Plant Science 102
Study Guide Section #2
2007
1. Why would you want to know what controls the growth and development of
plants?
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To manipulate plant growth, and predict production.
To optimize nutrient and agronomic practice to maximize crop
productivity and end use quality.
To allow plant breeders to genetically modify plants to increase
productivity or quality.
To determine the effects of pests and diseases on plant growth and hence
develop natural resistance.
To determine aspects of a plants growth to discover ways to kill them
(herbicides).
2. What does a plant have to do to survive?
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Plants need to produce energy from the sun through photosynthesis.
Uptake water and nutrients from the roots.
In take CO2 and H2O and exhale O2
Must have the ability to reproduce either sexually or A-sexually (i.e.
clonally).
Must be able (at least in part) to have some defense against pests and
other stress factors.
3. Identify the following plant cell components are briefy indicate their function.
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Cell wall: provides protection and structure.
Plasma membrane: controls movement of minerals, metabolites and water
into and out of the cell.
Chloroplast: site of photosynthesis, starch biosynthesis and starch
accumulation.
Golgi apparatus: site of synthesis of polysaccharides such as hemicellulose
needed for cell walls.
Mitochondria: site of all biochemical reactions of respiration.
Endoplasmic reticulum: site of protein synthesis.
Vacuole: site for storage of proteins.
Nucleus : site of the majority of the genetic information (DNA) and is the site
of transcription.
4. Identify the plant part in the diagram shown below.
5. Which plant cells can differenciate into different cell types?
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Meristem cells
6. What is the major function of the following cell types?
(a) Parenchyma cells
 Make up the majority of the fruit and vegetables we eat.
 In leaves they function in photosynthesis (mesophyll), while in stems and
roots they function in starch, sugar and oil storage.
 Adjacent to the xylem or phloem sieve they act as transfer cells.
(b) Collenchyma cells
o They are elongated with much thicker cell walls.
o Just underneath the epidermis and provide mechanical support
(c) Sclerenchyma cells
 These cells also have a supportive role, but these cells are actually dead
cells and have very thick cell walls with lignin.
 They form fibers that protect the phloem in the stem.
7. Meristematic cells in plants differentiate into three tissue types. Label the three
tissue types on the stem cross section shown below.
Ground tissue
Vascular tissue
Dermal tissue
8. What is the major function of Vascular tissues?
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The major function of phloem is to transport sugars and amino acids
throughout the plant: from leaves to roots, and to developing fruit
and seed; and from senescing to growing.
The major function of xylem is to transport water and minerals from
the root to the shoot.
9. What is the major function of stometes?
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Stomates are small holes or pores in leaves and stems that regulate gas
exchange.
10. What are the tree primary regions of root development?
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At the root tip ia a region of cell division (apical meristem), moving up
the root is then a region of cell elongation, followed by a region of cell
maturation.
11. What is the difference between cells that result from mitosis compared to cells
that result from meiosis?
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Mitosis starts with a diploid somatic cell and results in two diploid
somatic cells.
Meiosis starts with a diploid sex cell and results in four haploid cells.
12. What is the function of a seed endosperm?
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The cells in the endosperm will divide to produce cells that will store
energy for the seed to utilize when it germinates.
13. Crop plant species can generally be categorized into self-pollinators or outpollinators. What are the major characteristics of each pollinator type.
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Self-pollinating crop species are:
o Tolerant to inbreeding
o Few deleterious recessive alleles
o “Closed” flowers
o Little heterosis
Out-pollinating crop species are:
o Intolerant to inbreeding;
o Have many deleterious recessive alleles which results in inbreeding
depression when plants become homozygous.
o Have flower morphology that promotes cross pollination (i.e.
monacious, diacious, or self-incompatible).
o Have high heterosis (hybrid vigor).
14. What is the difference between a homozygous locus compared to a heterozygous
locus.
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A homozygous locus has identical copies of both alleles (i.e. AA or aa),
whereas a heterozygous locus had different alleles (i.e. Aa or aA).
15. Label the following part on the flow diagram below.
16. List three reasons for treating seeds.
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To enhance germination (including seed priming)
To apply fungicides, or insecticides or nutrients.
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To increase the size of small seed for better seed placement (i.e.
pelletization).
17. List two methods of A-sexual (clonal) propagation in crop plants.
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Budding and grafting onto various root stocks:
o Rosaceous top fruits, citrus, avocado, grape.
 Leafy cuttings:
o Pineapple, strawberry.
 Leafless cuttings:
o Sugar cane.
 Tubers, bulb, etc.:
o Potato, various bulb flowers, sweet potato.
18. What is the major characteristic of the following plant growth hormones?
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Auxins
 Stimulates cell elongation.
 Mediates the tropistic response of bending in response to gravity and
light.
 Stimulates cell division in combination with cytokinins in tissue
culture.
Cytokinin
 Are generally found in higher concentrations in meristematic regions
and growing tissues.
 They are believed to be synthesized in the roots and translocated via
the xylem to shoots.
 Stimulates cell division.
Giberellic acid
 Stimulate stem elongation by stimulating cell division and elongation.
 Stimulates bolting/flowering in response to long days.
 Breaks seed dormancy in some plants which require stratification or
light to induce germination.
Abscicic acid
 Stimulates the closure of stomata (i.e. water stress brings about an
increase in absicic acid causeing stomates to close and hence reduce
water loss through transperation).
