Plants Flashcards
1
Q
About how many plant species have been described?
A
300,000.
2
Q
What are the ways in which plants enable life on land?
A
- Supply oxygen
- Supply food and materials for household items
- Stabilize the soil
- Provide shelter, and more
3
Q
What are secondary metabolites?
A
Secondary metabolites are plant chemicals that are not used for cellular metabolism. Instead, they are involved in long-term survival. They might attract pollinators or repel predators, for example.
4
Q
Where are secondary metabolites stored?
A
The central vacuole.
5
Q
How do humans use secondary metabolites?
A
Humans use them as fungicides, insecticides, rodenticides, pharmaceuticals, and recreational chemicals.
6
Q
What are the four main structures that plant cells have that animal cells do not?
A
- Cell wall
- Central vacuole
- Chloroplast
- Plasmodesmata
7
Q
What is the cell wall?
A
The rigid outer layer made of cellulose that maintains the cell’s shape and protects it from damage.
8
Q
What is the function of the central vacuole?
A
- Storage
- Breakdown of wastes and macromolecules.
- Enlargement is involved in plant growth.
9
Q
What are plasmodesmata?
A
Cytoplasmic channels that connect cells and allow for cytoplasmic streaming. (the gap junctions of plants)
10
Q
What is cytoplasmic streaming?
A
In cytoplasmic streaming, plant cells keep the cytoplasm of the cell moving through multiple cells so that materials can be shared.
11
Q
What is the general purpose of photosynthesis?
A
Photosynthesis converts light energy to the chemical energy of food.
12
Q
Where are the chloroplasts?
A
They are found in the mesophyll cells.
13
Q
Where does photosynthesis occur?
A
The chloroplast.
14
Q
Where do the light reactions occur?
A
The thylakoid membrane in the chloroplast.
15
Q
Where does the Calvin cycle occur?
A
The stroma in the chloroplast.
16
Q
What is the role of the stomata?
A
The stomata lie on the underside of a leaf and allow for the exchange of gases so that CO2 can enter the leaf and oxygen can leave.
17
Q
What are the inputs of the light reactions?
A
Light, water, NADP+, ADO, and P.
18
Q
What are the outputs of the light reactions?
A
ATP, NADPH, and O2.
19
Q
What is the overall goal of the Calvin cycle?
A
The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO2 into G3P (sugar).
20
Q
What is carbon fixation?
A
The conversion of CO2 into organic compounds.
21
Q
What fixes carbon?
A
Rubisco–the most abundant protein on earth.
22
Q
What are the inputs for the Calvin cycle?
A
ATP, NADPH, and CO2,
23
Q
What are the outputs for the Calvin cycle?
A
Sugars.
24
Q
How many carbon dioxide molecules does the Calvin cycle start with?
A
3 CO2 molecules.
25
In the Calvin cycle, what happens after the input of three CO2 molecules?
There is an input of 6 ATP and 6 NADPH, taking the reaction from carbon fixation to reduction, finalizing in the production of G3P--the output.
26
What does the addition of two G3P molecules yield?
Glucose.
27
To regenerate the Calvin cycle, what must happen?
There must be an additional ATP to regenerate the Rubisco protein, and then the cycle can begin again.
28
What is the function of xylem?
Xylem brings water and minerals upward from the roots.
29
What is the function of phloem?
Phloem transports sugars and other organic nutrients throughout the plant, in any direction.
30
How is teosinte an example of selective breeding of crops?
Teosinte was selected for larger kernels that were better attached to the cob, and from that breeding came maize (also known as corn).
31
If you select a wild mustard plant for leaves, what do you get?
Kale
32
If you select a wild mustard plant for axillary (side) buds, what do you get?
Brussels sprouts
33
If you select a wild mustard plant for apical (tip) bud, what do you get?
Cabbage
34
If you select a wild mustard plant for flowers and stems, what do you get?
Broccoli
35
If you select a wild mustard plant for stems, what do you get?
Kohlrabi
36
What is transgenic modification?
The genetic modification of an organism to yield better genetics according to the situation (such as making insect-resistant plants)
37
How is insect-resistant maize made?
The production of Bt protoxin.
38
How do transgenic cassava plants reduce world hunger?
Cassava is a primary food for 800 million of the world's poor. Transgenic cassava plants are bigger, are enriched in protein, iron, and beta-carotene (vitamin A precursor), and have less cyanide.
39
How many people die each year from malnutrition?
30 million people.
