LABORATORY 9

GYMNOSPERMS & ANGIOSPERMS

LEAF TISSUES AND TYPES

 

Tracheophytes are true vascular plants meaning that they possess both xylem and phloem and have true roots, stems, and leaves.  Last week you studied the primitive tracheophytes which means that they produced no seeds.  Tracheophytes, which produce seeds, are called spermatophytes and include both gymnosperms and angiosperms.  Gymnosperms are much older evolutionarily speaking than angiosperms and they lack the enclosed chambers or ovaries in which the angiosperm seeds develop.  Angiosperms also produce flowers to attract pollinators, fruits to ensure seed dispersal, and a “packaged” seed complete with plant embryo to improve the likelihood of success.

 

The largest group of gymnosperms is division Coniferophyta.  This taxon of conifers is named for the reproductive structure of these plants, the cone.  Most conifers are evergreen and include firs, spruce, hemlock, pine, yews, junipers, cedars, cypress, redwoods, and sequoias.  Conifers are xerophytes.  Xerophytic plants are adapted for dry climates. Based on their storage of water, plants are otherwise described as hydrophyic or mesophytic.  In this lab, you will compare the photosynthetic organs, the leaves, of a xerophyte and a mesophyte.  Make a point of contrasting these two leaf types in your laboratory report.

 

DIVISION CONIFEROPHYTA

 

Examine the prepared slides listed below.  Compare the microscope images with those in your Photographic Atlas and your text. In your pre-lab write up, use a compass or circular object to draw a circle representing your microscopic field for each of the slides listed below. Beneath each circle identify the plant specimen or tissue illustrated, the power of magnification used, and the type of section (c.s., l.s., etc.)  Look up the page number for each reference below and record in the appropriate space below.

 

1.    Pinus staminate slide - Atlas page __, Figure ___

     This is the male cone, also known as the microstrobilus.  The miscrosporophylls possess microsporangia in which microspores are produced.  The microspores mature in male gametophytes or pollen grains.

     Sketch the staminate cone or microstrobilus and label the microstrobilus, microsporophylls, microsporangium, microgametophyte, and pollen grains. Determine the N number of each of these structures and write the N number beside each label.

 

2.  Pinus ovulate slide - Atlas page ___, Figure ___

     This is the female cone also know as the megastrobilus or ovulate cone.  Analogous to the microstrobilus, the megastrobilus possesses megasporophylls which bear megasporangia in which the female gametophytes, the ova, are produced.  Sketch the megastrobilus and label the integument, megasporangium, megagametophyte, archegonium, micropyle (little gate).  Determine the N number of each of these structures.    

         

3.   Pinus larico leaf  slide - Atlas page __ , Figure _____

     Sketch and label the stoma, endodermis, mesophyll, epidermis, phloem, xylem, resin ducts. What is the function of each of these components?

 

4.    Herbarium specimens - Examine the herbarium specimens showing staminate cones and ovulate cones.  Compare the various cones. Note the differences in size, the location of the cone on the branch, and the structure of the cone.

 

DIVISION ANTHOPHYTA

    

Anthophytes are flowering plants. They are the most diverse of all plant forms with more than 235,000 species now classified compared with just over 700 species of gymnosperms.  We are dependent on these abundant organisms for many essentials:  oxygen, food, building materials, textile fibers, medicinal preparations, cosmetic preparations, soil formation and soil protection, etc.  In this lab, we will focus on leaf structure and consider the two other prominent plant organs, the root and the stem, in the next lab.  

 

1.    Ligustrum leaf  slide - Atlas pages __, Figures ____and Figure ___ on page ___ of your text. 

Sketch the cross section and label the following: the upper and lower epidermis, palisade and spongy mesophyll, bundle sheath, xylem, phloem, and trichomes.

 

2.    Tradescantia  slide - Atlas page ___, Figures _________ and Figure ____ in your textbook. 

Sketch the surface view of this common mesophytic leaf.  Label the epidermal cells, guard cells, and stomata.  How is the stomata regulated?

 

3.    Study the leaf model.  Compare the model with the slide, diagram, and photograph of the mesophytic leaf.  Identify the upper and lower epidermis, the stomata, the guard cells, the palisade mesophyll, the spongy mesophyll, the vein, the xylem, the phloem, the petiole, and the stem.

 

4.  Herbarium specimens - Using Figure ____ on page __ of the Atlas, and Figure ___ on page ___ of your text describe the leaves of the specimens provided as to 1) venation, 2) margin, 3) complexity, and 4) arrangement on the stem.  List and describe several common leaf modifications.

 

          Leaf Arrangement

 

          Leaf Margins

 

          Leaf Shapes

 

          Leaf Types

 

          Leaf Venation

 

         

5.    Whole plant structure - Refer to Figures ___ and ____ on page ___ of the Atlas and Figure ____ on page ___ of your text.  Sketch a prototypical angiosperm.  Label the following parts:  roots (primary & secondary), stem, petiole, node, internode, leaf axial, axially or lateral bud, terminal bud, margin, veins, midrib.  How do you determine whether a plant has a compound or a simple leaf?

 

6.    Monocots and Dicots - Make a table comparing the characteristics of the two angiosperm classes:  Monocotyledons and Dicotyledons. Include cotyledons, venation, and arrangement of vascular bundles, root system, and flower parts.   What is a cotyledon?

 

Terminology

 

Listed below is vocabulary common to the study of the Plant Kingdom.  You will hear and read these words in the context of your study in BOTH lecture and lab.  Work to attain ownership of these words as a part of your working vocabulary. Define these words and work to recognize them, use them, and understand them in describing plants.

 

angiosperm

Coniferophyta

microspore

gymnosperm

Cycadophyta

microsporangium

leaf

Ginkophyta

microsporophyll

phloem

Gnetophyta

megaspore

photosynthesis

Anthophyta

megasporophyll

root

Moncotyledones

megasporangium    

spermatophytes

Dicotyledones

pollen grain

stem

conifer

stoma

tracheophyte

xerophyte

endodermis

vascular

mesophyte

resin duct

xylem

hydrophyte

mesophyll

trichome

epiphyte

epidermis

palisade (mesophyll)

spongy (mesophyll)

venation

palmate venation

pinnate venation

parallel venation

simple leaf

compound leaf

palmately  compound leaf

pinnately compound

petiolate

leaves opposite

leaves alternate

leaves whorled

gametangium

 

 

Margins:

Whole plant structure:

 

          entire

shoot apical meristem

internode

          serrate

terminal bud

leaf axial

          doubly serrate

flower

lateral

          incised

lead blade (lamina)

buds

          undulate

stem

triangular

          lobed

petiole

stipule

Leaf shape:

lanceolate

Leaf arrangements:

even pinnately compound

 

 

cordate

simple

 

oval

palmately compound

 

         

odd pinnately compound

 

 

Ń Reality check

 

1.     What is the difference between bryophytes and tracheophytes?

2.     What tissues are found in tracheophytes that are absent in bryophytes?

3.     What is the function of guard cells?  Where are they located?  How are they regulated?

4.     How do you distinguish between a simple leaf and a compound leaf? 

5.     Explain the difference between xerophytes, mesophytes, and hydrophytes.

6.     Compare a mesophytic leaf with a xerophytic leaf.