Part I.  Each multiple choice question is worth 3 points.

1. Which one of the following statements concerning the plant microtubule cytoskeleton is INCORRECT?
 (_____) a. A band of microtubules in the cortex of the cell appears to mark the future plane of cell division.
 (_____) b. Plant cells, in contrast to animal cells, have microtubules running parallel to the plane of the plasma membrane.
 (__X__) c. Microtubules run perpendicular to the direction of cellulose microfibrils, thereby providing additional mechanical support to the cell.
 (_____) d. Plant cells have centrosomes (MTOCs).
 (_____) e. Rotation of the microtubule-containing spindle is required for repositioning the plane of cell division.

2. Which one of the following statements about the primary growth of a plant is INCORRECT?
 (_____) a. Cell differentiation or maturation usually follows cell elongation.
 (_____) b. Apical meristem gives rise to cells  of all three tissue types:  dermal, ground and vascular.
 (__X__) c. Lateral roots and branches each originate from the same type of meristem tissue at the surface of the plant.
 (_____) d.  Epidermal tissue contains a waxy water-impermeable coat called the cuticle.
 (_____) e. Meristem tissue contains cells that are dividing at different rates.

3. Which one of the following statements concerning CO2 fixation is INCORRECT?
 (_____) a. Rubisco, the enzyme that catalyzes the initial fixation of CO2, is an extremely abundant protein in plants.
 (_____) b. Not all plants do CO2 fixation during the day.
 (_____) c. The enzymes of the Calvin cycle are located in the stroma of the chloroplast.
 (__X__) d.  C4 plants do not have a complete Calvin cycle.
 (_____) e.  CO2 fixation can be inhibited by O2, leading to photorespiration.

4. Which one of the following statements concerning fermentation is INCORRECT?
 (_____) a. Fermentation enables some cells to produce ATP without the help of oxygen.
 (__X__) b. Fermentation helps regenerate NADH from NAD+.
 (_____) c. Alcohol production by yeast is an example of fermentation.
 (_____) d. The final electron acceptor during fermentation is an organic molecule.
 (_____) e.  Lactic acid is produced by muscles during fermentation.

5. Which one of the following statements concerning cytokinesis is INCORRECT?
 (_____) a. A contractile ring of actin filaments helps form the cleavage furrow of animal cells.
 (__X__) b. Cytokinesis is required for the division of one nucleus into two.
 (_____) c. Cytokinesis of some cell types results in two different sized daughter cells.
 (_____) d. Plant cell cytokinesis requires vesicles derived from the Golgi apparatus.
 (_____) e. Plant cells do not generate a cleavage furrow during cytokinesis.

6. Which one of the following statements concerning plant stress responses is FALSE?
 (_____) a. Under drought conditions, deeper roots continue to grow while growth of more shallow roots is inhibited.
 (_____) b. Trees growing in coastal marshes often develop aerial roots above the water to provide access to oxygen.
 (_____) c. Evaporative cooling through transpiration is one way plants deal with excessive heat.
 (__X__) d. Many of a plant's responses to water deficit help the plant conserve water by increasing the rate of transpiration.
 (_____) e. Plants exposed to high salt levels in the soil sometimes produce organic compounds called compatible solutes or even pump salts out of the plant.

7. Which one of the following is NOT an electron donor during the electron transfer reactions of photosynthesis or respiration?
 (_____) a. H2O
 (__X__) b. O2
 (_____) c. NADH
 (_____) d. Photosystem I
 (_____) e. FADH2

8. Which one of the following is NOT used by plants to prevent self-fertilization?
 (__X__) a. Carpels lower than stamens.
 (_____) b.  Plants are only one sex:  male or female.
 (_____) c. Male part of flower develops later than female part.
 (_____) d. In the same plant, pollen grains will not adhere to female part of flower.
 (_____) e. In the same plant, tube cell of pollen grain cannot grow down through female tissue to reach egg.

9. Which one of the following is NOT true for ethylene?
(_____) a. Its synthesis is stimulated by auxin.
(_____) b. Ethylene is a gas.
(__X__) c. Ethylene inhibits fruit ripening.
(_____) d. Cytokinins from the root inhibit ethylene production.
(_____) e. Ethylene promotes leaf abscission.

10.  Which one of the following is NOT a characteristic of guard cells?
 (_____) a. Attached to each other at two places.
 (_____) b. Contain proton pumps.
 (_____) c. Sensitive to the plant hormone abscisic acid.
 (__X__) d. Use actin filaments to contract.
 (_____) e. Contain transverse bands of cellulose microfibrils.

11. Which one of the following is NOT properly matched to its function?
 (_____) a. expansin ­ cell wall expansion
 (__X__) b. chlorophyll ­ phototropism
 (_____) c. phytochrome­ control of flowering time
 (_____) d. gibberellin ­ plant hormone
 (_____) e. UTP, CTP ­ anabolism

12. Which one of the following statements concerning glycolysis and the Krebs cycle is INCORRECT?
 (_____) a. Both glycolysis and the Krebs cycle produce ATP by substrate level phosphorylation.
 (_____) b. The Krebs cycle product citrate inhibits glycolysis, helping to synchronize the rates of glycolysis and the Krebs cycle.
 (__X__) c. The end product of glycolysis, pyruvate, is used directly as a substrate by one of the Krebs cycle enzymes.
 (_____) d. The Krebs cycle is in the matrix of the mitochondria, while glycolysis is in the cytosol.
 (_____) e.  Glycolysis results in hydrolysis and synthesis of ATP.

