DPBioY2 - 2020 - 9.2 Phloem Transport
DPBioY2 - 9.2 Phloem Transport
2 marks for your questions
3 marks for your reply
2 marks for submitting by July 2nd, 2020
DPBioY2 - 2020 - 9.3 Plant Growth
DPBioY2 - 9.3 Plant Growth 2 marks for your questions 3 marks for your reply 2 marks for submitting by July 16th, 2020
If the phloem cells are living in order so they can recognize the concentration gradients made, then why are xylem cells dead when they need to recognize those same concentration gradients?
ReplyDeleteHow do sieve element cells function differently since they do not have a nucleus, ribosomes and vacuoles?
How is sucrose co-transported with hydrogen ions?
How does the specialization of cells work in plants?
To clarify, water is transported in xylem due to pressure, while nutrients are transported in phloem due to concentration gradients?
Is phloem sap the same as tree sap?
What is purpose of oligosaccharides in the translocation?
To answer your last question oligosaccharide is what is being translocated, oligosaccharides are carbohydrate molecules made of a small number of monosaccharides
DeleteTo answer your 3rd question,
DeleteActive transport uses ATP energy to pump Hydrogen ions across the concentration gradient outside of the companion cells. Due to there being a higher concentration of Hydrogen outside of the companion cell, they naturally will follow the concentration gradient and merge back inside through the transport proteins. This movement back across the gradient generates energy, kind of like how ATP synthase does in a way. However, the same protein that is now filled with energy from the hydrogen crossing back over will simultaneously allow sucrose to actively travel across the gradient, making it a co-transporter.
To add onto Melissas statement about your last question,
DeleteIn symplast routes where the sucrose travels between the cells through interconnections, the sucrose reaches the companion cell. If there was too much build up of sucrose, the concentration gradients will become incorrect in meeting the plants needs of sucrose as the water and pressure would be greatly altered as more sucrose builds up. So, when sucrose enters into the companion cell, it is converted to oligosaccharide. This allows the plant to maintain a good sucrose concentration gradient and allow for proper transport into much needed areas by manipulating the water and pressure. By converting to another type of molecule, the concentration gradient cannot be affected.
To answer your sixth question, based off the website I found, https://www.gardeningknowhow.com/ornamental/trees/tgen/what-is-tree-sap.htm#:~:text=Xylem%20sap%20consists%20primarily%20of,sapwood%2C%20which%20produces%20carbon%20dioxide.
DeleteFrom the sounds of it, the xylem and phloem both make sap and that is what makes up the tree sap. So yes, technically they are the same thing but the xylem and phloem sap combined.
To answer your first question, I found a few websites that help clarify why xylem cells can be non-living and still be able to perform their function as they need to. Essentially, the transportation methods used by the xylem and phloem are vastly different. The phloem is dependent on its living cells because active transport is vital for it to carry out its function. The xylem is completely dependent on passive transport as well as pressure. Transpiration pull plays a huge role in this as it allows water to be pulled upward, out of the plant through the stomata of the leaves. Water can also move through the walls of the xylem to get to the phloem is the water potential inside of the phloem becomes too low. This process is simply osmosis, which is also a passive process. The xylem benefits from having non-living cells because it allows for more space inside the xylem for water to pass through it. For more on this topic, here are a few websites I found useful:
Deletehttps://msu.edu/~walwort8/page3.html
https://www.quora.com/Why-are-the-cells-that-make-up-phloem-alive
https://www.shmoop.com/study-guides/biology/plant-biology/plant-tissues#:~:text=There%20are%20two%20types%20of,more%20capacity%20for%20transporting%20water.
To answer your second question, I found a few sources that I found helpful. Sieve element cells are dependent on their companion cells to carry out certain functions because they lack a nucleus. These websites go into more detail if you'd like to do some more research on it:
Deletehttp://www.plantcell.org/content/11/4/739
https://www.dictionary.com/browse/sieve-tube-element
https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/sieve-element
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/sieve-elements
1. Do the xylem and phloem each have their own types of sap within them?
ReplyDelete2. Why do sometimes sinks becomes sources and sources become sinks?
