In this exercise you will learn about propagating plants asexually (from cuttings, etc.). It is expected that you have read the appropriate sections in the textbook prior to coming to class.
A. Observation. All vegetative cells contain two sets of chromosomes. Each set contains genes sufficient for a complete organism. Each cell uses only a small portion of the two genomes present in its nucleus.B. Question. Is it possible to make cells already specialized (for example as a leaf petiole parenchyma cell) change their developmental pathway toward something else (for example a root meristem)?
C. Hypothesis. An optimal concentration of rooting hormone (auxin, IAA) can cause roots to form from petiole cells of a leaf cutting.
D. Prediction. If the hypothesis is true, then one of three concentrations of rooting hormone should best stimulate the leaf petiole cells to form roots.
E. Experiment. You have already made leaf petiole cuttings of Pepperomia, Kalanchoe, and Saintpaulia, and placed them in the greenhouse. Retrieve the pots now.
The side of the pot should be labeled as to the location of the cuttings of various treatments. The cuttings were: untreated, treated with Rootone, Hormodin #1, or Hormodin #3. Carefully and gently uproot the cuttings so as not to damage any young roots, and observe the number of roots which have formed at the base of the petiole. Then gently replant the cuttings. You will observe the cuttings again later in the semester to determine the number of roots which may have formed later. Do not use the ° symbol!
Pepperomia Kalanchoe Saintpaulia Treatment ___ weeks ___ weeks ___ weeks ___ weeks ___ weeks ___ weeks Untreated Hormodin #1 Rootone F Hormodin #3 F. Analysis. Compare the numbers you have obtained above.
Considering that Hormodin #1 has the least auxin, Rootone is intermediate, and Hormodin #3 has the most auxin, at what auxin concentration does the Kalanchoe leaf root best?
none low medium high Why did you have an untreated cutting?
G. Decision.
The hypothesis: "An optimal concentration of rooting hormone can cause roots to form from petiole cells of a leaf cutting" is: rejected not rejected
A. Observation. As in Part I above. In addition, stem cells contain parenchyma in the pith, cortex, and phloem.B. Question. Could an optimal concentration of rooting hormone cause roots to form from simple stem parenchyma?
C. Hypothesis. At an optimal concentration, auxin causes roots to form from stem parenchyma.
D. Prediction. One of three concentrations of rooting hormone supplied cause the most root formation.
E. Experiment. Mung bean stems about 10 days old will be cut 3 cm below the cotyledonary node with a razor blade. Ten cuttings will be placed immediately in separate cups containing 20 ml of a test solution of Indole Butyric Acid (IBA) as in the chart below. After one or two days, the cuttings will have used up the test solution and distilled water will be added up to the cotyledonary node. After one week, carefully observe the 10 stems at each concentration for small bumps (root primordia) or small roots. Count the number of roots on each type of cutting and make any other necessary observations. Do not use the ° symbol!
0 M IBA 10-7 M IBA 10-5 M IBA 10-3 M IBA # Roots Average # Observations
F. Analysis. Compare the results above. Also make a graph of the results on the next page.
Which concentration of IBA maximally stimulated rooting? 0 10-7 10-5 10-3 M Do a t-test comparing 0M with the trial having maximum effect: t-statistic: ______ degrees of freedom: ______
same
t-value: ______ decision: different
What is the name of the kind of roots formed from stem tissue? _________________________________________
spelling counts!
G. Decision.
The hypothesis: "At an optimal concentration, auxin causes roots to form from stem parenchyma" is: rejected not rejected
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Five plants are propagated from the seeds from a single fruit on a plant. Five plants are propagated from leaf cuttings of the same plant. Compare the degree of genetic congruence between:
Mother and Seedlings: virtually identical some similarities completely different Seedling Siblings: virtually identical some similarities completely different "Mother" and Cuttings: virtually identical some similarities completely different "Sister" Cuttings: virtually identical some similarities completely different When roots form along the mung bean stem, are the cells of the stem:
___ being genetically re-programmed into a new pathway of development, orWhen shoots form from callus at the base of the Pepperomia leaf cutting, are the cells of the callus:___ continuing in their original genetic pathway?
___ being genetically re-programmed into a new pathway of development, orIf a plant was very bushy (had many stem tips) and continues to branch as it grows, how many individual plants could be cloned from it by stem cuttings?___ continuing in their original genetic pathway?
none a few as many as there are stem tips indefinitely many When cloning we hope to produce identical plants, but is it possible to obtain at least a few individuals which are different from the original plant?
yes no if so, by what
biological process?
Go back to the Course Schedule.