d any thing touching on human biology. But much to my surprise and against all of my plans, I later discovered that this same group of genes is also part of the human DNA.
This led to the obvious question as to what these seemingly “plant-specificâ genes do in people. Many years later, we now know that these same genes are important in animals for the timing of cell division, the axonal growth of neurons, and the proper functioning of the immune system.
But most amazingly, these genes also regulate responses to light in animals! While we donât change our form in response to light as plants do, we are affected by lab at the level of our internal clock. Our internal circadian clocks keep us on a 24 hour rhythm, which is why when we travel half way around the world we experience jet lag. But this clock can be reset by light. A few years ago I showed, in collaboration with Justin Blau at NYU, that mutant fruit flies that were missing some of these genes lost the ability to respond to light. In other words, if we changed their clocks, they remained in jetlag.
This led me to realize that the genetic difference between plants and animals is not as significant as I had once naively believed. So while not actively researching this field, I began to question the parallels between plant and human biology even as my own research evolved from studying plant responses to light to leukemia in fruit flies.
2. How do think people should change how they think about plants?
People have to realize that plants are complex organisms that live rich, sensual lives. You know many of us relate to plants as inanimate objects, not much different from stones. Even the fact that many people substitute silk flowers for real ones, or artificial Christmas trees for a live one, is exemplary at some level of how we relate to plants. You know, I donât know anyone who keeps a stuffed dog in place of a real one!
But if we realize that all of plant biology arises from the evolutionary constriction of the “rootednessâ that keep plants immobile, then we can start to appreciate the very sophisticated biology going on in leaves and flowers. If you think about it, rootedness is a huge evolutionary constraint. It means that plants canât escape a bad environment, canât migrate in the search of food or a mate. So plants had to develop incredibly sensitive and complex sensory mechanisms that would let them survive in ever changing environments.
I mean if youâre hungry or thirsty, you can walk to the nearest watering hole (or bar). If youâre hot, you can move north, if youâre looking for a mate, you can go out to a party. But plants are immobile. They need to see where their food is. They need to feel the weather, and they need to smell danger. And then they need to be able to integrate all of this very dynamic and changing information. Just because we donât see plants moving doesnât mean that thereâs not a very rich and dynamic world going on inside the plant.
3. You say that plants have a sense of smell?
Sure. But to answer this we have to define for ourselves what “smellâ is. When we smell something, we sense a volatile chemical thatâs dissolved in the air, and then react in someway to this smell. The clearest example in plants is what happens during fruit ripening.
You may have heard that if you put a ripe and an unripe fruit together in the same bag, the unripe one will ripen faster. This happens because the ripe one releases a ripening pheromone into the air, and the green fruit smells it and then starts ripening itself. This happens not only in our kitchens, but also, or even primarily, in nature. When one fruit starts to ripen, it releases this hormone which is called ethylene, which is sensed by neighboring fruits, until entire trees and groves ripen more or less in synchrony.
Another example of a plant using smell is how a parasitic plant called dodder finds its food. Dodder canât do photosynthesis, and so has to live off of other plants. The way it finds its host plant is by smelling. A dodder can detect minute amounts of chemicals released in the air by nei