What is Root Respiration?Plants need oxygen to breathe, not just through their leaves but through their roots as well. Oxygen from the soil is absorbed by the root hairs and carried throughout the root system to power various functions. This oxygen is used to aid in nutrient absorption and tissue development. The carbon dioxide that is produced is then released back into the soil, filtered, and discharged into the atmosphere.
Why Do Roots Need Oxygen?The respiration of roots is comprised of three types- maintenance, growth, and rhizospheric. Maintenance respiration provides the energy needed to keep the root alive, while growth respiration supplies energy for the development of new tissues. Rhizospheric respiration is contributed by the microbes in the soil around the roots, which use root exudates as fuel. These microbes are essential for nutrient cycling and sustaining soil fertility. Plant growth and development rely heavily on root respiration, but this process is extremely energy-consuming, utilizing up to three-quarters of the carbon taken in by the plant. The rate of root respiration can influence the overall growth of the plant above the ground.
How Insufficient Oxygen Affects PlantsThe amount of oxygen that plants need can vary. Most plants can't survive if there isn't enough oxygen in the soil. When the soil is saturated with water, it blocks oxygen from reaching the roots. This reduces the plant's ability to absorb water and causes yellowing and wilting of the leaves. Soil management experts are painfully aware of this issue. Plants can usually tolerate a short period of waterlogging. However, if they are submerged in water for an extended period of time, the oxygen supply in the soil will become depleted, and anaerobic pathogens will start to attack the roots. This can cause the plant tissues to break down, resulting in the production of methane and carbon dioxide. The term most often used for this condition is root rot. To learn more about root rot, check out our in-depth article on the subject, including how to avoid it.
Symptoms of Low Oxygen in PlantsThere are a few telltale signs that your plants may not be getting enough oxygen in the root zone. The most obvious symptom is wilting or yellowing of the leaves, which happens when the plant isn't able to absorb adequate amounts of water and nutrients due to an oxygen deficiency. Roots can also become discolored and mushy, another indicator that something is wrong with the oxygen levels in their environment. In fruiting plants, you will notice smaller fruit and lower overall yield. Plants that can't breathe have fewer available resources to fight off diseases and pests. They are more susceptible to fungal infections and common plant diseases. Pests and bugs tend to target these weaker, oxygen-starved plants. Finally, you might notice stunted growth or a general lack of vigor in your plants, both signs that they aren't receiving enough oxygen for healthy development. If you suspect any of these symptoms in your garden, it's important to take steps toward improving aeration as soon as possible so that your plants can get back on track!
How Do Roots Get Oxygen in Nature?Human beings are not the only ones who need oxygen to survive. Root systems also require it. Oxygen is taken in by soil pores and root hairs and then distributed throughout the roots. The plant roots then use photosynthates during respiration to carry out necessary functions like nutrient uptake and maintaining and increasing their tissue size. Certain plant species that grow in wet environments have advanced adaptations allowing them to attain oxygen. Wetland flora contains aerenchyma and an impermeable layer that stops oxygen from escaping through their roots into the ground. The plants then convey oxygen through internal pathways to the root sources. An example of this is how rice roots breathe when they are underwater. Mangrove trees have evolved a special adaptation to enable them to survive underwater during high tides. These trees produce pneumatophores, which are specialized breathing roots that feature tiny open pores that allow the roots to take in oxygen. When plants are submerged in water for too long, even highly adapted root systems can become deprived of oxygen, leading to death. In these instances, the roots switch to anaerobic respiration to remain alive and keep the plant functioning. However, if the lack of oxygen persists, the plant will start to decay, and the roots will rot.
Factors That Affect Root RespirationRoot respiration is essential for the growth and development of plants since it involves the use of carbohydrates. An excessive or limited rate of root respiration can have a negative effect on plant productivity. Many environmental factors influence root respiration, thus impacting plants.
Container - Moisture-retaining pots like ceramic, plastic, metal, or cement will discourage root respiration. Pots with solid walls keep oxygen away from the root zone. An ideal container should have both aeration and plenty of water drainage. Plenty of oxygen around the root zone has an added benefit. It stimulates the production of feeder roots. More feeder roots result in much healthier plants.
Soil - A soil structure that is able to retain a sufficient amount of water while allowing proper drainage is critical for plant respiration. Soil that has a heavy composition and is too packed to allow drainage will limit oxygen availability and thus affect root respiration.
Temperature - An increase in soil temperature can lead to a rise in the amount of oxygen used by roots as well as a higher rate of respiration per unit of root mass. Plants that can withstand prolonged heat without increasing their root respiration are more likely to use their resources for activities like nutrient uptake, root elongation, and membrane stability.
Nutrients - The amount of nitrogen, potassium, and phosphorous in the soil can influence the rate of root respiration. When soil is nutrient-deficient, there are fewer bacteria present, and respiration decreases. Having rich soil with plenty of organic matter will increase the amount of oxygen that the plant is able to use.
CO2 - It is generally accepted that increased atmospheric CO2 leads to higher levels of CO2 in the soil. As a result, this has been observed to cause an increase in root growth, which is associated with greater total respiration of the roots.
Climate- Temperature is the main influencing factor on root respiration, which tends to be higher in summer and lower in winter. However, the strength of this seasonal effect can differ across ecosystems.