Consider the following statements regarding the transport of phlo...

Question

Consider the following statements regarding the transport of phloem sap. Select True or False for each statement.
T/F This is a passive process that is driven by the evaporation of water from leaves.
T/F Sugars tend to move from sources to sinks.
T/F Phloem sap moves through sieve-tube elements under positive pressure.
T/F Sieve-tube elements and vessel elements are commonly involved in the transport of phloem sap.

Accepted Answer

Hi everyone. Let's look at our next question. This one says from the following four descriptions identify the ones that are true regarding sugar transport. So we've got four different statements that are not our answer choices that our answer choices give us various combinations of these four statements. So we gotta make sure we kind of keep everything straight here. So we'll start by labeling which of the statements given first are true or false. So choice P says sugar is mainly transported by pressure flow. Well, this is true. Um Let's think a little bit about the process of sugar transport. Um We have sugar being produced in the leaves, so this is called the source of the sugar. They're doing photosynthesis and producing sugar and that sugar is being actively transported into flow um cells and the leaves as the sugar is. The molecules are actively transported. Water follows by osmosis because as the sugar molecules enter this flow them cells, um sugar concentration goes up and so as moses leads water to diffuse into those flow themselves to dilute the solute concentration as water follows into those flow um cells, the trigger pressure and those cells increases and that forces the fluids with the sugars through the flowing tubes of the plant that with enough through the flowing tubes until they reach those areas. Those newly growing areas of the plant where sugars will be needed. So the young shoots, um budding leaves and growing roots and we'll call those the sinks. So growing parts. When it gets to the sinks sugar again, is actively transported into those cells that need it. And then water follows by osmosis. This decreases the pressure in those cells. And now we have a situation set up where we have this pressure flow transporting the fluid through the flow um tubes from the source the leaves to the sinks, those growing parts of the plants. So as we C. P. Here, sugar is mainly transported by pressure flow is true. Then statement Q. Says sugar transport is due to an osmotic li generated pressure gradient. Well as we explained there that is true. Then statement are says sugar transport is always from leaves to fruits while this is false because we see it does come from the leaves, but also goes to those growing parts of the plants, those growing roots, young shoots and developing and budding leaves. So statement are is not true. And finally statement S sugar is transported by flowing. Yes that is true, that's the main sugar transport um vehicle in the plate. So we have three true statements and they are P. Q. And S. So now we go down to our answer choices and find the one that has P. Q. And S. And that is choice C. Giving us our three true statements about sugar transport. P sugars mainly transported by pressure flow. Q. Sugar transports due to an osmotic osmotic generated pressure gradient and S. Sugar is transported by flowing. See you in the next video

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