SB6 - Plant Structures And Their Functions Flashcards
How do plants and algae get energy
Trap energy transferred by the light from the sun
Energy transferred to glucose in photosynthesis - glucose and products made from it are stores of energy
What is biomass
The materials in an organism are its biomass
Plants and algae produce their own and so produce their own food
They are producers in food chains
What is photosynthesis simply
A series of chemical reactions catalysed by enzymes
Tell me the word equation for photosynthesis
Carbon dioxide and water = glucose and oxygen
Where does photosynthesis occur
In chloroplasts which contain a green substance called chlorophyll that traps energy transferred by light
What type of reaction is photosynthesis
Endothermic reaction as energy enters from its surroundings and so products have more energy than reactants
What happens to glucose molecules
Glucose molecules are linked to form a polymer starch - stays in chloroplasts until photosynthesis stops
Starch is broken down into simpler substances which move into cytoplasm to make sucrose
What can sucrose be used for
It’s another type of sugar molecule
Sucrose is transported around the plant and may be used to make:
- starch (in a storage organ such as potato)
- other molecules for the plant (such as cellulose, lipids, or proteins)
- glucose for respiration (to release energy)
Tell me about palisade cells
They are near the top of a Leaf packed with chloroplasts - adapted to allow leaf to absorb maximum light
Tell me about stomata
Leaves contain microscopic pores called stomata or singular stoma
They allow carbon dioxide to diffuse into the leaf
Allow oxygen producer escape into the air and as well as water vapour
Tell me about guard cells
The stomata are opened and closed by stomata
In the light, water flows into pairs of guard cells making them rigid
This opens the stoma
At night water flows out of the guard cells so they shut
Why are leaves thin
So carbon dioxide does not have to diffuse far into the leaf
What’s gas exchange
The flow of different gases into and out of a leaf eg carbon dioxide and oxygen
What’s reduced concentration of air molecules
Causes a lower rate of photosynthesis in high mountains
How can temperature affect rate of photosynthesis
The reactions in photosynthesis are catalysed by enzymes that work better in warmer conditions
What’s the limiting factor
The factor that prevents a rate increasing
Carbon dioxide concentration, temperature and light intensity can be limiting factors
The maximum rate of photosynthesis is controlled by the factor in shortest supply
What’s a linear relationship
Between two variables
What’s direct proportion
If line in graph goes through the origin - it shows the two variables are in proportion
As one increases the other one does too
What’s the inverse square law
Used to calculate new light intensity
1/new distance from light source ^2
What is water absorbed by plant roots also used for
Carrying dissolved mineral ions
Keeping cells rigid - otherwise they will wilt (stems and leaves will droop)
Cooling the leaves - when it evaporates from them
Photosynthesis
Tell me about root hair cells
The outer surfaces of many roots are covered with root hair cells
They are extensions to increase surface area so water and mineral ions can be quickly absorbed - also have thin walls so the flow of water into the cells is not slowed down
Tell me about osmosis and diffusion
Particles Constantly move in random directions and so particles in a fluid diffuse down a concentration gradient
This is diffusion inside plant roots as the cell walls have an open structure allowing water particles to diffuse towards the middle of the root
Water passes into the cytoplasm of root hair cells by osmosis
Tell me about active transport
Mineral salts are naturally occurring ionic compounds
Plants need the ions to from new substances
Eg nitrate ions are needed to make proteins
The concentration of ions in root hair cell is greater than in the soil
Proteins in the cell membrane pump the ions into the cell and so is an example of active transport
What’s transpiration
The evaporation of water from leaves keeps them cool and helps dissolved mineral ions move up the plant
The flow of water into a root up the stem and out of the leaves is transpiration
Tell me about xylem vessels
Xylem vessels form continuous pipes leading from a plants roots to its leaves
Inside the vessels is an unbroken chain of water due to weak forces of attraction between water molecules
Water is pulled up the xylem vessels in the stem as water evaporates from the xylem vessels in the leaves
As the water vapour diffuses out of s leaf, more evaporates from the xylem vessel inside the leaf
What makes diffusion faster
The bigger the difference between the concentrations makes it faster
What factors increase transpiration
