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February 22, 2010
Quiz 3 feedback
First, remember to go over this material, because quiz questions are a favorite place for getting final questions.
People did fairly well on this, especially considering the difficult material about transport across membranes. Be sure to use your homework and the animated powerpoints to reinforce your understanding and knowledge (and memory) of these topics. For learning this kind of thing, you want to do facts first, then processes.
1. Cl- normally has to be brought into the cell with some kind of active transport, because we are moving a negatively charged ion into a negatively charged cell, where it doesn't want to go. If it is headed out, though, it is usually passive. For the same charge reasons, K+ is usually passively transported into cells.
Glucose, like sucrose, has no charge. If a cell is moving this, it is probably moving lots of it, and so it has to move it actively to get it into a high-concentration area. Cells mostly use sucrose to move sugar around, though, which gets twice the stuff moved in one event.
Nitrate is just like Cl-, and the cell has to move lots of NO3- in (homework example), which uses up a lot of protons for cotransport. Phosphate is just the same--cells have to work to get everything but positively charged solutes into cells.
2. Good job on the cotransport/countertransport question. Remember that no ATP is used directly in the transport process, just secondarily to set up all those H+. These are via symports and antiports.
3. For transport across membranes, all substances have chemical potentials. In the case of water we call it SP, for its effect on the chemical potential, which is expressed as how it is reduced from zero by the solutes. Similarly, all movement is due to differences in the overall potential.
Only charged ions are moved because of electrical charge (electrical potential), and only water uses pressure potential, because the value of this is almost zero for low-concentration solutes.
4. Some common ways plants help take up (uptake is not a verb, however commonly used as such) minerals from soil are H+ excretion to displace ions from soil particles, mycorrhizae to take up P (and other microbial associates for perhaps other things), and excreting enzymes to help with Fe uptake (OK as a noun), which is hard work, as we'll see.
5. I'm sure you studied the Nernst equation, so I had to give you a question (and most people did pretty well). For K+, it moved (in the question), so you know there had to be a difference in overall potential (of K+), which is represented by the Greek letter mu. Mu nought (little zero as subscript), however, is the same for K+ on both sides of the membrane, so it isn't moving anything. Ditto the constants R and F (just like T in the helpful example). Z is also the same on both sides of the membrane, so it, too, has no effect, but I gave people credit for this because of the way the question was stated. It is C (and concentration) and E (charge) that determine how much gets in (and these make up mu). Generally a good job here.
Scores ranged from 18 to 24.
Posted by bergv at 8:44 AM
February 18, 2010
Quiz 2 topics
mineral deficiencies in soil
assistance for roots in getting minerals
P/mycorrhizae experiment
minerals moving in soil & xylem
mineral toxicity
all those ways of getting things across membranes
*active vs passive
*pumps and their characteristics and limitations
*primary and secondary active
*the route
*the energy source
similarities and difference in any of these
how we can tell one from another in the lab
how cells can move solutes "uphill" energetically
the factors of the ECP relationship (conc, charge), and how this compares to water
the names and meanings of the terms (and their parts) in the Nernst equation
how we know if active transport is going on
the numbers 10x = 59 mV
what's important for moving X+, X-, uncharged solutes
how we can tell which way ions will move through channels
how we measure these things in the lab
how solutes get into/out of cells
Posted by bergv at 12:59 PM
February 16, 2010
Feedback from transpiration abstracts
For both graphs and abstracts, there are models in your course manual. Please follow them. I'll have to use less Clairol on gray hair, and you'll get a better grade.
Do present your results of various treatments as a percentage of contro values (8"9% of control value"). This is the easiest for the reader.
Excised leaves were placed in ABA, FC OR water (not and water).
You can be specific in your conclusion--it should line up with your objective, which included the two hormones you tested.
Overall, a creditable first job. See comments on graphs for further feedback.
Posted by bergv at 5:19 PM
Feedback from transpiration graphs
Pretty good job on these graphs. If you get docked for something in your graph title (say, undefined ABA in title), you will not also get docked for it in the abstract title.
For this graph we had 3 numbers, each associated with a different treatment, so it's a bar graph (no top tick marks). The Y axis is Transpiration (mol/m^2/h) [but you should use real superscripts, not the solidus /]. the X axis is Treatment (there are no units), with the specific treatments under the associated bars. Always use standard abbreviations: m means meter, but mol means mole; hr means Henrys, a magnetic term, but h means hour; etc.
