Download Lectures 6 and 7, Exam I Answers

01-30-12
Lectures 6 and 7, Exam I
Warm Up
1. What is a protoplast? Parts of plant cell internal to cell wall.
2. What are the three types of plant life cycles? How many years do each kind last? Annual- plant that
completes its life cycle in a year or less; biennial- 2 yr life span; perennial- can live many years.
3. What are the three types of cells of plants and what are each of their functions? Dead or alive at
functional maturity? Lack or have secondary cell wall?Parenchyma cells- least specialized, think and
flexible, lack secondary cell wall, typical plant cell, and responsible for house-keeping functions
(photosynthesis); collenchymas cells- lack secondary cell wall (flexible), grouped into bundles
(flexible, structural support); sclerenchyma cells- have thick secondary cell walls strengthened by
lignin, more rigid, cannot elongate when mature, occur in parts of the plant that have stopped
growing in length, dead at functional maturity, support. Two types: sclereids and fibers= strength.
4. What are the two different types of meristems? What kinds of plants have each? What growth is each
kind responsible for? Apical and lateral. ALL have apical at root and shoot tips- elongation. Lateral
are in woody plants- increase in girth.
5. What kind of meristem is involved in secondary growth? There are two types of this meristem. What
do each of these create? Lateral. Vascular cambium and cork cambium. Vascular cambium
produces secondary phloem and xylem, (secondary vascular tissue). Cork cambium creates cork
cells laid down external to the cork cambium.
6. What are three organelles ONLY found in plant cells? Chloroplasts, cell walls, vacuole.
7. What is suberin? Periderm? As cork cells mature, a waxy substance accumulates in the cell walls.
Suberin impedes evaporative water loss. Periderm is the cork cambium + cork.
01-30-12
Lectures 6 and 7, Exam I Worksheet
1. Primary growth in roots:
a. What are initials? What are derivatives? Root cap? Draw a picture of the initial and derivative
cells and how they divide to form each.
In the meristem, the stem cell creates two daughter cells by mitosis. The cell that stays in the
meristem to produce more cells is called the initial. The cell forced to differentiate is called the
derivative cell. The root cap is the covering on the tip of the root which protects the aical meristem
as it grows and pushes further into the ground.
b. Label the growth zones on this root tip, and explain what happens in each zone. What
zone includes root hairs? What are they extensions of?
The derivative cell is then in the zone of cell division closest to the root tip. During all of this,
the initial cell in the meristem keeps dividing and making more derivative cells. Then those
cells in the zone of cell division are moved into the zone of elongation where they lengthen.
Pushes tip further into the soil. Then the derivative cell divides and differentiation of its
daughter cells to different types of tissues occurs: dermal cells, ground tissue, vascular tissue,
etc in the zone of differentiation. Zone of differentiation; epidermal cells.
2. Primary and secondary growth: What tissues form during primary growth? What tissues are formed
in secondary growth? What role does the vascular cambium play in this growth, (draw using initials and
derivatives).
Primary xylem and phloem, vascular cambium. Then vascular cambium then forms
secondary phloem and xylem during secondary growth. Vascular cambium first forms two
daughter cells from a cambium initial: one is another cambium initial and the other is a
derivative cell that becomes either xylem or phloem, usually xylem. Then the second
cambium initial becomes one cambium initial and another cell that becomes either xylem
or phloem, and it continues this way.
3. Why are there age rings in a tree? Explain using the picture shown.
The age rings are depicted, because xylem cells are different
sizes depending on the different times of the year. During the
spring, the xylem cells are larger enabling rings to form.
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4. What role does the cork cambium play in secondary growth. What kind of cells produce it? After what?
What does the layers of bark include?
Cork cambium produces cork cells. After multiple layers of secondary growth is added,
parenchyma cells become the cork cambium. Bark includes phloem+ cork + cork cambium.
5. What is heartwood and sapwood?
Movement of Water
1. A cell is in a solution. The solution is hypotonic to the cytosol if it has less solutes.
The solution is hypertonic to the cytosol if it has more solutes.
2. In osmosis, water moves from an area of low solute concentration to an area of high solute
concentration.
3. How does water movement in animal cells differ from that of plant cells? Incorporate the
following into your answer:
 What extra factors must we take into account? Cell wall; which makes pressure
something that has to be taken into account.
 In plant cells, water moves from high water potential to low water potential.
 Explain the water potential equation.
Water potential= solute potential + pressure potential
As solute concentration increases, solute potential decreases, and vice versa.
Pressure potential is directly proportional to physical pressure.
4. In the picture below, what is happening in each beaker? Which does a plant prefer?
In the left diagram, there are more solutes in the solution compared to the inside of the
plant cell, (if we do not consider pressure), and the water is moving out of the cell. The solution is
hypertonic to the cytosol. In the right diagram, there are more solutes in the cytosol compared to
the solution, (if we do not consider pressure), and the water is moving into the cell. The solution is
hypotonic to the cytosol.