Genetics-Exam 3 Flashcards
1
Q
What kind of growth do plants show?
A
Indeterminate growth
2
Q
What is indeterminate growth?
A
Growth with no genetically predefined limits (plants), humans show determinant growth which is growth tp a genetically predetermined size
3
Q
What are two unique traits of plants?
A
they can be very big and very old (bristlecone pine can be more than 5000 years old)
4
Q
How do plants deal with the world and damage?
A
chainsaw syndrome/lawnmower man, plants operate by soaking up damage and replacing bits lost by indeterminate growth by growing again; they just deal with it
5
Q
How are plants similar to animals?
A
Plants have to perform many same functions as animals like:
- reproduce
- obtain nourishment
- disperse
- fend off pathogens
- monitor and respond to the environment
- but plants have to do the same functions as animals but without the use oof a nervous system and muscles
6
Q
How do plants operate?
A
able to make lots of STUFF, very productive because of photosynthesis, almost 90% of biomass is plant-derived
7
Q
What does it mean to be biologically successful?
A
reproductive success despite all stresses: like insect herbivory, salt, competition, drought, flooding
8
Q
Why is water intrinsic to plant life?
A
evolutionary history of plants shaped how biology operates on land; plants evolved in water to love in land
9
Q
What are the adaptations and specializations plants developed from the transition to land from the ocean?
A
- waxy cuticle
- stomata
- vasculature
- pollen
- seeds
- support (lignification)
- nutrient/water scavenging systems
- organ specialization (roots, shoots, leaves)
10
Q
Why was there no life before oxygen?
A
Most life cannot survive, as oxygen provides bulk of energy to eukaryotes and is required to burn food/fuel, during this time very little oxygen in the atmosphere
11
Q
What was the oxygen revolution?
A
2.7 billion years ago, O2 began accumulating in the atmosphere; oxygen production builds up energy metabolism making biology feasible, from 2.7 to 2.3 billion years ago many prokaryotic groups went extinct, however some able to adapt and use cellular respiration to harvest energy—eukaryotes
12
Q
Why did the oxygen revolution occur?
A
via photosynthesis by cyanobacteria and later eukaryotic algae produced O2; allowed life to emerge very quickly after cellular life emerges you get photosynthetic cellular life
13
Q
When did plants start emerging?
A
around 500 Ma small plants, fungi, and animals emerged on earth, since colonizing earth, plants have diversified into roughly 390,000 species- most angiosperms
14
Q
What is the relationship between land plants and algae?
A
land plants do not include photosynthetic algae but can give clues to where land plants come from, believed that photosynthetic algae and plants have a common ancestor
15
Q
What did the common ancestor between plants and algae look like?
A
common ancestor looked like alga, lead to photosynthetic algae and plants
16
Q
What is the closest living relative to land plants?
A
charophytes which are green alga, look like plants and are photosynthetic, not ancestor plants but like “sisters”; comparisons both nuclear + chloroplast genes point to charophytes the closest living relatives of land plants
17
Q
What adaptations allowed plants to move to land?
A
charophytes have layer of durable polymer called sporopollenin that prevents exposed zygotes from drying out (reproduction is hard) acts like armor; sporopollenin also found in plant spore walls (prob ancestor had same trait)
18
Q
What challenges did the move to land give plants?
A
movement onto land by charophyte ancestors provided unfiltered sun (also a challenge bc more UV rays) and more CO2 and O2 and nutrient-rich soil.
However, posed many challenges
- less buffered
- lack of structural support
- reproduction on land is hard
- scarcity of water
- inaccessible nutrients in soil
19
Q
How did plants deal with the lack of structural support?
A
- already had rigid cellulosic cell walls + hydrostatic skeleton; had holdfast and rhizoids (like roots but not real roots)
- roots later and modified stems/leaves to make tendrils/hold things (later on)
- made new things-strengthening tissues (like xylem (lignin-wood) and collenchyma (later on)
20
Q
How does algal fertilization occur?
A
ex: Ascophyllum, “fire and forget”, have both male (sperm) and female structures (egg), dumps at edge of ocean as tide goes down so sperm can swim to egg (bc water)
21
Q
How does modern day alga laminaria fertilization occur?
