DPBioY2 - 2020 - 9.1 Transport in the Xylem
DPBioY2 - 9.1 Transport in the Xylem
2 marks for your questions
3 marks for your reply
2 marks for submitting by June 18th, 2020
2 marks for your questions
3 marks for your reply
2 marks for submitting by June 18th, 2020
-How is Malic acid broken down by plants such as cacti? What are the steps involved in this process?
ReplyDelete-What are the structures in halophytes that are responsible for removing salt build-up and how do they carry out this function?
-What is the function of the cambium?
-What is the function of the cortex?
-What is the function of the pith?
-What is the casparian strip and what is its function?
-Is a harder plant exterior indicative of having more lignin or that solely dependent on size?
Membrane proteins are used in halophytes to pump salt against the concentration gradient by active transport within root cells. So it requires energy to keep the salt out.
DeleteOhh, yes, that would make sense. The wording in the textbook made it seem like it was more complicated than that, so I was curious as to what exactly it meant. Thank you so much for the clarification!
DeleteThe cambium is a layer of cells that continuously divides and is located between the phloem and xylem tissues, it is responsible for secondary growth of roots and stems (resulting in an increase of thickness).
DeleteThere is some more info on this website: https://www.britannica.com/science/cambium
A pith is a soft spongy tissue in the stem of vascular plants (which is a plant that havs lignified tissues for carrying water and minerals) . It s function is to store and transports nutirents throughout the plant.
DeleteFor your 4th question,
DeleteThe cortex is a tissue of unspecialized cells that sits between the epdiermis cells located more towards the outside of plants, and the vascular bundles located more towards the inside. The cortex functions as a transport mechanism for materials through diffusion and may also be used for food storage such as starch.
Source: Videos from class.
The Casparian strip is a waterproof function for plant roots protecting them from unregulated influxes of water and minerals
DeleteThe cortex is the innermost layer of the endodermis and its function is to allow for the storage of and transport of nutrients throughout the plant. It is similar in structure and function to the pith.
DeleteFor your Malic Acid Question in CAMP plants.
DeletePhotosynthetic tissue of CAM plants contains both PEPcase (enzyme) and rubisco (enzyme). During the night, when stomata are open, CO2 is fixed by PEPcase to form malic acid, which accumulates in plant tissues. During the day, stomata close and malic acid breaks down to release the fixed CO2, this is then incorporated by rubisco in the Calvin cycle. Rubisco is activated by light, and has a lower affinity for CO2 than PEPcase.
1) Do some plants have thicker wax cuticles than other ones? If they do, does it give them an advantage in survival?
ReplyDelete2) Have some plants evolved to change the shapes of thier leaves in order to help with water loss
3) How does humidity affect transpiration rates in plants?
4) If there was a sudden rise in humidity in a desert would the plants react postitively or negtively?5) What about if there was a large drop in humidity in a more often humid dense forest?
To answer your third question as the amount of humidity in the air surrounding the plant increases the rate of transpiration decreases, it's easier for water to evaporate into dry air.
Deletehttps://www.usgs.gov/special-topic/water-science-school/science/evapotranspiration-and-water-cycle?qt-science_center_objects=0#qt-science_center_objects
For your first question,
DeleteYes, plants that are in water scarce environments have thicker waxy cuticles through processes of evolution. This indeed gives them an advantage in survival as the thicker barrier and makes it more difficult for water to evaporate. In extremely wet environments, plants may also have thicker cuticles to prevent excess water from entering the cells. A common and well-known example of this quality would be aloe vera plants.
For the second question,
DeleteYes, plants have evolved to change the shaped of their leaves in order to help with water loss. In a study, https://onlinelibrary.wiley.com/doi/abs/10.1111/aec.12474 , scientist measured narrow leaf hop bushes, across south Australia. They had found that leaf area increased by more than 10 times and the specific leaf area of plants more than doubled, this was due to rain fall, temperature and soil.
https://biodiversityrevolution.wordpress.com/2017/06/12/why-is-leaf-shape-important-to-plants/#:~:text=Plants%20have%20different%20shaped%20leaves,leaves%20over%20time%20and%20space!&text=The%20shape%20of%20leaves%20can,is%20referred%20to%20as%20plasticity.
In regards to your fourth question, desert plants have certain adaptations that allow for them to survive in their dry environment. If there was a sudden rise in humidity, this would allow them to collect more water to add to their stores for drier times, which would be a positive effect. Rainforest plants are also adapted to their wet environment but would likely be negatively affected by a sudden drop in humidity because these plants have less adaptations to conserve water.
