Plants Lectures Flashcards
Describe Bryophytes
- among the first land plants (simplest)
- evolved at same time as amphibians (live on land and in water)
- evolved 450 million years ago
- commonly live in moist areas (need water for reproduction)
Why is it important for bryophytes to live near water?
they need water for reproduction!
How has the CO2 and O2 concentration in the atmosphere changed through time?
- initially O2 low and high CO2: photosynthesis develops: slowly changes over time
- then plants take over and O2 skyrockets
- CO2 increasing again due to humans
What is the bryophytes role in succession?
- primary succession
- produces rhizoids: secrete acidic compounds to dissolve rock surfaces an produce small pockets of soil
- first plants to colonize on rock surface : lichen
What is an epiphytic plant community? Which plant is apart of this?
Grow on trees: bryophytes grow on trees for mechanical support (sunlight), do not take nutrients from the tree
How do bryophytes support tundra ecosystems?
- provide food for herbivores in a treeless ecosystem
Why might bryophytes be useful to human health?
- have medicinal properties: such as anticancer and antimicrobial activities
Why are bryophytes a source of fuel?
- sphagnum moss
Why might bryophytes be an indicator of air quality?
- they are effective bioindicators of air quality: lots = good oxygen levels
low / none = highly polluted area
Can bryophytes tolerate harsh environments?
- some bryophyte species can tolerate harsh environmental conditions
-eg; moss in dry deserts, moss in Antarctica - in general! most require warm moist environments but there are exceptions (for motile sperm)
describe the relationship between bryophytes and other phylogenetic groups
- bryophytes are transitional between the charophycean green algae and the vascular plants
- eukaryotic algae evolved form prokaryotes: red algae, brown algae, then green algae
Why did bryophytes evolve from green algae?
- peroxisomes evolved to detoxify phosphoglycolate:
- bryophytes evolved from green algae when peroxisomes evolved to address photorespiration : which produced carbon dioxide and phosphoglycolate
What are the bryophytes similarities to green algae?
→ Bryophytes have many similarities to green algae
Both have motile cells
Both contain chloroplasts with well developed grana: chlorophyll a and b as well as carotenoids
Cell walls are composed mainly of cellulose
Mitotic spindles remain during cytokinesis
The pigment phytochrome is present (greenish blue, can’t see because of small concentration) - important for spore germination
What are cell walls of bryophytes made of?
- mainly cellulose
What are the challenges of living in a terrestrial environment?
- challenges for life on land:
- high potential rate of desiccation in air
- spatial separation of nutrients, energy, and carbon source
- limited support of the plant body
- no easy medium for gamete dispersal
- difficult for offspring dispersal
What are the structural and physiological solutions to the challenges of life on land?
Desiccation – epidermis, stomata and cuticle
Transport – xylem and phloem
Support – lignin and wood
Sexual reproduction –flowers
Dispersal – seeds and fruit
What are 5 important characteristics of plants?
- plants are multicellular eukaryotes
- plants are autotrophs animals are heterotrophs
- plants cell walls composed of mainly cellulose
- plants have two adult forms that alternate in producing each other
- plants have a multicellular embryo protected within the female parent
Describe alternation of generations
- → Diploid sporophyte produces haploid spores by meiosis
-spores grow into gametophytes
→ haploid gametophyte produces gametes by mitosis
Gametes are non flagellate eggs and smaller flagellated sperm fuse into single-celled diploid zygotes
Zygotes grow into sporophytes
What does isomorphic mean?
- gametophyte and sporophyte look identical: must chemically identify them
Describe alternation of generations in bryophytes? Vascular plants? Which generation is dominant?
