BY 124 SI 09/17/15
The particles in soil are important because they __________.
a) eliminate spaces for air and facilitate drainage
b) are charged and hold ions needed by plants
c) fill spaces and keep oxygen out of the soil
d) are composed of nitrogen needed by plants
e) supply humus needed by plants
Fertilizers are usually enriched in __________.
a) nitrogen, phosphorus, and potassium
b) all essential nutrients
c) molybdenum, copper, and magnesium
d) iron, manganese, and zinc
e) calcium and boron
Why do farmers need to be concerned with the pH level of soil?
a) The pH level of soil affects anion exchange and influences the chemical form of
minerals.
b) Plants may turn blue if the pH is too high.
c) The pH level of soil affects cation exchange and influences the chemical form of
minerals.
d) The pH level of soil affects water levels.
e) None of the listed responses is correct.
If a plant's leaves are yellowing, it may be that the plant is deficient in the elements needed to
make chlorophyll, one of which is __________.
a) copper
b) magnesium
c) molybdenum
d) phosphorus
e) sulfur
Soil could be deficient in any of the following nutrients. If you had to supply one of them, which
would be needed in the smallest amount?
a) phosphorus
b) sulfur
c) molybdenum
d) potassium
e) nitrogen
When you add "plant food" to your potted geraniums, what are you actually providing the plant
with?
a) vitamins and amino acids
b) complex carbohydrates
c) minerals
d) sugars
e) all of the listed responses are correct
What supplies the energy for most of the microorganisms in the rhizosphere?
a) earthworms
b) mycorrhizae
c) plants
d) soil bacteria
e) nitrogen-fixing bacteria
Nitrogen fixation is __________.
a) performed by fungi inhabiting root nodules
b) the recycling of nitrogen from organic matter in the soil
c) the use of nitrogen to build molecules such as proteins and nucleic acids
d) the conversion of nitrogen gas in the air to a form usable by plants
e) the absorption of N2 from the soil
Which of the following organisms can fix nitrogen?
a) lichens
b) Azolla
c) Legumes
d) Rhizobia
e) Mycorrhizal fungi
Legumes (members of the pea family) have roots with swellings called nodules that __________.
a) produce antibiotics that protect the plant from soil bacteria
b) contain nitrogen-fixing bacteria
c) provide a steady supply of sugar to the host plant
d) increase the surface area for water uptake
e) form fungal hyphae
Which of these describes the initial interaction between Rhizobium and a soybean root?
A) there is nodule growth in response to secretions from Rhizobium.
B) Vesicles containing bacteria bud into cortical cells.
C) The nodule develops vascular tissue.
D) An infection thread is initiated in the root hair of the legume.
E) Soybeans secrete chemical signals that are detected by Rhizobium.
In root nodules, the plants provide __________, and the bacteria provide __________.
a) amino acids…ATP
b) carbohydrates…fixed nitrogen
c) carbohydrates…nitrogen gas
d) an aerobic environment…fixed nitrogen
e) ATP…nitrogen gas
Mycorrhizae develop __________.
a) only in plants such as mistletoe that parasitize other plants
b) when soil is too compact and lacks sufficient air spaces
c) as stored nutrients to support the plant when necessary
d) between roots and beneficial fungi
e) to control the evaporation of water from leaves
Which of the following is true of mycorrhizae?
a) arbuscular mycorrhizae do not have a dense mantle ensheathing roots.
b) Arbuscular mycorrhizae penetrate the cytoplasm of root cells.
c) Ectomycorrrhizae are found in many crop plants, such as wheat and maize.
d) The fungal hyphae of ectomycorrhizae form arbuscules.
e) None of the listed responses is correct.
By trapping insects, carnivorous plants obtain __________, which they need __________.
A) phosphorus…to make protein
B) sugars…because they can’t make enough in photosynthesis
C) nitrogen…to make protein
D) nitrogen…to make sugar
E) water…because they live in dry soil
What does topsoil consist of?
a) mineral particles
b) living organisms
c) humus
d) all of the above
e) a and b
A conformational change in a substance called phytochrome __________.
a) causes a plant to bend toward light
b) causes changes in a plant in reponse to stresses such as water storage
c) leads to de-etiolation
d) is responsible for gravitropism
e) triggers fruit drop
What happens after a phytochrome is activated by light?
a) de-etiolation occurs.
b) cGMP activates a protein kinase.
c) The phytochrome receptor moves from the plasma membrane into the cytoplasm.
d) Ca2+ channels are opened, and guanylyl cyclase is activated
e) Genes for proteins that function in de-etiolation are transcribed
f) Both B and D occur after reception
What is growth that results in curvatures of whole plant organs toward or away from stimuli
called?
a) heliotropism
b)
c)
d)
e)
phototropism
thigmotropism
gravitropism
all of the listed responses are correct
You are interested in determining what part of a plant is actually sensitive to light for
phototropism. A good first experiment would be to __________.
a) shine light from one side only. Then measure the auxin diffusing down the stem on the
light and the shaded sides
b) cover one part (for instance, the tip or base) with an opaque barrier before
beginning light treatments
c) remove the apical meristem and apply auxin before beginning light treatments
d) try light treatments of different colors to see which promotes flowering the fastest
e) spray auxin on just one part of the plant at a time to determine which one stimulates
flowering
In addition to interacting with auxin in the control of apical dominance, newly discovered plant
hormones help to establish mycorrhizal associations by attracting mycorrhizal fungi to the plant
roots. What are these hormones called?
a) strigolactones
b) brassinosteroids
c) gibberellins
d) cytokinins
e) none of the listed responses is correct.
