Topic 8 Review
Name:
1. The hierarchical organization of plants is divided into two systems. What are
they? Briefly describe them. What do they consist of?
They are organized into a root system (roots) and a shoot system (stems and leaves)
Roots rely on sugar produced by photosynthesis in the shoot system, and shoots
rely on water and minerals absorbed by the root system
1. Roots

Are multicellular organs with important functions:
1) Anchoring the plant
2) Absorbing minerals and water
3) Storing organic nutrients

A taproot system consists of one main vertical root that gives rise to lateral
roots, or branch roots

Adventitious roots arise from stems or leaves

Seedless vascular plants and monocots have a fibrous root system
characterized by thin lateral roots with no main root

In most plants, absorption of water and minerals occurs near the root hairs,
where vast numbers of tiny root hairs increase the surface area

Many plants have modified roots

Plants may also have a symbiotic relationship with fungi at the tips of the
roots, termed mycorrhizae which assist in the absorption process and are
found in the vast majority of all plants
2. Stems

A stem is an organ consisting of:
Topic 8 Review
a.
Name:
An alternating system of nodes, the points at which leaves are
attached
b. Internodes, the stem segments between nodes

An axillary bud is a structure that has the potential to form a lateral shoot, or
branch

An apical bud, or terminal bud, is located near the shoot tip and causes
elongation of a young shoot

Apical dominance helps to maintain dormancy in most nonapical buds

Many plants have modified stems

Modified stems include:

Stolons—horizontal stems growing along surface of ground
(strawberry)

Rhizomes—horizontal stems growing underground (iris)

Tubers—some end in enlarged tubes where food is stored
(potatoes)

Bulbs—vertical, underground shoots with leaves modified for
food storage (onion)
3. Leaves
a. Are the main photosynthetic organ of most vascular
plants
b. Leaves generally consist of a flattened blade and a stalk
called
the petiole, which joins the leaf to a node of the stem
c. Some plant species have evolved modified leaves that serve various
functions
Topic 8 Review
Name:
2. What is the difference between terminal and apical buds?
An axillary bud is a structure that has the potential to form a lateral shoot, or branch
An apical bud, or terminal bud, is located near the shoot tip and causes elongation of
a young shoot
3. The leaves are the main photosynthetic organ in most plants.
4. Plant organs are composed of three tissue types. Briefly describe them. What
parts of the plant do they contain?
1. Dermal
a. is the single layer of closely packed cells that cover the entire plant
and protect it against water loss (a waxy layer termed the cuticle in
the leaves) and invasion by pathogens like viruses and bacteria
2. Vascular Tissue System

Carries out long-distance transport of material between
roots and shoots

Two types of Vascular Tissue:
a. xylem-transports water and dissolved mineral upward from root
into shoots
b. phloem-transports organic nutrients from where they are made to
where they are needed

