The part of the plant we generally see is above the ground, but the condition of the visible section of plant life is a direct product of what is going on below. To understand how to provide the best conditions for your roots, you need to understand a little about roots themselves. I’ll try not to sound too geeky.
Kinds of Roots
Roots take on many different forms. You have encountered this when you pulled weeds out of the yard or flowerbeds. Some plants have fibrous roots—thin, hairy branches lying close to the surface of the ground. Most grasses have this type of root system. Interestingly, so do most trees; the difference is the roots of trees are so much thicker than the roots of grasses, but when you look at the size of the root in comparison to the plant itself, the ratio is similar. Another common type of root is a taproot. A taproot is one big long root, although it will have smaller root hairs to help anchor it. Taproots are the ones that make you want to scream, because when you try to pull them out of the ground, they often break off and regrow. Dandelions are a common taproot, but so are carrots. Trees can have taproots that extend 40 to 50 feet down. Such deep roots explain how some trees remain in the ground despite hurricane force winds.
Another type of root system combines the two, with a taproot that extends deep into the soil and prop roots that are above the surface; corn is a plant with such a root system. The neatest roots are those that require no soil at all, but simply grow in air. Known as aerial roots, these plants, such as many orchids, absorb their nutrition from a host plant and the air. Now, what particularly interests gardeners are the roots that are good to eat; these roots store nutrients and are yummy. Tuberous roots, such as sweet potatoes, are in the fleshy root category. Strangely enough, a sweet potato is part of the root, but a white potato is part of the plant’s stem, as are rhizomes, such as ginger, and corms, such as arrowroot. Bulbs, such as onions, are also modified plant stems and have fibrous roots.
Parts of a Root
All root tips are covered by a root cap, which are special cells that perform several interesting functions. First of all, they provide a protective covering for the plant’s apical meristematic cells. These cells are like human stem cells in that they have the ability to become any type of cell needed in the root, from root hairs to xylem. The root cap also has organelles in its cells that detect gravity and tell the root cells to grow down instead of up. Additionally, root cap cells provide a lubricant that makes it easier for the root structures to penetrate the soil.
The xylem cells of the root transport water and nutrients up through the stem without expending any energy. As the plant transpires (loses water through its leaves), the cohesion and adhesion properties of water (hydrogen bonding between water molecules) pull up through the xylem more water with dissolved minerals. The phloem cells of the root move sap both up to the leaves and down to the root tip.
95% of the water roots take in from the soil is put out into the air through transpiration.
An acre of corn can put 400,000 gallons of water into the air in just a few months.
Each root hair is a single cell that can grow to the astounding length of 1.5 millimeters.
To prevent tangled roots, a cell that forms a root hair sends a message to all adjacent cells telling them not to form root hairs.