Second Plant Lab:  Angiosperms, Vascular Architecture, Secondary Growth, and Review

MiraCosta College

Biology 202

This is the second two lab activities dedicated to plant biology.

Today's activities:  I found a couple more of those goofy PowerPoint slide shows that pertain to last week's lab.  The pictures are a little different and there are no "prompts," so it would be a good review, while it throws in a few more things that we didn't get to talk about last week.

The main objective for today is to survey some of the anatomical and physiological aspects of plant vasculature--a lot of xylem and phloem talk.  We'll survey the angiosperms first, then look at the roots, stems and leaves of monocots and dicots, paying attention to the location and layout of the various vascular elements.  The last issue--kind of a fun one for me--is the structure of wood, which is the product of plant secondary growth, i.e., in girth as a tree grows thicker.

Slideshow A.  Click HERE.

[This shows some photosynthetic eukaryotes that we didn't get to see last time, and it shows three levels of multicellularity in green algae.]

Slideshow B.  Click HERE.

[This is another slide show with mosses, liverworts, ferns and horsetails.  Use this to test yourself at identifying these basal plants.]

Slideshow C.  Click HERE.

[This is another show with gymnosperms.  Another opportunity for self-test on last week's content.]

Slideshow D.  Click HERE.

[This is a show surveying the different groups of flowering plants.]

Slideshow E.  Click HERE.

[This show overviews the general vascular architecture of dicot and monocot (and to a certain extent gymnosperm) stems, roots and leaves.]

Slideshow F.  Click HERE.

[This short show covers the issues of plant secondary growth and the structure of wood.]

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Lab Objective questions:
1) Why is the Gymnospermae a paraphyletic taxon?  What group of gymnosperms is most closely aligned with flowering plants?  Which group might be second closest, and what non-molecular character states can we use to unite these groupings?
2)  Which types of flowering plants are "basal" to the angiosperm portion of the tree of life?  Why is inappropriate to identify these plants as "dicots"?
3)  What are the main characteristics that distinguish monocots from dicots?
4)  What are some examples of representative monocots?
5)  What is the difference between tracheids and vessel elements?  What kind of plants have vessel elements?
6)  In tissues where xylem is composed only of tracheids, how do individual tracheids "communicate," i.e., pass xylem sap from one to another?
6)  Why are mature xylem vessels A) nonliving and B) heavily reinforced?
7)  In what sense are phloem vessel elements A) living cells (in contrast to xylem vessel elements) and B) necessarily continuous with each other via the pores in the sieve plates?
8)  In the vascular bundles of stems, how do monocots and dicots differ in the "layout" of xylem and phloem?
9)  In the vascular core or stele of the root of a dicot, how does water pass from the soil into the xylem?
10)  Where is the endodermis in the root of a dicot, and what doe it "do"?
11)  In the layout of a typical dicot leaf, what are the two "layers" of mesophyll cells, and how are they different in appearance and function?
12)  What is the vascular cambium, and where does it occur in the vascular bundles of a dicot?
13)  How does the "vascular bundle" layout of a dicot stem meld into the "vascular ring" layout as the plant matures into one having woody stems?
14)  How does continual production of xylem and phloem from the vascular cambium result in secondary growth in the case of a dicot plant?
15)  In woody plants growing in seasonal climates, what do the growth rings represent?
16)  Axillary rays are what you see running perpendicular with the growth rings in the wood on the back of a violin (this is the "fiddleback figure").  How must the maple trunk be cut in order to produce a board that can be used to make the violin back?
17)  What is the difference between "hardwood" and "softwood" (and it has nothing to do with the hardness/softness!)?
18)  Genetically engineered Douglas fir will grow to harvestable size in half the time relative to natural stands of Douglas fir.  Boards (e.g., two-by-fours) cut from such wood is substantially weaker than boards of the same dimensions cut from natural trees.  Why?