Plant Structures And Their Functions Flashcards
What is the word equation for photosynthesis?
Carbon. + Water. —————————> glucose + oxygen
Dioxide Light energy
Where does photosynthesis occur?
In chloroplasts which contain chlorophyll which traps light energy for photosynthesis
Why is photosynthesis an endothermic reaction?
Since energy enters from the surroundings, the products of photosynthesis have more energy than the reactants
What happens when glucose molecules are made?
They link together to form a polymer called starch which stays in the chloroplasts until photosynthesis stops.
How is sucrose made?
When starch is broken down into simpler substances and moved into the cytoplasm which are then used to make sucrose, which is then transported around the plant
What can sucrose be used to make?
Starch (in a storage organ e.g. potato)
Other molecules for the plant (e.g. cellulose,lipids,proteins)
Glucose for respiration (releases energy)
In order from top of leaf to bottom, what cells are in the leaf?
Waxy cuticle Upper epidermis Palisade Cell layer Air space Spongy mesophyll Lower epidermis Guard cell and stomata Waxy cuticle (again)
How is the cuticle adapted?
It protects the cell from pathogens as it acts as a physical barrier
The waxy cuticle is water proof/water repellent
How is the upper epidermis adapted?
It is thin so it allows a lot of light in for photosynthesis
How is the palisade layer adapted?
They are packed with chloroplasts so they can absorb a lot of light for photosynthesis
How are the air spaces/spongy mesophyll adapted?
Large surface area to allow for a greater amount of gas exchange
How are the stomata adapted?
They can open and close to allow carbon dioxide to diffuse into the leafs but also allow less or more gas exchange
How are the guard cells adapted?
Help the stomata open and close because when it is light (day time), water flows into the guard cells, making them rigid. This causes the stomata to open.
At night, water flows out of the guard cells so they lose their rigidity so the stomata closes, to prevent any gas loss or water vapour loss.
What is it called when a factor prevents a rate from increasing?
A limiting factor
What are some limiting factors for photosynthesis?
Carbon dioxide concentration, temperature and light intensity
Once a factor is limiting, what does changing its supply change?
The rate of photosynthesis
What does a straight line on a graph show?
A linear relationship
What is the method for Core Practical: Light intensity and Photosynthesis?
1) Decide on the different distances between algae and lamp
2) For each distance you will need one clear glass bottle and an extra bottle
3) Add 20 algae balls to each bottle
4) Add same amount of indicator solution to each bottle and put caps on each bottle
5) Find our pH at start by comparing colour to pH scale
6) Set up a tank of water between lamp and area where you will place your tubes
7) Cover on bottle in foil so it’s in the dark
8) Put your bottles at the different distances you measured at start. Put bottle covered in foil next to the bottle closest to the lamp
9) Turn in lamp and wait until colour changes
10) Write down all your solutions pH
11) For each bottle calculate the ‘change in pH/hour’
12) Plot a graph of results
What is water (absorbed by plant roots) used for?
Carrying dissolved mineral ions
Keeping cells rigid
Cooling the leaves
Photosynthesis
How is a root hair cell adapted?
Have a large surface area so more water and mineral ions can be absorbed
Also have thin cell walls so the flow of water isn’t slowed down
How does water travel in a root hair cell?
Water enters by diffusion - Water diffuses through cell walls
Water enters by osmosis - Tiny tubes join the cytoplasm of some cells together to allow water to be diffused
How are mineral ions obtained in a plant?
Through active transport (against a concentration gradient)
What is transpiration?
Water moves into the root hair cell by osmosis. This moves water from a high concentration to a low concentration.
Xylem vessels are continuous pipes running from root to leaf
Evaporation of water from the leaf pulls water up the xylem.
Water will then diffuse out of the leaf via the stomata.
From a high concentration to a low concentration, down a concentration gradient.
What is translocation?
Glucose made in the leaf is turned into sucrose.
