type of crop, for example, we will rather choose lamps that diffuse more red light. And if we want to keep them in the vegetative stage, we will prefer a light that diffuses more blue-violet.
It goes without saying that the duration of lighting has a strong impact on the results we wish to achieve. It is difficult to give a precise number of times, because everything depends on the needs of the plant in question. For example, if you want to induce flowering in a type of crop, or to start seedlings, you can light up to 16 hours per day! But as a general rule, we are not so wrong in providing a dozen hours of light per day to our plants and giving them a rest period at night. Because, yes, they need it too.
That said, in most cases, gardeners want plants to have good overall growth and be healthy. And to meet these needs, the ideal would be to look for light that reproduces the spectrum of the sun as closely as possible.
Incandescent bulbs
Let's not beat around the bush: this type of lighting is of poor quality for your plants. We avoid.
Compact fluorescent bulbs (CFL)
This type of bulb is definitely better than an incandescent bulb for your plants' needs. This is a type of lighting which can be interesting for example for seedlings and seedlings.
The spectrum of this type of bulb is generally either warm white or cool white, but the model offered by the company SunBlaster (which offers several good quality horticultural accessories (including heating mats and thermostats ), is 6 400K, which mimics sunlight Sunblaster compact fluorescent bulbs also come in 2700K, for gardeners who want to induce flowering instead. These bulbs are suitable for propagation and growth and are compatible with all standard sockets. They are available at 26 watts, which is equivalent to 100 watts with an incandescent bulb. They provide 1,700 lumens.
T5 fluorescent tubes
T5 horticultural fluorescent tubes (and not your office neon lights, T12) generally provide a good spectrum (good quality of light) and are particularly interesting for seedlings and seedlings. But generally, the number of lux is low. Depending on the model of fluorescent tube you choose, they can sometimes be bulky and fragile.
That said, the SunBlaster company has models of T5 fluorescent tubes with integrated reflector which are already mounted on the ballasts and which simply have to be plugged in. These fluorescent tubes are equipped with reflectors which allow better diffusion of light and offer a complete spectrum of light ( Full Spectrum ), which imitates sunlight quite well. They are offered in different sizes (12 in. / 690 lumens, 18 in. / 1120 lumens, 24 in. / 1500 lumens, 36 in. / 2450 lumens, 48 in. / 3730 lumens) so they can fit into most spaces. gardening.
The T5H0 is also available without a reflector , but the advantage of the reflector is to diffuse the light more widely over the plant canopy, penetrating deeper into the plant's foliage, without consuming additional energy.
It's what they call the T5HO Nanotech Combo , which includes: electronic ballast, 6400K fluorescent, 6' power cord with on/off switch, 14" link cord, clips for hang the ballast or attach it to a flat surface.
The 6400K T5HO lamps have a spectral distribution with peak intensity between 435 nm and 615 nm, wavelengths suitable for photosynthesis. These lights are ideal for propagation and long term growth.
The company also offers replacement lamps (including 2700K T5HOs for gardeners who instead want to induce flowering), so there is no need to repurchase the complete kit once equipped.
These lamps emit little heat, which is interesting unlike some models previously offered. Fixtures can therefore be placed 6 to 8 inches above the plant's canopy, maximizing photosynthetic response and growth.
Horticultural LED lamp
Horticultural LED lamps are currently the best options on the market in terms of lighting quality and energy savings. They produce less heat than fluorescent tubes, but more light, and the light they emit is continuous, which is not the case with many standard horticultural lamps which emit intermittently, although this is invisible to the naked eye. The fact that the light is continuous makes it even closer to sunlight and makes them more effective than other lights.
The Sunblast company offers a truly high-performance product with its LED lighting.
There is the LED Sunblaster Self Cooling , which is offered in different sizes (12 in., 18 in., 24 in., 36 in., 48 in.) and whose main attraction is that it does not emit any unwanted heat.
And there is the LED Sunblaster Prismatic lens , offered in the same dimensions (12 in. / 1600 lumens, 18 in. / 2500 lumens, 24 in. / 3400 lumens, 36 in. / 5000 lumens, 48 in. / 6700 lumens) (offers more than double the lumens of the T5HO), with the same appeal, but featuring a prismatic lens. This improvement causes light to pass through a prism that refracts and reflects the light in a 90 degree beam angle rather than 120 degrees, like older models. This ensures that more light reaches the plant canopy and significantly reduces losses. These LED light strips have a full spectrum with a maximum of 6400K, which is suitable for all horticulture uses: seed, general cultivation, propagation, micro green vegetable production, etc. In terms of wavelengths, this is probably the type of lamp that currently provides the broadest spectrum (between 400 nm and 700 nm). The improved light output of this horticultural lamp model stimulates faster growth.
The LED Sunblaster Prismatic lens is also sold in kits: the electronic ballast, a 6400K fluorescent, a 6' power cord with on/off switch, a 14" connecting cord, clips for hanging the ballast or attach it to a flat surface.
Accessories offered by Sunblaster
The Sunblaster company offers several accessories and thus meets various needs that one might have when installing their different lamps, whether to hang them or to assemble the ballasts together, which is quite interesting when one has a long surface to illuminate:
Extension connectors for T5HO and LED ballasts :
Suspension clips with rings for T5HO and LED :
Suspension clips for T5HO and LED :
Connections for T5HO and LED :
We can therefore see that it is not because we do not have natural light in our home or that we do not have enough lighting that we should deprive ourselves of having plants. There are a multitude of solutions to fill the lack of lighting, for different types of spaces, for different budgets. We simply need to understand how lighting works to be able to choose what best suits our needs and those of our plants!