3. How does sinks and sources changing cause a change in the direction which biochemicals are being transported?
3. How does photosynthate normally get distributed throughout a plant?
For your second question,
DeleteAs new parts of the plant developed, for instance lets look at leaves, they require energy. They are not fully developed and do not have the capability to photosynthesize their own sources of energy. However, as they reach maturity their photosynthetic capabilities come into play. The role then switches as the leaves are able to photosynthesis and provided needed energy to devolving portions of the plant.
To answer your first question, they both have sap within them and they are very similar. The sap in the xylem contains water, hormones, nutrients and minerals and phloem sap contains water, hormones, nutrients, minerals and sugar. Therefore the only difference between them really is that the phloem sap contains sugar where the xylem sap does not.
DeleteHere is the website I used if you would like to read more about the sap: https://www.gardeningknowhow.com/ornamental/trees/tgen/what-is-tree-sap.htm#:~:text=Xylem%20sap%20consists%20primarily%20of,sapwood%2C%20which%20produces%20carbon%20dioxide.
To answer your third question, as a plant is growing, its leaves become the source since they carry out photosynthesis. The phloem moves the products of this process to a sink for storage. Then, the products may be moved back up the phloem to be used in another area of the plant such as a growing flower bud. Thus, the direction of phloem transportation is dependent on this sort of new growth and the location of sources or sinks. This allows the movement inside the phloem to be biodirectional.
Deletehttps://www.toppr.com/guides/biology/transport-in-plants/phloem-transport/#:~:text=Since%20transportation%20of%20water%20always,position%2C%20the%20movement%20is%20bidirectional.
http://www-plb.ucdavis.edu/courses/bis/1C/nlu-w11/lectures/Phloem.pdf
For your last question, photosynthates are just sugars made by photosynthesis. These are transported throughout the plant via the phloem and translocation which is how the photosynthates can get from sources to sinks.
Delete1. Why are companion cells necessary in order for the success of the sieve cells.
ReplyDelete2. What factors impact the pressure of the phloem and allow it to travel in both directions?
3. Does the symplast route of sucrose translocation use the same idea of active transport to form a concentration gradient like the aplast route?
To answer your first question the sieve cells go through an incomplete autolysis where many of the organelles are degraded and eventually eliminated (cytoplasmic ribosomes, Golgi bodies, and nucleus). Since the sieve cell has lost these organelles the companion cell performs the many of the genetic and metabolic functions that the sieve cell would ensuring its success. This is possible for the companion cell since they both share the same parent cell.
Deletehttp://www.plantcell.org/content/11/4/739
In regards to your second question, solute concentration is one factor that impacts the pressure of the phloem because the water inside the phloem (which is attracted to the solute by osmosis) creates positive pressure. The transport in the phloem can travel in both directions because there is no one source, per se, of the sap in the phloem (ex. the model looks much different than that of the human heart and the arteries and veins responsible for the transport of blood).
DeleteFor your 3rd question, the symplast route uses passive transport from sucrose accumulating in the sieve tubes. Water osmosis from high to low concentration of potential then causes sucrose to move. This is more passive than the aplast route which uses active transport.
Deletehttps://alevelbiologystudent.weebly.com/94-translocation.html#:~:text=%E2%80%8BSymplast%20Route%3A,the%20phloem%20by%20mass%20flow.
1. How do the rigid cell walls of the Sieve cell help create high pressure?
ReplyDelete2. When they use the Aphids to help measure the rate of phloem transport, how does the radioactive 14C relate to the rate of transport and how do they calculate it?
3. Are the plasmodesmata pores a way for the sugar to transport into the root system or can they only be transported by active transport?
For your first question,
DeleteThe rigid cell walls create pressure because water is incomprehensible. This means that it wants to stay at a fixed volume, but those cell walls won't allow the water to do this because the phloem is too small to hold the amount of water needed to balance out the solute concentration and the differing width sizes of the phloem that the rigid cells walls make, creates a bunch of pressure inside the phloem.
