Plants Flashcards
Why would it be advantageous to have less holes on a plant in the desert (stomata)
To reduce water loss due to large difference in temperature and the subsequent evaporation
Where does the CO2 come from in order for photosynthesis to occur?
CO2 enters through the stomata
What happens once the glucose is created in photosynthesis?
Glucose is transported around the plant in the phloem vessels for: life processes, cellulose, starch for storage
Where does the water come from in order for photosynthesis to occur?
Water is absorbed by the root hair cells and is transported to the leaf by the xylem vessels
What are the four adaptations for photosynthesis?
1) Green chlorophyll to absorb sunlight
2) Large surface area to maximise the amount of sunlight they can absorb
3) Veins (xylem and phloem) to allow the transportation of water, mineral ions and glucose
4) Thin easy diffusion
What happens after a plant reaches optimum temperature?
The cells in the plant will denature
Adaptation of epidermis
Thin and transparent to allow more light to reach the palisade cells
Adaptation of palisade cells
This is where most photosynthesis occurs, therefore contains tightly packed chloroplasts, and are at the top layer to absorb more light and increase the rate of photosynthesis
Adaptations of spongy mesophyll
Air spaces allow CO2 to diffuse through the leaf
Adaptations of SA:V
Large internal SA:V allows efficient absorption of CO2 and removal of O2
Adaptations of stomata
Allows movement of gases into and out of the leaf
Test for starch
1) Heat a leaf in boiling water for 5 secs - kill the cells, arrest all chemical reactions and make the leaf permeable to alcohol and iodine solution
2) Heat in ethanol for 5 mins - removes chlorophyll
3) Wash with water and spread onto white tile
4) Add iodine solution for 1 min
5) Wash away iodine solution
* Parts that contain starch are blue-black
What is osmosis?
The net movement of water from an area of high water potential to low water potential through a partially permeable membrane
How is water transported from the soil to the xylem vessel?
Water is taken up by the root hairs of the plant epidermis and is carried across the root cortex by a water potential gradient. It enter the xylem and is transported to all parts of the plant
What is active transport?
The movement of dissolved molecules into or out of a cells through a cell membrane
Low to high concentration
What do xylem vessels do?
Transports water and minerals through the plant
What do phloem vessels?
Transports sucrose and amino acids up and down the plant
Guard cells in the day
Stomata is open as the guard cells take in water - turgid
Guards cells at night
Stomata closed, loses water and becomes flaccid
What do phloem vessels do?
Moves food substances that the plant has produced
Transport of the substances is called translocation
What do companion cells do (phloem)?
Provide energy
Control sieve tubes
What do sieve tubes do (phloem)?
Perforated end so it’s cytoplasm connects one cell to the next
What is transpiration?
The evaporation of water from a surface of a leaf/plant
Light intensity - transpiration
Rate of transpiration increases in light (more aroma open)
Temperature - transpiration
High temps increase rate of transpiration
Humidity - transpiration
Lots of humidity means slower transpiration rate
Reduction in diffusion gradient
Quicker in dry air
Wind speed - transpiration
Rate of transpiration increases with faster air movements
Moving air removes any remaining water vapour
Which indicator is used to investigate the effect of light on gas exchange?
Hydrogen carbonate indicator
Colours of solution in different CO2 concentrations
High - Yellow
Normal - Orange
Low - Purple
Leaf in light
Purple colour - more photosynthesis occurs, more CO2 absorbed
Leaf in dark
Yellow colour - more respiration, more CO2 given out
Leaf in dim light
Orange colour - CO2 levels are equal
Why is stomata found on the upper surface of a water lily?
To maximise air exposure
On the underside, water contact would interfere with exchange of CO2 and O2
Why is transpiration important to plants?
Transpiration produces a cooling affect upon the plant in hot conditions and also enables the transportation of water and mineral salts from the soil to the leaves
What is a limiting factor
Something present in the environment in such short supply that it restricts life processes
Variables for pondweed in water
Light - use a lamp and vary the distance of the lamp to the pondweed to control the light intensity
CO2 - add sodium hydroxide to absorb and remove CO2, add sodium bicarbonate to increase CO2
Chlorophyll - use variegated plant
Magnesium minerals ion
Magnesium is needed to build chlorophyll
Deficiency - leaves turn yellow
Nitrate mineral ion
Nitrates are needed to produce amino acids to build protein and dna
Deficiency - leaves turn yellow and stunted growth
Adaptations for gas exchange
Internal air spaces in spongy mesophyll layer
Guard cells around stomata
Flattened shape (larger SA:V)
Thin (short diffusion distance)
Stomata during the day
Guard cells will absorb water by osmosis
Thick inner walls will split open
Stomata opens
Net exchange of gases
Stomata during the night
Guard cells will lose water by osmosis
Thick inner walls will stick together
Stomata closes
Net exchange of gases does not occur
Uses in a plant of the carbohydrate produced in photosynthesis
Respiration
Used to make cellulose/lignin
Used to make starch
Used to make chlorophyll
