Atmospheric CO2 has been increasing rapidly since the late 1800s, largely due to human activities. Recall that CO2 enters leaves through stomata and can then be used for photosynthesis. However, transpiration occurs as a result of water evaporating through stomata. How have plants responded to elevated CO2 levels? What impact, if any, do you predict elevated CO2 levels will have on the number of stomata in leaves, and on the transpiration rate?

Video transcript

Hi everyone. Let's look at our next problem. It says from the following four descriptions identify the ones that are true regarding cohesion tension theory. Well, let's first just recall from our content video what that cohesion tension theory is and that states that the water ascent entries is due to the pole of transporation from a continuous column in the asylum conduit running from roots to leaves. And cohesion refers to that tendency of water molecules to stick to each other due to that hydrogen bonding. And then the tension of water evaporating through this tomato as they evaporate due to that cohesion due to capillary action. The attraction of the water molecules to the xylem vessels. Um The water molecules move up to take the place of the water molecules that have evaporated and that through capillary action through that cohesion between water molecules pulls the water up from the roots up to the leaves. So, with that in mind, let's look at our statements here. Those aren't our answer choices. Those are four statements determine which are true or false. And then use the answer choice is to identify which ones are true. So W says, the greater the rate of transpiration, the greater will be the ascent of sap. This is true, since as transpiration, if water is evaporating more quickly again, since it's getting pulled up through that cohesion, as water evaporates, the faster it's evaporating the faster the sap, which is that fluid including water um and the dissolved nutrients that's moving up. Uh So that is true statement X says the transpiration pole is the main force behind the ascent of sap. And that is true. That is the essence of this theory. That the main reason sap ascends is the pole that results from water evaporating through transpiration and then cohesion capillary action, causing that upward movement. As a result, Y says the greater the ascent of sap, the lower will be the rate of photosynthesis. Well this is false. Um the greater the ascent of SAP would be caused by a greater rate of transpiration. Since again, SAp is ascending due to the pole of transpiration. Well, the greater the rate of transpiration, the greater the rate of photosynthesis. And that's because you're getting more water being brought up to the leaves. The water is needed in photosynthesis. And transpiration occurs through this to maatta and Maatta being open for that greater rate of transpiration allows a greater rate of gas exchange, providing the C. 02. That is used in photosynthesis. So, a choice or a statement why is false. Easy says cohesion is a force of attraction between water molecules and that is true. Do that. Those hydrogen bonds. Um Water molecules are attracted to each other and that force is called cohesion. So we see that we have three true statements here, W. X. And Z. So now we go down to our answer choices and find the one that correctly identifies those three. And that would be choice B. Which has just W. X. And Z. Not Y. Which is false. So which statements are true regarding the inclusion intention theory? The greater the rate of transpiration, the greater will be the ascent of SAP. The transpiration pulls the main force behind the ascent of saP, and cohesion is a force of attraction between water molecules. See you in the next video.