A
live @ edge of ocean
- laminaria alga- diploid organism (2N) undergoes meiosis
- Produces haploid product-spore (n) so meiosis does NOT produce gamete but a single cell
- Spores germinate and build ANOTHER organism by mitosis (n)
- Gametophyte (organism built by mitosis) with one individual creating egg, other sperm (2 gametes)
- gametangia: specific regions that undergo mitosis to make gametes - Once gametes form zygote form sporophyte (2n) and cycle repeats
- –this is a good way to reproduce bc gametophyte can make lots of eggs and sperm
22
Q
What is alteration of generations?
A
gametophytes are haploid and produce haploid gametes by mitosis, fusion of gametes produces diploid sporophyte which produces haploid spores by meiosis
23
Q
What are the 5 derived traits of plants?
A
- 5 key traits appear in nearly all land plants but absent in chorophytes
1. alternation of generations
2. walled spores produced in sporangia. Spores encapsulated in protective wall produced by sporangia
3. multicellular gametangia gametes
4. multicellular, dependent embryos
5. apical meristems (growth/branching) likes you grow by branching/roots branches
24
Q
What is a multicellular-dependent embryo?
A
plants are great parents, as they take next generation, embryo and plant, protect and nourishment which improve survival and reproduction of future generation
25
What are characteristics of moss (a byrophyte)?
1. major life stage is the gametophyte ( the "moss" part)
2. sporophyte (very small plant) is dependent on the gametophyte (very big plant)
3. waxy cuticle for waterproofing and in some cases stomatal pores (gas exchange)
4. size LIMITED by lack of vascular system and support tissues
5. no true leaves (again bc no vascular system)
6. flagellated swimming sperm REQUIRE film of water to move to an egg, so mostly limited to damp areas
7. no roots, just rhizoids
8. yet mosses are hardy colonizers (Huge Carbon sinks and resilient to drying + extreme environmental conditions)
26
What are seedless vascular plants?
- lack seeds
- depend on water during fertilization
- BIGGER than moss (bc has vascular system)
- have vascular plumbing system: Phloem and xylem (structure/support and internal transport)
- gametophyte tiny, sporophyte big thing we see
- well-developed roots and leaves (apical meristems)
27
Why does a vascular system allow formation of true leaves?
allow for movement of things made locally to move to other parts of plant
- xylem allows for rigidity to hold out leaf/framework and can do photosynthesis
- interconnected tubes (phloem) which allows for internal transport sysyem
- important to getting big
- *vasculature allows for TRUE leaves and roots
28
What is the reproductive cycle of Seedless Vascular Plants (like ferns)?
- switched from bryophyte, gametophyte is tiny part of plant while sporophyte is the dominant part, from this point gametophyte continues to get smaller and smaller (in gymnosperms and angiosperms--can't even see gametophyte)
- spores are dispersal stage of organisms, fern leaves have pastures on back which are spores which can move through the environment
29
What traits do seedless vascular plants have?
1. early vascular plants had independent branching sporophytes (apical meristems)
living vascular plants have:
2. life cycles dominated by sporophytes
3. vascular tissues called xylem and phloem
4. well-developed roots and leaves
5. seedless so depend on spores to disperse sperm
30
What are the features of gymnosperms?
- pollen (spores): allows for dispersal and reproduction and eliminates the need for film of water
- transfer part of seed where ovules are (like sperm)
- pollen contains sperm
- have seeds (but don't make fruit tissues) but can make cones
31
What is pollen and how does it play into the production of sperm?
- microspores develop into pollen grains, which contain the male gametophyte but pollen is NOT the male gametophyte
- pollination is the transfer of pollen to the part of a seed plant containing ovules
- * pollen eliminates the need for a film of water + can be dispersed great distances by air or animals
- if a pollen grain germinates, it gives rise to a pollen tube that discharges sperm into female gametophyte within the ovule
32
Why did seeds change the world?
- seeds consist of an embryo and nutrients surrounded by a protective coat. Bc plants are awesome parental care, as they give it nutrients, makes it possible to establish in uninhabitable places
- enabled them to move through the terrestrial environment to become dominant producers, originated 360 million years ago
33
Why do seeds provide evolutionary advantages over spores?
got tiny plant packaged with resources to build sporophyte, may remain dormant for days to years until conditions are favorable for germination (plants banking biology over time), seeds have a supply of stored food
34
What do gymnosperms make?
bear "naked" seeds usually cones (but not fruit tissue), seed are exposed in cones, angiosperms seeds are embedded in tissues of fruit, most gymnosperms are cone-bearing plants called conifers, they do NOT make flowers
35
What is a flower?
