Orchid roots and leaves

Sometimes terrestrial orchids have tuberous roots. The epiphytic orchids, however, have aerial roots that are highly developed, and they typically hang from trees that are green and thick. The roots of the epiphytes have a dual function; they are the structures that are responsible for capturing the nutrients the plants need, and they function as a means of attachment.

The roots of this type of orchid typically have a spongy epidermis, consisting of several layers of dead cells at maturity and thickened cell walls, called a canopy. The canopy is a fluffy, white sheath that completely surrounds the root.

If the weather is dry, its cells are filled with air, but when it rains they fill with water. According to some authors the canopy is a fabric that absorbs water, but according to others water has never been observed from the canopy to the root cortex.

The canopy’s main function seems to be mechanical protection, while preventing the excessive loss of water from the roots during periods of water deficiency. Moreover, when the sail fills with water it becomes transparent, allowing light to reach the green tissue of the roots and thus facilitate photosynthesis.

Different types of leaves on orchids.
Rhizome or aerial stems arise from the leaves, which are simple and vary in size. They usually alternate, spiral, distichous or whorl, are often plicate, basal or along the stem, sometimes reduced to sheaths or scales, usually with parallel venation and sheathing at the base.

They may be present sessile or petiole and have no stipules. The species that are adapted to periods of drought have fleshy leaves that act as a reserve for water in times of shortage.