40
How many children go blind each year because of vitamin A deficiency?
More than 250,000.
41
What is the first step in making a transgenic plant?
Transgenes are inserted into a Ti plasmid, and reinserted into the bacterium, Agrobacterium.
42
What is done with Agrobacterium after transgenes are inserted into it?
The totipotent tissue of a plant is infected with Agrobacterium, which transfers the Ti plasmid--and the transgenes--to the plant.
43
How does transformation after being infected with Agrobacterium occur in a plant?
Transformation is done on shoot or leaf tissue that forms a callus when grown on agar medium.
44
How do animals and plants differ in their responses to signals at the organismal level?
Animals commonly respond by moving while plants respond by altering growth and development.
45
Why are leaves green?
Chlorophyll absorbs violet-blue and red light. Chlorophyll reflects or transmits green light, giving the leaves their green color.
46
How does chlorophyll respond to far-red light?
Far-red light is at the extreme end of the visible light spectrum. Far-red light goes right through the leaf and is neither reflected nor absorbed. It is not involved in photosynthesis.
47
What is de-etiolation (greening)?
Growing in response to light. The elongation of stems slows, leaves expand, and chlorophyll is produced.
48
What induces de-etiolation?
It is induced by the light-mediated activation of a phytochrome receptor that differentially responds to red and far-red light.
49
What happens when light activates the phytochrome receptor?
The receptor turns on guanylyl cyclase, which produces cyclic GMP, which activates a signal transduction response and transcription factors that affect gene expression.
50
Besides guanylyl cyclase, what other response do activated phytochrome receptors have?
They activate calcium ion channels, which causes calcium to flow into the cell, acting as a second messenger to activate additional kinases. These kinases affect gene transcription involved in the greening response.
51
What is auxin?
Auxin is a family of hormones with similar structure and activity; the most important is indoleacetic acid (IAA).
52
What is phototropism?
Phototropism is growth towards sunlight.
53
What did the experiment with the refracting prism show?
Plants responded to red, orange, yellow, and green light by growing straight up. However, blue light (and somewhat violet light) induced the most curvature of coleoptilea. Phototropism is dictated by blue light.
54
What happens to the auxin at the tip of a plant when light strikes it?
It migrates to the opposite (shaded) side of the plant, and then down, telling the cells in the middle and opposite side to elongate dramatically.
55
What did the Darwin experiment reveal?
That phototropism occurs only when the tip of the plant blade is illuminated. When Darwin cut the tip off of a plant and illuminated it, it did not grow.
56
Why didn't the plant with its tip removed grow in response to light in the Darwin experiment?
The receptor that senses light and uses auxin to elongate the cells in response is in the tip of the blade, so by removing the tip, the receptor was also removed.
57
In Darwin's experiment, what was the difference in results between plants that had an opaque cap on their tip and plants that had a clear cap on their tip?
The plants with the opaque tip did not grow in response to light while the plants with the clear tip did.
58
In Darwin's experiment, what happened when an opaque piece was put on the stem of the plant?
The plant still bent in the direction of the light, because the receptor for the light is in the tip, not the stem.
59
What was the conclusion of the Boysen-Jensen experiment?
Phototropism occurs when the tip is separated by a permeable barrier but not an impermeable barrier.
60
In the Boysen-Jensen experiment, what was the difference in results between plants with a tip separated by gelatin and plants with a tip separated by mica?
In the plant with gelatin, the auxin was able to move through the permeable gelatin, so the plant bent in response to light. In the plant with the mica, the auxin was not able to move through, so the plant did not bend in response to light.
61
Where are blue-light photoreceptors located?
The tip of the coleptile.
62
How is auxin moved?
Auxin is moved in a polar manner by transport proteins, such that it travels downward on the shaded side.
63
How does auxin move in a horizontal plant?
When a plant is horizontal, auxin moves to the bottom.
64
What is the effect of auxin in the roots?
In roots, auxin slows growth on the bottom side of the root, curving the root downward. This is positive gravitropism, meaning the plant grows with gravity.
65
What is the effect of auxin in shoots?
In shoots, auxin speeds growth on the bottom side of the shoot, curving the shoot upwards. This is negative gravitropism, meaning the plant grows against gravity.
66
In the cell, what does the presence of auxin do?
The central vacuole expands, and auxin increases the activity of proton pumps, which pump H+ from the cytoplasm.
67
What is the result of increased activity of the proton pumps (pumping H+ out)?
