Plant Hormones and Senescence

by Jason Amores Sumpter
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jibber Alan Zahra, class of plant hormone involved in the regulation of growth. They induce cell division in the stem leading to stem elongation. They're also involved in fruit growth and seed germination. Now, with our three plants that you can see right here, we are showing the difference in plant morphology based on exposure to Jibber Allen's, which are confusingly abbreviated G. A. I don't make the rules, guys. I don't need these things. So as you can see, this plant in the middle is a normal looking plant, and it has a normal inter node length right there, and this plant received a normal amount of jibber Allen's. So we'll say jibber. Allen's put the equal sign. They're just like normal. This plant received a lot of Deborah Allen's, and that's why it has this crazy big Internet length right there and just a generally long stem. In contrast, this little guy over in the end didn't get a lot of jibber Allen's, and that's why it has a very short stem and especially has like no inter node length, really tiny. They're in terms of germination. It's actually water being absorbed into the cell, which let me get my head out of the way here. Water being absorbed into the seed rather sell into the seed will stimulate the Chipper Allen's and those as they are hormone are gonna influence the gene expression of the of the seed. And that will lead to the production of amylase, which will start turning the starch in here into sugars which will feed this organism and lead thio its growth and, of course, breaking free from its seed coffin. Now, if seasick acid is another important hormone that we've mentioned previously, this hormone is involved in stone mata opening and seed dormancy. Now you might recall that of seasick acid is produced in the roots and will make its way up to the chutes where it will influence STA model closing. Now we had talked about before how blue light photo receptors can play a role in stay mata opening and closing. Obsessing acid will supersede whatever signal those blue light photo receptors air giving. So even if the blue light, you know, even if the signal coming from the blue light photo receptors is contradictory to the ab seasick acid, these abs seasick acid wins out that hormonal signal is more powerful now. Dormancy is that period of arrested growth prior to germination, and it doesn't end until there's the right stimuli and conditions for the seed to respond. Thio obsessing acid is thought to actually inhibit germination. And these jibber Allen's we were just talking about induce germination, so hope you're noticing a pattern with these hormones. They often have balancing rolls, one will turn something on and the other will turn something off. This gives. Lastly, I just want to mention brass, no steroids thes air, a class of plant hormone that air involved in, uh, growth as well, but specifically in cell elongation and division. And they're gonna play a role in regulating overall plant body size. Now the last thing I want to talk about is sin essence. This is the sort of technical term for aging. This is what you might think of as biological aging, and it's usually marked by a gradual deterioration of function. Right, so your cells gradually deteriorating function as they age. Uh, you know, the organism as a whole gradually deteriorates in function as it ages, and there's actually ah, hormone for plants that is closely associated with this process. That hormone is ethylene. It's actually a gas at room temperature on Earth. So under normal conditions, this is a gashes hormone, which means it's going to be able to diffuse through the air. That's Uhh! Well, get back to that in a second, actually, So ethylene plays a role in sin Essence. Uh, one of those roles is in the process of obsession, which is going to be the shedding of part of an organism in plants. Usually we talk about Leif obsession and leaves, as you know, our obss ized during the fall. That's why I have this beautiful fall background behind my head now. The reason for that is because cells in the petty oh, which is that stock on the leaf. Those cells are going to react to ethylene and that ethylene is going to trigger enzymes to degrade the cell walls there in the petty. Oh, that's why the leaf will snap off right perfectly at the base of the petty. Oh, if you've noticed that, but leaves always break off right At that point, it's because thesis is there are degraded due to enzymes, which are signaled by this hormone. Now fruits ripen when exposed to ethylene. You can see in this nice image here we have a ripening and aging banana, and, as, uh, the fruits are exposed to ethylene, starch is converted to sugar and the cell walls are broken down. So that's why you know, if you eat a really super green banana like that, it's going to be, uh, like, tougher and also, you know, just not nearly a sweet. It's going to be kind of like potato, not very palatable. As starch is converted into sugar, the fruit gets sweeter. That's why uhh these, you know, fruits down on this banana down. In the end, you know, this has been exposed to a lot of ethylene. It's going to be really, really sweet and sugary if you bite into it. So that is, um, wife. For example, if you have an overly ripe banana near some green bananas, those bananas will go bad really quickly because ethylene is a gashes hormone and that overly ripe banana is going to be giving off ethylene and influencing those under ripened bananas to ripen probably faster than they should. So nice little life hack here if you're ever struggling with unripened avocados there. Too hard. Throw them in a bag with a ripe banana. Those guys will get nice Really fast. All athletes. A beautiful thing. All right, That's all I have for this video. See you guys next time.