Friday, February 22, 2019

My Year of Orchids: Roots must be for storage too

I’ve started to look at the orchids differently. Part of it is that they’re part of a larger community of epiphytes in my garden. They share the canopy with bromeliads, air plants, cacti, ferns, and gesneriads (cousins of the African violet). There are even epiphytic milkweed relatives called Hoya in my garden. I guess it’s been a busy few months collecting, planting and establishing.

Janet half jokingly admonished yesterday that my kids want to enroll me in Orchids anonymous. I laughed because by the time they find me a chapter it will have to be Epiphytes anonymous. These fascinating plants just get more and more fascinating.

So the question of roots as storage. It began with my Dendrobium anosum, which is developing flower buds all along the big cane. Interestingly they began to enlarge in earnest once the last few leaves at the tip died. I’m sure this is some kind of apical dominance situation, with the last leaves sending a hormonal message to hold off on flowering until they drop off. All a matter of resource management and coordination I guess.

It occurred to me that the cane is an important resource reservoir for the plant and I asked my friend Minh if the canes are perennial, which he confirmed. So canes in the case of Dendrobiums, instead of the pseudobulbs we’re used to considering as storage organs. It’s interesting to me that in all the individuals I have in the garden the pseudobulbs, as well as canes, are robust and plump. And on some very happy Dendrobiums I’ve seen the canes thicken to almost obscene proportions.

I took another look at some of my roots, the wanderers that hold tight to their woody substrate and grow pretty much in a straight line in the direction of water flow (either into or away from the orchid). They are also plump, especially in comparison with other roots of the same plant. It occurred to me that these might play several roles: not just as explorers but also establishers of territory, absorbers of water, and organs of storage for water, carbohydrates, and other resources the orchid plant needs. So storage as well as these other roles, and I have to mention that these wanderers act as a kind of sensory organ too, feeing out sources and the direction of water. More evidence of the “intelligence “ of orchids. Pretty cool!

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