Vascular tissue of a stem or root is collectively called the
stele
3.Ground Tissue System
Topic 8 Review
Name:
i. Refers to any tissue not dermal or vascular
ii. Pith-ground tissue internal to vascular tissue
iii. Cortex-ground tissue external to vascular tissue
iv. Include cells specialized for photosynthesis, storage
and support
1. In angiosperms the stele of root is a solid central
vascular cylinder
2. The stele of stems and leaves is divided into vascular
bundles (strands of xylem and phloem)
5. Compare xylem and phloem.
a. xylem-transports water and dissolved mineral upward from root into
shoots
•
Water conducting cells
•
Dead cells with secondary walls
•
Stain red
b. phloem-transports organic nutrients from where they are made to where
they are needed
•
Sugar-conducting cells
•
Stain green
•
Alive at functional maturity
Topic 8 Review
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6. What is the difference between annuals, biennials, and perennials?
Life span of flowering plants:
•
Annuals complete their life cycle in a year or less
•
Biennials require two growing seasons
•
Perennials live for many years
7. Meristems are perpetually embryonic tissues. There are two types, what are
they?
Apical meristems are located at the tips of roots and shoots and at the axillary buds
of shoots. Apical meristems elongate shoots and roots, a process called primary
growth
Lateral meristems add thickness to woody plants, a process called secondary
growth
8. There are two lateral meristems: the vascular cambium and the cork
cambium
The vascular cambium adds layers of vascular tissue called secondary xylem (wood)
and secondary phloem
The cork cambium replaces the epidermis with periderm, which is thicker and
tougher
9. The Root cap protects the delicate meristem of the root tip. The root tip
contains three zones of cells in various stages of growth. What are they?
1. Zone of cell division
Topic 8 Review
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i. Near tip and includes the apical meristem
ii. Quiescent center is made up of reserve replacement cells
2. Zone of elongation
•
Cells elongate and push root through the soil
3. Zone of differentiation
•
Elongated cells complete their differentiation and become
functionally mature
•
Region where root hairs develop
•
Farthest from root tip
10. What is the stomata? What is its purpose? How does it open and close?
The epidermis in leaves is interrupted by stomata, which allow CO2 exchange
between the air and the photosynthetic cells in a leaf
Each stomatal pore is flanked by two guard cells, which regulate its opening and
closing
2. When guard cells take in water, they become turgid and the gap between cells
increases.
3. When guard cells lose water, they become flaccid and the gap between cells
decreases.
4. Changes in turgor pressure results primarily from the
reversible uptake
and loss of K+ by guard cells
 Stomata open—guard cells accumulate K+ and gain water
 Stomata closed—guard cells lose K+ and lose water
Topic 8 Review
Name:
5. Generally, stomata are opened during the day and closed at night.
11. Be able to label the leaf anatomy presented on pg. 202.
12. The loss of water from leaves is called Transpiration. What does it create?
(Hint: use image on page 203)creates a force within the leaves that pulls
xylem sap upward. Transpiration produces negative pressure in the leaf,
which exerts a pulling force on water in the xylem, pulling water into the leaf
Involves:
Cohesion
Adhesion
Tension (Negative Pressure)
13. Phloem can flow both ways between shoots and roots. It moves from sites of
sugar production or to sites of
sugar use of storage.
14. The uptake of water across cell membranes occurs through Osmosis
, the
passive transport of water across a membrane. Describe this process in
terms of water potential.
Topic 8 Review
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15. What are aquaporins? The transport proteins (channels) in the plant plasma
membrane specificially designed for the passage of water
16. What is root pressure?
Root pressure occurs when water diffusing in from the root cortex generates a
positive pressure that pushes sap up. Root pressure does not have the force to push
water to the tops of trees.
17. Briefly explain the cohesion – tension hypothesis?
Describes how transpiration provides the pull for the ascent of xylem sap, and the
cohesion of water molecules transmits this pull along the entire length of xylem
from shoots to roots
Water is lost through transpiration from the leaves of the plant due to the lower
potential of the air. The cohesion of water due to hydrogen bonding plus the
adhesion of water to the plant cell walls enables the water to form a water column .
Water is drawn up through the xylem as water-evaporates from the leaves, each
evaporating water molecules pulling on the one beneath it through the attraction of
hydrogen bonds.
18. What is translocation?
Translocation—transport of organic products of PS by phloem throughout the
plant
-in angiosperms it involves sieve-tube members
-direction varies
Topic 8 Review
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19. What is the difference between sugar source and sugar sink?
Sugar source—an organ that is a net producer of sugar such as mature leaves
Sugar sink—an organ that is a net consumer or storer of sugar, such as a tuber or
bulb
20. What are the four symbiotic relationships formed with plants that your book
mentions? List an example of each.
Mutualistic –
1. Rhizobacteria
•
Free-living rhizobacteria thrive in the rhizosphere, and some can enter roots
•
Rhizobacteria can play several roles:
-Produce hormones that stimulate plant growth
-Produce antibiotics that protect roots from disease
-Absorb toxic metals or make nutrients more available to roots
2. Bacteria in the Nitrogen Cycle
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Nitrogen has the greatest effect on plant growth and crop yields
•
The nitrogen cycle transforms nitrogen and nitrogen-containing compounds
•
Most soil nitrogen comes from actions of soil bacteria
•
Plants absorb nitrogen as either NO3– or NH4+
•
