Relations of the Whole Plant
Goals and Objectives
Explain the process of transpiration and the
role of vapor pressure differences in controlling the movement of water
between plant leaves ana the atmosphere.
Be able to discuss how environmental factors
regulate the rate of transpirational water loss from a plant.
Be able to describe the anatomy of the water-conducting
system in plants.
Be able to explain how the anatomy of the
vascular system in plants is involved with maintaining a column of water
in tall trees.
Be able to describe how water from the soil
is taken up by plant roots.
Water Relations of the Whole
Goals and Objectives
Give a definition of transpiration.
Draw a cross section view of a plant (Dicot)
leaf. Label the following structures: cuticle, upper and lower
epidermis, palisade mesophyll, spongy mesophyll, vascular bundle, air space
(and the substomatal air space), stoma, guard cells, stomatal apparatus.
For each of the structures listed above in
question #2, give a definition and describe the function of the structure.
How is the cuticle involved in water lose
What are the two stages of the transpiration
From where does the majority of water in a
Explain the difference between stomatal and
cuticular transpiration. Which of the two is more important in water
lose from a plant?
Give some examples of how cuticular transpiration
can vary in regard to leaf anatomy.
What is the driving force for transpiration?
What occurs to the liquid water in the leaf
Define these three terms and explain how these
three terms are related: vapor density, vapor pressure, saturation
What does Raoult's law describe? What
are the components that make up the equation for Raoult's law and what
do they tell us about vapor pressure?
What affect does solute concentration have
on vapor pressure? What affect does temperature have on vapor pressure?
How does this affect the movement of water from the leaf to the atmosphere?
Describe how humidity, temperature, and wind
speed affect transpiration.
In chapter one you looked briefly at the water
and photosynthate conducting tissues of a plant (i.e. the xylem and phloem
respectively). Take some time now to make a list of the different
xylem cells and their characteristics.
Illustrate the structure of a bordered pit
pair. How does this structure control the movement of water and air
in the xylem cells? Why is this important? (NOTE: If you are
answering these question as you read the chapter, you should be on page
45 of the text. The answer to the last part of this question (Why...?)
can be found on pages 52 and 53 - so make sure you come back to finish
this question later.)
In an evolutionary sense vessel elements are
more advanced than tracheids. How did Poiseuille's equation help
show that vessels could "move" more water than tracheids?
Describe how root pressure is developed in
a plant and indicate how important root pressure is to the assent of water
from the soil to the leaves of a plant.
Describe how capillary action occurs in a
plant and indicate how important capillary action is to the movement of
water in a plant.
Describe the cohesion theory of water movement
in the plant. (NOTE: in lecture I will talk about the cohesion-adhesion-tension
theory; these are the same thing.)
Movement of water through a plant is driven
by transpiration and maintained by the cohesion-adhesion-tension of the
water column. In order for movement of water to occur, the water
column in a plant must not be broken. Answer these series of questions
to find out how plants maintain their water columns.
What portion of the root absorbs the most
water? What adaptation is responsible for increasing surface area
and allowing increased water uptake by the plant root.
Illustrate the cross section of a Dicot plant
root. How does the internal structure of the root aid in absorption
What is tensile strength?
What is the range of water tension in the
xylem for temperate deciduous trees?
What is meant by a metastable state?
If water under tension in xylem is in a metastable
stare, how is stability of the water column achieved?
What is cavitation? Why does it occur
What is an embolism? What does it do
to the water column in the xylem ?
Going back to question #16, describe how the
structure of vessels and tracheids help in entrapment of embolism.
give some example of how embolisms are removed
from the water column.