- structures of flower are all produced on the sporophyte as a flower made by sporophyte, inside flower is female gametophyte (haploid) live inside sporophyte tissues where its protected and nourished because it's very delicate
- pollen (the product of the spore) makes the male gametophyte as it grows within the tissues here, pollen lands on stigmatic surface and then germinates and grows tube of tissue down through style/stock and get down to ovary, so inside tube of tissue it will make male gametophyte and the male gametophyte will make sperm
- so the male and female gametophyte are NEVER visible/outside so don't need film of water
36
What groups are angiosperms split into?
Angiospermssplit into 2 groups based on their morophology and "seed leaves" (cotyledons)
37
What are cotyledons?
cotyledon:in seeds there are little embryonic plant, leaves inside a seed
38
What is a monocot?
monocot: single seed leaf that contains 1 cotyledon plant, more than 1/4 of angiosperms are monocots, this group grasses support most of agriculture ex: orchids, grasses, palm tree
39
What is a dicot?
dicot: contain 2 cotyledon plants, more complicated than monocots
40
What do angiosperms need?
root and shoot system which become packaged into seed
41
What is a seed?
- seed contains tiny plant that sits in soil which takes up water + germinates when conditions are good
- grow new plant, like tiny version of plant
- radicle
- hypocotyl
- plant pushes through soil then cotyledon/s unfold (2 if dicot, 1 if monocot)
- plant will then go on to make true leaves
42
What is a radicle?
where embryonic root comes from, will eventually grow into root system, shoot forms after
43
What is a hypocotyl?
where shoot elongates, part of embryonic shoot
44
Why are cotyledons successful?
once germinated, unfold cotyledons which can be photosynthetic so they can power the plant, in many seeds cotyledon is packed with nutrients and resources in order to feed thee embryo as it grows into tiny plant (food storage)
45
Difference between dicot and monocots (monocot focus)
- like dicot, monocots produce embyronic root-radicle which develop into full root system
- embyronic shoot different, as it produces structure-coleoptile versus in dicots have a hypotcotyl
- coleoptile: embryonic shoot bit, rolled up tube so once it gets above soul it unfurls with true leaves
- cotyledon remains in the seed, as its not going to be photosynthetic AND not carried up to surface of soil like a dicot
- what cotyledon does is transport nutrients inside seed into embryo to build new plant
- ex: maize nutrients stored in tissue called endosperm
46
What is primary growth?
occurs in both monocots and dicots, phrase of growth in plant where plant gets taller and makes more branches= longer organs
47
How is primary growth powered?
by apical meristems which are at tips of each growing bit, meristems are able to undergo constant cell division and make lots of cells bc plants have indeterminate growth
-* meristems involved in primary growth at the apex/tip of each plant organ
48
What are the two key systems in angiosperms?
shoot system and root system
49
What is the shoot system?
1. photosynthesis: capture light and power cells
| 2. Reproduction: make flowers to do sexual reproduction
50
What is the root system
1. Mine soil for minerals and water
2. anchorage to hold down and not fall over
3. Storing carbohydrates (in some plants)
51
What are the 3 basic plant organs
shoots, roots, and leaves
52
What is the importance of vascular system (in relation with the 3 basic plant organs)?
- plants take up water/minerals from below ground
- plants take up Co2 and light above ground
- vascular system allows exchange so roots can rely on sugars produced by photosynthesis in shoot system, shoots reply on water and minerals absorbed by root system
53
How does root system work?
the primary root is the 1st root to emerge, then primary shoot branches to form lateral roots (side roots) which then improve anchorage + water absorption
54
What are the two kinds of roots?
taproot and fibrous root
55
What is a fibrous root?
highly branched and very fine, not necessarily deep but good at exploring the upper level of soil and mine the surface layers, usually used to control erosion
56
What is a taproot?
thicker than fibrous roots but still has branching, allows to grow deep into the soil and get very deep water, strong anchor (ex:mesquite tree)
57
Where does absorption of water and minerals occur in roots?
- most plants, absorption of water and minerals occurs near the tips of the roots and older roots hook the roots to plant
- tips fuzzy-root hairs greatly increase the surface area of root to take stuff
58
What are some root adaptations with specialized functions?
