Science of Hydroponic Growing Systems: Plant Physiology, Chemistry, and Physics

Written by Linus Li


Posted on April 27 2023


  1. Introduction
  2. Plant physiology in hydroponic systems
  3. Chemistry in hydroponic systems
  4. Physics in hydroponic systems
  5. Conclusion


Hydroponics refers to the method of growing plants using mineral nutrient solutions in water without soil. In hydroponic systems, the roots are immersed in or exposed to nutrient solution, which is supplied with all the essential elements for plant growth. By eliminating soil, hydroponics allows for improved control over the supply of water, nutrients, oxygen, and carbon dioxide to plants. This level of control enables significant increases in crop yield, quality, and productivity. At the same time, hydroponics reduces costs, environmental impact, and resource usage compared to traditional soil-based agriculture.

As a result, hydroponic growing systems have gained increasing importance in commercial agriculture and for home growers. When implemented effectively, hydroponics can help address major issues such as limited arable land, climate change, food insecurity, and sustainability of agricultural practices. By understanding the science behind hydroponic systems, including plant physiology, chemistry, physics, benefits, and challenges, we can optimize these systems to revolutionize sustainable food production.

Plant physiology in hydroponic systems

In hydroponic systems, plants receive the nutrients they need through their roots absorbing nutrient solution instead of from soil. As a result, plant roots adapt to efficiently uptake nutrients in solution form. Root hairs and surface area increase, while root structures change. At the same time, plants maintain the ability to photosynthesize light energy into chemical energy stored in ATP (Adenosine triphosphate) and NADPH (Nicotinamide adenine dinucleotide phosphate).

Photosynthesis and respiration continue to drive growth in hydroponic environments, but the availability and form of carbon, oxygen, and nutrients differ from soil. Nutrient solution maintains a balance of essential elements like nitrogen, phosphorus, potassium, calcium, and magnesium that plants require to thrive. When any one nutrient is deficient or in excess, it can lead to symptoms of dysfunction. Proper pH and concentration testing helps prevent imbalances.

Other environmental factors such as light intensity, temperature, humidity, and CO2 levels also impact plant growth in hydroponics as they do in soil. However, the effects of these factors may manifest differently due to differences in available nutrients, water delivery methods, and system configuration. Care must be taken to optimize conditions for photosynthesis and healthy growth, including the prevention of photoinhibition or overheating of nutrient solution.

Science of Hydroponic Growing Systems

Chemistry in hydroponic systems

In hydroponic systems, nutrient solutions are carefully formulated to provide all the essential elements plants require to grow. These solutions contain macronutrients such as nitrogen (N), phosphorus (P), and potassium (K) which are needed in large amounts, as well as micronutrients like iron (Fe), calcium (Ca), magnesium (Mg) and others which are needed in small amounts. Maintaining the proper balance of nutrients is critical for plant health and productivity.

Nutrient solutions are tested regularly to ensure the pH remains in the optimal range for plant uptake and that concentrations of each nutrient meet recommended levels. Imbalances in major nutrients will lead to stunted growth, while those in micronutrients cause visual symptoms such as leaf discoloration, twisting or spots. These imbalances must be corrected through testing and adjusting nutrient solutions to prevent deficiency or toxicity.

Nutrient solutions often require pH buffers and chelates to keep nutrients in a soluble form that can be absorbed by plant roots. Without these compounds, nutrients may precipitate and become unavailable for uptake. Some nutrient solutions also contain beneficial microbes to promote better absorption and utilization of nutrients. Inorganic, organic or blended nutrient solutions are used depending on the specific goals and approach.

Physics in hydroponic systems

Several physical principles come into play in delivering nutrient solutions and oxygen to hydroponic plants. Hydrostatic pressure refers to the pressure exerted by a fluid at equilibrium due to gravity. In hydroponic systems, hydrostatic pressure drives the flow of nutrient solution and oxygen from reservoirs up to the plants. Capillary action allows solution and oxygen to travel through small diameter tubing, emitters and air stones.

Viscosity determines how easily a fluid flows and its resistance to shear forces. Properly concentrated solutions and adequately oxygenated nutrient solutions have an ideal viscosity for delivery through typical hydroponic components. If a solution is too viscous, components can clog and delivery will not occur. If too runny, the solution will not travel through its intended path by capillary action alone.

Techniques for delivering solutions and oxygen in hydroponic systems include drip irrigation, subirrigation, ebb and flood, deep water culture, aeroponics, and media-based systems like perlite, coco coir or soil. Drip and subirrigation deliver solution slowly with emitters, while ebb and flood systems deliver with a flooded, recirculating reservoir. Deep water culture systems fully submerge plant roots. Aeroponics uses pressurized oxygen without growing media. Media provides physical support, moisture retention and aeration around roots.

The availability and delivery of oxygen also deserves consideration. Oxygen is required for respiration and healthy root function. While oxygen is naturally dissolved in solution, delivery methods can increase concentration through pressurized air or the formation of oxygen bubbles. Pumps, air stones, aquarium air pumps and supplemental aeration increase oxygen levels when needed.

Science of Hydroponic Growing Systems


In conclusion, hydroponic growing systems represent a promising approach to sustainable agriculture with significant potential benefits yet also real challenges to consider. By understanding the science behind hydroponics including how plant physiology, chemistry, physics, benefits and challenges interact in these systems, we can better realize the potential benefits of improved yield, quality, efficiency and environmental sustainability.

With continued technological advancement, hydroponics is poised to transform agriculture. Improvements in system automation, equipment design, and resource management will increase feasibility, reduce costs, and minimize risks. Widespread adoption at commercial and smallholder scales allows more robust infrastructure, knowledge sharing, and policy development to support the emerging field. Some power equipment are important too.

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