- bryophytes: gametophyte is dominant, sporophyte attached to gametophyte
- vascular: sporophyte is dominant, gametophyte is attached to sporophyte
Describe the gametophyte terms
Gametophytes
- Produces haploid gametes
- Antheridia: gametangia producing sperm
- Archegonia: gametangia enclosing an egg
- Sperm swim to egg and fuse to form diploid zygote
- Zygotes grow into sporophytes
Describe the sporophyte and terms
- Zygotes remain sheltered and fed within gametophyte tissue
- Young sporophytes are embryos
- When mature, spores are produced in protective enclosures known as sporangia
- Plant spore cell walls contain sporopollenin to help prevent cellular damage
- During evolution, plant sporophytes become larger and more complex
What is sporopollenin?
- plant sure cell walls contain sporopollenin to help prevent cellular damage
What is a moss cushion?
- reproduction in mosses occurs when a thallus is covered in a film of free standing water
Describe the bryophyte diversity
- the bryophytes are grouped into three phyla:
- liverworts, hornworts,, mosses (Bryophyta)
What are embryophytes?
- another term for plants, a multicellular embryo is retained within the female gametophyte
What are polysporangiosporophytes?
- plants with branching sporophytes and multiple sporangia
What are the bryophyte diversity relationships?
- liverworts group more closely related to green algae, hornworts more closely related to vascular plants
What are liverworts?
- the earliest living land plants most closely related to green algae
- 5200 species
- 3 major types of liverworts and two main categories : complex thalloid liverworts, leafy liverworts
Are gametophyte or sporophytes dominant in liverworts?
- gametophyte is dominant
- dichotomously branched
- gametophytes or marchantia are unisexual
- gametangia are borne on specialized structure called gametophytes or gamtangiospores
Describe the vegetative structure of the liverwort
- the vegetative body of a bryophyte is called a thallus - dichotomously branched
- it is haploid
- no lignin, true stomata, true roots, and xylem and phloem
- no roots, have rhizoids
Describe asexual reproduction in liverworts
-simple fragmentationm
- in marchantia, the gamma are produced in special cup like structures known as Gemma cups
–> the gamma are dispersed primarily by splashes of rain
Describe the sexual lifecycle of liverworts?
- exhibits and alternation of heteromorphic generation
- two most critical events are meiosis and fertilization
- the gametophyte generation is initiated with meiosis
- the sporophyte generation initiated with fertilization
- within the archegonium the zygote develops into an embryo (young sporophyte)
- as the embryo increases in size the calyptra also increases in size
- the sporophyte is permanently attached to the gametophyte by the sporophyte foot
Describe spores and elaters in liverworts
- mature spores (red spheres) and elaters (green strands) from a capsule of marchantia
- elaters twist and help release spores inside
Descrive mosses
- the genuine Moses belong to the phylum Bryophyta
- some groups of mosses have both specialized conducting tissue and stomata
- conduction tissue of masses consists of hydroids and leptons
- three main classes
What are the conduction tissue of mosses called?
- consists of hydroids and leptoids
What are the three main classes of mosses?
- sphagnidae: sphagnum moss (peat moss)
- andreaeidae: granite moss
- bryidae: true mosses
*the bryidae contains the vast majority of moss species
Which kind of moss contains the majority of species?
- the bryidae
Describe sphagnum moss
- classified into two genera: sphagnum (peat moss) and ambuchanania
- typically lives in bogs (global)
- occupy more than 1-3% of the earth’s surface
- sporophytes quite distinctive: red to blackish brown capsules
- pseudopodium: the gametophyte derived stalk that raises the sphagnum spore capsule
Describe the sphagnum sporophytes
- distinctive: red to blackish brown capsules
What raises the sphagnum spore capsule of sphagnum moss?
- the pseudopodium
Describe the leaves of sphagnum moss
- the leaves are one cell layer thick and are composed of two distinctly different types of cells:
- large dead cells
- narrow green or occasionally red pigmented living cells
What are some uses for sphagnum moss?
- soil amendment and planting medium: high water holding capacity, increases soil acidity
- phenolic compounds: antibacterial and antioxidant activities
- diaper material, packing material- superior absorption/antisceptic properties: due to dead cells
- source of fuel (peat)
- stores large amounts of organic carbon
- reduce amount of CO2
Why are sphagnum moss so good for packing material and dressing material?