1. Support ex:prop roots
2. storage (full of nutrients) used to store resources for next year
3. air supply (ex: man-grooves grow submerged in water)
59
What are the 2 types of shoots?
shoots that make flowers (reproductive) and shoots that don't (vegatative)
60
What is elongation growth?
plants can get longer by making existing cells BIGGER + grow, in stems cells in internode get longer and longer
61
What are the core features of the shoot system?
1. hold up leaves
2. make flowers
3. power primary growth
- -can take shoots and modify into other things
62
What are examples of plant modified stems?
some shoots can be underground like rhizomes
- rhizomes: underground shoot with roots attached ex:bamboo
- stolons:above ground shoots that creep along ground + make new plant with spread ex:strawberries
- no sexual reproduction in either situation bc its cloning which means plants have multiple ways to reproduce
63
Why are sweet potatoes and irish potatoes different?
- irish potatoes is the "storage" organ underground, what plants use to drive production of new shoot material, new plants for next year
- sweet potato is the underground root, irish potato is not
64
What is the function of leaves?
- leaf is the main photosynthetic organ
| - leaves intercept light, exchange gases, dissipate heat, defend plant from herbivores and pathogens
65
What are the parts of a leaf?
generally consists of a flattened blade and a stalk called a petiole which joins lead to node of stem
- petiole: joins leaf to stem
- midrib: there is vasculature that holds leaf out
- veins:vasculature
- tip: the tip of the leaf
66
What are some evolved modified leaves and their functions?
1. spines" like cactus leaves turned into defense (not photosynthetic)
2. tendrils: grab hold of things and pulls itself up --are NOT modified leaves in some species even if they have same function
3. reproductive leaves, not sexual reproduction but division of cells aka cloning until lead falls down to make the new individual
4. storage leaves ex:onions pack storage resources
67
How do monocots and eudicots differ in arrangement of veins/vascular tissue of leaves?
- most monocots have parallel veins, expansion in one direction (add to bottom and extend upward-parallel veins)
- most dicots have branching veins, expand in lots of dif directions (leaf veins stretch in net to get larger-branching veins)
68
Are algae considered plants?
No, but they are distantly related to plants. All plants are terrestrial (on land) while algae are aquatic
69
What are angiosperms?
flowering plants (as some plants don't make flowerrs)
70
What three groups are plant tissues made out of?
1. dermal tissue
2. vascular tissue
3. ground tissue
- -each tissue system is continuous throughout plant
71
What is ground tissue?
tissues that are not dermal or vascular, ground tissues internal to vascular tissue is pith while ground tissue that external to vascular system is cortex
72
What is ground tissue comprised of?
includes cells specialized for storage, photosynthesis, support, and transport
73
What is a parenchyma cell?
thin and flexible cell walls, are the least specialized but have the ability to divide and differentiate, can grow but no active cell division, * allows to kick cells that weren't in division to divide and repair so can turn into specialized cells
74
What is a collenchyma cell?
grouped strands that help support young parts of plant shoot have thicker and uneven cell walls, but provide flexible support without restraining growth (ex: celery stringy bits)
75
What is a sclerenchyma cell?
rigid bc of thick walls strengthened by ligin (wood stuff), dead at functional maturity
76
What is the vascular tissue system?
vascular system facilitates the transport of materials throughout plant and also provides mechanical support
77
What are the two vascular tissues?
xylem and phloem
78
What is the xylem?
conducts water and dissolved minerals upward from roots into the shoot, cells are dead when functional
79
What is the phloem?
transports sugars from where they are made to where they are needed (up and down), not thick cell walls likee xylem, have alive cells
80
What does the vascular parenchyma do?
packing, general-purpose
81
What is the structure of xylem?
- tissues have lots of holes/tubes where water can move, are dead cells
- 2 key structures: vessel elements and tracheids
82
What is a vessel element
individual xylem cells stacked on top of each other all interconnected with columns stacked next to each other with holes between them but end bits missing
83
What is a tracheid
like set of straws with holes drilled sideways so ends of straws are pinched off+closed; angiosperms have lots of vessel elements and tracheids, most gymnosperms have lots of tracheids
--both serve same function: allow water to flow up
84
What is different about phloem and xylem cells?
xylem cells are dead when mature+ functioning in transport, strong material cellulose and lignin
85
What is the structure of the phloem?
phloem composed of sieve-tube elements that are alive at functional maturnity but lack organelles, need living cells to transport sugar; coupled with each sieve tube there is a functional cell called a companion cell which has all proper cell organelles
86
What is a stele?
