1). Fifteen years ago, your parents hung a swing from the lower branch of a large tree growing in your yard. When you go and sit in it today, you realize it is exactly the same height off the ground as it was when you first sat in it 15 years ago. The reason the swing has not grown taller as the tree has grown is that
a). the tree trunk is showing secondary growth.
b). the tree trunk is part of the primary growth system of the plant, but elongation is no longer occurring in that part of the tree.
c). trees lack apical meristems and so do not get taller.
d). you are hallucinating, because it is impossible for the swing not to have gotten taller as the tree grew.
2). Cloning animals is a relatively new phenomenon, but cloning plants has been done for a long time. Which of the following plant cell types would be the least successful to clone a plant from?
a). a mature xylem vessel element
b). a mature stomatal guard cell
c). a quiescent center cell
d). All of these would work for cloning a plant.
e). None of these would work for cloning a plant.
3). If you were to relocate the pericycle of a plant root to the epidermal layer, how would it affect root growth?
a). Secondary growth in the mature region of the root would not occur.
b). The root apical meristem would produce vascular tissue in place of dermal tissue.
c). Nothing would change, because the pericycle is normally located near the epidermal layer of the root.
d). Lateral roots would grow from the outer region of the root and fail to connect with the vascular tissue.
4). In a variation on the old "guess your weight" game, you are playing "guess how big this structure will get" at the yearly carnival. There are a number of bizarre plant structures to choose from, but having read this textbook, you are confident of certain victory. Which of the following plant structures would you choose so that you could accurately predict the final size?
a). an oak shoot
b). a lotus flower
c). a bamboo root
d). the root of a tomato plant
5). When you peel your Irish potatoes for dinner, you are removing the majority of their
a). dermal tissue.
b). vascular tissue.
c). ground tissue.
d). Only a and b are removed with the peel.
e). All of these are removed with the peel.
6). You can determine the age of an oak tree by counting the annual rings of _______________ formed by the __________________.
a). primary xylem/apical meristem
b). secondary phloem/vascular cambium
c). dermal tissue/cork cambium
d). secondary xylem/vascular cambium
7). Which of the following does not arise from meristematic activity in a plant?
a). secondary xylem
b). boarder cells
e). All of these arise from activity of plant meristems.
8). Mosses are thought to resemble the primitive plants that first inhabited the land. Interestingly, these plants lack a vascular system. Therefore they should lack
a). mesophyll cells.
9). Plant organs form by
a). cell division in gamete tissue.
b). cell division in meristematic tissue.
c). cell migration into the appropriate position in the tissue.
d). rearranging the genetic material in the precursor cells so that the organ-specific genes are activated.
Test Your Visual Understanding
1). From this cross section of a plant organ, predict the identity of this tissue.
Answer: This figure shows a dicot root because the xylem elements are organized in a star pattern with phloem between the "arms" of the star.
Apply Your Knowledge
1). Plant organs undergo many modifications to deal with environmental challenges. Define your favorite modified root, shoot, and leaf, and make a case for why it is the best example of a modified plant organ.
Answer: There are many ways to answer this question, as long as you specify which organ is modified, describe the modification, and make your case that the modification provides a solutions to an environmental challenge. To answer this question, start by reviewing examples of modified roots (p. 743), modified stems (p. 747), and modified leaves (p. 751). If you choose pneumatophores, for example, explain that these are modified root outgrowths of submerged roots. These modified roots extend above the surface of the water, allowing the plant to obtain enough oxygen to survive.
2). You design a grand scheme to construct a "super plant" that can increase photosynthetic productivity well above normal levels. To do this, you pack the leaves with palisade parenchyma (mesophyll) cells. Would this increase the photosynthetic productivity of a leaf? Why or why not?
Answer: Increasing the number of mesophyll cells, the site of photosynthesis, could increase photosynthetic productivity. There are, however, many other factors to consider. Photosynthesis requires sufficient gas exchange and water. If you do not increase the stomata on the surface of the leaves the rate of photosynthesis is likely to be limited by the availability of oxygen and the amount of water made available through transpiration. Remember, it is the ratio of oxygen to carbon dioxide that affects the efficiency of RUBISCO, the key enzyme needed to fix carbon dioxide in the Calvin cycle (you can review the biochemistry of photosynthesis in chapter 10 and look ahead to p. 785 for more information on the affect of carbon dioxide on photosynthesis.) In summary, you may increase photosynthesis, but you might not have a "super plant."
3). You have identified a mutant maize plant that cannot differentiate vessel cells. How would this affect the functioning of the plant? Devise an environment that would maximize the growth of this mutant.
Answer: The mutant maize plant would not be able to transport enough water if vessel cells failed to differentiate. As the plant grew, it would wilt, have stunted growth, and perhaps not survive. Remember that there would be some water transport through the tracheids, but this would not be sufficient.