Evolution of Land Plants & Structures of Plant Bodies Flashcards
What does “alternation of generations” refer to?
1. Fertilization of gametes into zygote
2. Zygote divides by mitosis into sporophyte
3. Sporophyte produces spores by meiosis
4. Spores divide by mitosis into gametophyte
5. Gametophyte produces gametes by mitosis–> RESTART.
Therefore there are 2 phases: Haploid gametophytes and diploid sporophytes.
How do gametophytes produce gametes?
By mitosis
What does it mean for gametes to be iso-gametes? What is the opposite?
If the sperm and egg are similar in morphology. If they are different, they are hetero-gametes.
What is it called when spores are similar in morphology? What is it called when different?
homosporous; heterosporous.
At what point in the “alternation of generation” process is there germination?
When the spores develop before dividing by mitosis into gametophytes.
What is the purpose of the waxy cuticle?
To promote water conservation by preventing water loss.
What is a stomate?
A pore in leaves used for controlled gas exchange (including water vapor)
What type of plant did stomates first appear in?
Mosses.
What are bryophytes and what is an example of one?
A plant that doesn’t have any vascular tissue. Ex. Moss
What is the difference between lower pteridophytes and advanced pteridophytes?
Lower are microphylls whereas advanced are megaphylls.
What is the difference between microphylls and megaphylls?
The leaves of microphylls are small with one central vein whereas the leaves of megaphylls are large with a complex vascular system.
What plant first had microphylls?
club-mosses
What plant first had megaphylls?
ferns
In plants, what is the technical name for the structure that contains the sperm?
Antheridium
In plants, what is the technical name for the structure that contains the egg?
Archegonium
What type of reproduction does Chlamydomonas, the green algae we saw in the lab, undergo?
Sexual AND asexual modes. (asexual reproduction refers to the multiplication of the haploid gametophytic phase)
Is it necessary for both gametes and spores to be similar or different?
No. Some plants can be heterogametes (different) and homosporous (same) Ex. the coleochaete.
What does matrotrophic mean? Give two important examples of matrotrophism.
It means “parasitic on its mother”. In bryophytes, the sporophyte is matrotrophic on the gametophyte. In gymnio & angiosperms, it’s the opposite: the gametophyte is matrotrophic on the sporophyte!
What plant has the largest motile sperm? How many flagella does it have?
Horsetail, it is bi-flagellated
What are sporangia?
Spore-making structures inside the little bumps on the underside of fern megaphylls.
What is the difference between gymnosperm and angiosperm?
In gymnosperm, the seeds lie naked and unprotected on the outside of the structure whereas in angiosperm the seeds are enclosed in the ovary (the fruit)
In bryophytes and pteridophytes, the sperm is motile. What about in gymnosperms and angiosperms?
In gymno- & angiosperms, the sperm is NOT motile.
What is the advantage of having a dominant sporophyte?
The sporophytes are HAPLOID which means better protection against genetic mutations.
What is the difference between taproots and fibrous roots?
Taproot systems have one main thick root with long thin branches.
Fibrous roots on the other hand have many branches of similar thickness (like a bush of roots underground)
What type of roots does grass usually have?
Fibrous
What are internodes?
The angle at the intersection of branches and stem/trunks
What is the canopy?
The overall space and shape that the branches/leaves/etc. take up.
How do we determine the difference between a leaf and a leaflet of a compound leaf?
A leaf must have a BUD in its axle.
What characterizes a monocot vs a dicot plant? Think of leaves, think of nodes, think of the vascularization of the stems.
- Monocots have long narrow leaves (like grass) with parallel veins vs dicots are wider (maple, etc.)
- Monocots leaf nodes are way lower on the stem, forming a sheath around it before sticking out.
- The vessels in dicots are made of bigger bundles that are around the outside of the stem, vs. in monocots the vessels are smaller and thinner and are spread all throughout the stem.
What is the leaf of a monocot plant called?
The leaf blade
What does “phyllotaxy” refer to?
The leaf configuration around the main axis.
There are 4 phyllotaxies. Name them.
- Opposite
- Alternate
- Whorled leaves (around the stem)
- Rosette (on the ground)
How do stomates work?
Two rectangular guard cells are side by side, when they get swollen/turgid the walls expand in a way that they split apart in the middle, creating a pore for gas exchange
Which leaves grow larger, those in the sun or those in the shade?