vascular tissue of a root or stem, but different structure in monocots and dicots
87
What does the stele of a root look like ?
for angiosperms (both monocots and dicots) stele of a root is a solid central cylinder
88
What does the stele in a stem (and leaf) look like for a dicot?
divided into vascular bundles on the periphery of stem where strands of xylem and phloem
89
What does the stele in a stem (and leaf) look like in a monocot?
vascular bundles are evenly distributed throughout the stem
90
What is secondary growth?
growth by getting fatter and thicker
91
What are apical meristems?
allow for primary growth, apical meristems are located at the tips of roots and shoots and elongate them
92
What is a root cap?
protects apical meristem as root pushes through the ground
93
What are the 3 zones of cells that growth occurs behind root tip?
Zone of:
1. Cell Division
2. Elongation
3. Differentiation/Maturation
94
What is the quiescent center?
group of slowly dividing cells in the root meristem that can become reativated to divide and replace a damaged apical meristem (making a new meristem
95
What is the zone of elongation?
roots get longer by cells elongating
96
Where do branch roots come from?
lateral roots arise form within the pericycle, the outermost cell layer in the vascular cylinder. percycle has the ability to divide when it wants to branch/make a lateral root
For process: root erupts from inside the root its growing and pushes itself outwards
97
Why is vasculature important for lateral roots and shoot branch?
the position of new lateral roots or shoot branches is determined by the root and shoot vascular architecture
98
How does primary growth look like in shoots?
a shoot apical meristem is a dome-shaped mass of permantenly dividing cells at shoot tip with leaves developing from lead primordia along sides of apical meristem
99
What is the central zone in shoots?
central zone of cells of the shoot apical meristem are slowly dividing and serve a similar purpose to the roots quiscent center
100
What is the leaf primordia?
gives rise to new leaves
101
What are axillary buds?
develop from meristematic cells left at the bases of lead primordia, lateral meristems add thickness to woody plants in process called secondary growth
102
What does secondary growth require?
requires 2 lateral meristems, the vascular cambium that makes new secondary xylem (from the inside) and secondary phloem (from the outside) and the cork cambium which makes the periderm, tissue that replaces the epidermis (on very outside)
103
What is the vascular cambium?
adds layers of vascular tissue called secondary xylem (wood) and secondary phloem
104
What is the cork cambium?
replaces epidermis with periderm which is thicker+longer
105
Why can't monocots make a vascular cambium?
vascular bundles scattered throughout stem, so can't make structure bc vascular bundles in wrong place
106
How does xylem and phloem work?
Vascular systems move stuff (like nutrients) dissolved in water by bulk flow of water, at the cellular level pressure and osmosis help with bulk flow
107
What is water potential?
Y=Ys+Yp
bigger y=more potential molecule of water has to move somewhere else
Ypressure= is positive if pumped and negative
Yosmosis= is negative and gets more negative as solute levels rise (more stuff=more negative)
108
What is osmosis?
Osmosis is the diffusion of water across a semipermeable cell membrane, starts at 0 for pure water and gets more negative (pressure also 0 so water potential of pure water is 0)
109
Summary of Pressure and Osmosis
1. Water always moves from more positive to more negative water potential
2. More dissolves solutes, more negative water potential
3. More dissolved solutes, more water wants to move into an area by osmosis
110
What are the 3 big states that plant cells are in?
1. Plasmolyze: if more dissolves stuff outside then inside, water moves out of cell and cell shrinks
2. Flaccid: when everything at an equilibrium, there is no net exchange of water, water potential same inside and outside
3. Turgid: more dissolves stuff inside cell then outside, water moves inside the cell and cell swells (plants like this)
111
What is turgor pressure?
when water moves into cell bc of osmosis, cytoplasm swells and pushes against cell wall increasing pressure, what makes plants rigid
112
How do plants drive water movements?
they can use the salt concentrations to drive water movement, can manipulate water potential
113
What is transpiration?
when water moves up from the roots to the leaves
114
How does water movement work in the xylem?
water movement driven by water potential, water taken up through the roots and lost in the air, water sucked up through the xylem pulling water column by tension, cohesion allows for water molecules to form strong column
115
What is a stomatal pore
on each side of the hole are 2 special epidermal cells called guard cells that open or close pore depending on water conditions. This allows for the retention or influx of water depending on conditions
116
What are guard cells functions?