- superior absorptive and antiseptic properties due to dead cells!
What preserves the bod people in a peat bog moss?
- tannic acids
Describe granite moss?
- rock moss
- belong to the class Andreaediae
- live on rocks often at high elevation in soils of cold temperate regions
- the only plant life encountered in dry windy cold mountainous microenvironment
- a unique feature of granite moss: formation of four vertical slits in the sporangium
What moss would you expect to find in dry mountainous environments?
- granite moss (rock moss)
- lives on rocks at high elevation and in soils of cold temperate regions - dry windy cold mountainous microenvironment
What are the two types of cell death? Provide examples
- programmed cell death : genetically encoded, an active process
- eg; apoptosis and autophagic cell death
- necrosis: accidental (injury eg; frostbite) and passive process
Describe the relevence of apoptosis in animal cells
- tissue remodelling: important in development (webbed fingers)
- elimination of unwanted cells
- cells that have completed their function (eg; tail of the tadpole)
What species are good for studying PCD? Why?
- nematode worms for studying PCD: cell death occurs at precisely defined times and location, 131 cells undergo PCD, have identified 4 proteins central to the execution of the death program
What is one major reason cell death is important in plant development?
- no plant development without cell death!
How many plant species develop holes?
3
Why are plants important?
- photosynthesis: the process by which plants and certain other organisms (photosynthetic bacteria and algae) use solar energy to make their own food
- no other way to produce inorganic carbon into organic carbon, oxygen: life on earth would be impossible
- animals and other organisms unable to make their own food:
-they can survive only by obtaining food directly or indirectly from plants
How does photosynthesis support life?
- oxygen, primary producers, sugars: the building blocks of life
What are the phases of photosynthesis?
- the light reaction: occur in thylakoid membranes, use light energy and H2O to generate chemical energy in the form of ATP and NADPH and release O2 as a by product
- the Calvin cycle (dark reactions): synthesises three simple 3-carbon sugars, using ATP and NADPH from the light reactions and CO2 from the air. Takes place in the stroma.
- the light reaction: occur in thylakoid membranes, use light energy and H2O to generate chemical energy in the form of ATP and NADPH and release O2 as a by product
Where in the cell does photosynthesis occur?
- takes place in chloroplasts
- typically around 3-5 micrometers in diameter
- chloroplasts can be circular or elongated (also are moving)
- a typical cell may contain between 5-50 chloroplasts
- mitochondria appear red, chloroplasts green!
What is cytoplasmic streaming?
- the directed flow of cytoplasm within a cell
- for even distribution of nutrients between organelles, parts of cells, etc.
What differentiates between the animal and plant cells?
Animals and plant cells are similar except for three components:
1. Cell wall
2. Plastids (eg; chloroplasts, amyloplast, chromoplast, etc)
3. Large central vacuole (smaller vacuole indicates younger cell)
Fully mature plant cell: 90% of cell filled with large vacuole
Animals and other organisms are unable to make their own food but what are some exceptions to this rule?
- sea slugs steals photosynthetic machinery from algae that it grazes on, and lines its digestive tract with this to provide energy
- first non functional gene transfer
–> non photosynthetic plants : saprophytic flowering plants (Indian pipe, snow plant)
–> parasitic plants: eg; dodder plant
What are some human uses of plants?
- fundamental source of food: crops, beverages, herbs and spices , corn rice wheat
- medicines : plants can alleviate the symptoms of many medical conditions
- plants provide fuel, shelter, paper products: wood, construction material, paper
What are some medicines that plants can provide?
- Willow bark produces salicylic acid similar to asprin
- Cinchona bark source of quinine use for malaria
- Ephedra source of ephedrine (powerful antihistamine)
- Rosy periwinkle plant source of vinblastine and vincristine, to disrupt, the division of cancer cells and kill the cells
- Pacific Yew (Taxus brevifolia)-Taxol for the treatment for ovarian cancer
How do we feed the world’s growing population?
