Revision Assignments & Questions               

 

The assignments and questions are provided 'as-is' for revision and self testing. A great deal of the information required can be obtained from the The Virtual plant and should not take too long to find.

 

A. General Structure & Function Principles      

 

These questions generally require longer answers, and could be considered as 'essay questions' suitable for a terminal examination or test. You should therefore prepare full context answers, and should also where appropriate, include neat accurate diagrams that help to substantiate your answers.

You may well have to do some additional research to find all the answers needed here!

 

  1. If you are given a section of plant material that you have not seen before, highlight the criteria that you could apply to help you determine if the specimen is a stem, a root or a leaf. Please consider your answer carefully, and use valid criteria only.
  2. All higher vascular plants can be grouped into Angiosperm or Gymnosperm. List, and briefly explain the significance of some of the key issues that can be used to separate these groups in terms of their anatomy.
  3. Why are some leaves dorsiventrally flattened and others not? Give reasons and examples that substantiate your answer.
  4. Give an account of the morphological and structural variations in leaf form.
  5. Does leaf form reflect a potential environmental niche? Explain how this relationship may be inferred from a particular structure or structures, and what criteria you would use to make this determination?
  6. Stem and leaf structure may be important indicators of the environment in which a plant grows. Look through the exercises in the Virtual plant as well as other relevant references, and select some examples that suggest potential environmental niche occupancy. Your answer should include a table, which lists what you consider to be significant features that are present or absent. State why the criteria that you have chosen are relevant.
  7. Explain why monocotyledons do not produce characteristic secondary growth which is a common feature of many dicotyledonous plants?
  8. How is secondary thickening of stems (in palms for example) achieved in monocotyledons? What cell and tissue types are most likely to be involved in generating the secondary thickening?
  9. Explain the differences in terms of ontogeny, structure and function, and use  tracheids and vessels, or sieve tube members and sieve cells as the specific tissue examples in your answer.
  10. Why do some plants develop hollow stems and petioles? Your answer should explore this question with reference to plant architecture.
  11. Does leaf form reflect the environment that the plant lives in or not? Give examples that substantiate your answer.
  12. Sieve plates and lateral sieve areas are common to dicotyledonous phloem. Explain the difference between the two structures and discuss their  functions in long-distance as well as short-distance transport.
  13. Using suitable examples, account for the difference between a hardwood and a softwood.
  14. Most of the species that you will ever see using a microscope have vascular bundles that contain xylem and phloem tissue.  Of these, the majority of stems will have phloem tissue exarch to the xylem. Some, however, will have phloem tissue endarch to the protoxylem as well.  Make a series of drawings that show the basic differences between these vascular bundles and then comment on any significance that you think this may bestow on the plant.
  15. Make a comparison of the differences between a dicotyledonous stem, and a monocotyledonous stem at the end of primary growth.
  16. Define primary growth, and then give examples of cell and tissue types that can be classified as primary growth forms.
  17. List key factors that can be used to separate stem from root, and then, using the factors that you have listed, give examples that support their being classified as key factors.
  18. The xylem is, at first glance a fairly simple tissue, with most cell types classified as being dead at maturity. Is this in fact, a good classification of xylem? Include in your answer your defence for your conclusion.
  19. Embryonic tissues are mostly parenchymatous, but a vascular system will develop in close proximity to the embryonic tissue soon after germination. Explain the processes that are most likely to occur which lead up to the emergence of the first-formed elements of the vascular system.
  20. The word proto reflects the origin of certain tissues within the developing plant body. Explain what this word means with respect to the formation of transport tissues in plants as well as their structural and physiological characteristics.
  21. Compare and contrast the structure of a collateral to a bicollateral vascular bundle. Use appropriate labeled diagrams to illustrate your answer.
  22. Give an account of the formation of the first periderm in stems. Identify the regions of the periderm, as well as the tissues most likely to be involved in its formation. Can you find examples  in the Virtual plant that illustrate periderm formation?
  23. Examination of shoot and root apical meristems shows a superficial similarity in structure. Careful examination however, reveals that the similarity is entirely superficial.   Discuss the structure of typical shoot and root apices, and give an account of the tissue systems that they form, as well as the role of the quiescent centre during development.
  24. Xerophytes  and hydrophytes face a common problem - water. Explain how these two very different groups of plants deal with available water. Your answer should include reference to examples from the The Virtual plant and other sources.
  25. The phloem is possibly the single-most unique tissue in the angiosperms, given its specialized role in uptake, transport and unloading of assimilates. Describe the differences between these three components of the phloem's activity.
  26. The cortex of roots is delimited by an endodermis and the stele in roots, by a pericycle. Discuss their roles in terms of their structure and their function, and contrast this to the situation in comparable regions of an herbaceous dicotyledonous stem.
  27. Write an essay entitled 'Monocotyledonous stems - how similar or (dissimilar) are they to dicotyledonous stems?
  28. The cambium - the lateral meristems in control of differentiation.

B. Functional Anatomy                                       

 

The questions listed below require shorter answers (about 5-10 lines maximum) only - most of these could benefit from neat accurate drawings as well. Many (if not most) of the answers can be obtained from the Virtual Plant.

