What Are Stomata On Cannabis Plants
Have you ever heard someone say that some amphibians breathe through their skin? It’s true! Frogs have a weird membranous skin that exchanges oxygen and carbon dioxide with their surroundings when wet. That’s part of why it’s so important not to handle frogs, because their skin is sensitive not only to the chemicals humans use on their hands and clothing, but to our own oils and the environment around us. This is relevant when thinking about cannabis cultivation because most plants, cannabis included, have a similar mechanism for exchanging gasses with the atmosphere. They do this with things that look more like the pores we have on our skin, those little dots that pair with our hair follicles and produce oils. On plants, these openings are called stomata, or stoma when there’s just one of them. Stomata are found all over the underside of cannabis leaves. They’re much smaller than our skin pores, and can be heavily influenced by the presence of things like moisture, light, heat, and chemicals in the surrounding environment. Under a microscope they look a little bit like little eyes or mouths. Unlike our pores, which contrary to popular belief don’t actually open or close more in the presence of heat, stomata have the ability to open and close to different apertures, like the irises of our eyes. The opening itself is the stoma part, and each stoma’s opening and closing is regulated by two guard cells, which collect and sense concentrations of carbon dioxide in the atmosphere.
What Do The Stomata Do On Weed Plants
Imagine if, instead of holding hair follicles and releasing oils, the pores on our skin were how we took in oxygen. Imagine inhaling not through your mouth and nose, but through a million tiny holes all over your skin. While the stomata on weed plants don’t exactly breathe in the same rhythm we do, with a definite in and out phase, they do exchange gasses with the atmosphere all the same. And their primary function, to put it really simply, is to exchange gasses and water vapor with the surrounding environment. When plants are very young and haven’t developed their root systems yet, cannabis seedlings will intake both water vapor and carbon dioxide from the atmosphere through their stomata. That’s why tiny cannabis sprouts need a relative humidity of sixty-five percent until they get their first few true leaves and a couple of strong roots. As they get older and their vascular tissues and root systems become more established, stomata are used less for water intake and more for carbon dioxide intake, oxygen output, and the retention of moisture within the plant. Why is this important? Carbon dioxide intake is vital to the process of photosynthesis, which takes CO2 and water and, using energy absorbed from sunlight, rearranges their atoms to make sugars and starches that go to making more plant tissues. The stomata also release oxygen, which is the byproduct of the photosynthesis of carbon dioxide and water into carbohydrate sugars. Stomata’s favorite thing to do is intake carbon dioxide.
Stomata In Different Climates
It’s useful to think of the guard cells that border each stoma as lips or eyelids, which are sensitive to the environment around them and can take reflexive action if they sense a certain stimulus. Just like you might flinch and close your eyelids when there is too much dust in the air in order to protect your eyes from the particulate, guard cells will react, sometimes strongly, to the presence of certain stimuli. Guard cell action that closes and opens the stoma is regulated primarily by water content, the presence of carbon dioxide, and the concentration of dissolved sugars, potassium molecules, and certain acids within the plant. Guard cells have the ability to both release and absorb water, which changes their size and effectively opens and closes the stomata. Light and moisture are the two main variables that affect the motion of guard cells and will affect stomata in different climates. We get into more about how the presence of moisture, light, and carbon dioxide affect stomata further down, but it’s important to consider the environment your plants are in as a whole as well as looking at the individual components. Stomata aren’t selective about what they absorb, and that’s really important to know. This is why keeping your growing space, and the leaves of your plants, free from a lot of dust, strong cleaning products or other concentrated chemicals, and home fragrances is important, as stomata will absorb harmful things right along with the good.
CO2 and Light Effects On Stomata
Stomata generally open in the day and close at night, but it’s more than just an on and off, binary rhythm controlled by the presence of light. Stomata guard cells are sensitive to the quality and intensity of light, as well as the presence and concentration of carbon dioxide in the environment and within itself. The regulation of carbon dioxide is controlled by a gradient. It can be a little much to wrap one’s head around, but basically if the environment has more carbon dioxide than the plant needs, the stomata will often close or open less fully. The same is true if there isn’t enough light or carbon dioxide, because the plant will try to conserve what it already has instead of continuing its processes and running itself into a deficit. To make things slightly more complicated, CO2 and light effects on stomata are linked. When there is a lot of intense light around, plants are able to absorb more energy and carry out their metabolic processes, including photosynthesis, much faster. This clears up stored carbon dioxide in the plant, which leads to a deficit of it within the plant tissues, which creates the gradient between the plant’s interior and the more carbon dioxide rich surrounding atmosphere. This, in turn, causes guard cells to open stomata further and intake more CO2. If light is low, metabolism is slower, carbon dioxide can build up, the gradient will lower, and stomata will not open as fully. Not enough photosynthesizing, and the plant will get sick.
How To Control Cannabis Plants Stomata
If there is either too much or not enough carbon dioxide, moisture, or light in the atmosphere or in plant tissues themselves, plants will close their stomata or only open them very narrowly. This is done in an effort to regulate more effectively how much of each variable is coming on and going out of them. And plants that don’t have what they need to continue their metabolic processes are in trouble. This delicate, often invisible, balance that keeps stomata open for the right amount of time to keep plants running healthily can be difficult for cannabis growers to monitor. The dismay at working on a plant only to have it stop producing has led many growers to investigate how to control cannabis plant stomata. It’s generally considered inadvisable to try and do this artificially, since it’s such a complicated feedback loop that any extra stress on the system can wreak more havoc than it solves. The best thing to do for a plant that looks like its metabolic processes are being interrupted is to try and troubleshoot which variable in the system it is missing or overloading on and address that problem, rather than artificially forcing the stomata to open or close. Blue light is implicated in the opening of stomata because blue light is much more present in direct, bright, and intense light. While adding blue LED light will temporarily cause stomata to open more, without addressing the root issue you are inviting more stress onto the plant.
Stomata Response To Moisture
The regulation of moisture within a cannabis plant is closely linked to the regulation of its internal temperature. When plants are too warm, water within their tissues absorb heat. That water is turned into gaseous water vapour due to the added heat energy and that gas is then expelled, usually through the opened stomata. However, if it’s too hot out and a plant is going to exhaust itself and its water supply by cooling, it will close its stomata to avoid losing more moisture than it can handle. Once plants close their stomata while overheating, there’s now no way for the heat to escape, and wilting or burning will commence after not too long. What’s even worse is that as plants stop expelling water vapor, this in turn further decreases the humidity in the surrounding air which continues to dry out both plant and environment. Conversely, when faced with a continually humid environment, plants don’t close their stomata at all. Carbon dioxide or sugars will then potentially start to build up in the plant, depending on whether or not other variables are present in sufficient amounts to continue metabolism. These dramatic stomatal responses to moisture are the reason why maintaining optimal light and humidity for your plants at all times is an important part of growing. If the stomata stay closed, or open too narrowly, for too long due to the lack of light, moisture, heat, or carbon dioxide, or due to a nutrient deficiency, especially a lack of potassium, metabolic processes can’t continue.