DeleteWhat is the purpose of the casparian strip?
ReplyDeleteWhat is the pith of the helix in the xylem?
When it comes to drawing the xylem, I am still confused what exactly we need to include.
How does the metabolic rate of the cells in the root cortex affect the movement of water in the symplastic route?
How does the plant determine if the water moves through the apoplastic or symplastic route?
To clarify, water moves up the xylem because of low/negative pressures, not high pressures? How does this work?
A casaparian strip is a band of waterproof tissue thats found on the sides and walls of roots. Its purpose is to help prevent water from entering the pericycle unless its through the cytoplasm. of an endothermic cell. If there was no casaparian strip, there would be no form of filtration of ions and those ions would be able to enter the xylem.
DeleteWater moves up the xylem because of adhesion pulling the water up the xylem to replace the water loss due to transpiration. That creates low pressure.The low pressure generates a pulling force called transpiration-pull that is strong enough to move the water upwards.
DeleteThe pith is also commonly referred to as the medulla. It is a layer of spongy tissue that is made of mostly parenchyma. This part of the plant has evolved to maximize storage. In most plants, the pith is a solid structure within the xylem.
Deletehttps://www.cactus-art.biz/note-book/Dictionary/Dictionary_P/dictionary_pith.htm
To answer the third question,
Deletefor the drawing of the xylem i followed the drawings on managebac and labeled what it had. So I labelled the pit, spiral lignin, annular lignin, cell wall and sieve plate. i also made a separate diagram showing how that water flows
Here is also a really good website that has more drawings and labelled diagrams. https://myflyingboxandme.blogspot.com/2019/12/labelled-xylem-cells-diagram.html
To answer your 5th question,
DeleteI think this article explains the difference of choice very well. The choice is seemingly dependent on where the water needs to go, and how it needs to travel.
https://www.vedantu.com/biology/apoplast#:~:text=In%20the%20symplastic%20route%2C%20the,water%20movement%20occur%20by%20osmosis.
1. Why is the secondary xylem become helical?
ReplyDelete2. What is the shape of the primary xylem structure?
3. How does transpiration and evaporation work with underwater plants?
4. In xerophytes, how is malic acid released during the day?
To answer your fourth question malic acid gets accumulated at night and then becomes decarboxylated during the day in order to release CO2 which is then be used during the Calvin Cycle to make triose phosphate.
Deletehttps://www.toppr.com/ask/question/stomata-can-open-at-night-in/
For your third question,
DeleteSubmerged plants (hydrohytes) actually do not have any stomata. They rely solely on epidermal cells to absorb all nutrients and gases that dissolve in the water. Considering that water fully surrounds them, the plant's epidermal cells would relegate how much water is needed and let in via principals of transport proteins and osmosis. This water would then be used for metabolic processes and photosynthesis.
Source: https://www.wyzant.com/resources/answers/696817/do-aquatic-plants-have-stomata#:~:text=Completely%20submerged%20plants%20(hydrophytes)%20do,gases%20that%20dissolved%20in%20water.
For your second question, according to: https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/30%3A_Plant_Form_and_Physiology/30.2%3A_Stems/30.2C%3A_Primary_and_Secondary_Growth_in_Stems, the primary xylem is actually multiple xylems around the cambium (like shown in the dicot stems) in a half oval shape and the secondary xylem is a ring around the cortex.
DeleteTo answer your first question,
DeleteThe secondary xylem becomes helical because the walls are going through a process of strengthening and thickening, where the structure becomes helical, then scalariform, then reticulate, and finally pitted.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4246902/
1. What is the difference in functions between the primary and secondary xylem?
ReplyDelete2. Is lignin the only molecule that keeps the xylem from collapsing due to the low pressure or are there also other molecules?
3. Can someone explain what cavitation is and clarify its role in the xylem?
For your first question, The difference between primary and secondary growth is that the increase of length of the shoot and the roots is primry. Seconday growth is when theres a growth in thickness of a plant. Primary occurs from cell division in the shoot apical meristem while secondary occurs after cell division in the lateral meristem.