But reduce concentration of water molecules outside the stomata
Wind moves water molecules away from the stomata
Low humidity means little water in the air
Higher temps so particles move faster and so will diffuse
Greater light intensity - makes stomata wider
Tell me about xylem
Xylem cells die and Thor top and bottom cell walls will disintegrate
To create long empty vessels so water can move easily
Why are xylem vessels rigid
Becuase they have thick side walls and rings of hard lignin and so water pressure inside the vessel does not burst or collapse on them
The rigid xylem vessels also help to support the plant
Tell me about phloem
Plants make sucrose and glucose and starch made in photosynthesis
Sucrose is translocated in the sieve tubes of the phloem tissue - the large central channel in each sieve cell is connected to its neighbours by holes, through which sucrose solution flows
What do companion cells do
They actively pump sucrose into or out of the sieve cells that form the sieve tubes
As sucrose is pumped into sieve tubes, the increased pressure causes the sucrose solution to flow up to growing shoots or down to storage organs
Why do leaves have large surface areas w
To collect enough light
The energy transferred by light is trapped by chlorophyll packed into discs inside chloroplasts
The energy is then transferred to glucose during photosynthesis
The chloroplasts in a cell can move yoward or away from the light - as protection from bright light
Why are leaves thin
So carbon dioxide does not have to diffuse far before reaching photosynthesising cells
X
Carbon dioxide diffuses through the Leaf through open stomata
Tell me about spongy cells
They are irregularly shaped and do not fit together so air spaces are created - allowing gas to diffuse easily inside a leaf
What supplies the water for photosynthesis
A network of xylem vessels
Tell me the layers of a leaf starting from the bottom of the leaf
Cuticle
Guard cells and stoma in the lower epidermis
Layer constant spongy cells with xylem vessels, phloem tissue and air space
Layer of palisade cells
Upper epidermis
Cuticle
Tell me about epidermis cells
They form the outer layers of a leaf, holding the leaf together and protecting the cells inside
They are transparent, allowing light to pass through them easily and also produce a waterproof waxy cuticle to help prevent water loss and stop microorganisms and water entering the leaf
Tell me some adaptions of trees in cold environments
In winter many broad leaved deciduous plants lose all their leaves to prevent water loss when soul is frozen
Most conifers don’t do this and have needle shapes leaves with a much smaller surface area and very thick cuticle - this shape creates less wind resistance than broad leaves - allowing conifers to withstand high winds and collect less snow
How can plants reduce water loss in hot environments
Trapping water vapour close to their leaves which slows the rate of diffusion out of leaves
Conifers achieve this by having stomata located in small pits, where water collects Becuase it is less exposed to air movement
Other plants use tiny hairs to trap water vapour
Tell me some adaptions of cacti on dry environments
Some have hairs
Spines instead of leaves to minimise surface area of the plant
Cacti stomata only open at night
Carbon dioxide is taken in at night and stored for use during the day
Thick cuticle
Stomata only found in valleys of the stem
What is a stimulus
Change in environment that causes a response by an organism
What’s a tropism
Responding to a stimulus by growing towards or away from it
What’s a phototropism
A tropism towards the light is a positive phototropism
A tropism away from the light are negatively phototropic
Give an example of a positively phototropic thing
Plant shoots
Give an example of a negatively phototropic thing
Plant roots
What are positive phototropisms caused by
Caused by the plant hormones - auxins
Where are auxins produced
In the tip of the shoot
What happens with auxins
They cause cell elongation and move to the shady side of a plant to elongate cells to Point it to grow toward the light
Who did experiments about auxins
Charles Darwin did experiment to see what was going on when plant shoots bend towards the Light
So Frits warmolt went suggested how auxins worked with the extraction and purification of auxins
Where other than tips of shoots are auxins found
Auxins are found in root tips where they have the opposite effect to that in the shoots
Tell me about auxins in the roots
Auxins cause cells to stop elongating
What’s a positive gravitropism,
in roots, auxins cause cells to stop elongating and cause growth towards the direction of gravity
This helps roots to anchor the plant in place to reach moisture underground
What do gibberellins do
Help seeds to germinate and start to grow roots and shoots
