Answers to End-of-Chapter Questions – Brooker et al ARIS site Chapter 35 Test Yourself Questions 1. Where would you look to find the gametophyte generation of a flowering plant? a. at the shoot apical meristem b. at the root apical meristem c. in seeds d. in flower parts e. none of the above Answer: d. The microscopic male and female gametophytes, which produce sperm and eggs, are located within flower organs. 2. What is a radicle? a. an embryonic leaf b. an embryonic stem c. an embryonic root d. a mature root system of a monocot e. an organism that has extreme political views Answer: c. A radicle (note spelling) is an embryonic root. 3. What is the correct term for a plant that does not reproduce in its first year of life, but often produces flowers and seeds within the following year? a. an annual b. a biennial c. a perennial d. a centennial e. none of the above Answer: b. A biennial is a plant that does not reproduce until the second year of life at the earliest. 4. Which of the following terms best describe the distinctive architecture of plants? a. radial symmetry and apical-basal polarity b. bilateral symmetry and apical-basal polarity c. radial symmetry and absence of apical-basal polarity d. bilateral symmetry and absence of apical-basal polarity e. absence of symmetry and absence of apical-basal polarity Answer: a. Plant architecture is characterized by radial symmetry and apical-basal polarity. 5. Which is the most accurate description of how plants grow? a. by the addition of new cells at meristems that include stem cells b. by cell enlargement as the result of water uptake c. by both the addition of new cells and cell expansion d. by addition of fat cells e. none of the above Answer: c. Plants grow by both the addition of new cells at meristems (which involve stem cells) and by cell expansion as the result of water uptake. 6. Where would you look for leaf primordia? a. b. c. d. e. at a vegetative shoot tip at the root apical meristem at the vascular cambium at the cork cambium in a floral bud Answer: a. Leaf primordia are produced at vegetative shoot apical meristems. 7. Which leaf tissues display the greatest amount of air space? a. the adaxial epidermis b. the abaxial epidermis c. the palisade parenchyma d. the spongy parenchyma e. the vascular tissues Answer: d. The spongy parenchyma is named for its abundant air spaces, which facilitate carbon dioxide absorption by photosynthetic cells of the leaf. 8. What is an adventitious root? a. roots that develop on plant cuttings that have been placed in water b. buttress roots that grow from tree trunks c. the only kinds of roots produced by monocots, because their embryonic root dies soon after seed germination d. any root that is produced by stem (or sometimes leaf) tissue, rather than developing directly from the embryonic root e. all of the above Answer: e. An adventitious root is one that is produced by stem or leaf tissue; examples include the root systems of monocots, roots that grow on plant cuttings, and buttress roots. 9. During its development, a tracheid will elongate in a direction parallel to the shoot or root axis. Based on this information, what can you say about the orientation of cellulose cell-wall microfibrils and cytoplasmic microtubules in this developing tracheid? a. The microfibrils will be oriented perpendicularly (at right angles) to the long axis of the developing tracheid, encircling it, but the cytoplasmic microtubules will be oriented parallel to the direction in which the tracheid is elongating. b. Microfibrils and microtubules will both be oriented perpendicularly (at right angles) to the elongating axis of the tracheid. c. Microfibrils and microtubules will both be oriented parallel to the direction of tracheid elongation. d. Microfibrils will be oriented parallel to the direction of tracheid elongation, but microtubules will be perpendicular (at right angles) to both the microfibrils and the elongating tracheid. e. None of the above. Answer: b. Microtubules influence the direction in which microfibrils are synthesized, such that they have the same orientation. The encircling microfibrils restrict cell expansion to the direction perpendicular to microfibril orientation. Recall the example of tape bands on an inflating balloon. 10. What are examples of woody plants? a. trees b. shrubs c. woody vines, known as lianas d. all of the above e. none of the above Answer: d. Trees, shrubs, and woody vines (lianas) are the three types of woody plants. Conceptual Questions 1. What would be the consequences if overall plant architecture were bilaterally symmetrical? Answer: Plants would be shaped like higher animals, with a distinct front (ventral surface) and back (dorsal surface). By comparison to radially symmetrical organisms, bilaterally symmetrical plants would have reduced ability to deploy branches and leaves in a way that would fill available lighted space, and would thus not be able to take optimal photosynthetic advantage of their habitats. 2. What would be the consequences if leaves were radially symmetrical (shaped like spheres or cylinders)? Answer: In a radially symmetrical form, leaves would not have maximal ability to absorb sunlight, and they would not be able to optimally disperse excess heat from their surfaces. 3. Why are most tall plants also woody, rather than herbaceous? Answer: Although tall herbaceous plants exist (palms and bamboo are examples), the additional support and water-conducting capacity that is provided by secondary xylem allow woody plants to grow tall. Experimental Questions 1. Why did Elle and colleagues begin their investigation by growing Datura wrightii plants from seeds in a greenhouse? Answer: By doing so, they were able to start with a fairly uniform population of experimental plants that were mature enough to have developed defensive features such as trichomes. If they had started the plants outdoors, many of the seedlings could have been lost to drought or other stresses at an early stage in the experiment. 2. Why did Elle and colleagues move the mature plants outdoors, but treat only half of them with herbicide? Answer: Outdoors the plants were exposed to normal selective pressures, such as herbivorous (planteating) insects. By spraying some of the plants (and thereby removing the impact of insect herbivores) the investigators could compare the success of plants having different types of trichomes under conditions in which herbivores were present or absent. 3. Why did the investigators keep track of plant growth as well as plant reproduction during the experiment? Answer: By so doing, the experimenters were able to observe the protective effect of sticky trichomes, a result that would not have been observed had they only monitored seed production. Collaborative Questions 1. Find a tree stump or a large limb that has recently been cut from a tree (or imagine doing so). Which of the following features could you locate with the unaided eye: the outer bark, the inner bark, the secondary xylem, the vascular cambium, annual rings? Answer: You would be able to locate the outer bark, secondary xylem, and annual rings, but the inner bark and vascular cambium would likely be too thin for you to see without the use of a microscope. 2. Which physical factors would you expect influence shoot growth most strongly? Which physical factors would you expect most strongly influence underground root growth? Answer: You would expect shoot growth to be particularly responsive to light, humidity, temperature, wind, and carbon dioxide concentration, because these physical factors influence photosynthesis. You would expect soil water, soil minerals, obstructing soil particles (such as rocks), and gravity to most strongly affect the growth of underground root systems.