Ethylene
 Stimulates the release of dormancy.
 Stimulates shoot and root growth and differentiation.
19. The ratio of auxin to cytokinin in a tissue dictates growth of axillary meristems.
Circle the ratio which is most likely to cause the meristem to under go cell
division and start to grow.
(a) High auxin / Low cytokinins
(b) Low auxin / High cytokinins
20. Which synthetic plant growth hormone is used as a herbicide? Is this herbicide a
giberellin, auxin or cytokinin?
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2,4-D or 2,4-Dichlorophenoxyacetic acid
It is an auxin.
21. What range of light energy is not generally absorbed by atmospheric gases?
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Between 400 and 700 um.
22. The visible light spectrum is also called what?
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Photosynthetic active radiation
23. Light intensity is one important factor of photosynthetic efficiency. What causes
increased and decreased light intensity?
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Increased light intensity is cause by the 23½o tilt of the earth. This
causes suns light to go through more atmosphere the further away from
the earths equator.
24. Why is there greater light intensity in Idaho during the summer months compared
to the winter months?
 The 23½o tilt of the earth results in Idaho being physically closer to the
sun in the summer months compared to the winter months. In addition,
in the summer the angle of Idaho in relation to the sun means that the
sun energy passes through less atmospheric gases. The reverse would be
true in the winter months.
25. Which wavelengths of light energy (red, blue or green) are least absorbed into
plant leaves for use in photosynthesis? What is the major result of this?
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Red and blue light is absorbed more than green light which is
reflected off leaf surfaces resulting is the green color of our plants.
26. What is the major result of photomorphism in plants?
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Photomorphism in plants causes a plant to increase stem growth as a
result of competition from neighboring plants.
27. If the ratio of red light to far-red light is low in a plant the plant is experiencing
high or low competition from a neighboring plant?
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High competition.
28. List two things in a plant that might be affected by day-lengh?
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Flowering
Bud dormancy
Formation of vegetables or storage organs.
29. In regard to plant flowering, describe the difference between long-day plants and
short-day plants?
 Long-day plants require short nights in order to flower.
 Short-day plants require long nights to flower.
30. What is a plants critical day length?
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The critical day length of a plant determines the minimum (or
maximum) night period necessart to initiate flowering.
31. List the two major atmospheric gases.
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Nitrogen (N2)
Oxygen (O2)
32. What is generally believed to be the major cause of global warming?
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Increased burning of fossil fuels that result in higher concentrations of
carbon monoxide and carbon dioxide in the earths atmosphere.
33. Approximatly what proportion of a plants weight is accounted for by water?
 ~90%
34. Delete the least appropriate word from the following sentences. Bob the pine tree
had to stratify/vernilize seeds from pine trees in order to get uniform
germinantion. However, his sister Betty, was more interested in
stratification/vernilization treatments to get her winter wheat to flower.
35. In photosyetem I, two water molecules are convereted into what?
 One oxygen molecule, three positively charged hydrogen atoms and
four electrons.
36. What is the function of Rubisco in the Calvin Cycle of photosynthesis?
 Rubisco can either catalyze carbon dioxide and a 5 carbon molecule
into two 3 carbon molecules or it can catalyze oxygen and a 5 carbon
molecule into a two carbon molecule and one three carboln molecule.
37. Complete the photosynthesis equation below:
6CO2 + 12H2O = C6H12O6 + 6H2O + 6O2
38. Label the components of the photosynthesis diagram below.
H2O
Light
CO2
NADPH
& H+
Light
Reaction
ATP
Pi
Calvin
Cycle
ADP
NADP+
O2
C6H12O6 = Glucose
39. What are the three primary soil types?
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Sand
Clay
Silt
40. Soil that is saturated with water and with very little air is said to be what?
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Waterlogged
41. Soil which has the correct mix of water and air is said to be what?
 At field capacity
42. What types of soil would most likely have the particle size shown below
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2 to 0.02 mm in diameter = sand
0.02 to 0.002 mm in diameter = silt
Smaller than 0.002 mm in diameter = clay
43. What causes soil compaction?
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Use of heavy farm machinery and inappropriate cultivation.
44. List four macro plant nutrients.
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Calcium
Potassium
Magnesium
Nitrogen
Sulfur
Phosphorous
45. Label the diagram below with appropriate water potential that will result in water
movement from the soil to the plant leaves.
Air -95 
Water potential
Leaf -0.8 
Stem -0.7 
Root -0.6 
Soil -0.4 
46. List four micro plant nutrients.
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Boron
Iron
Copper
Nickel
Chlorine
Zinc
Manganese
47. List the major importance of the following plant nutrients.
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Nitrogen
o Stimulates leaf and stem growth
Potasium
o Promotes general plant vigor, disease resistance, and sturdy plant
growth.
Phosphorous
o Important for good seed germinantion and early root development.
Calcium
o Important ingredient in plant cell walls.
48. If a plant nutrient is mobile within a plant, would deficiency of the nutrient be
noted first in old leaves or young leaves?
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Old leaves.
49. List two plant nutrients that are mobine in plants and two that are impbile in
plants.
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Mobile = Nitrogen, magnesium, potassium, sulphur
Imobile = Zinc, calcium, boron, phosphorus, iron
50. What two factors can influence nutrient uptake in plants.
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Soil temperature
Soil Ph