Bacteria break down organic compounds or use N2 to produce NH3, which is
converted to NH4+
•
Nitrification is carried out by bacteria that convert NH3 into NO3–
3.Fungi and Plant Nutrition
Topic 8 Review
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1. Mycorrhizae are mutualistic associations of fungi and roots
2. The fungus benefits from a steady supply of sugar from the host plant
3. The host plant benefits because the fungus increases the surface area for
water uptake and mineral absorption
4. Mycorrizal relationships are common and might have helped plants to first
colonize land
4. Symbiotic relationships that are not mutualistic
•
Some plants have nutritional adaptations that use other organisms in
nonmutualistic ways
•
An epiphyte grows on another plant and obtains water and minerals from
rain (Ex. Spanish moss)
•
Parasitic plants absorb sugars and minerals from their living host plant (Ex.
Mistletoe)
•
Carnivorous plants are photosynthetic but obtain nitrogen by killing and
digesting mostly insects (Ex. Venus flytrap)
21. What is pollination?
In angiosperms, pollination is the transfer of pollen from an anther to a stigma
Pollination can be by wind, water, bee, moth and butterfly, fly, bird, bat, or water
As pollen germinates, tube nucleus forms a pollen tube down the style toward the
embryo sac
•
At the same time, generative nucleus divides by mitosis to form 2 sperm
nuclei (male gamete)
Topic 8 Review
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•
Pollen tube penetrates micropyle
•
After landing on a receptive stigma, a pollen grain produces a pollen tube
that extends between the cells of the style toward the ovary
•
Double fertilization results from the discharge of two sperm from the pollen
tube into the embryo sac
•
One sperm fertilizes the egg, and the other combines with the polar nuclei,
giving rise to the triploid (3n) food-storing endosperm
•
After double fertilization, each ovule develops into a seed
•
The ovary develops into a fruit enclosing the seed(s)
22. What does a ripe ovary develop into? What do the ovules develop into?
After double fertilization, each ovule develops into a seed
The ovary develops into a fruit enclosing the seed(s)
23. How can a plant reproduce asexually?
Vegetative reproduction (fragmentation is an example in which an example, in
which pieces of the parent plant break off to form new individuals tht are exact
genetic replicas of the parent
24. What is tropism? What is the difference between phototropism (positive and
negative), gravitropism, and thigmotropism?
Topic 8 Review
Name:
A trophism is a plant growth response from hormones that results in the plant
growing either toward (positive) or away (negative) from a stimulus
•
Phototrophism is the growth of a shoot in a certain direction in
response to light.
•
Positive phototropism is the growth of a plant toward
light
•
Negative phototropism is the growth of a plant away
from light
Gravitropism is a plant’s response to gravity
•
Roots show positive gravitropism
•
Shoots show negative gravitropism
•
Auxins play a key role in gravitropism
2. Thigmotropism is directional growth as a response to touch
•
Ex: tendrils
25. List the 5 plant hormones mentioned in your review book and briefly
describe which actions each is in charge of:
Topic 8 Review
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a. Auxin (natural auxin—IAA–indoleacetic acid)
b. Cytokinins
•
Stimulates cell elongation
•
Promotes root formation
•
Regulates fruit development
•
Enhances apical dominance
Topic 8 Review
Name:
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regulate cell division
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Anti-aging effects (keeps cut flowers fresh)
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Slow apoptosis
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Promote stem elongation
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Promote seed germination
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Contributes to fruit growth
c. Gibberellins
d. Brassinosteroids
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Promote cell elongation and division
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Promotes xylem differentiation
•
Slow leaf abscission
•
Promotes seed dormancy until optimum conditions
•
Drought tolerance (closes stomata during water stress)
e. Abscisic acid
.f Ethylene (gas)
•
Promotes fruit ripening
•
Prepare for leaf abscission
•
Initiates triple response (growth maneuver so a shoot
can avoid an obstacle)
26. What is a phytochrome?
Phytochromes are pigments that regulate many of a plant’s responses to light
throughout its life
•
Responses include seed germination and shade avoidance
Topic 8 Review
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Name:
Phytochromes exist in two photoreversible states, with conversion of Pr to Pfr
triggering many developmental responses
•
Phytochromes absorb mostly red light
27. What are circadian rhythms?
Circadian rhythms are physiological cycles that have a frequency of about 24 hours
and that are not paced by a known environmental clock.
•
In plants, the surge of Pfr at dawn resets the biological clock.
•
The combination of a phytochrome system and a biological clock allow the
plant to accurately assess the amount of daylight or darkness and hence the
time of the year
28. What is photoperiodism?
Photoperiodism is defined as a physiological response to a photoperiod (the relative
lengths of night and day).
•
Important in plant life cycles such as flowering
•
It is night length—not day length—that controls flowering and certain other
response to photoperiod.
29. Compare short-day, long- day plants, and day – neutral plants.
Short-day plants require a period of continuous darkness longer than a critical
period (length of day) in order to flower. These plants usually flower in late
summer, fall, and winter
Long-day plants flower only if a period of continuous darkness was shorter than a
critical period. They often flower in late spring or early summer. They are actually
short-night plants.
Topic 8 Review
Name:
Day-neutral plants can flower in days of any length