Weds. 10:25 - last posting, see you tomorrow

42. can you please explain the tea bag example as it
relates to the spongy mesophyll and transpiration.

42 The tea bag is just a model for the spongy mesophyll cell - a wet teabag on a plate is like a spongy mesophyll cell in contact with the internal air spaces.

41. what does the pericycle tissue do and what types of cells make it up? are they
alive when functioning or not?

41, The pericycle is made up of only parenchuma cells - living parenchyma cells, we did not talk about its function in this course - water flows through it and it is a source of branch roots.

40. what is the casparian stip?

40. a ribbon of suberin (wax) that fills the apoplastic pathway between root endodermis cells.

39. how much do we need to know about the precise placement of pollen on animals

39. just the definition of precise placement

38. Is it impossible to have both short and long styled flowers on the same plant?

38. Yes.

37 Would I be correct in assuming that pollen is a generative cell that lands on
the stigma, and that it matures into sperm as it works its way down the style?

37 Not quite - the pollen is a generative cell plus the tube cell that surrounds it, and the generative cell divides by mitosis to make the two sperm.

36 Do we only need to know the characteristics of hummingbird and bat pollination
syndromes?

36 Yes.

35 What are the terms for variation in pollen flow and distribution of stamens and
pistils in flowers and on plants?

35 The words you need to know are outcrossing, selfing, monoecious, dioecious, perfect, and imperfect

34. What do you mean when you say that the traceary elements are dead when they
function? How is that possible?

34. They are like pipes - the water flows through what amounts to the skeleton of a formerly living cell.

32. Does the ovule become the seed and the ovary the fruit? And is that what
we need to know about the fate of these components?

32. Almost - remember that the seed coat comes from the integument and the nucellus together.

31. What are the components of the vascular cylinder and their functions? Is
that the xylem, phloem, pericycle?

31. Yes - but learn the functions of the cell types, not the tissues.

Weds 1010 P.M.

30 What type of cells make up the cortex?

30 Parenchyma

29 What type of cells make up the endodermis between the casparian strips?

29 Your question doesn't make sense, but I can tell you that endodermis cells are parenchyma cells.

28 Are there any pericycle cells located outside of the endodermis in the cortex?

28 No, there arne't even any in the endodermis.

27 What type of cells make up the epidermis?

27 Parenchyma.

26 Is the structure of the epidermis in the root and leaf similar, except for the
addition of stomata and cuticle to the leaf epidermis?

26 Yes, ignoring the root hair in the root.

25 What are the structural features of the guard cells?

25 chloroplasts and differentially thickened cell walls

24 Could you explain the key points of the cohesion, adhesion, transpiration
theory that we should be familiar with?

24 See question 11 on line.

23 Could you explain the significance of the tea bag analogy?

23 The wet tea bag on the counter gives you a sense of what the spongy mesophyll cell is like, being in contact with the internal air spaces.

22. i just have a question about the first sample question
for test four.
the question is which is not part of the symplastic?
and plasmodesmaata is a choice and in my notes i have
that plasmodesmata is the passagewasy between cells
why is that not the answer? i understand that the
cell wall is a part of the symplast but the
plasmidesmata is also part of the apoplastic route right?

22. No, the plasmodesmata are what connect the symplstic route from cell to cell, because they are tunnels of cytoplasm that connect cells.

21. Hi. Could you tell me what the difference between the apoplastic and symplastic pathway are, and the role of the plasmodesmata?

21. The apoplastic route lies outside the control of the cell membranes - between cells and within cell walls but outside the cell membranes - the symplastic route lies within the cell membranes; it is continuous between adjacent living cells because of plasmodesmata, which are tiny cytoplasm tunnels between adjacent cells.

20. Number 17 on the practice exam. I understand why a is correct, but why not d?

20. Nuts - the answer IS d, not a.

19. What is sporopollenin?

19. Not in lecture, not on this year's exam.

18. What is plantain?

18. not in lecture, not on this year's exam.

Weds., May 11, 930 P.M.-

17. when water is moving through the tracheary elements, which route is that
considered

17. The apoplastic route, because it lies outside the membrane-bound living body of the plant.

16. How is the potassium ion involved in the opening and closing of the stomata?

16. The pumping of potassium ions into the guard cells brings about osmotic water flow into the cells - this increase in the number of particles in these cells leads to their expansion, and the variation in cell-wall thickness means these cells bend as they expand, opening the pore.

