Other types of roots
The roots, or parts of roots, of many plant species have become specialised to serve many adaptive purposes besides the two primary functions that fine and coarse roots have.
Here are just a few different types!
Adventitious roots arise out-of-sequence from the more usual root formation of branches of a primary root, and instead originate from the stem, branches, leaves, or old woody roots. In some conifers adventitious roots can form the largest part of the root system. You won’t find these in your pipes!
Aerating roots rise above the ground and even above water in the case of mangrove swamps. Again, we don’t come across these in suburban Melbourne.
Aerial roots grow entirely above the ground, such as in ivy. They function as prop or anchor roots. One to look out for.
Contractile roots form bulbs or corms. Examples of plants that have contractile roots are hyacinths and lilies.
Haustorial roots rare roots of parasitic plants that can absorb water and nutrients from another plant, such as in mistletoe. Look up to find these in your tree canopy.
Propagative roots are roots that form adventitious buds that develop into aboveground shoots, termed suckers, which form new plants.
Stilt roots are amazing adventitious support roots, common among mangroves. They grow down from lateral branches, branching in the soil.
Storage roots are modified for storage of food or water. Carrots and beets are examples of these.
Structural roots are large roots that have undergone considerable secondary thickening and provide mechanical support to woody plants and trees.
Surface roots are our main trouble makers when it comes to blocked pipes. They proliferate close below the soil surface, exploiting water and easily available nutrients. Where conditions are close to optimum in the surface layers of soil, the growth of surface roots is encouraged and they commonly become the dominant roots.
Tuberous roots are a type of storage root, but with tuberous roots only a portion of the root swells. A sweet potato is a good example of this. You’re more likely to find these on your dinner plate than in your pipes!
Why roots invade pipes
When a seed germinates, it adds one cell at a time toward the best environment from which it might extract nutrients and moisture. The growing point of the root most easily through loosely cultivated soil and because the most common practice to lay pipes is by open trench, there’s usually plenty of back-filled soil lying around.
Another reason that roots find their way into pipes is because of vapour leaks. Because the water flowing through the pipe is warmer than water flowing through the soil, condensation appears on the crown of the pipe. As the warm moisture from the sewer pipe evaporates up through the soil, the vapours offer an excellent trail for the root to follow. If even a single vapour leak exists in the pipe, the root concentrates its efforts at that point.
In addition, since some pipe joint compounds are made of nutrient material, the root may entirely girdle the joint before entering the pipe. Once inside the pipe, the root takes on the appearance of either a “veil” or a “tail” type structure. If flows in the pipe are fairly constant, the root mass hangs down like a veil to the normal flow level where they accumulate deposits of grease, slime and other debris.
Other types of roots