Plant Flashcards
Origin of photosynthesis
Cyanobacteria
Develop multicellularity and cell specialization
Great oxidation event
Evidence of endosymbiosis
Both psi and psii evolved in bacteria
Replicate by fission
Own protein, DNA, behave independently
Peptidoglycan cell wall
At least 2 membrane
Today evidence
Secondary endosymbiosis
Common ancestor of plants comes from primary endosymbiosis
Phytoplankton
50% of global photosynthesis
Photosynthesis bacteria
Single cell photosynthetic eukaryotes
Brown alage
Not plant
Contain carotenoid
Thallus
Sexual asexual
Red algae
Carotenoid
Calcareous deposits in cell wall
Help build coral reefs, attract coral larvae, patch up broken coral, reinforce coral skeleton
Slow growing, vulnerable
Carotenoid function
Used in photosynthesis
Harvest blue light
UV protection
Viridiplantae
Green plant contain chloroplast
Green algae
Unicellular/multicellular species
Main primary producers in freshwater
Sexual/asexual
2.5by
Advantages move to land? Why hard?
Advantages:
Huge uncolonized land
Abundant light
Available CO2
Less herbivory
Challenges:
UV radiation
Dehydration
Dispersal
Gravity
Nutrients
Bryophytes
First land plant
No vascular tissue
No true roots
Grow in damp environment
Key innovations
Better Sunscreen:
UV absorbing compound(flavonoids, antrocyanins)
Cuticle: produced by epidermal cells
Reproduction:
spores in tough coat
Gametes in complex multicellular structure
Embryos retained on and nourished by the parent plant
Alternation of generation
Gametophyte phase dominant
Gametophyte, gametes, zygote
Gametophyte dominant lifecycle
Mature sporophyte2n,
meiosis, spores, developing gametophytes, mature, archegonia,
2n zygote, mitosis, developing sporophyte
Early Silurian landscape
Colonized by little mossy bryophyte like things, cannot grow very tall
Challenges on the nonvascular plants colonize land
Competition about space, light , water, and nutrients
To solve, they:
Colonized drier environment
Grow taller
Go deeper
The Mid Silurian landscape—key innovations: complexity
- Branching: compete for light, better disperse
- Branching allow different stems to specialized: some become root, others are still stems
- Branching cause Modularity: the difference between plants and animal
Earliest plants could not branch(or grow very tall), and also only green stems with no leaves
The Mid Silurian landscape—key innovations: dry
Stomata: most on the bottom of the leaf cuz less evaporation
Cuticle reduces water loos but also prevent CO2 enter plants
Stoma: opening pore with specialized guar cells that control the open and close of the stomata. Stomata allow gas exchange and prevent water loss
Cuticle and stomata evolved together, and stomata enable evolution of full cuticle
Key innovation: vascular tissue
Solve the problem of being tall : vascular tissue specialized reinforced conductive tissue
Transport and support
Earliest: thickened conducting cells
Xylem: primary wall with cellulose, lignin reinforce the cell(secondary wall), later increase structural support.
Tendency is to increasing differentiation, tissues are more specialized and have more structural support
The Mid Silurian landscape—key innovations: deeper
Roots
Nutrient & water acquisition, support, interface with symbionts (Mycorrhizal fungi)
Devonian
Plants start to grow taller and have branches
In late Devonian, have first tree like plants: Gilboa trees
Do not have very specialized structure, no leaves, vasculature tissue allowed it to get taller but no true wood
Trends in life cycle in the evolution to land
Nonvascular plants: sporophyte small, short lived, depends on gametophyte for nutrition
• Gametophyte-dominantlifecycle
Vascular seedless plants: sporophyte is much larger
& longer lived than gametophyte
• Sporophyte-dominantlifecycle
Seed plants: Gametophytes are microscopic
Advantages of being 2n
- 2 copy from both parents, increase the potential expression of trait to adapt to different environment
- 2 copy prevent direct express of a deleterious mutation
Vascular seedless plants nowadays
Ferns, clubmosses, horsetails
- vascular tissue
- complex leaves and roots
- sporophyte-dominated life cycle
- disperse via spores
Sporophyte-dominant life cycle
Spores(n)—mitosis—gametophyte(n)—mitosis—mature gametophytes—egg/sperms—fertilization—zygote (2n)—sporophyte(2n)—mature sporophyte(2n)—meiosis—spores
Fern
Hybridization play a major role in fern evolution
Today:
Roots similar to seed plants
Leaves produce spores
25-30% ferns live on other plants
Bioremediation: ferns can bioaccumulate heavy metals in their leaves
Allies, extant
Extant: not extinct
Environmental variation plants need to deal with
Light and UV
Water (drought and flood)
Temperature (high, low, variable)
Ice
Wind
Nutrient availability
Salt
Metals
Herbivores
Pathogens
Seed plants—key innovation
Include both gymnosperms and angiosperms
Innovations: woods, seeds, and pollen
Woods: building strength and get big & tall
Carboniferous forests
Why they can make up today’s coal bed, didn’t decay?