13. Which one of the following statements concerning plant relations with microorganisms is INCORRECT?
 (_____) a. Fungi called mycorrhizae help plants obtain inorganic nutrients from the soil.
 (__X__) b. Free living soil bacteria called Rhizobia are attracted to the root hairs of any plant exposed to nitrogen-deficient soil.
 (_____) c. Fungi called mycorrhizae are allowed entry into the cortex of the plant root.
 (_____) d. Plants provide a low O2 environment for N2 fixation by bacteria.
 (_____) e. The cuticle of plants prevents entry of most microorganisms.

14. Which of the following is NOT part of the transpiration­cohesion­tension mechanism for the ascent of xylem sap?
 (_____) a. Loss of water from the mesophyll cells, which initiates a pull of water molecules from neighboring cells and eventually from the xylem.
 (_____) b. The transfer of transpirational pull from one water molecule to the next due to the cohesion caused by hydrogen bonds.
 (_____) c. The hydrophilic walls of the narrow tracheids and xylem vessels that help maintain the column of water against the force of gravity.
 (__X__) d.  Active pumping of water into the xylem of roots.
 (_____) e. The reduction of water potential in the surface film of mesophyll cells due to increased surface tension.

15. The movement of sap from a sugar source to a sugar sink
 (_____) a. occurs through the apoplast of sieve-tube members.
 (__X__) b. may translocate sugars from the breakdown of stored starch in a root up to developing shoots.
 (_____) c. is similar to the flow of xylem sap in depending on tension, or negative pressure.
 (_____) d. depends on the active pumping of water into sieve tubes at the source end.
 (_____) e. results mainly from diffusion.

16. Which one of the following statements concerning the microtubule cytoskeleton during mitosis is INCORRECT?
 (_____) a. MTOC (centrosomes) duplicate before mitosis.
 (__X__) b. Microtubules attached to kinetochores are highly unstable throughout mitosis.
 (_____) c. Microtubules extending from MTOCs to the cell cortex help position the MTOCs closer to the plasma membrane.
 (_____) d. Microtubule motors help move chromosomes and MTOCs during mitosis.
 (_____) e. The stability of microtubules changes after cells enter mitosis.

17. Which one of the following statements about plant defense mechanisms is FALSE?
 (_____) a. Plants store poisons in their vacuole.
 (_____) b. Cell wall degrading enzymes are a constitutive defense against microbes.
 (_____) c. Electrical signals are used by plants to rapidly activate systemic plant-wide defenses.
 (__X__) d. Oligosaccharides are a universal signal for attack by pathogenic microbes.
 (_____) e. Alarm hormones can spread through the plant or through the air to activate plant defense mechanisms.

Part II.  Essay questions (best 5 of 7, 10 points each)

18. Noncyclic electron flow by the thylakoid membrane is more useful to the plant than cyclic electron flow.  Explain briefly, emphasizing the useful product(s) of each.

 Noncyclic electron flow is used to generate a pH gradient plus transfer electrons to NADP+ to form NADPH.  The pH gradient is used for ATP synthesis.  Cyclic electron flow is only used for pH gradient formation and subsequent ATP synthesis by the ATP synthase.  Because no electrons are lost, no NADPH can be formed.

19. Give two examples of programmed cell death and briefly explain why, for each example, death of particular cells is important for the plant.

 Phloem:  Sieve tube members are formed by programmed cell death that causes loss of cytoplasm and nucleus but not plasma membrane, allowing tube to be formed for sugar transport between different parts of the plant.

 Xylem:  Tracheids and vessel elements are cells that die, leaving only their cell walls, providing a low resistance pathway for fluid flow between roots and shoots.

 Megaspore:  3 of 4 megaspores die to devote more resources to the one remaining.

 Tube cell:  Helps sperm of pollen grain grow toward egg cell and then dies to allow more nutrients to sperm/egg.

 Seven cells (out of 8) derived from megaspore eventually die to allow more nutrients to zygote.

 Fruit cells die to give up nutrients to developing embryo.

Leaf cells during abscission die to help protect resources of plant from cold-induced damage.

20. Protein breakdown or degradation is required for regulation of the cell cycle.  Explain why degradation is important and what specific proteins must be degraded.
 
 Cyclin (and sometimes cyclin-dependent kinases) are degraded at the end of the phase of the cell cycle for which they are required.  Degradation of cyclin therefore is critical for the ending of S phase and M phase, respectively, allowing cells to move on to the next phase of the cell cycle.

21. Seed germination requires energy derived from digestion of storage materials.  What two specific parts of the seed are used for energy storage prior to germination?  How is conversion of starch to glucose (and sucrose) useful for expansion of the seed?

 Endosperm and seed leaves (cotyledons).  Conversion of starch to sugars increases the osmolarity inside the seed and promotes inhibition, the uptake of water, that is needed for expansion of the seed.

22. How does auxin stimulate cell expansion?  In phototropism, what side of the shoot has the highest auxin concentration?  What is the main source of auxin in a growing shoot?

 Auxin increases proton pump activity, thereby lowering the pH outside the cell and stimulating acid-activated expansins that break crosslinks in the cell wall.

 Dark side.

 Meristem.

23. Plants take up nitrate from the soil and then reduce nitrate to ammonia.  Where does this latter reaction occur and is this an energy-requiring reaction?  In nitrogen-rich soils, why do plants usually take up more nitrate than ammonia, the immediate substrate for amino acid biosynthesis?

 Chloroplast, yes.

 Bacteria quickly convert ammonia to nitrate, limiting the availability of the former nitrogen source to plants.

24. ATP synthesis during respiration or during photosynthesis requires energy.  What is the direct source of the energy used for ATP synthesis during oxidative phosphorylation?  Be sure to give a detailed description of this energy source.

 Proton electrochemical gradient across the membrane (inner mitochondrial or thylakoid) ­ made up of a chemical gradient of protons and an electrical gradient where the higher proton concentration and positive charge is on the side of the membrane opposite from the ATP synthase.