- 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
- 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.
- Why are some leaves dorsiventrally flattened and others not? Give reasons
and examples that substantiate your answer.
- Give an account of the morphological and
structural variations in leaf form.
- 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
- 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.
- Explain why monocotyledons do not produce
characteristic secondary growth which is a common feature of many
- 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?
- Explain the differences in terms of ontogeny,
function, and use tracheids and vessels, or sieve tube members and
sieve cells as the specific tissue examples in your answer.
- Why do some plants develop hollow stems and petioles?
Your answer should explore this question with reference to plant architecture.
- Does leaf form reflect the environment that the plant lives in or not?
Give examples that substantiate your answer.
- 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
- Using suitable examples, account for the difference between a
hardwood and a softwood.
- 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
- Make a comparison of the differences between a dicotyledonous stem, and a
monocotyledonous stem at the end of primary growth.
- Define primary growth, and then give examples of cell and tissue types
that can be classified as primary growth forms.
- 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.
- 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.
- Embryonic tissues are mostly parenchymatous, but
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.
- 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.
- Compare and contrast the structure of a collateral to a
bicollateral vascular bundle. Use
appropriate labeled diagrams to illustrate your answer.
- 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?
- 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
- 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.
- 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.
- 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.
- Write an essay entitled 'Monocotyledonous
stems - how similar or (dissimilar) are
they to dicotyledonous stems?
- The cambium - the lateral meristems in
control of differentiation.
- Find the micrograph of the Nerium oleander leaf
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?
- 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?
- Explain what the meaning of the term bicollateral
- Explain the difference between 'open' and 'closed'
vascular bundles with respect
to the vascular bundles in monocots and dicots.
- 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?
- 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?
- Discuss the physiological roles that the
Casparian strip may
play in the movement of substances into and out of the vascular core of
- Explain the function of the pericycle.
- Comment on the function of a companion
- Outline some of the important distinguishing features of hydrophyte
and mesophyte leaves.
- Does the bundle sheath serve any physiological roles? If so, name some and
briefly explain them.
- 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?
- What is the derivation and origin of cambial tissue formed in the interfascicular
region in stems?
- Discuss the function of fusiform and ray initials in
the further development of the plant body
- 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
- List the differences between a vessel, a tracheid and a fiber-tracheid.
- 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?
- 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?
- Find the micrograph of a TS of a young
Bougainvillea stem in
Plant. Look up the term conjunctive tissue. What does this
mean? Where does it occur in Bougainvillea?
- 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
- Define the word 'anomalous' and give a brief account of anomalous
anatomical structures that you have seen in practicals.
- Find an example in
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
- Define the meaning of the term, anomalous stem growth and give suitable
examples that illustrate the your answer, as well as the processes involved.
- Define the terms collateral, bicollateral, exarch and
- Define the meaning of protophloem and give a short account of its function
and lifespan in the
- Compare and contrast the functions of the periderm with that of the
- Name the regions involved in the formation of the periderm, and then give
a concise description of their function.
- 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
- 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
of the boundary layer cells, that you can find and show how these are either similar or
different in roots and stems.
- 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
- 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?
- 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.
- Sieve plates and lateral sieve areas are
common to dicotyledonous phloem. Explain the difference between the two
structures and comment on their potential function.
- 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?
- 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.
- 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
- Define uniseriate and multiseriate.
Explain how they are used to describe features of wood seen in transverse
and tangential longitudinal sections?
- Why do pits between tracheary elements
sometimes have borders?
- Describe the structure of a typical
bordered pit. How does this differ from a sieve plate pore?
- 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.