For some reason, the plant is known as garlic chives, not garlic chive.
Be careful in terms of consistent use of capital letters. Just because something is important or new to you doesn't mean it should be in caps.
It is great to put the abstract and graph on the same page (ideally abstract first, with graph for further illustration). This saves trees and toner for your grandkids. Write your abstract in Word,and keep that window open along with your SigmaPlot window. Then in SigmaPlot, click on your graph, then Edit/Select All/Edit Copy. Now you can paste your graph into the Word document, and can print it anywhere you can print Word. The graph and abstract each have to have a title (though it can be the same).
It's easy in SigmaPlot to use superscripts and subscripts, though I have to use ^ for superscript here, and haven't a clue about what to use for subscript. If you want, use water instead of H2O with no subscript. For /sq. m use m^-2, and for /h use h^-1. This was originally demanded by journals because the typesetting was easier, but is pretty much universal in the classier journals now.
Posted by bergv at 4:26 PM
February 15, 2010
Root growth
One of the things that you have to do for your G&D project is to determine where the growth takes place on roots of corn & beans (just the main root). This is a 24-hour project, with a photo at the beginning and one at the end. You'll have to put dots on the roots, then use ImageJ to analyze where the growth takes place. There are unbeautiful diagrams in your lab manual. (You could read through the project in your lab manual any time now.)
The roots will be ready for marking Wednesday or early Thursday--I have already started them in the lab, just to make your lives easier.
We will have a similar round of growth on corn and bean stems and leaves a little later.
Posted by bergv at 2:11 PM
UNIPlantCam
Now that we've figured out how to focus the camera manually, the pictures should be excellent. Remember that you will be cropping out most of the frame.
Remember that you are grabbing your pictures of seedling G&D from these images. You should be able to play movies eventually, and students in the past have been surprised to see what they revealed.
We will be growing the corn for about 10 days, and then beans for a little longer. We'll keep them alive after we finish the pictures, so you can be amazed at the further growth.
Posted by bergv at 1:37 PM
Round 3, feedback on test 1
Sorry I didn't get to this earlier.
I was pretty pleased with the scores on this test, with scores (including bonus points from labs) from 60 to 96. It's fairly common for someone to do badly on just this first test.
Do remember that I drop the worst unit test score (all 4 quizzes count as 1 test) and substitute the average of all the test scores (not including the final). This buffers a person with a single bad (or good) test, but does not affect someone who is an even, steady performer (good or bad).
I encourage you to go through your tests with the feedback (sections 1 and 2) in hand, and to ask me about anything that doesn't make sense. I'll be in the lab room (75) Monday from about 1-3 (though 2-2:30 might find me in the Biology office, where you are welcome to come get me), and Tuesday from about 1 to 1:45 (class 2-3:15). Then Wednesday we'll have lab.
You can look at your test any time I am there to get them for you.
I also hope that you'll sit down with me and go over your project to date.
Posted by bergv at 1:28 PM
February 9, 2010
Feedback from test 1, part 2
Continued, as promised.
5.Pressure potential changes quickest in xylem, and is still the primary thing that changes in live cells. The live cells shrink a little bit as water is lost, so solute potential changes a bit (maybe 10%); xyem cells hardly change volume at all, so they don't change solute potential. For soil, the action is almost all in the matric potential. 6. Very like the homework--you should all have done well. Remember that live cells have to have non-negative pressures, and that wet things have zero matric potential, and you've got most of it.
7. A cell in a solution for a long time will come to equilibrium with the solution, in this case -5 bars. If it is just barely plasmolyzed (stable condition), it has a zero pressure potential. So WP=SP=-5, rest =0.
8. Water under tension: German picric acid experiment, poking hole into tree and letting dye go in both ways, cutting branch under dyed water, direct measurement with pressure probe (UNI grad!), sounds of air entry...and more.
9. If you put tissue into concentrated solutions, the tissue will lose water to the (lower water potential) solution and become flaccid. In contrast, dilute solution will donate water to your tissue because the tissue has the lower water potential...and the tissue will get a little bigger. Some people are still wedded to the idea that just solute concentration (pretty much tied to solute potential) is the only thing moving water, and gave an explanation based on this, despite the fact that the question asked for water potential differences. There is an extra penalty for these people: a brief "quiz" (not graded) that shows how you get the wrong answer in many cases if you ignore pressure pushing or pulling the water. Animals mostly don't have much pressure (though blood pressure is pretty important), but plants have lots. This is a case of learning the "junior" version of something, a simplified version, and having trouble finding room in the brain for the "senior" version, which includes more factors.