OSMOSIS
they pump water inside (and solute) and swell- open pore/turgid
water leaves the cell (and solutes)-close pore/flaccid
117
What are the two paths water and dissolved mineral nutrients can enter the root?
symplastic and apoplast routes
118
What is the apoplast route?
is the cell wall space outside the plasma membrane, travel through cell wall to cell wall until get to layer called endodermis where Casparian strip is (made of suberin) which will prevent water and nutrients from passing unless it enters the endodermal cell
119
What is the symplast route?
is the cytoplasm inside the plasma membrane, crosses plasma membrane earlier than apoplast, can then follow plasmodesmata which connects symplast to cytoplasm of endodermal cells
120
What is the endodermis?
control point within the root that prevents anything from getting to the transcriptional flow of water then exported from endodermis same way as apoplast, control from soil to xylem and operates via diffusion and active transport
121
What is translocation?
for phloem, the process of transportation of sugars from sources to sinks is called translocation via sieve-tube elements
122
What is a sink?
is an organ that is a net consumer of sugar, like young leaves
123
What is a source?
is an organ that is a net producer of sugar like mature leaves (can always change ex: young leaf(sink) and mature leaf(source))
124
What is pressure flow and how does it work in the sieve tube of phloem?
movement occurs via pressure flow, where sugars are loaded into the phloem cells at the source, osmosis then occurs drawing water into the area of the sieve tube. Pressure then builds in the sieve tube causing water to flow along the interconnected sieve tube cells carrying dissolve sugar with it. At the sink, the sugars (sucrose) is removed (unloaded) and the water potential of the sieve tube rises, forcing water to leave from that area. Water influx at the source and efflux at the sink causes a directional flow of water that moves the dissolved sugars from source to sink by bulk or mass flow
125
What is the sucrose proton H+ symporter?
pump to move sucrose into sieve tube, eventually sugar ends up in cell walls outside sieve tubes and accumulate inside of cytoplasm at source end, uses H+ as energy source
126
Summary of pressure flow
if we pump lots of sucrose then bc the sieve tube has a plasma mebrane, osmosis brings in lots of water and the water pressure at start end (sink end) increases in pressure
127
What are essential elements?
Plants require certain essential elements to complete life cycle, cannot complete lifecycle if these component/s are missing
128
How many essential elements are there?
17 essential elements, used hydroponic cultures to determine this
129
What are macronutrients?
elements required in large amounts, consists of: carbon, oxygen, nitrogen, phosphorus, sulfur, potassium, calcium, magnesium
130
What are micronutrients?
only needed in small amounts. chlorine, iron, manganese, boron, zinc, copper, nickel, molybdenum
131
How does plant nutrition involve other organisms?
microbes and plants can interact in the soil, as secretions from roots alter microbial activities + provide support to microbes
132
What is rhizobacteria?
free-living bacteria that occupy rhizosphere
133
what is the rhizosphere?
layer of soil closely surrounding plant roots
134
what is an endophyte?
nonpathogenic bacteria that live between the cells of host plant tissues
135
Why are rhizobacteria and endophytes useful to plants?
produce useful chemicals/compounds that plant can use )(like nitrogen)
136
What's special about legumes and nitrogen?
bacteria associated with legume plants can actually fix nitrogen to be used by plants, in roots there are swellings called nodules that house bacteria, bacteria get in return sugars and housing (low O2 levels so good environment for bacteria)
137
What is the mycorrhizae?
mutualistic associations of fungi+roots, fungus benefits from steady flow of sugar and host plant benefits bc fungus increases surface area for water uptake and mineral absorption, fungi also secrete growth factors form root growth and branching
138
What are trichomes?
trap humid air, act as physical deterrents, contain chemical defenses; look like little hairs fuzzies on plant
139
What is the angiosperm lifecycle?
- gametophyte development
- pollination
- double fertilization
- seed development
140
where do flowers arise from?
floral meristems and evolved from shoots and leaves
141
How can petals and sepals be modified?
petals and sepals can be modified to increase the efficiency of pollination, such as attracting animals or insects to visit the flower
- anthers producer the pollen
- carpels contain ovules and produce egg cells
142
What are flowers made of/ 4 whorls?