15. Could you also explain the signifigance of the proton pump in nutrient uptake?

15. I didn't teach about the proton pump, only the potassium pump, which uses energy to move potassium ion towards the side of the membrane with a grater concentration of potassium ion.

14. what does the spongy mesophyll do?

14. gas exchange and a little photosynthesis

13. what is the fate of the components of the ovary and the ovule in the
fruit and seed?

13. ovary becomes fruit
integuments and nucellus become seed coat
zygote becomes embryonic sporophyte
first endosperm nucleus becomes endosperm tissue
female gametophyte is dismantled and reused

12. how do perfect flowers separate stamen and pistil function in space
and time?

12. This question covers the whole territory from maples to foxgloves - such examples as heterostyly related to separation in space; foxgloves separate sexes in time. So you need to know how each of these plants promotes outcrossing.

11. I have a quick question for you, you indicated on the study guide that we
should know the cohesion-adhesion-transpiration theory and I was wondering if
you could give a brief overview of this concept, as well as how it relates to
the lifting of water from the spongy mesophyll cells.

11. The key is the evaporation of water from the spongy mesophyll cell walls. This evaporation decreases the volume of liquid water in the plant body, but the water, being cohesive and adhesive, clings to the cell wall cellulose fibers. This creates a tension, which the system seeks to relieve by lifting more water up into the plant trying to return the volume to the original.

Weds. May 7 11 AM.

10. In question #35:
Where is pollen from a long-styled flower deposited on a bee? The answer is on
her mouthparts.
I thought that in a long-styled flower the bee would need to stick its head
into the flower to reach the stamen that's hidden, and therefore the pollen
will be deposited on her head and in the case of the short style flower the
pollen will only be deposited on her mouthparts because the stamen is at the
top. Can you explain this?

10. She doesn't stick her head in the flower, just her mouthparts. The mouthparts carry th epollen load from the long-styled flower. The short-styled flower, with anthers protruding, place pollen on the bee's head.

9. I also want to make sure I understand the numbers of mitotic divisions:
The male goes through 2 mitotic divisions from spore to sperm?
the female goes through 3 mitotic divisions from spore to mature gametophyte?

9. You are right on both counts. The second mitosis of the male gametophyte happens in the pollen tube as it is growing down the style.

8. How much do you want us to know about the design and function of the endodermis?

8. Know how the water is channeled - know what suberin is and where it is located, know how it interferes with water flow.

7. what are the functions of the tracheary element?

7. Two: structural support and transport of water.

6. what specific parts of the cell wall do we need to know?

6. That the primary wall is made of cellulose fibers, while the secondary wall is made of cellulose fibers and lignin. Also know how lignin changes the ability of water to flow through the cell wall.

5. for the interior architecture of the leaf, do we just need to know the palisade parenchyma and the spongy parenchyma?

5. You need to know the stucture and function of both layers of the mesophyll.

4. What specific layers of the leaf do we need to know?

4. Also know the feature sof the epidermis and its included guard cells.

3. is the spongy mesophyll the same thins as the spongy parenchyma?

3. Almost. Mesophyll is a region, and spongy mesophyll is a tissue. Parenchyma is a cell type.

2. In question number 13, why do palisade cells shade
choroplasts? don't the chloroplasts want sun?

2. Yes, but not too much - remember that the chlorophyll is senstivie to heat and so must be cooled off reguarly by shading if it is to continue to function.

1. also, are the pallisade cells in the epidermis? if
not where are they?

1. The palisade parenchyma is the upper layer of the mesophyll, which is the leaf layer inside the epidermis.

Thurs. 10 PM

33. Are all cells in the xylem dead?

33. No, just the tracheary elements and fibers - the parenchyma is alive.

32. Are all cell in the vascular cylinder dead?

32. Vascular cylinder has three kinds of dead cells, tracheary elements, xylem fibers, and phloem fibers. All the other cell types are alive.

31. what is the difference between imperfect and perfect? and can you re-explain
monecious and diecious? ( and which is which....)

