Thigmotropism and Cytokinins

by Jason Amores Sumpter
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plants are able to sense and respond to physical stimuli like touch or wind growth or movement in response to this is called thing GMA trope is, um, climbing plants Use this in order to climb. They grow out tendrils like you can see here, and when they touch a surface or something to grab onto, there's a response that causes them to grow and wrap around on grip that object or surface, whatever they're touching. Venus fly traps will also use, uh, use this in order to shut on a unsuspecting insect or some form of prey. And this actually requires something pretty special because, as you can imagine, if you've ever tried to swat a fly, they can move pretty quickly, so the plant has to actually respond. Thio, that sensation of touch and move very fast to shut closed on the fly. So what a plant's gonna need to do is use an action potential, and this is an electric signal like what goes through the nerves in our bodies. But plants don't have nerves. They actually will move their action potential through plasma does Maada. So it's not going to be quite as fast as moving through a nerve, however, it will still be quite a fast signal. And if you're wondering how they generate that electrical signal, it's actually done by moving ions across the membrane. The specifics of this get pretty complicated. I wouldn't worry about it too much here. Just know that I am moving ions around the membrane. They can create a, you know, electric signals that they're able to transmit, and we will learn much more about action potentials when we talk about the nervous system. Now, it's also worth noting that plants that get a lot of physical stimulus, for example, uh, you know, Jesus just generally speaking, they often will not grow as tall. Uh, this is because of, um, you know our response to wind. If they're getting a lot of physical stimulus, it could be from lots of wind, lots of wind gusts and, in order, Thio not get blown over. Or have you know the plant body get broken in the wind. Plants will actually restrict their vertical growth so that they are less susceptible to being damaged by the wind. So this comes in many different flavors and varieties. All you really need to know is that plants are able to sense and respond to physical stimuli. Now plant growth is hormone regulated, and it's going thio be regulated by hormone or a class of hormones called cytokine ins. And these actually regulate growth by regulating the cell cycle. If you don't remember the cell cycle very well, I highly recommend you go back and check out the videos on cell division, especially the video on regulation. If you remember that stuff, hopefully you recall that there is a gate at G two. Uh, this is sort of like a a fail safe mechanism to make sure that you know, right before my toast, this happens. That's what that M is, that right before my toe sis check, all systems were go. This is the point of no return, and cytokine ins are actually going to cause cells to pass that G to checkpoint and continue dividing. So they're the gatekeepers. Essentially, now this hormone is produced in the roots, and it's transported throughs asylum to target tissues. So it's going from roots up. And it's thought that in terms of a pickle dominance, which you might recall is in part regulated by oxen, it's thought that cytokines actually play a role in there, too, and that the ratio of cytokine ins to oxen is in part what determines, uh, that a pickle dominance. It's thought that site Hakkinen's play a role in growing outward in growing and bushy nous, whereas Oxen plays a role in vertical growth. All right with that, let's flip the page.