Wednesday, July 24, 2019

A New Look at Orchids

In an ongoing and apparently permanent glitch, YouTube does not provide links to videos that have been uploaded. Here is a current list of my Darwin YouTube videos that have been posted but do not get publicized:

I wish to tell you about the second one, about orchids. The URL is indicated above.

Most people see orchids as amazingly beautiful flowers. Many people are utterly captivated by them. They are, in a way, the dinosaurs of the plant world, except that they are not (yet) extinct.

But we can also see them as amazing examples of plant evolutionary success. As explained in a previous video, plants are engaged in a continuous, silent struggle for not just survival but evolutionary fitness. Everything a plant does with its resources, the food it gets from photosynthesis, must be efficient. Every part of a plant must pay its own way. If a plant invests its resources in a process or organ that does not pay for itself, it risks extinction just as surely as if it fails to invest in something essential. The silent struggle of plants is more like a marketplace than a battlefield. In the previous essay I explained that flowers have to pay for themselves.

Orchids are an amazing example of extreme plant adaptation to success in the marketplace of plant competition. First, consider the flowers. They are really big in comparison to the rest of the plant. They represent a big expenditure. They had better be successful in attracting pollinators, or else the plant has wasted a lot of energy for nothing. Orchids live up in the branches of tropical rainforest trees (they are epiphytes). They are scattered far apart from one another. The flowers have to be big and showy to attract their pollinators from a great distance. Also, they are very complex, so that only the correct pollinators, the ones most likely to visit another orchid of the same species, can pollinate them.

Epiphytic orchids also have succulent leaves. Though it may rain every day in the rainforest, it gets hot and dry between the rains. An epiphyte, with its roots hanging out in the air, can quickly dry out unless it has some adaptation, such as succulent leaves, to slow down its water loss.

The roots stick out in the air. Since they absorb rain, they do not have tiny root hairs. But since they are in the air, not the ground, they absorb sunlight. This is an opportunity for the orchid plant to get in a little extra photosynthesis. Epiphytic orchid roots are green!

I am working on a book, tentatively entitled Silent Struggle: The Hidden World of Plants. Watch for it!

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