“It’s easy to tell when your plants are supercharged.  You don’t need any fancy meter for that – it’s visually apparent.  Every time you open the door to your garden your plants almost roar at you!  The speed of their development is shocking – even over a single day – they are visibly taller, fuller, bigger, and happier.  I love it when my garden is cranking like this.” – Kevin, indoor gardener, N. California.

Supercharged plants.  Sounds rather pleasant doesn’t it?  But what exactly are we talking about? A supercharged growing environment is one where no single thing your plants need is in short supply.  Think of it like a series of links in a chain.  The rate of your plants’ development is only ever going to be as fast as the weakest link allows.

So what are these links?  Well, the obvious examples include: plant genetics, light levels, temperature, CO2, and relative humidity.  The not so obvious example is oxygen.  This odorless, colorless gas plays a critical role in plant growth and bloom.  In fact, despite being all around us, it could be the crucial component that is holding your plants back…

WORDS: Jim Lepard

The Key Benefits of Oxygen for Plants

Oxygen usually makes up 45% of the dry tissue weight of a plant.  It is a macro-element, along with nitrogen, phosphorus, hydrogen, carbon, potassium, calcium, sulfur and magnesium.

Oxygen provides essential energy for plants to turn their sugars into cell structure.  In other words, plants need oxygen to grow!  Oxygen is also used by plants to control their stomata – tiny but crucial “breathing apparatus” in their leaves.

We tend to think of plants creating oxygen as the end product of photosynthesis but, as with many natural processes, the complete picture is more cyclical.  Plants also use oxygen in two major ways.  They uptake it through their roots and they absorb it via their leaves.

At night most plants reverse the process of photosynthesis and switch to burning carbohydrates and oxygen while producing carbon dioxide and water. So it’s important to make sure that oxygen levels are maintained in the indoor garden, especially at night when plants aren’t producing it via photosynthesis.  Most growers achieve adequate levels of oxygen at night by using extraction fans to bring in a steady supply of fresh air.

Oxygen and Stomata

Stomata consist of pores called stoma, which are bordered by two specialty guard cells. The guard cells regulate the size of the opening of the stoma (pore).  Because the stoma is responsible for the exchange of gases (i.e. oxygen and CO2) plus water vapor, it is critical that stomata are healthy and working properly.  If the stomata are oxygen deprived from the root zone, they begin to shut down and the size of the stoma opening becomes smaller due to the loss of turgor pressure in the stomata guard cells, restricting the exchange of gases and water vapors.  If the flow of water slows in the plant, the plant cannot cool itself and begins to suffer from overheating – visually apparent from wilting.  The uptake of nutrients in the water is also affected, along with the flow of oxygen.  This further compounds the problem, resulting in necrosis of the plant’s leaves. Photosynthesis is slowed as well, leaving the plant sick and weak, unable to fight off insects and disease, resulting in lower yields and eventual death of the plant.

Dissolved Oxygen

Many growers overlook the importance of dissolved oxygen levels in their nutrient solution.  When oxygen levels in a nutrient solution are raised, you essentially give your plants the ability to process more gases and water vapors, resulting in a cooler, faster growing and higher yielding plant. Root systems work more efficiently when highly oxygenated.  This is because oxygen affects the electrical charge of water and nutrients allowing the roots to uptake using less energy.

Increased oxygen levels also help to reduce water borne pathogens and fungi, such as the dreaded pythium and saprophytic fungi.  By elevating oxygen levels, the grower instantly creates a more suitable environment for aerobic bacteria (our friends). The more friendly bacteria we have, the greater their effectiveness in combating any anaerobic bacteria (our enemy).

Cooler water is capable of holding on to more oxygen than warmer water.  So when a nutrient solution starts to warm up, its ‘hold’ on dissolved oxygen decreases. For example, the oxygen content of a fully aerated solution 68°F (20°C) is around 9ppm, whereas at 86°F (30°C), it drops by over 16% to 7.5ppm.

Popular Methods of Increasing Oxygen Levels
Growers who appreciate the importance of dissolved oxygen have historically tried a variety of methods to increase levels in their nutrient solution.  It’s fairly straightforward to improve levels, but far harder to achieve ‘supercharged’ levels.

1. Surface to Air Contact
A submersible pump is placed into the nutrient reservoir.  When switched on it creates turbulence in the nutrient solution which increases its contact with air. The barrier between the water and air is broken (like a waterfall hitting a pool) allowing oxygen to be absorbed into the water.  The more turbulence at the surface, the greater the oxygen absorption.

2. Forced Aeration and Air Stones
This is one of the most popular methods used by growers today. Air pumps or compressors are used together with air stones or perforated pipe placed in the bottom of the nutrient tank. An air stone is traditionally a piece of limewood or porous stone but can also be made from fiberglass.  When air is pumped into the stone it creates very fine bubbles.  As these fine bubbles rise in the nutrient tank, some of the oxygen is absorbed by the nutrient solution.

There is currently some controversy surrounding the efficacy of air stones.  One theory suggests that larger bubbles rising in the nutrient solution absorb smaller suspended bubbles on their way up and air dissipates out of the solution.  In one test the oxygen levels in a nutrient solution actually dropped after running the air stone for 50 minutes!  Other growers (and aquarium owners) swear by them!

3. H2O2  (Hydrogen Peroxide)
Hydrogen Peroxide is known for increasing oxygen levels and its high oxidizing properties.  When H2O2 is first introduced to the nutrient solution there is a spike in oxygen levels and the plants receive a boost of oxygen.  However, the oxygen levels quickly drop off, especially with an air pump and aeration or agitation of the water via a water pump circulating through the system.  Along with the higher amount of oxygen, comes the high level of oxidization.  This is fine if the plants are suffering from any fungi or pathogens that may be in the system.  However the indiscriminating oxidizing effect of H2O2 can also attack a healthy root system.

Double air diffuser

4. Air Diffusers
The large scale solution.  Air diffusers force concentrated atmospheric oxygen into the nutrient solution. These systems achieve very high oxygen levels but they have to be regulated carefully and tend to be used by large commercial greenhouses that can afford the room and cost of such equipment.

5. Electrolysis
Oxygen is produced through electrolysis when a DC current is passed through an anode and cathode in an acid or salt solution.  As the solution passes by the anode and cathode the current separates the oxygen atom from the hydrogen atoms at a molecular level, leaving the oxygen suspended in the water. The plant absorbs some of the beneficial hydrogen but because hydrogen is 16 times lighter than oxygen, most of it is disbursed through the surface of the water.  The benefit of this method of raising oxygen levels in a nutrient solution is that oxygen is not being forced into the water.  The oxygen is actually being generated from the water, within the water.

Still not convinced about the importance of oxygen?  Then check out this basil crop, brought back from the brink of death after a spell of freakishly hot weather!  How? Oxygen levels were raised in the nutrient solution using electrolysis. The basil was infested with pythium (root rot) but started to recover almost immediately!

Healthy white roots appearing days after the nutrient solution was regularly treated with oxygen electrolysis.

Basil roots 10 days after the beginning of electrolysis treatment.

Incredible! After being all but overcome by pythium, the roots of this basil plant have been restored to health after 21 days of electrolysis treatment.

If your plants are not fighting root rot and disease, there’s no doubt that you will harvest bigger, heavier crops – without the need for chemical pesticides or supplements.

Now take a deep breath. Feels good, doesn’t it?