 

  1. Find the micrograph of the Nerium oleander leaf within The Virtual Plant, and after examining the structure of the stomatal crypts, explain their function. What you think would happen if the hairs were not present?
  2. The potato plant, (Solanum tuberosum) is one of a small group of plants that contain both internal and external phloem. Do you think that this type of phloem arrangement (forming bicollateral vascular bundles) confers any structural or physiological advantage, specifically in terms of phloem (assimilate) transport? Give an indication of what you think the advantages that a dual phloem system may have over a single one?
  3. Explain what the meaning of the term bicollateral vascular bundle.
  4. Explain the difference between  'open' and 'closed' vascular bundles with respect to the vascular bundles in monocots and dicots.
  5. What is meant by the term protoxylem lacuna? How does this develop? Is it common to all vascular plants? Is it functional in any way?
  6. Passage cells serve specific physiological functions in the plant. Briefly explain who their structure relates to their principal functions. In which parts of the plant do they occur?
  7. Discuss the physiological roles that  the Casparian strip may play in the movement of substances into and out of the vascular core of roots.
  8. Explain the function of the pericycle.
  9. Comment on the function of a companion cell.
  10. Outline some of the important distinguishing features of hydrophyte and mesophyte leaves.
  11. Does the bundle sheath serve any physiological roles? If so, name some and briefly explain them.
  12. Discuss what you interpret the term,  'limited secondary growth' to infer. Give some examples of plants that undergo limited secondary growth? Are these generally woody or herbaceous plants? What are the advantages to plants that undergo only limited secondary growth?
  13. What is the derivation and origin of cambial tissue formed in the interfascicular region in stems?
  14. Discuss the function of  fusiform and ray initials in the further development of the plant body
  15.  The xylem is composed of proto and metaxylem elements, as well as associated vascular parenchyma and other non-tracheary elements. List all the components of the xylem, and list their major distinguishing characteristics.
  16. List the differences between a vessel, a tracheid and a fiber-tracheid.
  17. Phloem tissue is composed of a number of different cell types. list these and briefly explain the function of the different cell types. What are the major differences between angiosperm and gymnosperm phloem?
  18. The first-formed xylem elements are usually much narrower than later formed elements. They also have thin (porous) primary walls.  Discuss the arrangement of the secondary wall thickening in these protoxylem elements. Why does this specific type of thickening occur? Is there any advantage to this arrangement?
  19. Find the micrograph of a TS of a young Bougainvillea stem in The Virtual Plant. Look up the term conjunctive tissue. What does this mean? Where does it occur in Bougainvillea?
  20. The fibers that are associated with primary phloem are to all intents and purposes, very similar  to those which are produced in the cortex of a developing stem. briefly explain the ontogeny of the two fiber groups, and explain why these should be classified (based on origin) differently? Find a few examples in the Virtual Plant to help illustrate your answer.
  21. Define the word 'anomalous' and give a brief account of anomalous anatomical structures that you have seen in practicals.
  22. Find an example in The Virtual Plant which illustrates  a newly-formed secondary xylem vessel. Describe the processes that are on-going during the development of this vessel. Do they have lignified walls during the early stages of development? If not, why not? Why is lignin necessary?
  23. Define the meaning of the term, anomalous stem growth and give suitable examples that illustrate the your answer, as well as the processes involved.
  24. Define the terms collateral, bicollateral, exarch and endarch.
  25. Define the meaning of  protophloem and give a short account of its function and lifespan in the growing plant.
  26. Compare and contrast the functions of the periderm with that of the endodermis.
  27. Name the regions involved in the formation of the periderm, and then give a concise description of their function.
  28. Define the term perivascular and comment on the ontogeny of perivascular tissues. Now explain the fundamental differences and similarities between cortical sclerenchyma, phloem and xylem fibers and perivascular fibers.
  29. The boundary of the cortex and stele in young Gymnosperm stems is formed by the (a) starch sheath; (b) pericycle; and (C) the endodermis. List the functions of the boundary layer cells, that you can find and show how these are either similar or different in roots and stems.
  30. An atactostele is, in terms of evolution, considered to exhibit the most advanced stelar anatomy in the angiosperms. Can you name some plants which have atactosteles in their stems? What anatomical characteristics are associated with this stelar structure?
  31. Define the term hypodermis. What plant parts are associated with this structure? What do you think its principal functions are? Do all plants have an hypodermis?
  32. Name the functional components of phloem tissue. Explain the roles that each of the cell types you have named have and how they interrelate. Explain the differences between angiosperm and gymnosperm phloem.
  33. Sieve plates and lateral sieve areas are common to dicotyledonous phloem. Explain the difference between the two structures and comment on their potential function.
  34. Fibres may have primary or secondary walls. Describe the difference between those with primary, and those with secondary cell walls. What is a septate fibre? Are fibres universal in structure as well as in their distribution?
  35. Find a micrograph of a young dicot root and a mature monocot root. Make simple plan diagrams of the primary vascular tissue (include the endodermis) of both and contrast this structure to a mature monocotyledonous root.
  36. Lignification in the xylem serves several important functions - some of these are physiological, others are structural. Write down what you think are the key functions of the lignified wall.
  37. Define uniseriate and multiseriate. Explain how they are used to describe features of wood seen in  transverse and tangential longitudinal sections?
  38. Why do pits between tracheary elements sometimes have borders?
  39. Describe the structure of a typical bordered pit. How does this differ from a sieve plate pore?
  40. Compare and contrast mechanical tissue with the xylem. How different are these cells really? List as many points of similarity and dissimilarity as you can think of.

 

 
Copyright CEJ BOTHA and DF CUTLER 2006. No part of this material may be reproduced or incorporated into other publications, electronic or paper, without the explicit approval of the authors and or the publisher.