Deletehttps://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/30%3A_Plant_Form_and_Physiology/30.2%3A_Stems/30.2C%3A_Primary_and_Secondary_Growth_in_Stems
Plant cells are constantly being filled with water, which allows them to stay rigid. Plant cells are made of both cellulose and pectin, which prevents them from completely collapsing under the pressure. No, this website is not always the most valid, but the comment is from a scientist and it makes a lot of sense. The comment is also supported by other websites, but I like the way this comment was worded because it is easy to understand.
Deletehttps://www.quora.com/What-prevents-The-plant-cell-from-completely-collapsing-and-how
Cavitation happens as a result of high tension in the xylem causing dissolved air in water to expand and fill the vessels or tracheids. The blockage it creates is referred to as an embolism. For more explanation, here's a website:
Deletehttps://www.biologydiscussion.com/plants/cavitation-and-embolism-in-vascular-plants-with-diagram/22732
1. Can someone explain the physics of "negative pressure" and the associated symbols for pressure?
ReplyDelete2. Are root cells the only plant cells which contain the Casparian Strip?
3. What are the basic physics regarding a plants control over its stomata? How exactly are xerophytes able to control opening their stomata to fit their environment?
Question 2:
DeleteYes, the casparian strip is found only on the walls of the endodermis of root cells.
For your last question, the pair of guard cells that surround each stomata control when the stomata open up. Environmental factors such as time of day, temperature, and CO2 availability are taken into consideration when opening up the stomata. With regards to how the stomata opens and closes, the vacuole size changes have something to do with this as well. Here is a site that talks a lot about this:
Deletehttps://www.nature.com/scitable/topicpage/plant-vacuoles-and-the-regulation-of-stomatal-14163334/#:~:text=A%20pair%20of%20guard%20cells,CO2%20availability%2C%20and%20temperature.
For your first question, plants can use hydraulics to generate force. Plants achieve this because of water potential.
Deletehttp://bio1520.biology.gatech.edu/nutrition-transport-and-homeostasis/plant-transport-processes-i/
Water potential, evapotranspiration, and stomatal regulation influence how water and nutrients are transported in plants. To understand how these processes work, we must first understand the energetics of water potential.
The water potential measurement combines the effects of solute concentration (s) and pressure (p):
Ψsystem = Ψs + Ψp
where Ψs = solute potential, and Ψp = pressure potential. Addition of more solutes will decrease the water potential, and removal of solutes will increase the water potential. Addition of pressure will increase the water potential, and removal of pressure (creation of a vacuum) will decrease the water potential.
Water always moves from a region of high water potential to an area of low water potential, until it equilibrates the water potential of the system. At equilibrium, there is no difference in water potential on either side of the system (the difference in water potentials is zero). In order for water to move through the plant from the soil to the air (a process called transpiration), Ψsoil must be > Ψroot > Ψstem > Ψleaf > Ψatmosphere.
Continue to find more information at the link I sent above. It really does a great job of explaining how it works. Just remember that the more negative the pressure, the more pull of water into that area.
1. What is the pith and its function?
ReplyDelete2. How does the environment effect the xerophytes and how they are able to open?
3. What would happen to a plant without lignin, and is that the only thing that keeps in from collasping?
This comment has been removed by the author.
DeleteFor your first question,
DeleteThe pith is located in the center of the stem and is made of parenchyma cells that can either be undifferentiated (I believe) or specialized for transport, photosynthesis or storage of nutrients throughout the plant. The parenchyma also allows for the xylem and phloem to transport materials between eachother.
I used Managebac and https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/pith#:~:text=3.5%20Myelophagy%20(Pith%20Breeders)&text=Pith%20is%20composed%20of%20undifferentiated,replaced%20by%20woodier%20xylem%20cells.
For your second question,
DeleteThe environment that xerophytes live in contains little water or moisture for them to absorb. So the xerophytes have adapted to these surroundings to avoid drought like having specific seasons for growth. An example is ocotillo plants survive as seeds and grow new leaves when water is available. Other xerophytes have adapted their structure to survive in a drought like growing deep roots to reach water deep underground or having shallow roots to absorb the rare moisture from the air. Some xerophytes even have a high concentration of salt in their cell sap to have low water potential to survive with the low amounts of water provided. There are a lot more examples on the website below. In plants that have Crassulacean acid metabolism (CAM) are able to open and close their stomata. The stoma opens in the night for carbon fixation because the cooler temperature will allow minimal evaporation of the water that the plant needs. This happens because the guard cells are triggered by the conditions of their environment and become turgid.
https://www.saps.org.uk/saps-associates/browse-q-and-a/164-can-you-give-me-some-information-on-xerophytes
This is for the 2nd question that I forgot to add.
