If a long-day plant has a critical night length of 9 hours, which...

Question

If a long-day plant has a critical night length of 9 hours, which 24-hour cycle would prevent flowering?
a. 16 hours light/8 hours dark
b. 14 hours light/10 hours dark
c. 4 hours light/8 hours dark/4 hours light/8 hours dark
d. 8 hours light/8 hours dark/light flash/8 hours dark

Accepted Answer

Welcome back. Let's look at our next question. It says a long day plant has a critical length of eight hours. What will happen if we expose this plant to 15 hours of light and nine hours of dark. So let's recall what a long day plant is from our content videos. And that is a summer blooming plant. And that means it's flowering when the days are longer, thus the name long day plant. And so the problem presents us with a plant with a critical length of eight hours. So what is critical length again? Critical length is the minimum amount of uninterrupted darkness needed to inhibit flowering and the long day plants. So this is kind of important to remember. It's we are calling it a long day plant and thinking of it as it blooms in, the days are longer. But in terms of the chemical signaling that goes on in the plant, it's the number of hours of uninterrupted darkness. That's what signals to the plant when flowering should start or stop. So, our long day plant in this question has a critical length of eight hours. So then it says, what will happen if we expose this plant to 15 hours of light and nine hours of dark? So, given this uh description of critical length, we know that it's the nine hours of dark. That's the key information here. So, since our critical length is eight hours, if the plant gets exposed to nine hours of dark, that's more than the critical length and therefore we know that flowering will be inhabited. So let's look at our answers and we do see that right away. When we look this over. Choice B. Is flowering will be prevented. Oops. So if we're on a test, we'd go right to that. There's our answer. But we'll just walk through the other answers to look at them. Choice A says flowering will be promoted. Obviously that's not the correct answer. Flowering is promoted when the days are getting longer and so there's less darkness when you have flowering being promoted. So Choice A. Not our answer. We said Choice be flowering will be prevented. Yes. That is what will happen when the flower has more hours of darkness than the critical length. Choice C. Says there's no effect on flowering. That's incorrect. We know that there is. And Choice D. Says flowering is permanently inhibited. Well, flowering is inhibited but not permanently. This is a seasonal plant. It will begin flowering again when exposed to less than the critical length of darkness. So Choice D. Not our answer. And were confirmed. That Choice be flowering will be prevented is the correct answer. Join us in the next video

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