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Osmosis In Plants: How It Works

February 14, 2022

Osmosis in plants is critical for the well-being of your cannabis crops. To successfully grow marijuana, we must know how to take good care of these plants.

What exactly is osmosis in plants? How will knowing about this help you take care of your weed? Let's dig a little deeper and go through some of the key points to help build our knowledge. Here goes!

Cannabis roots
Cannabis roots

What is osmosis in plants?

The simplest osmosis definition is "when roots absorb water from the soil." There’s more to the process than you'd expect. It’s best if we go into a bit more detail to understand what osmosis is.

The roots of plants don't have tiny holes on their tips to draw in water from the soil. So how do our plants absorb water? By the process of osmosis! 

It's a passive process between the root hairs and the soil. These hairs absorb water molecules through a semipermeable membrane. 

When your plant cells go through osmosis, water travels up to the rest of the plant. Dissolved nutrients can't penetrate through this membrane.

The process of osmosis in plants isn't only crucial for the germination of seeds. It's also essential for the complete well-being of the plant. 

Components that affect the rate of osmosis are: 

  • Pressure
  • Temperature
  • Surface area
  • Water potential
  • Concentration gradient

Where does osmosis occur in plants?

Now that we know what osmosis is, we need to understand where it occurs in marijuana crops. The predominant occurrence of osmosis is in the root cells. The transportation of water is from the soil into the root hairs and then to the cells.

Osmosis also occurs above the surface on leaves and other parts of the plant

Some examples of osmosis in plants are:

  • When water is absorbed from the soil by root hair cells
  • The opening and closing of the stomata on leaves
  • Turgidity of the plant stem 

What's the process of osmosis in plants?

The process of osmosis is complex. We can visualize it using a glass beacon. Fill it with water and place a plastic compartment (which fits in the exact diameter of the beacon) with tiny incisions down the center of it. 

When the process of osmosis happens, water molecules proceed through the incisions in the compartment, which plays the role of the semi-permeable membrane. 

This membrane only allows certain molecules to pass through during osmosis in plants, but not larger ones. Solutes (for example, sugars) can’t move through the incisions. 

Water molecules pass through the root hairs via this membrane and into the root cell walls. From there, plant cells allow osmosis to continue by letting water travel up the xylem and into the leaves. 

For a short while, the process stops when the water and nutrients balance. When the plant detects that it’s low on either, osmosis resumes.

Physical pressure, required for osmosis to occur, is stronger at the root's core. The soil that surrounds the crop has less pressure. Your cannabis plant depends on osmotic pressure gradients to collect water from the soil.

How osmosis in plants works
How osmosis in plants works

What is osmotic pressure?

Is osmotic pressure good or bad for osmosis in plants? It manipulates water movements in the crops and is the minimum pressure enforced to a solution like sugar in water.

The pressure prevents the inward flow of solvents like water from moving through the semipermeable membrane. While plant osmosis assists water molecules from moving into a root, osmotic pressure prevents it. It also manages cell stability.

Osmotic pressure assists with the transfer of solutes through the semipermeable membrane. It temporarily stops osmosis in the plant and helps other nutrients move through the plant. 

Why is osmosis important?

Why is osmosis important? It refers to how plant cells maintain their water intake. Osmosis in plants is crucial as it assists with the swelling of the softer tissue and helps with mechanical support, also known as turgidity.

The main focus of osmosis in plants is in the root zone. It has a vital role in controlling the opening and closing of stomata. Osmosis also encourages growth.

Plant osmosis controls:

  • The cell-to-cell dispersion of water
  • The transport of nutrients
  • Release of metabolic waste products from the plant

Without osmosis in your cannabis, you'll see wilting of the stem and leaves. 

How are osmosis and photosynthesis connected?

Osmosis in plants is essential for photosynthesis to take place. Water causes the guard cells to swell, allowing the stomata to open. When this happens, photosynthesis can then occur successfully.

Photosynthesis generates energy from the sun, water, and carbon dioxide. The plant then provides glucose and oxygen. 

Crops generate energy through the water in their roots and the sunlight they absorb through chlorophyll. Plant osmosis is a key player in photosynthesis.

How does osmosis affect cannabis plants?

Due to osmosis in plants, crops can stay upright because their cells maintain the right amount of tension

The process keeps your crops from lying flat and wilting, ensuring that you don't lose any buds during growth. A positive notion of plant osmosis is that it doesn't use up any of the crops' natural energy. 

The leaves of marijuana plants are unique. Its fan-like structure allows more water droplets to evaporate. It means the plant loses water at a faster rate. 

How does osmosis work? It keeps the absorption rate through the roots at a regulated pace. Allowing the constant movement of water through the plant to keep it from dying. 

The collaborative process of osmosis in plants and photosynthesis allows for progressive growth. It creates sugars that are essential to the production of buds and THC.

Osmosis in marijuana plants promotes the growth of stronger and taller crops that receive more sunlight.

What about nutrient absorption? 

Now that you know about osmosis in plants let's establish a habit of nutritional care for your marijuana crop. If the evaporation rate is higher in a plant, nutrients move faster through plant osmosis

Nutrients move up the stem and water to the leaves, where transpiration takes place—too many nutrients are absorbed into the plant in a short space of time.

It's vital to maintain a nutritional balance using the correct nutrients and dosages

Three of the main nutrients to feed your cannabis plant are nitrogen, potassium, and phosphorus.

These nutrients already exist in marijuana crops. They are present inside and outside the plant's cells. When plant cells allow osmosis, it ensures a stable balance of water flow and nutrients in the crop. 

How can osmotic pressure be managed in the root zone?

When adding nutrients to the soil, osmotic pressure rises on the surface. The soil is usually wet during this process. Over time the soil loses water through evaporation or osmosis in the plants' root hairs, but the nutrients stay behind.

When this process continues for too long, your growing medium becomes saturated with nutrients. It increases the concentration level and increases the osmotic pressure.

Establishing osmotic pressure is notoriously problematic for crops grown in pots. It's because the growing space is smaller. 

For plant osmosis to run its course, use high-quality nutrients. 

Make sure that you mix in the correct dosages. Even going the organic route can be beneficial to ensure that the process of osmosis takes place efficiently. 

Organic fertilizers have microbes that break down and leave humus, enhancing the soil’s storage of water and nutrients. Crops can control osmotic pressure within their roots. Sugar is the main molecule that raises these levels and turns them into starch.

Osmosis in plants is crucial during this time. It may be a bit tricky to immediately detect if there is too much osmotic pressure in your root zone. A helpful tip is to flush your system to be sure. 

Don't add too many nutrients when the soil is wet!

Water in weed leaves
Water in weed leaves

Osmosis uncut! The need to live and grow

As we've discovered, the process of osmosis in plants is essential—it goes beyond planting, watering, and watching. Keeping the nutrient levels balanced is a priority as it determines the life expectancy of the marijuana crops. 

The roots aren’t the only part that is dependent on osmosis, but also the leaves. The stomata require osmosis in plant cells to progress so they can open up and absorb energy. The sturdiness of a cannabis plant relies on osmosis taking place successfully. 

For crops to live and grow, plant osmosis needs to take place. Controlling the osmotic pressure is one way of ensuring this. Another measure for optimizing the process using high-quality nutrients

Check out the various nutrient options available at Homegrown Cannabis Co. for a step in the right direction.

About the author: Parker Curtis

Parker Curtis has around a decade of cannabis-growing experience, specialising in soil-less and hydro grows. He’s mastering outdoor, greenhouse, and indoor grows.

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