Most of us wouldn't welcome getting partially eaten by a wild animal — but it could be the best thing that can happen to a plant.
Half-eaten plants grow back bigger and faster than they would have if they'd never been attacked — it's all about doubling down on DNA.
Not only can plants grow back stronger than they would have if they'd just been left alone, they also gain a reproductive advantage. That's despite the fact that a substantial part of the organism has just been eaten, which is about as traumatic an experience as one could ever hope to have. The trick to their triumphant survival is known as endoreduplication, in which the plants start replicating their chromosomes over and over without making any new cells.
To give you some idea of how extreme the process is, consider Arabidopsis thaliana, a flowering plant in the mustard family. During reproduction, each parent contributes five chromosomes, so that the new plant has a total of ten chromosomes. Those plants that have survived an eating attack can end up with as many as 320 chromosomes in each cell. That's a whole lot of new DNA.
University of Illinois biologists Ken Paige and Daniel Scholes examined how different plants responded to being artificially grazed by clipping their central stems. Not all plants displayed an ability for endoreduplication, but those that did consistently grew back stronger and proved far more successful in passing along their seeds to the next generation. Indeed, those that rebounded back the best after being clipped were invariably the ones that responded by growing new chromosomes.
Ken Paige explains:
"The overall DNA content goes up in one of the cultivars after clipping, but it doesn't change in the other. And we think it's that added boost that increases its reproductive success. We've tracked the plants through generations, so we know that the ones that get eaten actually have up to a three-fold reproductive advantage over the ones that are never eaten. Now we are beginning to understand the molecular mechanisms that make this possible."
So what does all that extra DNA do? Unlike in species like humans, in which a sudden increase in the number of chromosomes would wreak havoc, these plants can put all those extra chromosomes to use making lots more proteins that can aid in growth and reproduction. The additional DNA also forces the cells themselves to get bigger, which in turn make the plant as a whole grow larger.
Daniel Scholes discusses the significance of this amazing ability:
"Because you have more DNA in the nucleus, you must have a greater nuclear volume, which causes your entire cell to get bigger. We tend to think that what you inherit is what you're stuck with. But we're finding that plants are increasing what they have, and for the first time we're beginning to understand how they do that, and why."