Germination, the process through which plants disperse seeds so that they can sprout and grow into new plants can be a little tricky, given that plants are immobile. Some like dandelions use wind, others by growing prickly fruits that stick to the fur or spine of animals. Then there are those that yield sweet fruit that animals seek out and devour. However, in order for that to work successfully, those plants have to get it really right!
That's because while the fruit has to be tasty, the seeds cannot be! In most cases, plants seem to get by this issue by making them indigestible so that they simply pass through the animal's body intact. However, one shrub in Israel's Negev Desert has devised one of the most innovative ways to propagate itself.
The sweet mignonette produces delicious little fruits that resemble blackberries, a favorite with the local spiny mice, who are constantly seeking them out. While the fruit is sweet, the 20 or so seeds hidden inside each tiny berry are what the scientists refer to as 'mustard bombs'. That's because as soon as the mouse bites into them, they release an enzyme that tastes like hot mustard, forcing the rodent to spit them right out - Similar to how we spit out watermelon seeds.
To test if this mechanism helps the plant germinate more effectively, the researchers went one step further by planting sweet mignonette seeds into Petri dishes and placing them in two locations - One right under the plant itself and the other in the rocky crevices where the mice usually retreat to enjoy the fruit and spit out the seeds. Sure enough, the seeds dispersed by the mice were a better location for the plant because they were not in the direct sunlight.
And if that was not enough to prove how smart the shrub is, the researchers conducted one more experiment - To see if the seeds covered in mice spit germinated better than the ones extracted straight from the fruit. The result? The seeds spit out by the mice germinated at twice the rate of the seeds that had not come in contact with the animal!
The findings of this unusually smart germination technique, published in the journal Current Biology earlier this year, has surprised scientists all over the world. According to University of Utah's Denis Dearing, who led the study, this phenomenon called 'directed deterrence' - Which means that the fruit is targeted to get eaten only by the one consumer that can help spread the seeds, has only been observed in a few other plants.
The best known and the one we can call relate to is chili peppers - If you have ever put one in our mouth, you may have noticed that chewing on the seeds can get a little spicy. That's because when mammals, who are capable of destroying the seeds with their teeth, chew on them, they release an enzyme called capsaicin. But birds do not feel the heat at all - That's because they do not crush the seeds while they are eating and therefore have been chosen as the natural dispensers of the seeds! Nature is pretty amazing isn't it?
Resources: Scientificamerican.com, redorbit.com