31. Perfect flowers have both stamens and pistils; imperfect flowers have one or the other.

Monoecious plants have both kinds of imperfect flowers.

Dioecious plants have two kinds of plants, both with imperfect flowers. One kind of plant has only female flowers, the other has only male. Our species is dioecious by this definition.

Thurs. 830

30. Sorry to be so last minute but I was just wondering about a couple things...
The practice exam indicates that the fundamenatl difference between tracheids
and vessel elements is the primary wall. But they both HAVE primary walls,
right? The difference is that in the tracheids it's not pitted, and in the
vessel elements it is?

30. Well not quite - in the vessel elements the primary wall has perforations, in the tracheids it is continuous.

29. Also when is the second mitotic division in the male angiosperm reproductive
cycle? The only one I have is when the microspores develop into the tube cells
and generative cells.

29. The second mitotic division is in the production of the sperm from the generative cell.

28. Likewise, when are the second and third mitotic divisions in the female? The
only one this time is between the megaspore stage and gametophyte.

28. To get eight nuclei in the mature female gametophyte, starting with one megaspore, you need three mitotic divisions.

27. Finally, in reference to question 1 (from the practice exam), how is the cell
nucleus involved in the symplast?

27. Since the nucleus is inside the membrane system of the cell is must be part of the symplastic route.

26. do vessels have perforations everywhere but their very ends?

26. yes - because each vessel element in the interior of the vessel has perforations at the top and bottom - the bottom and top cells of the whole vessel are closed at the exposed tips.

25. the cell wall is not a barrier to water during from cell to cell
movement...does this include both the primary and secondary cell wall?

Good question - no, because the portio nwith secondary wall is impervious to water because of the lignin.

24. Also, can water move freely in and out of even the cell membrane, its just that the
dissolved substances can't?

24. Correct.

23. the slide says that there is a double fertilization...i though that the fusion
of the sperm with the polar nuclei was not a fertilization. please clarify.

23. This is exactly correct - the second fusion, of the other sperm with the two polar nuclei, is no actually a fertilization, so the slide is wrong.

22. are chloroplasts contained only in the spongy parenchyma layer or are they also
in the palisade parenchyma?

22. They are very much in the palisade layer, four or five times more than in the spongy layer.

Thurs. 6 PM

21. Does the nucellus derive from the megasporgangium in the angiosperm, as it
does in the conifer? When?

21. The nucellus is the megaspoangium.

20. The female gametophyte in the angiosperm has 8 nuclei.
How many cells are in the female gametophyte of the conifer? 100s
How about in the male gametophyte of the conifer? 4 at dispersal
Do they have more cells than in the angiosperm? yes

19. Is the growth of the pollen tube into the style considered active
fertilization, (as opposed to the passive movement of the sperm in the conifer)?

19. you should compare passive movement of pollen on the pollen drop to pollen being carried by wind or animal to the stigma - both are passive.

18. Are pollenators on the flowers to eat the pollen (because of its nutritional
value), or are they there for other reasons?

18. Usually they are there to eat pollen (bees bats) but hummingbirds and sphinx moths just drink nectar.

17. Did you cover protogyny? No.

16. Why are tracheids pointed? So they fit together.

15. Still confused about H2O evaporating into airspaces. Does water leave
through the stomates as a vapor? Yes.

14. In practice test question #36, how is outcrossing possible if pollen is
moved by illegitimate union?

14. If the pollen moves between two different plants that both have the same style length in their flowers.

Thurs. 525 PM

13. My friend and I were wondering what makes the Caspian Strip... We know that it
blocks the apoplastic route and is made of wax.... but why would a plant need
to do this?

13. The wax plugs the apoplastic route with wax (suberin) in the endodermis layer to keep things it doesn't want out
of the vascular cylinder. (Since the symplastic route requires crossing membranes the plant controls wverything
that goes through this route.)

Thurs. 340 PM

12. what primarily controls water flow into the vascular cylinder? (ie, the endodermis cell membrane or the vascular cylinder cell membrane)

12. The key control is the membrane of the endodermis layer

Thurs. 1 PM

11. what is the difference between the pericycle and parenchyma cells? is the
pericycle made up of parenchyma cells?

