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? In the year 1915, the stomatal conductance of oak was approximately how many times higher than that of pine?
How about in the year 2010?

Question

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? In the year 1915, the stomatal conductance of oak was approximately how many times higher than that of pine?

How about in the year 2010?

Accepted Answer

Hi everyone. Let's look at our next question. It says which of the following factors can increase to model conductance. Looking at our answer choices, we want to be aware that we have a choice d all of the above So there's a chance that all are correct. And let's recall from our content video. So model conductance refers to that um water flowing or being drawn I should say up through plant from the root and out through open store Mata. So as we want to think about what would increase the model conductance stigma to being more open would result in greater to model conductance. See there. So let's look at our answer choices to see which factor would increase. To model conductance. Choice A says photosynthesis in the guard cells. Well when photosynthesis takes place in the guard cells we know that photosynthesis produces sugars, produces carbohydrates. Those are salutes. So photosynthesis in the guard cells increases the salutes in those cells. And as a result we recall when we have solute concentration, increasing water will flow into those cells by osmosis. So water goes into the guard cells that causes the guard cells to swell and that causes this tomato to open. So still open. So that means that photosynthesis and the guard cells will increase the model conduction because we have a choice D all of the above. I'm not going to choose A as the answer but I'm going to market correct choice B says the presence of blue light. Well blue light, there are blue light receptors in the guard cell membrane and this is a little bit long. So I'm going to kind of put an arrow to bring this down when blue light activates the guard cell receptors. So blue light activates receptors in guard cells. The result of that as it induces proton pumping out of the guard cells. Well that creates an electrochemical gradient. You're pumping those positively charged protons out and that causes the positively charged potassium ions along with other ions enter those guard cells through a channel down the electrochemical gradient. Well, what's the result of that? Solute concentration increases in those cells. And just as we saw on a that means by osmosis, water comes in the guard cells swell and the tomato open. So Choice B presence of blue light is another situation that will increase the model conductance. Well, if I were in a test in a hurry, I'd go ahead and select D all of the above. I've already got more than one correct answer but for the explanation, I'm just going to be thorough here. So we'll look at choice. See choice, he says, increase in light intensity. Well, an increase in light intensity will result in an increase in photosynthesis. And as we saw in choice A. That results in this tomato opening. So an increase in light intensity will also increase the model conductance. So our answer is indeed Choice D all of the above. As factors that can increase to model conductance photosynthesis in the guard cells. The presence of blue light and an increase in light intensity hope that helps see you in the next video.

Verified video answer for a similar problem:

Key Concepts

Stomatal Conductance

Photosynthesis

Transpiration