G rowing plants is fun – we have a natural happiness when we see fresh growth, juicy fruits and pretty flowers. In the wild plants grow in what there is, which is mostly soil but can also be sand, rock, peat or water. Plant roots are the plant’s tools to get water and nutrients from the ground to feed respiration and photosynthesis – the plant’s way of getting its dinner to grow strong and produce offspring. The root is essential in sucking up water from whatever it is growing in – often this water contains dissolved salts, minerals and nitrogen produced from microorganisms eating dead matter and mineral deposits that have spread out through the water table.
So a root sucks water, right?
To do this it has to be in water, so plant roots are highly adapted to live in both wet and dry pockets of the soil – the wet parts are often saturated with water, similar to hydroponics. A root in a wet part of the ground adapts to stay alive, but can die if it drowns from lack of oxygen or becomes disconnected from the main plant.
However, if the balance of water and oxygen is right, very fast water and nutrient uptake can occur through sprouting root hairs, sucking that wet part dry and taking out nutrients. Once nutrients in that wet part are depleted, the root grows deeper and finds another pocket of moist, nutrient rich earth – and that is why roots grow and develop in soil.
What about hydroponics?
Hydroponics is growing plants in nutrient rich water to provide the environment of that wet part of the soil where the balance between water and oxygen is good, but for the entire plant root system. So that very fast sucking up of the nutrient water happens for the entire root system.
You see the blue water in the above diagram? That is water, so roots in the wild are usually pretty much doing hydroponics already on the micro-level in wet parts of the soil – with the air pockets oxygenating that water to keep the roots alive. With Hydroponics, you can control the nutrient mix and the level of oxygen – to help healthy plant roots take up water and nutrients to grow as fast and strong as possible. The basic plant nutrients are Nitrogen (N), Potassium (K) and Phosphorous (P) and if provided these main nutrients, or macronutrients as they are also known, the plant can build new organs and tissue when they grow bigger, flower or fruit. Other nutrients are needed in many of these tissues and organs, but in smaller amounts, such as Sulphur (S), Selenium (Sn), and Iron (Fe), these nutrients and other less required ones are called micronutrients. Hydroponics mixes water with these nutrients, brought from organics or mineral deposits, so that plant roots take up not only high amounts of water, but high amounts of these nutrients also, as the nutrients are transported with the water going into the root hair. Plants work so well in hydroponics that you have to be careful not to over nourish them, as too much nutrients can kill or damage the plant.
Oxygen in the water is encouraged through water circulation and aeration, with many hydroponic systems designed to provide this oxygenation. A plant root is fuelled by sugar (from photosynthesis) and oxygen (from air), among other things. Underwater, oxygen is in low supply but diffuses throughout the water to go in through the roots and power respiration in the root cells, keeping them from drowning. Different plants need different amounts of this oxygen to stay alive, or have different efficiencies in doing so – so it is often important to aerate the water for some species to keep roots alive and healthy. In nature, plants often get flooded and have to stay alive and get oxygen from somewhere. In many plants, the structure of the stems and roots allows for a degree of oxygen transport from areas with lots of air, such as dry parts of the root or stems, to areas that need it, such as those in deep pockets of water. This survival mechanism is used in a type of hydroponics called Kratky non-circulating hydroponics, allowing a low oxygen water with an air gap above it to sustain plants without aeration or recirculation of the water.