- genetic engineering: golden rice, pest resistant, toxin resistant, herbicide resistant
What are five characteristics of plants?
- Plants are multicellular eukaryotes
- Plants are autotrophs - make their own food (Animals are heterotrophs)
- plant s cell walls composed mainly of cellulose
- Plants have two adult forms that alternate in producing each other
- Plants have a multicellular embryo protected within the female parent
→ each of these characteristics by itself is not unique to plants, but together they are useful for distinguishing plants from other organisms
What are two additional characteristics to distinguish plants from animals?
- both sexual and asexual reproduction
- indeterminate growth vs. determinate growth
What are the major types of plants?
- bryophytes
- seedless vascular plants
- Gymnosperms (non-flowering plants0
- Angiosperms (flowering plants)
- bryophytes
How long ago did bryophytes evolve from green algae ?
~450 million years afgo
Describe bryophytes (moss)
- Cannot transport water - no vascular tissue
- Require water for reproduction
- Seedless
Describe seedless vascular plants
Vascular tissues (xylem and phloem)
Required water for reproduction
Seedless
Describe gymnosperms
Vascular tissue
“Naked” seeds on cones
No flowers
What are the two types of cell death?
1) Programmed cell death
- active process
- genetically encoded
- eg; apoptosis and autophagic cell death
-2) necrosis
- passive process
- accidental ( injury eg; frostbite)
Describe the importance of cell death in animal cells
- removes harmful cells
- tissue remodelling: important in development: limb bud development, removal of webbed fingers
- cells that have completed their function: tadpole tails
Why are nematode worms good for studying PCD?
- have designated number of cells which undergo PCD: 132 - 4 proteins involved in intimating PCD
- cell death occur at precise times and precise locations
Describe the significance of programmed cell death in plants?
- development cannot happen without programmed cell death
- view notes for the full list!
Describe leaf morphogenesis
- 2 monstera plants develop holes in their leaves
- loss of pigment = developmental signal?
What is a plant? how might they be defined?
- generally green, grow but do not move, generally do no consume other organisms
- real definition more formal, no as simple
Why are plants important?
- photosynthesis
- plants and photosynthetic organisms (photosynthetic bacteria and algae) the only ones able to convert inorganic carbon into organic carbon and oxygen
- animals and other organisms cannot make their own food, must get it from elsewhere
What are the 3 ways photosynthesis supports life ?
- oxygen, primary producers, produces sugars: primary building blocks of life
What are the phases of photosynthesis?
- light reaction : fixes light, CO2, and H2O to form ATP, NADPH, and oxygen as a byproduct
- occurs in the thylakoid membranes
- dark reaction: Calvin Cycle: uses CO2 and NADPH/ATP from light reaction to form 3 important 3-carbon sugars
- occurs in the stroma
Describe chloroplasts in the cell
- photosynthesis occurs in the chloroplasts
- 5-50 chloroplasts within one cell
- 3-5 micrometres in diameter
(mitochondria = red, chloroplast = green)
Describe the difference between plant and animal cells
- generally the same except for 3 main differences: cell wall (made of cellulose), large central vacuole, chloroplasts
Describe the parts of the chloroplast
- stroma - empty space within the chloroplast
-thylakoid: disc shaped membrane sacs - granum: thylakoids stacked
- stroma lamella: non stacked thylakoids that connect granum
- stores starch in starch grains
Where do chloroplasts store starch?
- in starch grains!
Where do the dark and light reactions take place?
dark - stroma
light -thylakoid membrane
(both occur in the chloroplast)
Why is sugar so important?
- sugar is the source of both energy and organic materials for all living organisms
- 350+ billion tonnes of sugar produced by photosynthesizers each year
Do all animals and organisms require other organisms for energy?