This reduces the pH of the cell wall and increases membrane potential. It also brings in calcium and potassium. Then, by osmosis, the plant fills with water and expands.
68
What is the effect of reduced pH in the cell wall?
This activates expansins that break bonds between cellulose microfibrils and other cell wall components.
69
What is ethylene?
A plant hormone that is a gas.
70
What are the functions of ethylene?
1. Involved in the triple response to mechanical stress.
2. Fruit ripening
3. Leaf abscission (dropping leaves)
4. Senescence
71
How is leaf abscission induced?
Loss of leaves prevents desiccation. A decrease in auxin renders the cells of the abscission layer more sensitive to ethylene, inducing abscission.
72
What does a burst in ethylene trigger?
Apoptosis.
73
What is the purpose of fruit ripening?
Ripening protects immature fruits and facilitates seed dispersal.
74
How does ethylene trigger ripening?
It triggers ripening by softening and sweetening the fruit; using positive feedback, ethylene induces breakdown of cell walls and converts starches to sugars.
75
What is the plant's triple response to avoiding obstacles?
When an obstacle above is detected the plant releases ethylene, which has three effects on the plant.
1. Stem elongation slows.
2. The stem thickens, strengthening it.
3. Stem grows with a horizontal curvature to avoid the obstacle.
76
What is the receptor for ethylene?
ETR1.
77
When ethylene is not bound to ETR1, what state is CTR1 in?
CTR1 (negative regulator) is inactivated. CTR1's purpose is to inhibit ETR1.
78
What happens after ethylene binds to ETR1?
This inactivates CTR1 and cleaves and activates EIN2.
79
What happens after EIN2 is cleaved and activated?
EIN3--a transcription factor--is activated.
80
What does the activated EIN3 do?
It turns on the genes that produce ethylene's effects in the cell.
81
Blue light is involved in what processes?
1. Phototropism--the ability to grow towards the light.
2. Cryptochromes and inhibition of stem elongation because of the redistribution of auxin.
82
Red light is involved in what processes?
1. Seed germination
2. De-etiolation
3. Shade avoidance
83
What are phytochrome photoreceptors sensitive to?
Red light and far-red light.
84
What does the phytochrome switch respond to?
Far-red light.
85
What responses does the phytochrome switch have for far-red light?
1. Seed germination
2. Inhibition of vertical growth and stimulation of branching.
3. Setting internal clocks
4. Control of flowering
86
What happens when Pr is hit by red light?
It is sensitive to red light, so when hit by red light, it converts to Pfr.
87
What happens when Pfr is hit by far-red light?
It is sensitive to far-red light, so when hit by far-red light, it converts to Pr.
88
What is the plant's response to having a lot of Pr?
It will grow tall because it knows there is light above that it cannot reach at the moment.
89
What happens to seeds treated with no light?
They will not germinate.
90
What happens to seeds treated with red light?
They will germinate, even if put in the dark afterward. They go from Pr -> Pfr.
91
What happens to seeds exposed to red light, then to far-red light, then red light, then to the dark?
They will germinate. They go from Pr -> Pfr -> Pr -> Pfr.
92
What happens to seeds exposed to red light, then far-red light, then red light, then far-red light, then to the dark?
They will not germinate.
93
If the last light a seed is exposed to is far-red light, will it germinate?
No. If it ends on Pr they will not germinate.
94
If the last light a seed is exposed to is red light, will it germinate?
Yes. If it ends on Pfr it will germinate.
95
How do plants determine the time of year?
They use the photoperiod, which impacts flowering and other processes.
96
What determines the photoperiod?
The photoperiod is determined by the length of the night, using the phytochrome switch.
97
What are short-day (long-night) plants?
Plants that flower when night exceeds a critical dark period. A flash of light interrupting the dark period prevents flowering.
98
What are long-day (short-night) plants?
Plants that flower only if the night is shorter than a critical dark period. A brief flash of light artificially interrupts a long dark period, thereby inducing flowering.
99
What happens to short-day plants when there is a flash of red light during the night?
They will not flower because it goes to Pr.
100
What happens to short-day plants when there is a flash of red light followed by a flash of far-red light during the night?
It will flower because Pr goes back to Pfr.
101
What is thigmotropism?
The ability of plants to move.
102
How does thigmotropism work?
1. Physical stimulus.
2. Ions move across the membrane, leading to electrical impulses that move from leaf to leaf.
3. Turgor pressure is reduced in the pulvini at the leaf joints.
4. The leaf folds.
