Lab Topic 25 |
Investigating Primary and Secondary Growth in |
Roots and Stems |
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Whole Roots |
Tap Root Systems |
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Fibrous Root Systems
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Adventitious Root
Systems
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| Plant with Adventitious root | |
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| Edible Roots
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Root Histology
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Longitudinal
Section of a Young Raphanus Root |
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Raphanus (radish) seedling |
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fresh root cap |
•Observe the root hairs. What is their function? •Are root hairs present along the entire length of the root? Why or why not? •Root hairs are what type of cell?
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Cross
Section of Roots
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Dicot Roots |
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Mature Buttercup (Ranunculus) root c.s.Scanning |
Mature Buttercup (Ranunculus) root c.s.40X |
Mature Buttercup (Ranunculus) root c.s.100X |
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Immature dicot root stele, c.s. |
Mature dicot root stele,c.s. |
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Monocot Roots
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Fresh cross section of corn (Maize) root. |
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Cross section of mature monocot root |
Casparian strip in endodermis of mature monocot root. |
Immature cross section of corn (Maize) root |
High magnification of immature monocot root lacking casparian
strip. |
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B. Show a corn plant here | |
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| Fresh section of dicot root coming later. | ||
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| Short answer or comparitive questions regarding roots. |
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Stem Structure |
leaves |
| External Dicot Stem Structure |
A buckeye twig |
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Terminal bud |
Lenticels and leaf scar |
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Lateral buds arise in angle between stem and leaf petiole |
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Microscopic
Herbaceous Dicot Stem Structure |
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| Coleus | Coleus terminal bud | Coleus lateral buds |
Coleus l.s. at
low power |
Coleus l.s. at
medium power |
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Internal
Anatomy of Alphalpha Medicago Stems |
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Internal
Anatomy of Sunflower Stem |
questions |
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Internal
Anatomy of Woody Dicot Stem Structure |
Tilia c.s.
1 year stem |
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•Point to the location of the following: pith, xylem, vascular cambium, phloem, epidermis. •Describe secondary growth using these photos to illustrate your points.
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Tilia c.s. 3 yr. stem |
C.s. tree |
•Which tissue gives an indication of the age of the stem? •How old was this stem when it was used to prepare this section? •In which region would you find secondary phloem? •Where is the vascular cambium? •Where is the cork cambium? |
•Estimate the age of the tree from the wood section. •In which region would you find secondary phloem? •What produces secondary xylem? |
Structure of Wood |
new images |
new images |
new images |
•Locate the part of wood c.s. called heartwood, and sapwood. •Which is younger growth, heartwood or sapwood? |
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Internal
Monocot Stem Structures |
Corn plant |
fresh c.s. |
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Low power |
Medium power |
High power |
•What is one basic difference between a monocot stem and a dicot stem? •Is this a root or a stem? •Is this a cross section of a monocot or a dicot stem? •The pith of monocot stems is composed of what tissue? |
•Why doesn't secondary xylem and secondary phloem occur in monocot stems? •If we cut the tip of grass with a mower, why does it still grow? |
•What are the darkly staining structures? •What is their function? •What tissue is the outermost layer of the stem? •What type of cell makes up most of the cross section of a stem such as this? |
Testing the Water Tension Hypothesis- Why did the blue dye travel up the "stressed" sunflower stem faster than the "non-stressed" stem? What is the main function of the collenchyma cells found in this stem? |
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General and Comparative Questions about Stems- •Discuss the various functions of vascular tissues in stems. •How does the arrangement of vascular tissue differ for monocot compared to dicot stems? •What is the advantage of secondary growth? •What are the principle distinctions between herbaceous dicot and monocot stems? •How would you distinguish between a monocot stem and a monocot root? •How would you distinguish between a dicot stem and a dicot root? •What tissue is commonly called "wood"? •What is the role of the vascular cambium? Cork cambium? •Distinguish between primary and secondary growth in stems. •What are three functions of stems? •In a log taken from a large tree, are most of the cells dead or alive? What tissue is most common?
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