Those in the SHADE. Grow larger to capture all the light they can get.
Which leaves grow faster, those in the sun or those in the shade?
Those in the shade –> known as the “shade-escaping mechanism”
What are leaf stipules?
Structures that grow at the base of each leaf, which serve wtv purpose needed by the plant (can grow into spines, or tendrils, or can be leafy to help photosynthesis)
What part of the plant is the pitcher of a pitcher-plant?
The leaf blade
What direction of growth does the apical meristem play a part in?
Vertical (height of plant)
What direction of growth does the lateral meristem play a part in?
Thickness of stem/diameter increase
What is an important difference between the shoot apical meristem and the root apical meristem?
The root apical meristem has a root cap of dead cells to protect its meristem.
What is the difference between the vascular tissue of the shoot system and that of the root system?
In the shoot system, the vascular tissue is in bundles throughout the stem, whereas in the roots, the vascular tissue is in ONE bundle in the center of the roots.
What part of the plant survives the winter and engenders growth in the next spring?
The crown at the transition area between shoot and root systems
What is “ground tissue”?
The tissue in between the vascular bundles.
What does the cambium of a plant do?
It is responsible for cell division and therefore lateral growth
What does the xylem of a plant do, and where is it situated?
It transports water from the roots up, it’s on the central side of the cambium.
What does the phloem do, and where is it situated?
It transports glucose away from the leaves, and it’s on the outer side of the cambium.
What does primary plant growth refer to, where does it take place?
The vertical growth of both the shoot and root apical meristems.
What does secondary plant growth refer to, and where does it take place?
The lateral growth of the cambium.
Explain how growth rings come to be in trees?
The cambium produces xylem on the inside (and therefore the xylem in the middle keeps getting thicker. The xylem cells produced during rainy seasons are large, whereas the xylem cells produced during dry/cold seasons are smaller. Since the cell sizes follow a pattern that concords with the environmental pattern, you end up being able to see rings of alternating cell sizes.
What is heartwood made up of?
Dead xylem cells that no longer transport water.
What is the purpose of the root cap, aside from protection?
It senses gravity to help the roots grow downwards
Why is it so hard to rip off root branches compared to shoot branches?
Because the root branches vascular tissue is embedded so deeply in the root (remember it’s central instead of around the edges)
What part of the plant secretes chemicals to attract or repel other organisms?
The root apical meristem.
What are pneumatophores?
Roots that are sent up into the air to perform gas exchange for plants in swampy/wet areas.
How many petals do dicot flowers usually have? What about monocot flowers?
Dicot flowers usually have 5 petals, monocot flowers usually have only 3.
What is the thalamus of a flower?
The top part of the stalk, where the flower connects to the stalk.
What is the stamen, what are the 2 structures it contains? What sex are the gametes it produces?
The stamen are the thin stalks with the powdery blob on top. Technical terms: the filament is the stemmy thing, the anther is the powdery thing. The anther produces the MALE gametes.
The carpel is comprised of 3 parts, what are they? What sex are the gametes that the carpel produces?
- ovary
- style
- stigma
FEMALE
If there is more than one carpel, what are they collectively known as?
The pistil
What was the first experiment on the role of soil in plant growth? What was the conclusion?
Aristotle weighed the quantity of dirt a plant started with and then weighed the dirt again after significant plant growth, found that the soil was about the same mass. He concluded that the plant didn’t take anything from the soil.
What are the 4 types of transport? Do you know how they work?
- Osmosis
- Diffusion
- Bulk FLOW (pressure difference)
- Facilitated transport
What part of the plant takes part in bulk flow transport?
The xylem & phloem
What’s the difference between molality and molarity?
Molarity is mols/VOLUME, whereas molality is mols/MASS
There are 2 types of membrane cotransporters, what are they and what’s the difference?
Symporters which carry more than one molecule in the same direction, vs. Antiporters which carry more than one molecule in opposite directions.
How does waster get from the root hairs all the way to the xylem to be carried up to the rest of the plant?
There are three ways:
- Transmembrane route straight thru the cells by water channels.
- Symplastic route through the cells but via plasmodesmata
- Apoplastic route where the water can penetrate the cell walls but NOT the plasma membranes, so the water travels around the cells.
What is the structure that protectively surrounds the xylem vessels and doesn’t allow for apoplastic transport?