DeleteThe guard cells become turgid and open because of the accumulation of potassium ions in them and so the water potential decreases because of the increased solute. This results in water rushing into the guard cell and filling the vacuoles with water to store.
http://www.phschool.com/science/biology_place/labbench/lab9/guard.html#:~:text=Guard%20cells%20are%20cells%20surrounding,opening%20and%20closing%20the%20stomata.&text=In%20figure%20B%2C%20the%20guard,an%20excessive%20amount%20of%20water.
DeleteIn regards to your third question, I am under the impression that lignin is what creates the unique pressure inside of the xylem. Without lignin, the xylem would collapse and the stem of the plant would not be strong.
DeleteIn response to the comment above. The lignin is the strengthening structure that gives the xylem it's strength to prevent it from collapsing under increased negative pressure. Water columns would not be maintained in the xylem without the lignin enforcing the walls.
Delete1. What properties of fungi make it possible for them to help the absorption of water and mineral ions into the roots of plants?
ReplyDelete2. What properties of guard cells allow them to open and close the stomata in leaves?
Bates family = Claire Bates, by the way.
DeleteFor your 2nd question,
DeleteThe amount of water within guard cells determines whether or not the cells open or close the stomata. If the vacuole within the guard cells are full of water, turgor tension will push against the walls of the cells and cause it to form into a bean-like shape, therefore causing a space to open for the stomata. If there is a lack of water in the vacuole, the guard cell will shrink, closing the stomata.
To answer your first question, there is a symbiotic relationship between the fungi and the roots. The fungi increases the surface area of the roots and allows the absorption of more water and minerals. Here is the website if you would like to read more: https://bodell.mtchs.org/OnlineBio/BIOCD/text/chapter18/concept18.3.html
DeleteFor your first question, it's all about surface area. The fungi act as an extension of the root system and increase the surface area that the plant has. It allows the plant to extend into more soil region and access more minerals and water to not only the fungi, but also the plant. It's really all about surface area. The more surface area to volume you have, the better able you are to gather nutrients.
Delete1. What is the purpose of the xylem containing both the tracheids and vessel elements (as they both do the same thing)?
ReplyDelete2. Who came up with the Cohesion-Tension Theory?
For your first question, tracheids only contain pits for water molecules to transport through whereas vessel elements have spaces with pits AND perforations that the molecules can travel through. The main difference for this is because vessels have end plates which contain perforations whereas tracheids do not. This article and picture helped me a lot.
Deletesite:
http://www.differencebetween.net/science/difference-between-vessel-elements-and-tracheids/
image:
https://images.slideplayer.com/35/10448824/slides/slide_26.jpg
For your second question,
ReplyDeleteIt was hypothesized by Dixon and Joly in 1894. I'm not sure why but most websites would not give me their full names.
Here's the website I used: http://www.esalq.usp.br/lepse/imgs/conteudo_thumb/Cohesion-Adhesion-Tension-Theory.pdf
1. how does heat affect the rate of transpiration?
ReplyDelete2. how do fungi help plants absorb minerals?
3. Is cavitation seen in any other situations other than transpiration? (follow up question: can liquids other than water pass through the xylem?)
To answer your first question, heat increases the rate of transpiration because the higher the temperature is the more it will open up the stomatas and allow transpiration to occur. When it is colder the stomatas will close and decrease the rate of transpiration.
Deletehttps://www.usgs.gov/special-topic/water-science-school/science/evapotranspiration-and-water-cycle?qt-science_center_objects=0#qt-science_center_objects
For your second question, fungi can help plants grow and help with absorption of material through their structure. The fungal mycelium has long threads that stretches to distances, so they are able to take in water and nutrients from farther locations. What they are able to take in is then brought back close to the plant's roots, therefore helping plants to grow and absorb nutrients from different locations.
DeleteFor your third question, I have not seen cavitation used in any other way, but I might have missed something. To answer your follow up question, it could be possible but water has the cohesion and adhesion that is needed to go up the sides of the xylem.
Delete1. What is the structure of the xylem vessel?
ReplyDelete2. What does aperture mean?
3. What is the shoot of the leaf?
The xylem is made up of two main things: tracheids and vessel elements that allow the plant to transport water through both pits and perforations. Here is an image that is helpful to look at, as well as a summary on bioninja.
