Bot 305; Summer 2000 Name:
Test #1
Give succinct (40 words or less), precise answers in the space provided after each question.
Unless otherwise noted in the margin each section of each question is worth 3 points.
1. (a) What is the disadvantage of the single hypothesis approach to solving a research question?
The investigator becomes emotionally attached to that hypothesis or committed to proving it is correct, so that experimental designs or data interpretation can easily become biased.
(b) Describe evidence that could indicate that Backster tended toward a single hypothesis approach to the question of whether plants could respond emotionally or "know" the intentions of persons planning to harm them?
When the results did not agree with his bias he made up "excuses" for the plant -- e.g., the plant did not perform because it suspected the evil intentions of one of the observers.
2. (a) Rule 3 of Strong Inference emphasizes the need to carry out the experiment in such a way as to get a credible and interpretable result. Indicate one way the group at Cornell who published the 1975 Science article (Horowitz, Lewis & Gasteiger) improved on Backster's original experimental design.
(i) They used more plants than Backster did; (ii) They used electrically shielded room to reduce the interference of electrical noise.
(b) The group at Cornell enlisted as research assistants students open to believing Backster's original paper on how plants responded to the death of brine shrimp. Why was this considered an important part of the experimental design?
The Cornell group was aware of excuses Backster gave when results did not agree with his hypothesis (see answer to 1 (b) above), so to avoid this criticism they enlisted sympathetic research assistants.
(c) Who was Jagadis Bose and why did the authors of The Secret Life of Plants choose to highlight his discoveries?
Bose was a physicist who documented electrical responses in plants in the early 1900's. The authors highlighted his discoveries because they exemplified a case where unexpected plant responses were first rejected by the establishment and then accepted as true. The authors hoped readers would think that Backster's unconventional conclusions would also prove to be true ultimately.
3. (a) Why did the Cornell group consider it important to carefully analyze chart recordings for the periods 25 seconds preceding and following the boiling event?
This was a control to make sure there was no transient instability in the recording apparatus just prior or just after the boiling event, and it allowed them to evaluate how often the recording would change on its own without any boiling event.
4. (a) What is self-incompatibility and what advantage does it confer on plants that exhibit this trait?
SI = inability of pollen from a plant to successfully fertilize an egg of the same plant. It promotes out-crossing and reduces the chance that defective recessive traits will be expressed.
(b) What is the self-incompatible reaction in sporophytic self-incompatibility and where does it occur?
The sporophytic self-incompatible reaction is that the stigma secretes material that blocks the germination and growth of incompatible pollen grains, and this reaction occurs on the stigma surface.
(c) How many sperm cells are carried in the pollen tube, and what guides the tube to the ovary?
There are two sperm cells carried by the pollen tube, which is guided to the ovary by chemical gradients along the path (transmitting tract of the style) from the stigma to the ovary.
5. (a) What is the largest organelle in a fully mature plant cell? Ans:__vacuole_____________
(b) What organelle uses molecules derived from food to generate ATP in both plants and animals?
Ans.:___________mitochondrion________________
(c) What organelle is green and converts light energy into sugar? Ans.:__chloroplast
6. (a) In the film The Green Machine, did Backster claim he had proven that plants respond electrically to thoughts of people around them? Explain.
No, Backster did not claim that he had proven that plants respond electrically to thoughts of people, only that he had enough data for scientists to take this hypothesis seriously.
(b) In the film The Green Machine, Dr. Barbara Pickard measured plant electrical activity continuously over long periods of time. What was her principal finding in this experiment?
Dr. Pickard found that the plants exhibited occasional spontaneous bursts of electrical activity.
(c) In the film The Green Machine, Dr. McRobbie observed electrical activity in a single giant algal cell. What change occurred inside this cell when it was electrically stimulated?
When the giant algal cells were electrically stimulated the movement of the organelles in the cytoplasm stopped.
7. (a) What accounts for the electrical properties of single cells?
Plants are bordered by a membrane that is semi-permeable and that can discriminate between transporting positive and negative ions. This results in a charge imbalance across the membrane, which generates an electric voltage across the membrane
(b) What is the normal range of the electrical polarity of a cell, and what does it mean to say that a cell is electrically depolarized by some signal.
Normally the range of electrical polarity of a cell is negative inside, with a voltage of ca. –100 millivolts. When a cell is electrically depolarized it becomes less negative inside.
(c) Plant cells are electrically coupled to each other through low resistance pathways? What are these pathways, and what part of a cell is continuous across these pathways between two cells?.
The low resistance pathways are plasmodesmata , through which the cytoplasm of two adjoining cells are connected and continuous.