Chances are, you have a pretty good idea what a plant looks like. Roots, stems, leaves, flowers ... these are the things that make plants, plants. But it wasn’t always so.
Plants arose some 500 million years ago, and the fossil record is full of bizarre evolutionary dead-ends, as well as amazing innovations. For example, some extinct ferns looked much like modern ferns on the outside, but their insides appear jumbled. And then, there's the fact that early plants had no leaves.
"They're basically green, photosynthetic sticks," says Jonathan Wilson, a plant evolutionary biologist at Haverford College. "You would look right past them at a flower shop."
Over time, plants evolved more branches and took on claw-like appearances. And then, 360-370 million years ago, several plant groups suddenly - and independently - evolved flat leaves that we would recognize today. The impetus for this leap? Wilson says it was probably a drop in atmospheric carbon dioxide levels.
The ways that plants have responded to past environmental shifts, combined with an understanding of their modern physiology, could provide clues to how plants will respond to current environmental changes. The challenges are multiple: changes in availability of water, carbon dioxide, nutrients and minerals; shifting weather patterns; introduction of foreign plant and animal species; the extinction of others.
Wilson says many slow-growing plants, like redwoods and sequoias, won't be able to keep up with the rate of change and will be lost. Others may adapt. He predicts that the plants that will flourish are those that we currently consider invasive pests, like kudzu.
While knowing the past history of plants may help predict its future course, Wilson says that doesn't make the coming changes any more palatable.
"You could think of it as 'How exciting! You're living through one of these major mass extinction events on Earth,'" says Wilson. "But actually seeing it from the ground and being able to watch these changes day by day, and year by year, it's troubling."