At the Functional Ecology conference in Montpellier (see earlier posts), several times I heard the saying that plants cannot fly and as such have a significant limitation compared to other organisms.
Yet I strongly disagree with that saying, no matter how true it might look at first sight. Plants do fly, some of them even for large distances, just not in all phases of their live. As in all organisms, it is important to understand the live of a plant through the different life stages it is going through: germination – growth – flowering – seed production – dispersal – new germination. Even within the same plant species, factors working in on each of these life cycle stages can be totally different from the other.
Many plant species are highly mobile, either flying, swimming, rolling, jumping or passively travelling attached to other mobile organisms or things. They just aren’t mobile in every life stage; their mobility is limited to their live as seeds. Yet this easily overlooked phase of mobility is not trivial: it defines why plants grow where they grow, it defines if they can track climate change or not, it defines if they are capable to track fast – or slow – changes in their environment.
Even the duration of this phase is not necessarily neglegible. Many plants can stay mobile for a long time, until they find a spot to settle down, and especially for annual species the time spend as seed and as actual plant is not so different at all.
At the conference, I even gave a presentation about travelling plants, using their skills to hike uphill in the mountains. Such unusual travel plans will stay a significant component of my work in the next months, so stay tuned to learn some more!
UPDATE 5/4/17: There is a second – highly important – life stage in which plants fly: as pollen. While they can travel impressively large distances in this shape, they of course need to find a conspecific flower at the end of their trip. Yet this gives most plants two distinct options in their lives to travel! Should I convince you more that plants are not suffering from being sessile?
So here’s a burning question that I have for you, given the topic of the talk you gave: given that with global warming, plants are migrating UP to higher elevations… how in the world do pine trees, with their heavy cones (that tend to roll downhill easily), migrate UP a steep mountain slope, against gravity, and grow root, usually, into barren rock?
Very nice question, indeed! You’re right that for several plant species, travelling uphill might be a big issue. The basic law of gravity is by default going to direct heavy seeds downhill, and not up. Yet there are other ways to travel: you can be transported uphill by animals, or even humans, deliberately or by accident (e.g. stuck in mud on shoes or in animal fur).
Even then, the largest part of these big seeds will still be going downhill, which is the reason why for most of these species, tracking climate change will be very slow. If the good conditions are higher in the mountains, eventually those few seeds that will arrive there will be able to profit from it.
Growing roots into barren rock is another issue :). In most cases however, a little crack in a rock can be enough: a little bit of soil and water, just enough to grow a little. And then it is stubbornness, slowly slowly growing, following the cracks and profiting from weaknesses and changes over time in the rock. Impressive, indeed!
I agree. I am a backyard gardener and I observe my plants traveling all over, including flying through the air or hitching a ride with a bird. Nature is amazing!