This is translocated(moved) in the phloem.
These are sieve tubes connected together by holes
Companion cells actively pump the sucrose and amino acids in and out of the siege tubes.
This requires energy.
How is the xylem adapted for transpiration?
Contains dead cells with no cytoplasm and form an empty tube - this causes the water flow to be fast and not slowed down. Also, the lack of cell walls between cells mean the water flow isn’t slow also.
Tiny pores allow mineral ions and water to enter and leave the xylem vessels
Thick side walls and rings of lignin form rigid tubes that won’t burst or collapse - this provides support
How is the phloem adapted for translocation?
Pores - where sucrose solution can be pumped
Holes in ends of cell walls - allows liquids to flow from one sieve cell to the next
Small amount of cytoplasm(no nucleus) in cells - allows more space for the central channel
What is a potometer?
The air bubble moves along the tube as the plant loses water. The speed of the bubble gives a measure of the rate of transpiration
Why did wind increase the rate of transpiration?
The water vapour is removed quickly by air movement, speeding up diffusion of more water vapour out of the leaf
Moves water molecules away from stomata
Why does low humidity increase rate of transpiration?
There is a low water vapour in the air, increasing evaporation from the leaf so there is a higher concentration from the leaf to outside.
How does a higher temperature increase the rate of transpiration?
Particles move faster so they diffuse faster
Why does a high light intensity increase the rate of transpiration?
Cause the stomata to open wider allowing more carbon dioxide into the plant
How are conifers adapted to their windy and cold climate?
Have needle shaped leaves with a small surface area but thick cuticle - creates less wind resistance then broad leaves allowing them to withstand high winds
Have stomata located in small pits where water vapour collects - Reduces water loss by trapping water vapour close to leaves which slows the rate of diffusion out of the leaves
How are cacti adapted to their hot climate?
Spines instead of leaves - minimise the surface area so there is reduced water loss by transpiration and spines also protects from any predators
Stems store water and wide spread root systems that collect water from large areas
What is the plant hormone that regulates growth?
Auxin
What is phototropism?
Detects light (tropism that works towards light)
What does auxin do in the shoots?
Auxin is produced in tip of shoots.
In the shoot, auxin promotes elongation causing negative geotropism (going against gravity). Then, as the shoot/plant bends towards the light, auxin moves to the darker side of the shoot. This results in positive phototropism.
What is geotropism?
Detecting gravity ( tropism that acts towards gravity)
What happens with auxin in the roots?
Auxins have an opposite affect to the that in the shoots.
In roots, auxin causes cells to stop elongating and this causes positive geotropism as the roots are growing towards gravity.
What does gibberellin do?
Causes starch to turn into sugars which provides energy
Helps release energy for the seed to grow when germinating
What does Ethene/Ethylene do?
Co-ordinates fruit ripening
What is the hormone involved in Selective Weed Killer and how does it work?
Hormone: Artificial Auxins
Artificial auxins cause the plants to grow uncontrollably and this kills them. Weed killer uses this to kill plants with broader leaves e.g. dandelions, but not those with narrow leaves so farmers can kill weeds without damaging the crops.
What is the hormone involved in rooting powder and how does it work?
Hormone involved: Auxin
How it works: The auxins cause plant cuttings to develop roots quickly. Large numbers of identical plants can be produced quickly using cuttings, compared to growing plants from seeds
What is the hormone involved in seedless fruit and how does it work?
Hormone involved: Gibberellin
How does it work: Many plants only produce seeds after being pollinated which then allows egg cells to be fertilised, and seeds to be formed. Gibberellin causes plants to produce fruit without this, giving us seedless fruit
What is the hormone involved in Ripening fruit and how does it work?
Hormone involved: Ethene
How does it work: Fruit producers often pick unripe fruit and then ripen it when needed using a plant hormone gas called ethene. This makes sure that fruit reaches the shops in a “just ripened” condition