The casparian strip in the endodermis, the cells walls are waxy so water can’t penetrate them anymore. At that point water has to travel thru the actual cells by water channels or plasmodesmata
What does the cohesion-tension theory refer to?
The idea that plants have an open circulatory system so as water evaporates from the leaves it creates lower pressure that pulls water up from the xylem -> roots -> earth.
What is the difference between plant source tissue and sink tissue?
Source tissue is where sucrose is produced, sink tissue is where sucrose is transported to to be used (new buds, new leaves, etc.)
What makes nutrient-filled sap travel from the source tissue to the sink tissues?
Higher turgor pressure (solute) in the source tissue drives transport to the lower-pressure sink tissues.
What is the difference between micro and macro nutrients?
We need way more macro-nutrients than micro-nutrients.
Why does it make sense that overwatering a plant can be bad for it (or too much rain)?
Because certain nutrients that the plant needs are anions and so they can’t bind to the soil, they remain in the water. If the water is washed away too much, there won’t be any anionic nutrients for the roots to take up anymore (esp. NO3- and PO4(2-))
How does leg-hemoglobin work? Why is it important?
Leg-hemoglobin binds up free O2 like crazyy which allows for more free nitrogen and therefore better nitrogen fixation. This is important because otherwise the O2 would inhibit nitrogen-fixation too much for good nitrogen fixation.
Do all roots have nodules that contain leghemoglobin?
No, only the ones that are infected (symbiotically) by nitrogen-fixing bacteria.
What is a coleoptile?
A new, growing shoot of a plant
What tropisms is auxin related to? What effect does auxin have on plant cells?
Phototropism, geotropism. Causes plant cells to elongate.
How does auxin affect root and shoot cells differently?
In root cells, the higher concentration of auxin in the lower cells (due to gravity) inhibits their elongation, therefore the top side cells elongate more and the root curves down (positive geotropism). However: in shoots, the accumulation of auxin in lower cells causes INCREASED cell elongation, causing the shoot to curve upwards.
Explain the phenomenon called “apical dominance”
Growth is emphasized at the the apical meristem of a plant because it has a higher concentration of auxin. However, if the apical meristem is removed, more lateral shoots appear because they aren’t kept dormant by their lower amount of auxin.
Is dwarf plant growth permanent?
No, it can be reversed with application of giberellin
What does the plant hormone ABA (abscisic acid) do?
Causes seed dormancy, needs to be eliminated before the seed can germinate.
In Borthwick et al’s experiment on light and germination, what was the result?
When the most recent light the seeds were exposed to was red (the equivalent of white light) they germinated within a few days. When the most recent light was “Far-red” (the equivalent of darkness), they only germinated ~50% of the time.
How does Short-day plant flowering work?
The plant will only flower if the photoperiod is SHORTER than their critical period.
How does Long-day plant flowering work?
The plant will only flower if the photoperiod is LONGER than their critical period.
How does Day-neutral plant flowering work?
The plant will only flower if the number of leaves it has produced is sufficient. The flowering is independent of photoperiods.
Explain the development of the female gametophyte in 4 steps.
- The megasporocyte in the ovule undergoes meiosis, resulting in 4 megaspores.
- 3 of the megaspores degenerate.
- The remaining megaspore undergoes mitosis to result in 8 haploid nuclei.
- 6 of the nuclei get put into new little cells at each pole of the mature embryo sac, while the last 2 stay loose in the embryo sac (which is in itself like a big cell with 2 nuclei).
Describe the 3-4 steps of the development of the male gametophyte.
- The anthers contain many microsporocytes -> A microsporocyte divides by meiosis into 4 microspores.
- Each microspore divides by mitosis into 2 cells. One contains the other. The container cell is called Tube cell, the inside cell is called the Generative cell. These two around surrounded by a protective outer coat, and the whole thing is a grain of pollen (the male gametophyte).
(4. Later, the generative cell divides into actual sperm cells)
What plant hormone is autocatalytic?
Ethylene
What are some examples of biotic stresses?
Bacteria, being eaten by animals, etc. Due to biological agents.
What are some examples of abiotic stresses?
Temperature extremes, pollution, oxidative stress, strong wind, flooding, etc.
What are the 3 plant stress response types?
- Avoidance/resistance
- Tolerance
- Escape
What are aerenchyma? What circumstances is it common to find them in?
The are air spaces in plan tissues, to permit gas exchange for tissues that are submerged in water.
