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Osmosis in Cannabis Plants

Osmosis Effect on Cannabis Plants

Not all growers are science enthusiasts, so they may not remember learning about osmosis in high school. Having a basic idea of how marijuana plants exhibit osmosis can help growers maintain a healthy balance of nutrients and ensure their health throughout the growing cycle. Read on for a quick refresher course on how osmosis works and how this vital physical process affects plant growth.

What Is Osmosis?

Osmosis is a specialized type of diffusion that moves molecules or atoms through cell walls and other semi-permeable membranes. It always works the same way. Pure water will always move toward the side of the membrane with more dissolved solids, or solutes.

Before discussing its effects on marijuana plants, let’s review a common experiment used in schools across the country to clarify how osmosis works. Not only does this phenomenon occur exactly the same within different strains, like 3 kings strain or alien technology strain, but also among all plants on Earth! Some growers might have performed this experiment themselves. It involves separating water with a solute, usually salt, from pure water using a semi-permeable membrane. Each time the experiment is performed, students observe as the pure water gets pulled through the membrane, while the solutes stay on the other side.

Osmosis continues until the water on the two sides of the membrane has reached an equilibrium. The water on the side that contains more solutes is usually diluted as a result.

Essential Terminology

There are a few other biological terms growers need to know if they want to learn and talk about osmosis in marijuana plants. Here are a few of the most important of them:

  • Diffusion is any process by which molecules are transferred from areas of high to low concentration, including osmosis.
  • Solutions are mixtures made up of multiple substances.
  • Solutes are the dissolved substances.
  • Solvents are the liquids into which the solutes are dissolved.
  • Hypotonic solutions are solutions that contain lower levels of solutes.
  • Hypertonic solutions contain higher levels of solutes.
  • Isotonic solutions contain a balanced quantity of solutes.
  • Semi-permeable membranes, sometimes called selectively permeable membranes, allow solvents and some solutes to pass through but create a barrier against other dissolved solids.

What Does That Have to Do with Growing Marijuana?

The cell walls that surround each cell of a marijuana plant function as semi-permeable membranes. They allow the plant to store essential nutrients and minerals, which are unable to escape into the surrounding environment. Since plant cells typically contain higher concentrations of solutes than the water in the soil, they can leverage the power of osmosis to draw in water. When you buy Blue Dream seeds, you are basically setting yourself up for an exciting two or three month long science experiment!

Unlike most biological processes at work in marijuana plants, osmosis occurs spontaneously without any expenditure of energy. Just like in the experiment described above, osmosis pulls water through the plant’s semi-permeable cell membranes into the cells, only stopping when an equilibrium is reached. That’s beneficial to plants for a few reasons, which will be described in detail below.

Osmotic Pressure

Since plant cells contain a high concentration of solutes, they draw in a lot of water. As more water moves into the cells, they start to swell. This swelling is what allows plants’ stems to stay upright, turns their leaves toward the sun, and prevents them from wilting.

Unlike animal cells, which can burst open when exposed to hypotonic solutions that contain lower amounts of dissolved solids, plant cells thrive under these conditions. They’re designed to exert counterpressure in hypotonic solutions. In fact, plant cells exposed to the kind of isotonic solution that animal cells love would shrivel and die. Plants that maintain healthy osmotic pressure grow taller and straighter, allowing them to get more sunlight.

Turgor and Plasmolysis

The term “turgor” refers to the pressure exerted on cell walls when they are under tension. It is caused by osmosis when cell membranes are exposed to hypotensive solutions. As the cell absorbs water, the membrane expands until it puts pressure on the cell wall. The wall then creates counterpressure. The result is stiff, firm, healthy plant tissue.

When a plant’s cells are exposed to an isotonic or hypertonic solution, it loses turgor. Eventually, this causes the cell membrane to break away from the cell wall, causing a state known as plasmolysis. The plant will wilt, and if the cells are left in a state of plasmolysis for too long, they will die. That’s why it’s so important for growers to ensure that their crops get plenty of water.