10. Positive pressure situations: guttation, maple sap "running", vines in spring refilling xylem. In the first and third cases, solutes, combined with lots of water and no transpiration, results in water entering the xylem (and not leaving, thus the pressure). In the maple sap situation, water in the ice (requires below freezing) in the twigs melts (requires above freezing), and goes into the lower water potential cells and xylem. Maples have lots of sugar in early xylem, and unusual condition.
11. xylem would be very likely to have -1 bar PP and SP. A live cell couldn't have the negative PP, and soil couldn't have any PP except zero. This situation would be likely to occur with saline soil and lots of water in the soil (WP=-2 bars).
12. Stomatal opening is the overwhelming factor controlling transpiration. Other things may have indirect effects..but mostly they dry out the plant enough to get it to close the stomates..
13. If you are in a walll, you are in the apoplast. If you are in the xylem, you are in an apoplast. Only in cytoplasm (including plasmodesmata) are you in the symplasm. Dr. Gerrath told me that the reason cells form plasmodesmata rather than pinching off into two separate cells is that there is lots of ER in the middle, where the cells are pinching off, and it gets in the way of the pinching off.
14. Capillary action hold water in gaps or pores or flaws in cell walls, so air can't enter. It does not lift water up trees. Many people branched off into explanations of adhesion-cohesion theory or other things. The polar nature of the molecule is responsible for the cohesion. For the part of the wall that isn't pores, we need adhesion. The pores/gaps/flaws in the wall is the only place where capillarity acts. But generally, people did well on this difficult concept, even if there was a bit of (well, a lot of) DNAQA (does not answer question asked.
Posted by bergv at 8:59 PM
Feedback from Test 1, part 1
This is where you get feedback from the tests, potentially useful considering my favorite source of final topics is the unit tests (though there is a topics list for the final).
1. Walls and membranes are quite permeable to water, but only walls are generally and unselectively permeable to solutes (how solutes get through is next in the class). Remember the sewn model in class? One of the objectives was to show that most wall material is quite flexible (like membranes). In woody plants the wall is thick, and therefore rigid, but this is not generally the case. Walls are strong (we build our clothes and houses out of them), but membranes are flimsy. Both walls and membranes are needed for turgor pressure to develop (water and solutes, too).
2. The most popular example of bulk flow was xylem sap in the xylem (various parts specified, all right. It is a great way to move lots of solution fast and far. Various cell-to-cell (one of these could be xylem) movement through a membrane provided good examples of osmosis, which has the advantage of selecting (and largely excluding) solutes while allowing water (never in excess) to move.
3. The matric potential (of water) is extremely low (very negative) in dry hydrophobic substances such as peas and clay. This is what makes clay soil hold on to its water (even against pull from plants), and causes seeds to imbibe water.
4. There are basically three common ways in which tracheids or vessel elements develop embolisms. The first is by air pulled in through flaws in the cellulose walls, and the second is by the water column actually breaking from being pulled too hard (perhaps around some flaw in the wall that disturbs some of the bonds with the water molecules). The third method, largely (but not totally) restricted to vessel elements, is through the expansion of embolisms in nearby cells.
*****
outside pages graded first, then inside
****
15. Water movement would increase through an endodermis without Casparian strips, because the water could go through the usually lower flow resistance of the walls...or through both walls and membranes, which would have the lowest resistance of all.
Minerals would also move more through an endo without the strips, because they could move only through the membranes, which are highly selective and limited in how fast they can transport solutes.
16. A leaf has an axillary bud right where it joins the stem. A simple leaf has one at the base of the petiole of the single blade, while the compound leaf has where the whole leaf (many leaflets) joins the stem.
17-18. Most people got these...look them up in the notes if you need further information. Be specific..this is a physiology course.
19. Killing creeping charlie but not grass with borate takes advantage of the different tolerances of different plants. CC is very sensitive, so it dies with a small dose, but grass is less sensitive, so as long as you don't overdo it, you'll end up with a grass lawn.
20. Fertilizing houseplants with macronutrients is unlikely to harm them (as long as you don't kill them osmotically, which is hard). But if your fertilizer has micronutrients, then you could easily damage the plants. At first they would get better, but then as the micronutrients in the soil build up to toxic levels, you would see toxicity symptoms.
