Basic Woody Plant Biology Starbuck

Page 5 (Figure 5) . Mortality can occur over a period of several months , as with Dutch elm disease or pine wilt disease. In most cases, however , the ultimate failure of a tree or shrub was initiated by an event that occurred several years before actual mortality During the mor­ tality spiral, one stress predisposes the plant to another until finally the plant loses the ability to protect itself from even minor stress factors . At this point , opportunistic insects and decay organisms can quickly destroy the structural integri ty of the sterns , branches , and roots, and cause mechanical failure. When plant death is viewed as a mortal­ ity spiral , the impmtance of preventing stress becomes clear. Overirrigation and poor soil drainage , for example , have been shown to predispose some trees to attack by Phytoph ­ thora root rot. Infection with this disease often serious ly impairs the ability of a plant to take up water and nutrients from the soil , leading to a rapid decline . Defoliation by insects or diseases drastica lly reduces the amount of carbohydrates a plant is able to manufacture and store . With limited carbo­ hydrate reserves , the plant has less energy available to defend itself from attack by other pests . In both cases, the beginning of a mortalit y spiral cou ld be prevented by good cultural practices such as judicious watering and insect control. Suggested Further Reading Dirr, M.A. 1998. Manual of Woody Landscape Plants Stipes Publishing , Champaign , IL. Esau , K 1977. Anatomy of Seed Plants. Wile y and Sons , New York, NY Fisher, K 2001. Taylor's Guide to Shrubs. Houghton Miffiin, Boston , MA. Hartman , JR., T.A.Pirone , and M.A. Sall. 2000 . Pirone's Tree Maintenance. Oxford University Press , New York, NY Kramer , Pj., and T.T. Kozlowski . 1979. Physiology of Woody Plants. Academic Press , New York, NY. Rehder , A. 1986. Manual of Cultivated Ii-ees and Shrubs Hardy in North America. Discorides Press , Portland , OR Symo nds , G.WD ., and A.W Merwin . 1963. The Shrub Identification Book. W illiam Morrow , New York, NY. Zimmerman, M.H, C.L. Brown , and M.T. Tyree. 1971. Trees: Structure and Function. Springer-Ver lag, New York, NY. A COLLECTION OF CEU ARTICLES Chris Starbuck is an associate professor of horticulture at the University of Missouri, Columbia, Missouri. l. Plant cells are different from animal cells because plant cells have a. a cell membrane b . a cell wall c. a nucleus d. mitochondria , and they perform cellular respiration 2. Photosynthesis occurs in organelles called a. chloroplasts b . mitochondria c. nuclei d. plasma membranes 3. The shoot tip, the root tip, and the vascular cambium are the main places in a plant where a. photosynthesis occurs b. meristematic cell division occurs c. starch is stored d. respiration occurs 4. Photosynthesis directly involves all of the following except a. chloroplasts b. energy from the sun c. conversion of C02 and water to sugar (photosynthates ) d. conversion of sugars to C02 and water in the mitochondria 5. Transpiration is a. evaporation of water from the stomata on a leaf b. plant cell division c. plant decline and death d. the same as respiration 6. Which of the following twig characteris­ tics is useful in determining how much growth a tree put on during the previous season7 a. bud scales b. leaf scar c. lenticels d. terminal bud scar 7. Most of the absorption of water and nutrients by tree roots occurs in a. lenticels and stomata b. root hairs and mycmThizae c. roots greater than 1 inch in diameter d. structural roots next to the trunk 8. Most of the volume of a tree stem is made up of a. palisade parenchyma cells b. phloem c. mesoph yll cells d. xylem 9. The roots of most woody plants can tolerate temperatures as cold as the aboveground parts can. a. true b. false 10. The organelles in cells that contain the pigment chloroph yll are called a. mitochondr ia b. cell walls c. chloroplasts d. stomates 11. The process in which sugars (starch) are oxidized to release energy is called a. photosynthesis b. respiration c. transpiration d. translocation 5