Delete- https://images.slideplayer.com/35/10448824/slides/slide_26.jpg (image)
- https://ib.bioninja.com.au/higher-level/topic-9-plant-biology/untitled-6/xylem-structure.html
For your second question, in botany, apertures are areas on the walls of a pollen grain where there are openings to allow for the pollen tube to pass through.
DeleteA plant shoot can either refer to a young plant that has begin to grow, or can be used to refer to a part of the plant which includes the stem, leaves and flowers. Here is some more detailed info regarding shoots:
Deletehttp://www.biologyreference.com/Se-T/Shoots.html
- What is the main difference between cohesion and adhesion?
ReplyDelete- Why is transpiration crucial to the leaf?
- Do xerophytes store water for later use, or are they accustomed to just receiving less water, therefore not requiring as much as other plants?
- If xerophytes do store water for later use, where and how do they store it?
To answer your first question, basically cohesion is the attraction between 2 molecules of the same substance while adhesion is the attraction of 2 molecules of different substances.
DeleteRegarding question three, it a yes to both statements xerophytes store for later use because of the lack of a constant presence of water. They also cut down water consumption by growing during the rainy season and saving water to hold them over to the rainy season.
DeleteTo answer your second question, Transpiration is important to the plant to produce a cooling effect to the plant at hot conditions and to enable the transport of water and mineral salts from the soil to the leaves
DeleteTranspiration is crucial to plants because it acts a coolant just like sweat in humans also it allows the passive transportation of mineral is and molecules in and through plants.
DeleteTo answer your last question since xerophytes stomates are locked tight in the the day, they fix carbon dioxide into malic acid at night to prevent excess transpiration and perform photosynthesis during the day to keep up with food production with the limited resource of water. As far as storage the "food" is densely packed in thick cuticle boundary to prevent evaporation of said resources. In addition the food storage most definitely has foul tasting and slimy textural defensive mechanisms to prevent herbivorous activity.
Deletehttps://www.ck12.org/biology/xerophytes/lesson/xerophytes-advanced-bio-adv/
1.Scientist have done research on plants that acquire H20 via their leaves in humid environments, what process do these plants do differently and what adaptations have they acquired regarding xylem flow and transpiration?
ReplyDelete2.What would happen to a cactus planted in a rain forest?
3.Are there specific root extension fungi for plants and ones that are more effective in certain environments?
4.How would a plant go about repairing a ruptured Xylem?
To answer your second question, if you put a desert cactus in a rain forest it would drown and die as they cannot tolerate a high level of sustained moisture
DeleteIn response to your 4th question a plant would repair its xylem using the osmotically driven embolism repair mechanism which plants utilize in repairing xylem.
DeleteIn answer to your 3rd question root extension fungi are called Mycorrhizal fungi and are more effective in jungle environments where water and minerals are abundant.
DeleteSorry for the late reply
ReplyDelete1. Is there anyway which the process of transpiration rat can be increased artificially?
2. How are the cell walls thickened in the xylem?
3. What can be the effects of cavitation?
#1 - Light. Plants transpire more rapidly in the light than in the dark. Temperature. Plants transpire more rapidly at higher temperatures because water evaporates more rapidly as the temperature rises. Humidity, wind and soil water also can effect rate of transpiration. This is a Skill that you will need to be able to address within a practical. It is also a good lab to manipulate for your IA's if you're interested in it.
Delete#2 - Cells with secondary cell wall thickening typically contain lignin. Lignin is a chemical substance that resists breakdown. Along with cellulose, lignin gives wood its strength. This allows trees to attain great size. In the proto-xylem, the secondary walls form first as annular and then as helical side walls. This is followed by scalariform and then pitted side walls in meta-xylem. The final stages of meta-xylem formation is scalariform thickening that eventually leads to pitted sidewalls.
3. Cavitation leads to breaking of the xylem water column. This process will stop the movement of water through that specific xylem tube. Too much cavitation within the stem can lead to plant death. Here is an article that talks about plant mechanisms to fix cavitation issues. Really interesting....
https://www.nature.com/articles/s41598-019-46092-0
Sorry for the extremely late reply
ReplyDelete1) Is there such a thing as conditions that are too wet for plants like how Halophytes are plants who survive in salty conditions and Xerophytes survive in dry ones?
2) How is the hormone absisic acid produced? (not why but how)
3) Im also a little confused on the process by which plant cells aquire mineral ions, could you explain it to me.