Humans and animals need to breathe, and so do plants. Plants have no obvious respiratory organs, but they can breathe through roots, stems, and leaves. Plant respiration needs to consume organic matter under aerobic conditions and release energy as an indispensable driving force for physiological activities such as growth and absorption. Plant respiration is to take in oxygen and exhaled carbon dioxide, and respiration usually takes place at night.
The oxygen needed by the stems and leaves of cannabis plants for respiration can be obtained in the air. When there is good ventilation in the room, the stems and leaves of cannabis can breathe normally to consume organic matter (glucose) to provide power for growth. And plants also produce a lot of oxygen during photosynthesis.
We should pay more attention to the oxygen in cannabis roots. The oxygen for root respiration is dissolved oxygen in the water. As long as the water is full of oxygen, the roots will get a fresh delivery every time the plant is irrigated or fertilized. As temperatures rise, the rate of respiration in the roots increases.
But sometimes, it will lead to root hypoxia if you are not careful. When the supply of O2 in the root system is insufficient, the aerobic respiration of the root system of the plant is affected or inhibited, and the energy metabolism is disordered, which in turn causes a series of physiological problems, such as the root system absorbs water, reduces nutrients, and reduces the rate of photosynthesis, which ultimately affects the normal growth and development of plants. So oxygen is an important nutritional factor in crop production.
The amount of oxygen in the water depends on factors: temperature, and salinity.
The solubility of oxygen in water decreases as the water temperature increases. For example, at 0 °C, 1 volume of water can dissolve 0.049 volume of oxygen at 1 standard atmospheric pressure, and at 20 °C and 1 standard atmospheric pressure, the solubility of oxygen is 0.031. This means cooler water contains more oxygen. So the lower the root zone temperature, the better? Unfortunately, a decrease in root zone temperature also drastically decreases the rate of root respiration, lowering the roots’ metabolism and productivity. Even though more oxygen may be available in a cooler root zone, slower root respiration rates slow the delivery of water and nutrients to the canopy.
Salinity is also an important factor in determining the amount of oxygen of water contains. The solubility of oxygen decreases as salinity increases. Because various alkalis, salts, and other inorganic substances in the water squeeze and fill the gaps between water molecules, resulting in a decrease in the dissolved oxygen in the water. This means freshwater can absorb more oxygen than saltwater.
Oxygen for the roots also comes from the soil. The primary soil gases are nitrogen, carbon dioxide, and oxygen. Gases fill soil pores in the soil structure as water drains or is removed from a soil pore by evaporation or root absorption. Therefore, you should choose a soil with good air permeability. Overwatering leads to hypoxia in the roots. This is also the reason why you should choose soil with good air permeability, and why the planting pot has holes in the bottom.
There are some tips to boost oxygen levels for the roots:
- Using breathable fabric planting containers and pots
- Enlarge air permeability of the soil: adding peat, perlite-based mix, or bark and wood fiber mix to the soil to ensure air-filled porosity at 15-25%. The higher the porosity, the more air space at the root of the plant.
- Cool down the water to keep the water temperature at 18-20 degrees Celsius: Use a water chiller, or add a frozen water bottle to the water.
- Increasing the oxygen concentration in the water by actively bubbling air through the air pump in the storage tank.
In conclusion, abundant oxygen helps cannabis roots expand, thicken and develop faster, powering plant growth. And we see the accompanying benefits, plants begin to absorb nutrients more aggressively. Generally, you need to recognize the benefits of oxygen for cannabis roots, and follow the above tips to avoid oxygen deprivation.