Plants Chapter 6 Test Flashcards
How can We describe photosynthetic organisms as?
The main producers of food and therefore biomass
What is photosynthesis in plants and algae?
An endothermic reaction that used light energy to react carbon dioxide and water to produce glucose and oxygen
Explain the effect of temperature as a limiting factor on the rate of photosynthesis
Temperature + rate of photosynthesis = proportional increase.
Colder= little particle movement means it's to cold to catalyse the process Hotter= enzymes denature (above 40*)
Higher temp= more collisions between enzymes and substrate (lock and key)
What is a limiting factor?
The factor directly affects the rate of photosynthesis on its own regardless of the level of the other factors.
Limit the amount of photosynthesis able to happen
What are the major limiting factors for photosynthesis
Light intensity - 1st limiting factor, can’t begin without light
Temperature
Carbon dioxide levels
Optimum temperature for photosynthesis
Between 10-20*
How can we tell from a graph when the limiting factor has changed?
When curved graph creates/changes to a straight line something else has become the limiting factor because the previous one now has enough, working at a suitable rate.
What are commercial used of auxins, gibberellins and ethene in plants
Auxins- used in weedkillers and rooting powders
Gibberellins- in germination, fruit and flow formation and the production of seedless fruit
Ethene- fruit ripening
What is the calculation for rate for transpiration?
Used within experiment with exploring rates of transpiration…
Distance moved by the air bubble / time taken for the air bubble to move that distance
How are plants adapted to survive in extreme environments
Waxy cuticle- allows excess rainwater to fall off
Size of stomata opening- can be altered by the plant in response to the availability of water and light intensity
Bigger surface area= more sunlight
Pointed drip tips -allow excess rainwater to fall off
Thin, flat, spongy mesophyll layer allow water loss
How do plant hormones control and coordinate plant growth and development?
Auxins is a plant hormone produced at tips of stems and roots and controls direction of growth of root tips and stem tips in response to different stimuli including light and gravity.
Role of auxins in phototropism and gravitropism
Phototropism- growth in response to the direction of light
Gravitropism- growth in response to the direction of gravity
Light and gravity can interfere with the transport of auxin causing it to be unevenly distributed
What does auxin do?
Moved in a solution to older parts of the stem and roots where it changes the elasticity of the cells. More elastic cells absorb mor at the and grow longer causing it to bend in the stem or root.
How is the structure of the root hair cells adapted to absorb water and mineral ions
A large surface areas to speed up osmosis
How are the structures of the xylem and phloem adapted to their function in the plant
Lignified dead cells in xylem transport water and minerals through the plant
Living cells in phloem use energy to transport sucrose around the plant
How water and mineral ions are transported through the plant by transpiration?
Water is absorbed from the soil and through root hair cells
Water moves by osmosis from root cell to root cell until it reaches the xylem
It is transported through the xylem vessels up the stem to the leaves
It then evaporates from leaves (transpiration) opening and closing of stomata is controlled by guard cells and can control rates of transpiration.
How does sucrose get transported around the plant by translocation
Phloem transports sucrose and amino acids up and down the plant. This is called translocation ( a transport of dissolved material within a plant )
In general this happens between where these substances are (the sources- leaves) and where they are used or stored (the sinks- growing shoot or roots)
Explain how the structure of the leaf is adapted for photosynthesis and gas exchange
EXTERNAL!!!!!!
Large surface area- absorb more light
Thin- short distance for co2 to diffuse into leaf cell
Chlorophyll- absorbs sunlight to transfer energy into chemicals
Stomata- allow co2 to diffuse into leaf
Explain how the structure of the leaf is adapted for photosynthesis and gas exchange
INTERNAL!!!!
thin cuticle - protect leaf without blocking light
Palisade cell layer at top of leaf- absorb mor light
Spongy layer- air spaces allow co2 to diffuse through the lead and increase surface area
Palisade contains many chloroplasts- to absorb all available light
What is the equation for photosynthesis and how do we balance It?
CO2 + H2O ——–> C6H12O16 + 6O2
Balance- add a 6 in front of Carbon dioxide, water and oxygen
How does a cacti survive in its extreme conditions? (2 points)
Stomata only open at night and CO2 is taken in at night and store for use during the day
Thick cuticle
Have spines instead of leaves which minimises the surface area and reduces water loss by transpiration
Roots have a large surface area
Explain the effect of light intensity on the rate of photosynthesis EXPERIMENT
Measure length of pondweed with ruler
Measure 200ml of water into beaker
Place pondweed into beaker
Use ruler to measure different distances away from light
Count how many bubbles of oxygen leave pondweed per minute
What can effect the rate of water uptake by a plant?
Light intensity- more light is more transpiration and less light is less transpiration- can’t evaporate
Air movement- faster in windy conditions- changes pressure on leaf
Temperature- higher=more transpiration lower=less transpiration
How can humidity effect uptake of water? Transpiration
Slower in humid conditions, diffusion of water out of leaf slows down if leaf is already surrounded by moist air
It increases concentration gradient because diffusion of water from inside plant to outside the plant through stomata will be increased.
What is the effect of light intensity on photosynthesis
On a graph is directly proportional- up then straight.
Without enough light a plant cannot photosynthesise very quickly, even if there is plenty of water and CO2. Increasing the light intensity will increase speed of photosynthesis
What is the Effect of Carbon dioxide on the rate of photosynthesis
On a graph is directly proportional- up then straight.
Carbon dioxide needs to react with water to form the products of photosynthesis- oxygen and glucose.
A plant cannot photosynthesise if there is insufficient CO2
How is a Xylem adapted to transport water
Xylem cell has a thick cell wall which provides strength
Lignin - supportive structure and prevents the xylem from collapsing under pressure from the water
Lignin- waterproof to prevent any water from diffusing out of the xylem
What is a tropism
A growth in response to a stimuli, plants grow towards sources of water and light which they need to survive and grow.
Gravitropism
Phototropism
What is active transport and what does move
The movement of dissolved molecules (minerals) move across a cell membrane from a lower concentration to a higher concentration. In active transport, particles move against the concentration gradient and therefore require an input of energy from cell
What is osmosis and what does it move
Osmosis is movement of WATER from a high concentration to a lower concentration of water
OR can be said as
Diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
What is diffusion in plants
Movement of particles in and out of cells down a concentration gradient (from high concentration to low concentration)
Eg- movement of carbon dioxide in leaves
What is the inverse square law calculation
Light intensity= 1 / distance2 in meters
Eg- plant is 20cm away from light
1/0.2m2 = 25 arbitrary units
What is the inverse square law calculation
measured in?
Arbitrary units
What are sieve cells in translocation
A Sieve tube has sieve cells which have pores in which nutrients can flow from cell to cell, it lacks most organelles so therefore the companion cell which contains them controls the movement of solutes