Lignin evolve before the evolve of the organisms can breakdown the lignin
The rise of trees
Tree: Single stem &branching &canopy
Stricter definition of tree: has wood and increases in girth干围
“Tree” is not a single taxonomic group—all are seed plant but not all seed plants are trees
Key innovation: wood
Vascular cambium
Produce new xylem tissue and phloem tissue,
Xylem: move water/nutrients up, phloem: moves sugars up and down
Live and dead xylem accumulate to form wood
Build support(girth) as they build height
Larvae eat phloem and xylem can kill the tree cuz this will blocking the transport of fixed carbon from the leaves to all of the other tissues in the plant
Key innovation: heterospory
Spores are different size
Small: microspores go onto become pollen
Big: megaspores go onto ovule with egg, not exposed to air, desiccation resistant, male gametophyte has to burrow to access female gametophyte
Key innovation: pollen
Spores evolve into pollen grains
• Tiny male gametophyte(2 to 3 cells)in tough coat
• Germinates->pollen tube
• Sperm cells swim down pollen tube to ovule
Pollen grain allowed efficient reproduction in dry habitats
•Can be exposed to air for long periods without drying out
• Carried to female gametophyte by wind or animals
Key innovation: seeds
Fertilized ovule—seed
Outer tissue becomes the protective seed coat
Seed grows and is provisioned提供 with energy by the mother plant (but no fruit!)
Cones open when seeds are mature to release for dispersal
Gymnosperm lifecycle
See slides
Gymnosperm: naked seed, include conifers, no fruit and flower
Gymnosperms today:
Cycads:
-Slow growing and long lived (up to 1000 yr)
-Large part of diet of some herbivorous dinosaurs
- Separate male & female plants: cones either produce pollen (male) or ovules (female)
- Still have motile sperm
Ginkgos:
Closest living relaDve is a cycad!
“Living fossil”
Only 1 extant species (wild but endangered in China, grown globally)
All other relatives (same order) are extinct! Been alone for 3+ million years
Only seed
Conifers:
Most diverse group of extant gymnosperm
All are woody and cone-bearing, most are tree
Dominate world’s largest forest biome
Pine: cold—thick bark厚树皮, cones shelter seed/snow—cone shaped, down-facing and flexible branches/dry—thin waxy needles, dense to reduce wind
Trees today
Cool down the city(urban heat island effect), but need to be more than 40%
Make temperature increase because give dark color on snow to absorb heat
Angiosperm radiation
when one lineage produces an unusually large number of descendant species adapted to many habitats
Associated with 3 key adaptations:
1. More efficient xylem
2.flowers
3.fruits
Enable angiosperms to transport water, pollen & seeds efficiently
Flowers associated with speciation. hardest step of speciation=reproductive isolation, flowers directly involved in mating and mate-choice
Flowers
Contain the reproductive organs: female parts (carpel), male parts (stamen), or both
• ♀: ovules develop in the ovary
• ♂: pollen grains develop in the anther
Later, plants enclosed carpels & stamens in petals which evolved from leaves
Highly diverse
Pollination
Pollen transfer from another to compatible, receptive stigma
Outcross pollination=pollen & stigma on different plants
Pollen land on wrong stigma is wasted, therefore have adaptations improve the chances of getting on the right pollen grains
About 80% of angiosperms use animal pollinators
Adaptive significance of floral traits
Floral traits can:
• attract good pollinators
• deter non-pollinating visitors
• manipulate visitor behaviour to maximize pollen transfer
Almost any floral trait can affect pollination, including:
• Colour
• Scent
• Shape
• Markings (including UV-visible)
• Position
• Pollinator rewards (nectar, heat)
• Flowering time (day, night, season)
Simple changes in flowers can lead to pollinator shifts
Angiosperm Radiation: fruits
After fertilization ovary tissue ripens—fruit
Most seed-dispersal structures develop from overly wall and/or ovary tissue
Protect developing seed
Seed dispersal
Seed dispersal—fruit
Not all fruits are meant to be eaten
Can dispersal by:
-Wind
-Animal fur
-Explosion
-Water
But some are meant to be eaten:
Animal eats fruit, seeds pass through gut, pooped out in new place
Or hidden and forgotten (squirrels)
Groups of angiosperms
Monocots & dicots
Monocotyledons (all grasses, corn, wheat, sugarcane, oats, rice), have lost some features like wordiness
Dicotyledons(bigger plants, everything else, including major food crops)
Monocots monophyletic, dicots paraphyletic, monocots evolved from dicots
Incredible modularity of angiosperm radiation
- Plants produce multiples of most morphological structures, that can take each other’s place
- Can create vastly different structures with the same tissue or analogous structures via different pathways/tissues
- Especially notable in angiosperms
- Allow huge flexibility for individuals and evolutionary lineages