- most do, but every rule has an exception
animals: sea slugs that eat photosynthetic algae steal their photosynthetic equipment and line their digestive tract: the first no functional gene transfer - non photosynthetic plants: saprophytic flowering plants: Indian pope, snow plant
- parasitic plants eg; dodder plant
What are the human uses of plants?
- food, beverages, medicinal uses
- 3 main crops: rice, wheat, corn
- provides paper, fuel, shelter
Describe all 5 plants useful for medicinal use
- willow plant: produces salicylic acid that acts like aspirin
- cinchona: produces quinine to treat malaria
- ephedra produces ephedrine: strong
- rosy periwinkle: vinblastine, vincristine:
- pacific yew: taxol for treatment
How do we feed the world’s growing population?
- GM plants (genetically modified)
- examples: golden rice, toxin resistant (BT plants), herbicide resistant, pesticide resistant
What are the 5 important characteristics of plants?
1) multicellular eukaryote
2) autotrophic
3) cell walls composed of cellulose
4) two alternate forms of generations that switch (one forms spores, other forms egg and sperm gametes)
5) multicellular embryo protected inside the female plant
NOTE: not unique to plants but aids in characterizing them
two more:
- both sexual and asexual
- indeterminate vs determinate (animals) growth
What are the major types of plants?
- bryophytes
- seedless vascular plants
- gymnosperms: non-flowering plants
- angiosperms: flowering plants
Describe concisely the major types of plants
bryophytes: moss, cannot transport water (no vascular tissue), require water for reproduction, seedless
Seedless vascular plants: have vascular tissue (xylem, phloem), seedless, require water for reproduction
Gymnosperms: vascular tissue, naked seeds on cone, no flowers
Angiosperms: seeds within fruit, advanced vascular tissue, flowers (most important part)
What is a unique feature of granite moss?
- 4 vertical slits in its sporangium
Describe bryidae
- true mosses
- contains most species of the moss
- have specialized tissue for water/food conduction
- no true vascular tissue, instead have leptoids (food) and hydroids (water)
Describe the polytrichum life cycle (true moss)
- mature gametophyte grows mature sporophyte
- capsule releases spores which form protonema
- become male and female gametophytes
- sperm splashed into archegonium to fertilize egg (eggs release malic acid to attract sperm)
- fertilized and embryo develop within archegonium (protected and nourished)
- sporophyte develops with calyptra around it
Describe spore production in the sporangium of true mosses
- seta: sporangium stalk
- capsule: sporangium
- calyptra: protective layer covering sporangium
- operculum: protective covering like a beanie
Describe spore dispersal in true mosses
- calyptra falls off and operculum bursts off revealing the peristome (ring of teeth): operculum tears apart revealing spores
What are splash cups?
antheridia often clustered with leafy structures called splash cups
- sperm discharged into a drop of water, then splashed out by rain
What are paraphyses?
- sterile hairlike filament present among reproductive organs of lower plants (algae, moss, fungi)
- protection, helps hold water around the stem
Describe hornworts
- horn shaped sporophytes
- sporophytes have stomata
- hornwort gametophyte more horizontal than vertical
- some species have N fixing bacteria in internal cavities in gametophytes
- many species tolerate drought conditions : completely dead, life cycle a few weeks: add water and regenerated!
- thanks to Heat Shock proteins: protects proteins = resurrection
what are the three major groups of vascular plants?
- seedless vascular: club moss, horsetail, whisk ferns, ferns
- gymnosperms: naked seeds plants (conifers, cicadas, ephedra, gingko)
- angiosperms: flowering seed plants (monocots and eudicots)
Describe seedless vascular plants
–> dominated landscape 350 million years ago
–> horticultural significance
–> ecological significance
- broken fern: absorbs arsenic from soil and water (stored in vacuole, detoxify)
- mutualistic association azalea and rice production: a mutualistic relationship between anaebona and azolla
–> other uses:
- fiddleheads of of the few edible parts of fern (ostrich fern)
- liquorice fern- medicinal properties
Describe the relationship between the water fern and cyanobacteria
- water fern azalea and mutualist with cyanobacteria: environmentally friendly fertilizer
What are the meristems and tissue systems of vascular plants?
