If you follow the Wandering through Wadis Facebook page, you might recall the photographs of orchids that I shared a few weeks ago. I had no idea that there were orchids growing in the desert, but after my friend sent me photos of the blooms she had seen, I obviously had no choice but to go see them for myself.
I had identified the orchids in my friend’s photos as Scarce (or Eastern) Marsh Helliborine (Epipactis veratrifolia) but, admittedly, I knew nothing about orchids. So I’ve been reading up on them. And I’ve learned a lot of fascinating things about orchids in general, but also about these rare beauties that are native to Sinai. (They are not found in mainland Egypt.)
Most orchids (more than 99% of all species) are epiphytic and use their roots to attach themselves to and grow on trees. The Scarce Marsh Helleborine, however, is a terrestrial, or ground, orchid and grows its roots firmly in soil.
This helleborine is a perennial herb and grows, from a fleshy rhizome, to be between 25 – 150 cm tall. The leaves are ovate (egg-shaped) and pointed at both ends. They grow along the stem and can be 8 – 25 cm long. The inflorescence, or cluster of flowers, grows atop an erect stem. The flowers are fairly open and are green to yellowish-green in color with purplish or reddish radial stripes. The lip, or bottom middle petal, is tipped in white. The upper part of the stems, bracts, ovaries, and sepals are covered in short, fine hairs. In Dahab, the orchids were found growing among native grasses in a wet area.
Like all orchids, this helleborine is dependent on a mycorrhizal symbiosis, a mutually beneficial relationship between a plant and a fungus, to complete its life cycle. The plant’s fruit capsule is full of microscopic seeds (in some species, over a million), but these seeds all lack endosperm. Endosperm is the tissue usually found inside seeds that provides nutrition to the plant as it sprouts. Because an orchid’s seeds don’t have this inborn nutrition, they rely on fungi to provide them with the nutrients they need to germinate. The chance of germination is so small that only a minute fraction of the released seeds grow into adult plants.
But before a plant can even produce any of these seeds, it must first be pollinated. And to help ensure that, the Scarce Marsh Helleborine employs a trick, a special mimicry, to lure pollinating hoverflies to its flowers. The flowers emit three chemical substances that are usually released as alarm pheromones among aphids. Aphids are the preferred diet of hoverfly larvae. So female hoverflies smell these chemicals, interpret this to mean that aphids are nearby, and proceed to lay their eggs near the source of the scent – the flowers. The hoverflies are rewarded with a small sip of nectar, but their larvae are doomed to starve because, when they hatch, there will be no aphids around to consume. (This is a strange contradiction from an evolutionary perspective because since the larvae die, the number of potential pollinators decreases.) The orchids are mimicking the aphids, taking advantage of the female hoverflies and deceiving them into pollinating the flowers.
As you can see, these rare orchid blooms are not only beautiful but also full of amazing natural wonder!
Resources:
Wandering through Wadis 