11. Yes.

10. Is the porhyrin ring the only functional part of the chlorophyll (capturing
light and making sugar in photosynthesis.)?

10. No, the long tail has a function too, which is anchoring the molecule in the thylakoid membrane.

9. Question 2: Regarding the endodermis, is all we need to know that the
endodermis controls what gets into the vascular cylinder, and the casparian
strip is made out of a wax known as suberin that keeps fungi out, and the right
balance of nutrients in?

9. This is pretty close, but the key with the casparian stirp is that it blocks the apoplastic route but not the symplstic route.

8. on the study guide you say we need to know the
structure and composition of the cell wall. do you
mean the secondary cell wall or both? and what is the
structure and compostion of the two?

8. Yes, know that the primary wall is only cellulose and the secondary wall is cellulose and lignin. Also know that pits are holes in secondary walls and perforations are holes in both, only in vessel elements.

7. I have a question on number 17 of the practice exam. Am I correct to say that the apoplastic route of water flow
is between the cell wall and the cell membrane? Also, am I
correct to say that the cell wall lies exterior to the cell membrane. Also, that the cell wall is less selective about
what gets through from the soil to the interior, where then it
must pass through the cell membrane, which is very selective, in order to flow in the symplastic route? If I am
correct with these statements, then the answer to 17 should be
b, not a. B states that the cell wall lies interior to the cell membrane, and that is NOT and characteristic of the cell
wall. A states that the cell wall is part of the apoplastic
route, and this is a characteristic of a cell wall, because it is one of the borders to the apoplastic route.

7. Same question as below: I assume you mean question 7 - You are right - the answer is b, sorry.

I'll change the web version.

Weds. 10 PM.

6. Could you please explain what is the difference between tracheary element and
vessel element?

6. A vessel element is one kind of tracheary element - the kind with perforations.

5, Could you please clarify for me the following questions from the practice
exam?

1. Which of the following is NOT part of the symplast (internal pathway)?
a. cell wall
b. plasmodesmata
c. cell cytoplasm
d. cell nucleus
a
Do you not have to move through the cell wall in order to flow into a cell?
I thought the answer would be (d)since I think that entry into the nucleus
is highly regulated and might exclude even the symplastic pathway.

Once the water is in the symplast, it does not cross through cell walls to stay in the symplast, it goes through plasmodesmata, which are holes in cell walls lined with cytoplasm.

7. Which of the following is NOT a characteristic of cell walls?
a. Cell walls are part of the apoplast (external water pathway).
b. Cell walls lie inside the cell membrane.
c. Cell walls are made of fibers.
d. Cell walls allow passage of most compounds through
a
Doesn't the apoplastic pathway flow between and through the cell membrane?
I marked (b). I thought the cell wall was the exterior layer of the cell.

No - the apoplastic pathway reaches to but not into or through the cell membrane - it's everything ouside of the membrane system.

17. What do guard cells have that other epidermis cells do not?
a. chloroplasts
b. thickened cell walls
c. capacity for shape change
d. all the above
a
My notes indicate that guard cells have all of the above.

Whoops - the key is wrong, you are right.

36. Which of the following is possible if primrose pollen is moved by
illegitimate union?
a. selfing
b. outcrossing
c. selfing or outcrossing
c
How does outcrossing occur if pollen is moved from the stamen of a flower to
the pistil of that same flower? Isn't that part of the definition of
selfing?

Illegitimate union is between a long stamen and a stigma on a short style or vice versa - this can be on the same or different plants.

4 Also, can you explain the serial homology of pistil/stamen to leaves and
shoots?

4. No, I can't explain it the way I might the origin of the integument from a group of branches. The contention exists without high-quality support.

Wednesday April 30 - first answers:

3. Could you please explain to me the significance of the palisade mesophyll being
elongated?

3. The palisade layer is elonated so that chloroplasts can be rotated in and out of direct sublight. The chloroplasts need shade so they don't heat up too much - if they heat up too much the chlorophyll will become non functional.

2. Also, in flowering plant reproduction: Can you explain why there
are 2 fertilizations?

2. I can't explain why, except that the fertilizations yield two different things, one yields the embryo and the other yields the endosperm.

1. What is the function of Tracheary elements?

1. Tracheary elements have two functions, structural support and transport.