For your 2nd question,
DeleteThe radioactive 14C is fixed by plants during photosynthesis. This will release radiation that can be detected using film or other radiation detectors. As the carbon metabolizes, it can be found in different molecules within the plant. Therefore, both the formation and movement of the 14C can be traced. This allows scientists to figure out the rate of transport through which sugars are being transported (as carbon makes up sugar)
3rd question:
DeleteYes, the plasmodesmata pores are connecting sieve element cells and companion cells. Those pores move metabolites like sugar from the companion cells to the sieve element cells, which can later move down the sieve tube to root cells, its called symplastic loading.
https://ib.bioninja.com.au/higher-level/topic-9-plant-biology/untitled/phloem-loading.html
1. Why do phloem have sieve plates?
ReplyDelete2. What would happen if phloem tissue was damaged in a plant?
3. What changes the direction of flow in the phloem?
4. Why is it important for phloem sap to be able to move in both directions? If it couldnt move in one direction what would happen?
To answer your first question the phloem has sieve plates in order to allow the transfer of materials between cells. It also acts as a barrier to prevent sap loss whenever an animal or insect damages or cuts the phloem. A protein formed in the sieve element is released from its anchor site and accumulates on the pores of the plate to form a clot and stop sap loss at the damaged site.
Deletehttps://biologydictionary.net/phloem/
To answer your second question, if phloem tissue was damaged in a plant, the plant would have travel transporting the sugar produced by the source to the sink in the plant. This would be because the Vascular tissue in the phloem has the job to transport nutrients throughout the plant. Here is the websites I used:
Deletehttps://msu.edu/~walwort8/page2.html
https://brainly.in/question/12195931#:~:text=Damage%20or%20cut%20in%20phloem,case%20it%20leads%20to%20death.&text=Phloem%20is%20the%20vascular%20tissue,sugars%20from%20source%20tissues%20(ex.
To answer the third question the change in direction of the flow in the phloem is determined by the concentration of solutes in the phloem.
Deletehere is a website i found helpful:
http://pol2e.com/Animated%20Tutorials/pol2e_at_2504_The_Pressure_Flow_Model/pol2e_at_2504_The_Pressure_Flow_Model_scr.html#:~:text=The%20direction%20depends%20on%20the,of%20solutions%20in%20the%20phloem.
For your last question,
DeleteI ended up using the same website as Kiyah. The phloem sap needs to flow in both directions because it needs to transport nutrients to all the sinks in the plant. If it only flowed one way, a lot of the plant would not get the necessary food and energy to carry out metabolic and other life processes, causing it to die. For example, if the roots did not receive any phloem sap, they would not have the resources to continue growing and would begin to die. When they die, water and solutes can no longer be taken in by the roots, so photosynthesis can no longer occur, leaving the plant to die.
1. How does a Geiger counter measure radiation?
ReplyDelete2. How do plants "fix" radiation as they do with carbon-14? What does this process look like?
3. What are all of the functions of a companion cell and what are the benefits of it to the plant?
4. What is the benefit of the sieve plate?
For your first question,
DeleteA Geiger Counter is a tube with gas and a positively charged wire in the middle of it. In the case of radioactive particles, what makes them radioactive is that they are unstable and thus have to keep breaking down until they become stable. Each time they break down, the energy from this causes nearby electrons to be "knocked off" their electron shell of a particular atom. All of these electrons combined are then attracted to the positive charge of the wire in the Geiger Counter. This makes a "click" noise to notify the handler that one radioactive atom has been detected. The higher amount of clicks means the higher amount of radiation.
Here's my source if you need more info:
https://cosmosmagazine.com/technology/how-does-geiger-counter-work/
the benefits of the sieve plates are protecting the phloem sap from animals as it blocks the flow when the phloem cell is damaged. They also allow fluid to flow between cells so without them there wouldnt be that flow
DeleteFor your 3rd question,
DeleteThe functions of a companion cell include performing many metabolic and genetic functions for the sieve elements. Both the sieve and companion cell share the same parent cell. The companion cell is also responsible for supporting the active transport of sucrose. The folding of the plasma membrane of the companion cell increases the phloem loading capacity using the apoplastic route.