A graduate student growing plant cells in a laboratory dish wants them to __________; therefore,
the student treats them with cytokinins.
a) divide
b) become dormant
c) establish mycorrhizal associations
d) grow roots
e) enlarge
Which hormone would a florist most likely spray on cut flowers to keep them fresh?
a) ethylene
b) auxin
c) cytokinins
d) brassinosteroids
e) gibberellins
As leaf lettuce matures, a tall flowering shoot extends beyond the basal, edible leaves. After the
plant bolts like this, it no longer produces broad, tasty leaves. Suppose you want to prevent
bolting so that you can harvest lettuce longer. You may want to prevent the plant from
synthesizing __________.
a) ethylene
b) gibberellins
c) abscisic acid
d) brassinosteroids
e) cytokinins
Seeds of many desert plants will not germinate until a heavy rain washes away their
__________.
a) auxin
b) phytoalexins
c) gibberellins
d) phytochromes
e) absicisic acid
The triple response to mechanical stress results in __________.
a) is promoted by cytokinin
b) the activation of kinase
c) decreased stem elongation
d) symmetric growth
e) thinner, weaker stems
__________ appear to allow a plant cell to sense its orientation with respect to gravity.
a) gibberellins
b) cytokinins
c) phytoalexins
d) phytochromes
e) statoliths
Describe cation exchange.
Roots perform cellular respiration and expel CO2 to the soil which combines with H2O to
give off H+ ions. These ions exchange with other positive ions associated with soil (calcium,
potassium, etc.) so the plants can take them up. Figure 37.3
What type of cultures do researchers use to determine which nutrients are essential?
Hydroponic Figure 37.7
Match. Some are functions, and some are deficiencies.
A = Nitrogen; B = potassium; C = molybdenum
Death of root and shoot tips; chlorosis in older leaves C
Micronutrient C
Macronutrient AB
Mottling of older leaves, with drying of leaf edges; weak stems; roots poorly developed B
Cofactor of many enzymes; major solute functioning in water balance; operation of stomata B
Component of nucleic acids, proteins, and chlorophyll A
Chlorosis at tips of older leaves A
Know the nitrogen cycle (Figure 37.10). What two forms of nitrogen do plants take in? What do
nitrogen-fixing bacteria change nitrogen to (1st step)? What changes bacteria ammonium to
nitrate? What bacteria can change humus to ammonium? What bacteria returns nitrogen gas back
to the atmosphere? What is this change?
Nitrate and ammonium; ammonia (which turns into ammonium through H+); nitrifying bacteria;
ammonifying bacteria; denitrifying; from nitrate to N2
Know Figure 37.12 (Development of a nodule). First step? 2nd step? 3rd step? 4th? 5th?
1) roots emit chemical signals that attract Rhizobium bacteria. The bacteria will emit signals
to stimulate root hairs to elongate to form an infection thread.
2) Infection thread containing bacteria penetrates the root cortex. Bacteria will bud into
vesicles and develop into bacteroids. Cells in the cortex and pericycle divide.
3) These dividing cells in the cortex and pericycle combine to form the nodule.
4) These nodules form vascular tissue supplying nutrients to the nodule and carrying the
nitrogenous compounds to the vascular cylinder for distribution.
5) Mature nodule forms; layer of lignin-rich sclerenchyma cells forms, reducing absorption
of oxygen and thereby helping maintain the anaerobic environment needed for nitrogen
fixation.
How do they maintain this anaerobic environment?
Lignified external layers limit gas exchange; leghemoglobin binds reversibly to oxygen (it’s
an oxygen buffer and reduces the concentration of free oxygen; it regulates the oxygen
supply for cellular respiration and helps to not let it disrupt nitrogen fixation) remember
that nitrogen fixation is very energy expensive; 16 ATP needed to convert 1 N2 to 2 NH3
Compare and contrast ectomycorrhizae and arbuscular mycorrhizae (endomycorrhizae). Figure
37.13.
Ectomycorrhizae – mantle of fungal mycelium ensheathes the root (surrounds it). Fungal
hyphae extend, absorbing water and minerals, especially PHOSPHATE. Hyphae also
extend into the extracellular spaces of the root cortex.
Endomycorrhizae – no mantle forms, but the hyphae extend into the root. It makes
extensive contact by branching of hyphae that provide a lot of surface area. They penetrate
cell walls, but NOT plasma membranes.
Know what epiphytes, parasitic plants, and carnivorous plants are.
What are the 3 stages of signal transduction?
Reception, transduction, response
Explain the process of greening or de-etiolation. Figure 39.4
Light hits the phytochrome (reception); cGMP produced and Ca2+ channels opened
(transduction) to activate kinases; kinases will activate transcription factors and genes are
expressed as the transcription factors are activated (response) then greening
Know the results of Darwin and Darwin, Boysen-Jensen, and Went’s experiments.
Darwin and Darwin = phototropism occurs only when the tip is illuminated
Boysen-jensen = phototropism occurs when the tip is separated by a permeable barrier but
not an impermeable barrier
How do gibberellins wake a seed from dormancy?
After the seed imbibes water, the embryo releases gibberellins, which will lead to the synthesis
of alpha-amylase which helps hydrolyze the endosperm.
What’s triple response in reponse to ethylene?
1) slowing of stem elongation 2) thickening of the stem 3) curvature that causes the stem to start
growing horizontally