What is the role of companion cells in the movement of sugars through plants? a. They are the sites of sugar production by photosynthesis. d. They are the sites where starch is converted to sucrose. c. They secrete sucrose, which draws sugars through phloem under negative pressure. d. They accumulate sucrose, which is then transferred to adjacent sieve-tube elements.

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Welcome back. Here's our next question blank move sugar and amino acids into and out of the sieve elements. Well, let's recall from our content videos that the sieve elements or sieve tubes um are long narrow tubes in the flow um of plants and therefore they're responsible for carrying most that fluid in the flow. Um And they're closely attached two companion cells and these companion cells regulate the flow of sugar and amino acids into those sieve tubes. So that's what we're looking for here. Companion cells which is choice B But let's look at our other answers to see why they're not the right choice. The first choice is bundle sheath cells. And this is actually tricky because bundle sheath cells do have a role in regulating the flow of molecules but they're in a different location. Bundle sheath cells are photosynthetic leaf cells packed tightly around leaf veins. So leaf cells and they do help regulate the flow of molecules into the vascular bundles that they're packed around. Um But not the sieve elements in the flow. Um Those are the companion cells and those two are you know, they're partners and in fact their sister cells that arise from the same mother cells. So when you think sieve elements, you want to think companion cells to keep that straight from the bundle sheath cells. So they are not our correct answer. We have choices flowing parent chema cells. Um parent crema cells are found in there called border or transfer cells and they're found in the tips of very finest finest branches and leaves, mainly. It's used mainly for food storage. But that's not the answer we're looking for. And just the xylem vessels while we're talking about the sieve elements are in the flow. Um, not the asylum. So that's not our answer. So again, which cells move sugars and amino acids into and out of the sieve elements? Those are choice be the companion cells. See you in the next video.

Verified Solution

Key Concepts

Companion Cells

Phloem Transport

Sucrose Loading and Unloading