Differences in Orchids' Roots & Shoots

Shoots

• New growth on an orchid originates from a node. A node may produce a root, stem, leaf or flower depending on what type of node it is. A flower spike grows from the base of the orchid and is a bright, almost lime green. It is not just a protuberance but it bears a secondary structure at the top of the shoot. This secondary structure and the brighter color identify a flower shoot versus a root shoot. A shoot grows upward in monopodial type orchids but a sympodial shoot grows outward and produces a basal structure called a pseudostem from which all other growth arises.

Terrestrial Roots and Rhizomes

• Most terrestrial orchids rise from rhizomes which are underground storage structures. They are responsible for the growth of new shoots and roots. The roots of planted orchids are thick and tuberous. You will not likely see these when the orchid is potted because they are underground, but the roots are lightly pigmented. When the plant needs to be repotted, the roots will grow out of the pot, signaling that it is time for a larger container or better potting medium.

Epiphytic Roots

• Epiphytic orchids grow in or up trees. They use aerial roots to attach themselves to trees or other vertical objects. The roots are almost woody and are covered in a substance called velamen. Velamen protects the outside of the roots and helps preserve water. Epiphytic plants can use their roots to brace themselves, but also to collect any nutrients and moisture from the air. The plants do not root in soil and require the ambient area to provide their needs.

Shoots vs. Roots

• Shoots are formative tissue while roots are for anchorage and uptake. Shoots can be supportive as well, where they lift a stem or leaves. Buds are the first step to a shoot and may become leaf, stem or flower shoots. The roots contain apical meristem tissue comprised of root cells and which sends out lateral meristem tissue. Roots make more roots but cannot make shoots. Shoots can become many types of orchid growth but cannot become roots. This is because of the specialized cells that make up each structure.