Nutrient Absorption

Marijuana plants also use osmosis to absorb nutrients. Since their cell membranes are selectively permeable, they can uptake only those solutes that are necessary for growth, such as nitrogen, potassium, phosphorous, and other macro- and micronutrients, while excluding potentially harmful substances.

As plants move nutrients from their roots to the rest of the plant and use them to fuel their growth, the concentration of these solutes in the cells of the roots drop. When they drop below the levels found outside the roots, it throws off the equilibrium and osmosis kicks in. It then continues to take place until the equilibrium has been restored.

Moving Nutrients

Osmotic pressure allows water and nutrients to travel from the plant’s roots throughout the rest of its cells. Since marijuana plants absorb most of their nutrients through the roots, some parts of the plants contain higher concentrations of nutrients, or solutes, than others. The pressure caused by osmosis pushes these nutrients throughout the plant, allowing nutrients to get where they need to go instead of building up beneath the surface of the ground.

Nutrient Deficiencies and Excesses

Since plants rely on osmosis to absorb and transfer nutrients, they become nutrient deficient if levels of vital nutrients in the soil are depleted. Even if there’s some nitrogen, potassium, or phosphorous left in the soil, the plants won’t be able to uptake it if they have just as much in their cells already.

Osmosis also explains why plants can wind up absorbing too many nutrients. They don’t mean to do it. It happens because osmosis creates an equilibrium on both sides of the cell membranes. The plants then move these higher concentrations of nutrients around to stems, leaves, and flowers, causing nutrient burns.

Opening and Closing Stomata

Stomata are microscopic holes found on the undersides of marijuana leaves that allow plants to absorb carbon dioxide (CO2) and exhale oxygen and water. These holes are composed of guard cells and auxiliary cells. The guard cells allow the stomata to open and close depending on environmental conditions, such as light levels, carbon dioxide levels, temperature, and internal water pressure.

The last of these environmental factors is where osmosis comes into play. When a plant’s internal water pressure gets too low after a period of drought or insufficient watering, it moves the guard cells to close its stomata and prevent evapotranspiration. This also prevents the plants from absorbing CO2, which they need to photosynthesize.

Technically, the evaporation of water through the stomata is not osmosis, but it is a form of diffusion. However, the movement of the guard cells is caused by osmosis. When the plant has plenty of water, the guard cells will be turgid and the stomata will remain open. This turgidity is caused partially by the cell’s ability to accumulate potassium ions, which alter their water potential.

When a stoma’s guard cells lose water due to low internal water pressure, they lose turgidity, causing the stoma to close. Marijuana plants also close their stomata at night or, in indoor grows, when the lights are turned off. The ability of the plant’s guard cells to accumulate and shed potassium explains how this is possible, even when internal water pressure remains the same.

Reverse Osmosis

Even growers who don’t remember their high school biology usually know about reverse osmosis. This process removes dissolved solids from a solution, leaving behind pure water, devoid of minerals and nutrients.

Reverse osmosis turns the natural osmotic process around by applying pressure on the side of a semi-permeable barrier with a higher concentration of solutes. The increased pressure causes water to travel backward through the barrier to the side with fewer dissolved solids, eventually achieving pure, clean water with a pH of seven and an EC of zero.

Growers who want to control exactly what minerals and nutrients their plants receive often buy distilled water, which is treated using reverse osmosis. That’s fine, but they should note that plants typically receive some of their calcium and magnesium from tap water. When using distilled water, they’ll have to supplement these minerals.

The Bottom Line

Osmosis is a relatively simple process, but it can be tough to understand. Growers who have taken the time to read through the preceding explanation should now know not just what osmosis is and how it works, but also how it impacts plant growth. Marijuana plants harness the power of osmosis not just to absorb water and nutrients through their roots, but also to move it throughout their various parts and to regulate both carbon dioxide intake and evapotranspiration. Those who understand the mechanics at work behind these regulatory processes are already one step closer to improving their plant’s health and increasing their yields. If you are looking for marijuana seeds cheap to grow yourself, look no further than the seed bank. When comparing cannabis seeds for sale online, our selection can’t be beat!