Unit 6 - Plant Structures And Their Functions Flashcards
What is photosynthesis?
The process of plants converting energy into a sugar called glucose
What is the biomass of an organism?
The materials in an organism
Why do plants and algae produce food for almost all other life on Earth?
They produce their own biomass
What part of the food change are plants?
The producers
What is the word equation for photosynthesis?
Carbon dioxide + water —> glucose + oxygen (energy transferred by light)
Where does photosynthesis occur?
In chloroplasts in chlorophyll
What is a endothermic reaction.
When the reaction absorbs the energy from the surroundings
What is an exothermic reaction?
When energy is released from the reaction
What is starch?
A polymer made from glucose molecules
What happens to the starch produced from then
It is broken down into smaller substances and moved to the cytoplasm where it is used to make sucrose
What is sucrose used to make in plants?
Starch
Glucose (respiration)
Other molecules such as lipids and proteins
What cells contain the chloroplasts?
Palisade cells
Give 3 adaptations of a leaf
Broad and flat to give it a large surface area
Palisade cells are near the go to absorb light easily,
Very thin so carbon dioxide doesn’t have to diffuse very far
What is the role of the stomata
To allow carbon dioxide to enter the lead by diffusion
What are guard cells?
Specialised cells that open and close the stomata
What causes the stomata to open and close?
When it is light, water flows into pairs of guard cells and make them rigid and open, at night, water flows out of and the stomata shuts
What does the stomata allow to leave
Oxygen and water vapour
What is gas exchange?
The flow of different gasses in and out
Why is the rate of photosynthesis lower in the mountains than at sea level? (2)
The concentration of air molecules is less in the mountains
Higher mountains are colder which make the enzymes for photosynthesis work slower
What is a limiting factor?
A factor that prevents a rate increasing.
What are the 3 limiting factors for photosynthesis?
CO2 concentration, light intensity, temperature
For a graph showing a limiting factor and rate of photosynthesis, why does the line become horizontal after some time?
Something else becomes the limiting factor
What does a straight line on a graph show?
A linear relationship
What must the line do on a graph to show that two variables are in direct proportion?
It must
go through 0,0
What does the inverse square law calculate?
The new light intensity when the distance of a light source changes
What is the equation for new light intensity?
New LI = Original LI x original d^2 / new d^2
If you double the distance from the light source, what happens to the light intensity
It halves from the original
Explain the core practical - Light intensity and photosynthesis
Place different glass bottles at different distances from light
Add 20 algal balls to each bottle and indicator, put on bottle caps
Compare colours of tubes with a pH range at the start
Set up water tank between light and bottles
Cover a bottle in kitchen foil and place next to the closest one to the lamp
Turn on lamp and wait for obvious changes
Compare colours to pH range and calculate ‘change in pH/hour’
How are some trees adapted to living in rainforests?
They have huge buttress roots to stop tall trees falling over and trap dead vegetation for minerals
What is the water absorbed by plant roots used for? (4)
Carrying dissolved mineral ions
Keeping cells rigid (not wilting)
Cooling leaves (evaporation)
Photosynthesis
How are root hair cells well adapted? (2)
Provide large surface area, faster absorption of mineral ions
Thin walls so flow of water is not slowed
What is diffusion
When particles move down a concentration gradient
What adaptation do plant roots have for diffusion?
The cell walls have an open structure allowing water particles to diffuse towards the middle of the root.
What is osmosis?
When solvent particles diffuse through a semi-permeable membrane
Where does osmosis occur in plants?
Water passes into the cytoplasm of root hair cells by osmosis
Give an example of how plants use mineral salts
Nitrate ions to make proteins
Why is active transport needed to pump ions into the root hair cells?
The concentration of ions inside a root hair cell is greater
How does water keep plants cool?
When it evaporates, it transfers the heat energy
What is transpiration?
The flow of water into a root, up the stem and out of the leaves
Why is there an unbroken chain of water in the xylem vessels?
The weak forces of attraction between the water molecules
Describe what happens in the xylem vessels to stop the flow breaking?
Water is pulled up the xylem vessels in the stem as water evaporates from the xylem vessels in the leaves. As water vapour diffuses out of a leaf, more evaporates from the xylem inside the leaf
What type of factors would cause water to be evaporated quicker?
Making a bigger difference between the concentrations so diffusion occurs faster
Give 2 factors which increase water evaporation
Wind
Low humidity
Give 2 factors that increase transpiration
Higher temperature, particles move faster
Greater light intensity, makes stomata wider
What causes the stomata to open?
Light
Give 3 adaptations for xylem vessels
Thick side walls of lignin to it won’t burst or collapse
Dead cells, no cytoplasm so forms an empty tube for water to flow
Lack of cells walls on top and bottom of cells
Give 3 adaptations of phloem vessels
Holes in ends of cell walls to allow liquids to flow through
Pores which sucrose solution can be pumped
Small amount of cytoplasm, more room for central channel
Where do plants make sucrose from?
The glucose and starch made by photosynthesis
How is sucrose transported?
It is translocated in the sieve tubes and phloem tissue
What is the role of companion cells?
They actively pump sucrose into or out of sieve cells that form the sieve tubes
Why do leaves have large surface areas?
To ensure they collect enough sunlight
What part of the plant traps sunlight
Chlorophyll
Where does CO2 diffuse into the plant
Through an open stomata
What are epidermis cells
They form the outer layers of a lead and hold it together, protecting the cells inside
Give 2 adaptations of epidermis cell’s
Transparent, allow light through
Waxy waterproof cuticle, prevent water loss
Why do many deciduous plants lose their leaves in the winter
Prevents water loss when soil water may be frozen
Why do conifers have needle-shaped leaves
Creates less wind resistance so they can withstand high winds
Why is the stomata of conifers located in small pits
Reduces water loss because water vapour collects there and is less exposed to environment
Why do some plants in the desert have hairs
To trap water
Give 3 adaptations of plants in the desert
Thick cuticle (prevent water loss)
Some have hairs
Spines instead of leaves (minimise surface area)
What is a stimulus
A change in environment that causes a response by an organism
What is phototropism
Responding to a stimulus which is light by growing towards or away from it
What hormones cause positive phototropism
Auxins
Where are auxins found for phototropism
In the tip of the shoot
How do auxins cause phototropism
They elongate the cells so they move to the shaded side to make it grow towards the light
What was Darwin’s experiment?
6 different shoot tips: 1. Intact shoot, 2. Covered with place paper, 3. Covered with transparent cap, 4. Tip removed, 5. Tip removed and replaced on an impermeable block 5. Tip removed and placed on agar block
What hormones cause gravitropism
Auxins
Where are aiding found for gravitropism
In the root tips
What do auxins do for gravitropism
They stop the elongation of cell so they move to the most downward side
What is the hormone to help seeds germinate?
Gibberellins
What hormones help fruit to ripen
Ethene
What do selective weed killers contain
Artificial auxins to kill plants with broad leaves but not with narrow leaves
What do auxins in root powders cause
Plant cuttings to develop roots quickly
What is a positive of gibberellins
It can make the seeds germinate faster (some only germinate at certain times)
What is photoperiodism
The response of an organism to the number of daylight hours in a day
How can farmers override photoperiodism?
By spraying plants with gibberellins
How are seedless fruits formed?
Gibberellins can cause the plant to produce the fruit without seeds being formed
Why do fruit producers use ethene?
They can transport the fruits while they are unripe and use the ethene to ripen them when they need them