4 whorls of organs are sepals,petals, stamens, and carpels
143
What happens in carpel?
meiosis produces a haploid megaspore that divides by mitosis to produce the female gametophyte, embryo sac
144
What does embryo sac contain?
contains the female gamete, egg, synergid cells that aid in signaling to the pollen tube, antipodal cells that provide nutrition and a central cell containing 2 polar nuclei
145
What does embryo sac contain?
contains the female gamete, egg, synergid cells that aid in signaling to the pollen tube, antipodal cells that provide nutrition and a central cell containing 2 polar nuclei
146
What is purpose of double fertilization?
ensures endosperms only develop in ovules containing fertilized eggs, the two fertilization events are linked
147
How does reproduction in angiosperms work?
1. anthers (sporophyte) meiosis produce a spore, microspore then undergoes mitosis producing two cells, tube cell and generative cell
2. Tube cell and generative cell are the male gametophyte and are encased in a strong polymer called sporopollenin, whole structure is the pollen grain
3. pollen grain blown and lands on stigma of the carpel another flower
4. pollen grain grows pollen tube down through style to reach the entrance intto the embryo sac called the micropyle (of egg cell)
5. tube burst releasing sperm into embryo sac
6. One sperm fuses with egg cell producing zygote, other fuses with the 2 polar nuclei creating endosperm (3n) tissue used for seedling growth
7. double fertilization only seen in angiosperms
148
What is coevolution?
joint evolution of interacting species in response to selection imposed by each other
149
What is a fruit?
is a mature ovary enclosing the seeds
150
What is tropism?
directional growth of plant either torwards or away from a stimulus
151
What is phototropism?
phototropism is the directional growth response to light
152
What light do plant shoots grow towards?
blue light
153
What was Darwins Experiment on coleoptiles?
showed that the light sensor is the tip of the coleoptile and communicates with the cells at the base of the coleoptile that show growth response to light
- communication through chemical released from coleoptile tip
- chemical is auxin
154
What was Darwins Experiment on coleoptiles?
showed that the light sensor is the tip of the coleoptile and communicates with the cells at the base of the coleoptile that show growth response to light
- communication through chemical released from coleoptile tip-acts like a sensor
- chemical is auxin
155
What is acid growth hypothesis?
auxin stimulates proton pumps in plasma membrane, proton pumps then lower pH in cell wall and activate expansins which are enzymes that loosen cell walls fabric; with cellulose loosened, cells can elongate driven by turgor pressure this allows cells to stretch +get longer---phenomenon where plant knows bottom from top nv of auxin flow is known as polar transport
156
What is the role of auxin in apical dominance?
auxins are produced in shoots and transported down stems, auxin transporter proteins move hormone from basal end of one cell into apical end of neighboring cell; this plays a role in plant pattern formation (big at bottom, smaller at the top; Christmas tree)
157
What is apical dominance?
is when the main shoot dominates and inhibits the outgrowth of other shoots so plant bigger at bottom then top. Auxin, plays a role and prohibits axillary bud growth however as you get further down a shoot the concentrations of auxin decrease leaving you a with a faster-growing bottom than a top.
158
What is etiolation?
tall and spindly, not green, very weak however reversible (via de-etiolation). Why it happens- no light so the plant will try to grow as tall as possible to get to a light source, de----do not make photosinthetic machinery (light sensed by phytochrome =red light sensor)
159
What is de-etiolation?
de-etiolation activates enzymes that:
- function in photosynthesis directly
- supply chemical precursors for chlorophyll production
- affect levels of plant hormones that regualte growth
160
What is phytochrome?
senses presence of red light via photoceptor protein
- Pr absorbs red light and converts to Pfr
- Pfr absorbs far-red light and converts to Pr
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Response to Pfr (lots of red light)
- active:turns on normal plant functions
- seed germination
- shade avoidance
- setting internal clocks
- control of flowering
- de-etiolation things
162
Response to Pr (lots of far red light)
- inactive:turns off normal plant functions
- detect shade
- etiolation: meaning plant will grow very fast
163
How does a plant know its being shaded?
sun produces both red and far red light, however, chlorophyll will only absorb red light driving photosynthesis, so the plant doing the shading will absorb most of the red light while the far red light passes through and hits the plant in shade. The plant detects via phytochromes that there is a lot of far red light but little red light (meaning lots of Pr and little Pfr) so it KNOWS its being shaded and thus undergoes etiolation
164
What is phototropin?
blue light sensor used for phototropism
165
Where is auxin made and how does it function in elongation?
made by coleoptile tip and then exported to the rest of the coleoptile, so accumulation of auxin on the shaded side of a coleoptile makes cells on that side elongate (faster) resulting in plant bending towards light source
