While people often become vegetarians or vegans to avoid causing harm to animals, there’s plenty of evidence that plants aren’t much happier about being eaten than any animal. Sure, fruit can be tasty and enticing so that a plant’s seeds will be distributed, but the leaves and stems themselves are more likely to be bitter or dangerously toxic for interested herbivores. If the plant itself is eaten, it will probably miss its chance to reproduce, a goal so significant that some plants actively respond to threats as they occur. This may mean trying to regrow lost leaves or stems that were chomped off. Or it could mean a plant will warn their kin to increase their production of nasty toxins to scare off incoming insects. Or, in plants known appropriately dubbed “overcompensators,” a single plant will adopt both strategies at once, fighting back the threat of being consumed so vigorously that they end up better off after being bitten than if they lived their whole lives untouched.
The ideal scenario for an overcompensating plant is to be nibbled on enough to trigger its defenses, without causing so much damage the plant can’t carry on. Once a primary stem is bitten or clipped, plants like the mustard Arabidopsis thaliana will increase their growth rate, regrowing the lost stem two to three times faster than it originally grew. To make sure the plant isn’t simply restocking some herbivore’s buffet, the plant will also increase the amount of toxins it produces so that it theoretically won’t get munched on again. This two-pronged strategy not only helps keep the plants alive, it may even give them a boost, as they have been found to enjoy greater reproductive success, spreading more seeds, than plants of the same species that never responded to danger.
Pumping out proteins
As from the energetic cost of tacking both toxins and regrowth at once, the weird part of these abilities is just how the plants make themselves grow faster. Normally growth involves a cell cloning its DNA then dividing into two so that each resulting cell is copy of the first, complete with cells walls, mitochondria, etc. Those cells can then do whatever job the original cell was doing before, like making proteins vital to the plant’s metabolism. These overcompensating plants speed up growth with a process called endoreduplication, which tries to get twice as much out existing cells, rather than having them split themselves in two. A cell’s DNA will be copied, but both copies stay put and go to work. This means that that first cell can kind of multitask, encoding two proteins simultaneously using both strands of DNA, but without the overhead of a second cell’s other organelles. As it happens, the molecular triggers for endoreduplication also help kick off toxin production, making overcompensating a rather elegant package for a plant to adopt.
Researchers are hoping that this package is also transferable to other plants. While 90 percent of herbaceous flowers currently engage in endoreduplication, there could be big benefits if commonly farmed crops used it more often. Responsive toxicity levels could reduce the amount of pesticides needed to protect plants like cotton. Higher growth rates would be appreciated in all kinds of crops, shortening the amount of time necessary to get a full year’s yield. There’s more work do be done, but farms may someday be able to significantly boost their crops’ growth with just a bit of well-intentioned pruning.
Source: Some plants grow bigger – and meaner – when clipped, study finds by Diana Yates, Illinois News Bureau