1. How exactly do companion cells keep phloem cells alive?
ReplyDelete2. Is there any pressure change when the phloem changes the direction of solute/sugar movement(towards the sink or towards the source)?
3. Where do the hydrogen ions come from and which cell are they pumped out of? For what purpose?
To answer the first question,
DeleteCompanion cells keep the phloem cells alive as the phloem is made up of sieve and companion cells. These cells contain mitochondria which produces ATP. These ATP then actively move sugars and other materials/nutrients between cells
In regards to your third question, hydrogen ions are made in all cells in cellular respiration. They are what create the concentration gradient in oxidative phosphorylation/ETC which creates ATP. So, I would assume that these H+ ions come from all of the cells in the plant since they are an essential molecule in the biological processes of all organisms.
DeleteIn answer to your second question there is no pressure change in the phloem merely a concentration gradient change providing for the bidirectional movement.
Delete1. How does the rigid cell walls of the sieve tube allow for the building of the high pressures?
ReplyDelete2. what are the benefits of phloem sap and importance of its movements within the phloem?
3. How is radioactive 14 c used in the process of measuring rates of aphids, what is the equation?and how is this process done?
First question,
DeleteThe build up of solute of sugar and carbohydrates draws water into the companion cells by osmosis. So since all the water rushes into the cell it becomes hypotonic and cannot extend outside due to the rigid cell walls and because water is essentially incompressible, resulting in high pressure.
To answer your 2nd question,
DeletePhloem sap is composed of mainly of sugars, minerals, and water. This sap is used to nourish the rest of the plant. The phloem transports this sap to important sinks within the plant.
For your third question, radioactively-labelled c is used to measure the rate of translocation. The plant is contained in an environment where the atmosphere is composed of radioactively labelled carbon elements. Once ingested by the plant, these molecules move up through the phloem. Aphids are also placed in this contraption near the stems, encouraged to feed off of the plant. The aphids consume sap from the phloem and this can easily be taken and measured by severing the aphids' stylets.
Deletehttps://ib.bioninja.com.au/higher-level/topic-9-plant-biology/untitled/translocation-rate.html
1. How does turgor pressure apply to the phloem?
ReplyDelete2. How specifically does water move from the xylem to the phloem (and then vice versa)? Osmosis?
3. Who came up with the Pressure Flow Theory?
In regards to your second question, I am under the impression that water moves between the xylem and the phloem by osmosis.
DeleteFor your third question, Ernst Münch is the man who came up with the pressure flow theory. Hes a german plant physioligist and he proposed it in 1930.
DeleteFor your first question, turgor pressure applies to the phloem because in phloem, when theres a high concentration of an organic substance, a diffusion gradient is created which draws water into the cells from the nearby xylem. This in turn creates turgor pressure.
Delete1. How does the solute concentration in the phloem lead to a positive pressure?
ReplyDelete2. How is pressure measured within the xylem and phloem?
3. If the negative pressure in the xylem prevents it from collapsing, how does the positive pressure in the phloem not lead to its collapse?
For your second question, pressure is measured in the xylem by putting a pressure transducer on the chamger. Its filled with silicone oil and some water and when its put into a xylem vessel, the pressure goes through the liquid medium and gets measured by the pressure transducer.
Deletehttps://onlinelibrary.wiley.com/doi/full/10.1046/j.1365-3040.2001.00697.x#:~:text=A%20pressure%20transducer%20is%20mounted,measured%20by%20the%20pressure%20transducer.
For your first question,
DeleteThrough active transport solutes like sucrose are moved from the source to companion cells to sieve cells. Therefore, the solute concentration is high and water potential is low. Resulting in an influx of water which increases turgor pressure at the source, so then pressure potential increases and positive pressure is created.
http://bio1520.biology.gatech.edu/nutrition-transport-and-homeostasis/plant-transport-processes-ii/
1. Is the phloem comparable to blood vessels in animals?
ReplyDelete2. What is a co-transport protein and what is its function?