What’s ethene gas
A plant hormone that helps fruit to ripen
Tell me about selective weed killers
They contain artificial auxins to kill plants with broad leaves but not with narrow leaves
Farmers can therefore kill weeds in wheat field without affecting the crop
How can artificial auxins kill weeds
Can make some plants grow uncontrollably which can kill them
Tell me about rooting powders
Auxins are also found in rooting powders which cause plant cutting to develop roots quickly
Large numbers of identical plants can be produced quickly using cutting, compared to growing plants from seed
Tell me about gibberellins
They are naturally released inside a
Seed to start germination
Some seeds need a period of darkness or cold before they can germinate but plant growers can use gibberellins to make there seeds germinate without this
What’s a photoperiodism
It’s a response to an organism to the number of daylight hours in a day
Some plants use this to flower at a certain time
Flower growers can override photoperiodism by spraying plants with gibberellins
How can gibberellins cause seedless fruits
Many plants only produce seeds after being pollinated which then allows egg cells to be fertilised and seeds to form
Gibberellins can cause some plants to produce plants without this and give use seedless fruits
Gibberellins can also be sprayed on some plants to make them bigger fruits
Tell me some benefits of ethene
Can be used to ripen fruit after being transported and so not damaging them, Unripened fruit can be kept for longer in cold storage without going off
Fruit producers often pick Unripened fruit and then ripen it using ethene
Ethene makes sure a fruit reaches the shops in a Just ripened condition
What is a stimulus
Change in environment that causes a response by an organism
What’s a tropism
Responding to a stimulus by growing towards or away from it
What’s a phototropism
A tropism towards the light is a positive phototropism
A tropism away from the light are negatively phototropic
Give an example of a positively phototropic thing
Plant shoots
Give an example of a negatively phototropic thing
Plant roots
What are positive phototropisms caused by
Caused by the plant hormones - auxins
Where are auxins produced
In the tip of the shoot
What happens with auxins
They cause cell elongation and move to the shady side of a plant to elongate cells to Point it to grow toward the light
Who did experiments about auxins
Charles Darwin did experiment to see what was going on when plant shoots bend towards the Light
So Frits warmolt went suggested how auxins worked with the extraction and purification of auxins
Where other than tips of shoots are auxins found
Auxins are found in root tips where they have the opposite effect to that in the shoots
Tell me about auxins in the roots
Auxins cause cells to stop elongating
What’s a positive gravitropism,
in roots, auxins cause cells to stop elongating and cause growth towards the direction of gravity
This helps roots to anchor the plant in place to reach moisture underground
What do gibberellins do
Help seeds to germinate and start to grow roots and shoots
What’s ethene gas
A plant hormone that helps fruit to ripen
Tell me about selective weed killers
They contain artificial auxins to kill plants with broad leaves but not with narrow leaves
Farmers can therefore kill weeds in wheat field without affecting the crop
How can artificial auxins kill weeds
Can make some plants grow uncontrollably which can kill them
Tell me about rooting powders
Auxins are also found in rooting powders which cause plant cutting to develop roots quickly
Large numbers of identical plants can be produced quickly using cutting, compared to growing plants from seed
Tell me about gibberellins
They are naturally released inside a
Seed to start germination
Some seeds need a period of darkness or cold before they can germinate but plant growers can use gibberellins to make there seeds germinate without this
What’s a photoperiodism
It’s a response to an organism to the number of daylight hours in a day
Some plants use this to flower at a certain time
Flower growers can override photoperiodism by spraying plants with gibberellins
How can gibberellins cause seedless fruits
Many plants only produce seeds after being pollinated which then allows egg cells to be fertilised and seeds to form
Gibberellins can cause some plants to produce plants without this and give use seedless fruits
Gibberellins can also be sprayed on some plants to make them bigger fruits
Tell me some benefits of ethene
Can be used to ripen fruit after being transported and so not damaging them, Unripened fruit can be kept for longer in cold storage without going off
Fruit producers often pick Unripened fruit and then ripen it using ethene
Ethene makes sure a fruit reaches the shops in a Just ripened condition
