Photoderiodism

by Jason Amores Sumpter
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plants like animals, experience circadian rhythms, these air daily cycles that will do things like fluctuate the concentration of a particular hormone based on the time of day. Now these cycles are maintained and generated internally by what you could think of as a biological clock. However, they can be influenced by the external environment, and plants can be can have their circadian rhythms influenced by what these things called crypto chrome's. Now these are going to be photo receptors that detect blue light and can have an influence on, for example, the turgid ity of the plant in response to daylight. Now this plant over on the left, as you can see, is perked up. Its leaves air open, and it's ready to absorb sunlight. This is going to be it's it's daytime condition. At night, the plant will lose targeted E and get droopy. Its leaves will close up, and it will not be in a prime position to absorb sunlight. However, it will give the plant certain other advantages. So this fluctuation over the day night cycle will allow the plant to maximize its photosynthesis and also, you know, do things like help protect it from environmental conditions by folding in it night. Now, some plants actually bloom in response thio seasonal changes and they detect this by sensing the lengths of the day night cycle. Now we call these physiological responses Photo period is, um and some plants are considered long day plants. These are gonna be plants that bloom when the days air longest, which is going to be during the summer. Some plants are called short day plants because they bloom when the days are shorter and the days air gonna be shorter during the spring and late summer fall. Now, obviously the days they're gonna be shortest in winter but hopefully realize why. It's not really a great time for plants to be blooming. However, that cold does have an effect on plants ability to bloom some plants, that is, and we call this vernal ization. It's essentially a pre treatment with cold that is necessary for the photo period blooming response to take place. Essentially, these plants are still going to be detecting lengths of those day night cycles, right, examining the relative length of day tonight to detect seasonal changes. However, they require a period of cold Before that photo period, response can kick in. And essentially, this is a way to ensure that they have passed through winter and are going to, for example, bloom in the spring time. And we call this vernal ization from the Latin Virna for spring. Now it should be noted that some plants bloom independently of day length, and we call these day neutral plants now. The day night cycle is going to have a NIF effect on when the plant blooms, but it's thought that it's actually ah, hormonal signal that causes flowering. Believe it or not, this hormone is yet to be discovered, and we simply called the hypothetical hormone Florida gin. So essentially florid gin is the hormone yet to be discovered that, uh, induces flowering. However, there's good evidence to suggest that such a hormone exists. It could just be trickier than you might realize toe. Actually identify these things when you know you don't know exactly what toe look for ID, like searching for a needle in a haystack. And before we leave, I just want to point you to this figure, because, honestly, it's just a really nice display of information, and this will actually show you day length based on your latitude on the earth and, uh, month, as you can see here. So very nice chart showing you when the days are longest and shortest. All right, that's all I have for this video. I'll see you guys next time.