- two apical meristems: root and shoot
- three tissue systems: dermal, vascular, ground
–> input apical meristem: (stem cells keep growing, no differentiation)
–> primary meristems:
- protoderm: epidermis (dermal tissue)
- ground meristem: ground tissue (parenchyma, collenchyma, sclerenchyma)
- procambium: primary xylem and primary phloem
What does the protoderm form?
- epidermis (dermal tissue)
What does the ground meristem form?
- ground tissue (sclerenchyma, parenchyma, collenchyma)
What does the procambium form?
- primary phloem and xylem phloem
What are the treachery elements?
- both function to transport water from root to shoot
- tracheids and vascular animals
What are tracheids?
- lack perforation plate, in all vascular plants
What are vessel elements?
- haver perforation in cell walls and can carry more water
- only in advanced plants
- highly differentiated, advanced species
- only angiosperms, not gymnosperms
Describe differentiation of vessel elements
- everything undergoes programmed cell death except the cell wall
Describe lead evolution: the two forms of leaves
- microphylls: simple, small leaves with a single vein down the middle
- megaphylls: leaves with branches veins
Describe the similarities in life cycles between vascular plants and bryophytes
- alternation of generations includes sporophytes and gametophytes.
- bryophytes and vascular plants have alternation of heteromorphic generations
- production of sperm and egg from antheridia and archegonia
Describe the differences in life cycles between vascular plants and bryophytes
- sporophyte-gametophyte relationship differs from bryophytes and seed plants
- both sporophyte and gametophyte are independent at maturity (gametophytes short lived)
- sporophytes of seedless vascular much larger than gametophytes
Describe the simplified vascular plant life cycle
- gametophyte –> archegonium and antheridium –> zygotę –> embryo –> sporopohyte –> sporangia –> spore mother cell (2n) –> meiosis –> tetraspores and spores
What is homospory?
- production of one type of haploid spore
- results in separate male and female gametophytes or bisexual gametophytes depending on species
What is heterospory?
- production of two types of spores in two different kinds of sporangia
- microspores (produced in microsporangia) and megaspores (produced in megasporangium)
- microspores –> microgametophytes, and megaspores –> megagametophytes
- RARE IN SEEDLESS VASCULAR
- heterospory is important as a precursor to formation of seeds and pollen
What are the three most important phyla during the Devonian period?
- vascular seedless dominated during Devonian period (350 million years ago)
- 3 most important phyla:
- rhynophyta, zosterophyta, trimerophytophyta (no living representatives)
Did early vascular plants have leaves?
- early vascular plants: no roots or leaves, branched stems with photosynthetic ability
What are the living seedless vascular plants?
- classified in two phyla:
1) Lycopodiophyta (lycophytes) - lycopodicae (club mosses - homosporous), selaginellaceae (spike mosses, heterosporous), isotoceae (quillwort- heterosporous)
2) moilophyta
- psilotopsida (whisk fern)
- marattiopsafa (small group of tropical ferns)
- polypodiopsida (true ferns)
- equisetopsida (horse tails)
Describe the extinct lycophyre trees
- modern lycophytes: small, herbaceous
- ancient lycophytes dominate forest 325-280 mya during carboniferous period (tall)
- all lycophytes have microphylls
NOTE: carboniferous coal swamp: decomposed in standing water = peat
Describe the life cycle of Lycopodium lagoons: example of homospory
- bisexual gametophyte: archegonium and antheridium in same gametophyte
- sporophyte grows: doesn’t need gametophyte which dies
- sporophyte indépendant at maturity
Is polytrichum moss exosporic or endosporic?
- exosporic: gametophyte develops outside spore wall