More coming later.
Posted by bergv at 2:27 PM
February 8, 2010
Lab handins for Wednesday
A couple points for those preparing their graphs for Wednesday (and all of the material is due W, not M): Our results consist of just 3 numbers (converted to the right units, of course). The X axis is the treatment, so what we have here is a bar graph. Just put the treatment labels in col 1 and the rates in col 2.
For your abstract, the best way to look at your rates is to take the control as 100% and have treatments that transpired less than that as being less than 100% (say, 75%). Similary, those that transpired more will have numbers more than 100%. This way a hurried reader will not make the mistake of seeing "60% less than" and bigger than "20% more than".
I should be in the lab T afternoon until my class at 2, then briefly after class gets out at 3:15.
Posted by bergv at 1:44 PM
February 3, 2010
Rest of test topics
Macronutrients and how they are used by the plant
Examples of micronutrients and how they are used by plant
Essential minerals
Ways we study mineral nutrition
mineral deficiencies, sufficiency, toxicity
soil particles/soil particle surfaces/water/plant--the route of uptake and resupply
all labs
favorite WR stories
Posted by bergv at 8:40 PM
February 1, 2010
Most topics for Test 1
Properties of liquids and solids
Adding negative and positive numbers
Bulk flow vs osmosis
Cell wall vs membrane
Pressure potential
Solute potential
The Water Potential Equation (write it out on test)
Osmotic pressure vs osmotic/solute potential
Evidence for water under tension
All labs to date (lab skills, plant parts, tissue & cell water relations, not G&D or computer skills)
Water loss/gain between cells, cells & solutions
Matric potential
Normal values of water potential factors and WP in plants, soil, air, seeds
Why live cells don’t have negative pressures
Gravitational potential
Xylem structure & function
How air/soil drive transpiration (numbers here)
Capillaries in holding water in xylem wall pores
Embolisms formed by air entering xylem through these pores
Transpiration (geography, biology, chemistry, physics)
Why don’t plants dry out in the air?
What controls stomatal movement (3 things)
Wilting (“permanent,” “temporary:” what, how different)
Why water goes into cells
Guttation
Root pressure
Maple story
Hydraulic lift
Favorite water relations stories (download)
Mangroves
Osmotic adjustment
Refilling embolisms
Hydraulic lift
Apoplastic, symplastic and transcellular water paths
Apoplast (2 parts)
Symplast
Endodermis (location, structure, function)
What the endodermis does for the plant
Route of water flow through root into xylem
Factors that determine water uptake
How the plant controls its water loss
What plants are made of
Macronutrients and micronutrients (start of latter)
(last class not included: it will be listed Wednesday or Thursday)
The best small thing you can do for your studying for this course is to go through the notes as you go along, listing the important topics and points as you go. I make up the test from my list.
Posted by bergv at 1:36 PM
Project Submissions
Here are some hints for you, based on what was turned in so far:
You will need a title page with the project title and your name and class and date. Now is a good time to make this. You can use the same one (except changing the plant) for corn & for beans, although if you want a fancy background, you might want to change it, too.
No pictures from sources other than your own plants are allowed (i.e., no web pictures).
If you want very early pictures of the inside of seeds, you can soak them for a day (any temperature will probably do, and split or cut them apart.
Use the web for labeled images to learn from. You probably want about 7-10 parts labeled on corn, and maybe just a couple fewer on beans.
Label things only once, when they first appear. Just label visible things, not things inside.
No narration is needed now, but you will need it at some time, so now wouldn't hurt. You can always change it later if you want.
You'll need those weights some time soon.
Crop out the ruler if possible, or put areas of copied background over it.
If you have further questions, just ask (or email), and if the questions seem of general interest, I'll post them (no names) and the answers here.
Posted by bergv at 1:25 PM
First test coming up
People are always curious about test structure, so here it is...
20 questions of equal value, though some are longer or more difficult than others.
Every kind of question: multi-sentence explanations, single sentence interpretations or explanations, similarity/difference, what if?, fill in blanks, matching, multiple multiple choice (check all that are true). No definitions.
You should have done a lot of your test studying over the weekend. If not, start today. See the web material (class website) for extra ideas. Remember to ask and answer questions, not just repeat and recite from you notes. You aren't parrots.
More here later today.
Posted by bergv at 8:39 AM