3. Are sieve tubes comparable to tracheids/vessel element?
In response to your second question a co transport protienb is a carrier protein that allows the transport of two different species (a solute and an ion) from one side of the membrane to the other at the same time.
DeleteFirst question, The Phloem is comparable to animal blood vessels. The phloem is bi directional meaning up and down while blood flows to and from the heart. Both vessels transport valuable nutrients alike therefore I think they are rightfully comparable only in regards to transport roles.
DeleteFor your third question, sieve tubes can be comparable to tracheids. For example, when it comes to structure, both lack a nucleus. Both are also crucial when it comes to maintaining structure for both the xylem and phloem. Both their structures (xylem's nonliving cells and enucleated sieves) allow them to have more space and perform their jobs more efficiently as well.
DeleteHow does a plant respond when a companion cell looses functionality or die?
ReplyDeleteCan sinks be converted back into sources for immediate plant use(can it be called unloading)?
What factors affect translocation in plants?
Explain why growing plants have a relatively higher Turgor pressure compared to a dormant plant.
In response to your first question if the companion cell cannot function than the sieve-tube member would die, ceasing phloem function, and thereby killing the plant.
DeleteFor your third question, factors that can affect translocation rate include rate of photosynthesis, rate of cellular respiration as well as the sieve's width.
Deletehttps://ib.bioninja.com.au/higher-level/topic-9-plant-biology/untitled/translocation-rate.html#:~:text=The%20concentration%20of%20dissolved%20sugars%20in%20the%20phloem%20sap%20will,which%20physically%20stresses%20the%20plant)
1. Are there other methods for measuring phloem transport rates apart from measuring using a Geiger counter and carbon-14?
ReplyDelete2. What are the use of companion cells?
3. What can cause problem in fluidity within the phloem?
Companion cells act as a host to the sieve tubes. The companion cells are loaded with mitochondria and genetic material to feed the sieve tubes and keep them alive. Now the reason the sieve tubes need to be alive to adjust gradients effectively which can only happen in living membranes. Keep in mind sieve tubes dont have nuclei so the companion cell allows the sieve tubes to be hollow to preform their job while maintaining life.
Deletehttps://www.britannica.com/science/companion-cell
Third question, Drought can prove to be an issue within the phloem without adequate water the sugar concentration becomes too high and the plant would no longer be able to regulate gradient concentrations properly. Thus leading to an inabiliy to move nutrients to needed sites.
Deletehttps://academic.oup.com/jxb/article/65/7/1751/2885053
From what I could find, the Geiger counter and aphids feeding on the phloem were one of the only methods used to measure phloem transport rates.
Delete- How are sinks able to turn into sources, and what would be their reasons for doing so?
ReplyDelete- Explanation as to what is meant by hydrostatic pressure gradients?
- What is the purpose of sieve plates?
- What is the apoplast pathway?
- Is apoplast pathway related to symplast route, and if so, how?
-What is meant by saying that there is a decrease in water potential?
To answer your third question, Sieve plates are thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged.By having sieve plates inserted in the phloem it helps to regulate the flow of carbohydrates throughout the plant since this permits communication at the junctions (sieve plates) delivering energy and nutrients where needed.
DeleteTo answer your fourth question, In botany, apoplast refers to the space formed in between the cells thereby creating a pathway through which materials can diffuse freely. The apoplast is comprised of non-living components, particularly cell walls and intercellular material.
DeleteTo answer your second question, The hydrostatic pressure gradient is the rate of change in formation fluid pressure with depth. Fluid density is the controlling factor in the normal hydrostatic gradient.
DeleteThis comment has been removed by the author.
ReplyDelete1) Besides using Aphids, what other experiments can be used to measure rates of phloem transport?
ReplyDelete2) What makes sieve tubes rigid and why is water incompressible?
3) What metabolic functions do companion cells perform for sieve elements?