Plant structures and their functions Flashcards
What are photosynthetic organisms?
Main producers of food and therefore biomass
What type of reaction is photosynthesis ?
an endothermic reaction that uses light energy to react carbon dioxide with water to produce glucose and oxygen
What effect does temperature, light intensity, carbon dioxide and chlorophyll have on limiting rate of photosynthesis?
Carbon dioxide : increasing CO2 concentration increases rate of photosynthesis, however above a certain threshold it stops as there’s another factor limiting the rate
— in warm & bright conditions CO2 is a limiting factor
increase in temperature : increases the rate of photosynthesis till 45 degrees as enzymes that catalyse the reaction begin to denature and rate drops sharply and stops completely
— in winter temperate is a limiting factor
light intensity : increases rate as more energy is provided till a certain threshold
— at night light intensity is the limiting factor
chlorophyll concentration : increases rate
— can be a limiting factor if plants grow in mineral deficient soil, thus can’t produce chlorophyll
What are leaf adaptations?
broad & flat — give large surface area to absorbs large amount of sun
palisade cells have lots of chlorophyll - absorb large amount of sunlight
stomata opens and closed by guard cells — allows co2 to diffuse in and out
leaves are thin : CO2 does not have a large distance to diffuse to reach cells
How is the stomata opened and closed by guard cells differed in seasons?
- in light, stomata opens due to water flowing in
- in night, stomata closes due to water flowing out so they lose their rigidity. it also allows oxygen produced by photosynthesis to diffuse out
How is the structure of root hair cells adapted to absorb mineral ions and water?
- the hairs provide large surface area to absorb water & minerals quickly
- thin cell walls so flow of water is not slowed down
How are xylem cells adapted to their function?
- dead cells w/ no cytoplasm -> long empty vessels so water can flow easily
- thick cell walls & ringe of lignin -> withstand water pressure & provide support
- lack of cell walls -> water flow is not slowed down
- tiny pores -> water & mineral ions enter & leave cell
Describe process of transpiration.
1) water evaporates at open stomata on leaf surface
2) water molecules are attracted to each other, some water molecules are pulled up by xylem
3) water evaporates in leaves abd water vapour diffuses out
4) this causes more water to be taken up by the soil, thus a continuous transpiration stream / cycle is formed.
What are factors that affect transpiration?
1 ) temperature increase - molecules move faster so evaporation happens at a faster rate so transpiration increased and rate of photosynthesis increases so stomata opens and water evaporates more
2) light intensity- increases rate of photosynthesis so stomata opens more and water evaporates more
3) increase in humidity - reduced concentration gradient of water -> slower rage of diffusion. -> decreases rate
4) wind - concentration of water vapour is lower around lead so steeper concentration gradient thus diffusion is faster and this increases rate
How is the phloem adapted to its function?
holes in cell walls - liquids move from one sieve cell to the other
little cytoplasm - more room for central channel
lots of mitochondria - provide more energy for active transport
companion cells - actively pump sucrose in and out of cells
living cells - use energy to transport sucrose around the plant
How is sucrose transported around the plant through translocation?
sucrose is translocated in sieve tubes
sieve cells connected by channels by holes so sucrose can flow through
companion cells pump sucrose in and out of the cell immediately or for storage
How is the structure of the leaf adapted for its function?
leaves are broad - large surface area to collect light
chloroplasts move away from sunlight - protection
leaves are thin - co2 doesn’t have to diffuse far to reach chloroplasts
irregularly shaped spongy cells - create air spaces so gases diffuse easily inside the lead
upper epidermis is transparent - light can pass through easily
waxy cuticle - prevents water loss & stops microorganisms entering leaf
How are plants adapted for extreme weather?
Deciduous plants lose all their leaves - prevents water loss when soil water is frozen in water
coniferous trees
have needles shaped leaves - smaller surface area and less wind resistance so they can withstand the high wind
have stomata in pits - traps water vapour near lead so rate of diffusion slows down which reduces water loss
cacti
stomata’s only open at night - co2 is taken in for night & stored for the day
small spikes - reduces surface area roe water loss & drops animals from eating it
Phototropism
plant shoots are photographic to get light
1) shoot too exposed to the light, auxins accumulate to shades side
2) cells on shaded sides elongate so shoots grow towards light
3) root exposed to light, auxin moves to shade
4) auxin inhibits elongation on shaded part so the root bends down
Gravitropism
roots are gravitrophic
