Bio y9 2nd half - plants Flashcards
in Guard cells the stoma is open when…
there is light and an excess of water
this means the Guard cells are swollen / turgid
in Guard cells the stoma is closed when…
it’s dark and when there’s a drought
this means the Guard cells are shrunken / flaccid
cuticle
protects the leaf
upper epidermis
Epidermal tissues cover the leaf letting light penetrate through
palisade cell
contains lots of chloroplast’s to absorb lots of light energy carrying out photosynthesis
Spongy mesophyll
irregularly shaped to have many air spaces between the cells for gases to diffuse easily and to reach all cells
Lower epidermis
Has many stomata which allow gases and water vapour to diffuse
Protect the underside of the leaf
Guard Cells
Surround this stoma on the underside of the leaf open and close the stoma to allow CO2 to get to the cells and oxygen to leave via diffusion. Also allows for some water movement.
Root hair cells
narrow tubes with large surface areas
large surface area to increase the rate of mineral ions absorption.
contain lots of mitochondria , which release energy from glucose during respiration in order to provide the energy needed for active transport.
Xylem
Thexylemtransports water and minerals from the roots up the plant stem and into the leaves.
most of the cells that make up the xylem are specialized cells called vessels.
Vessels
Lose their end walls so the xylem forms a continuous, hollow tube.
Become strengthened by a chemical calledlignin. The cells are no longer alive. Lignin gives strength and support to the plant. We call lignified cells wood.
Transport in the xylem is a physical process. It does not require energy.
Phloem
Thephloemmoves food substances that the plant has produced by photosynthesis to where they are needed for processes such as:
growing parts of the plant for immediate use
storage organs such as bulbs andtubers
developing seeds.
Transport in the phloem is therefore both up and down the stem.
Translocation
teansport of substances in the phloem
Sieve tubes
specialised for transport and have nonuclei. Each sieve tube has a perforated end so itscytoplasmconnects one cell to the next.
companion cells
transport of substances in the phloem requires energy. One or more companion cells attached to each sieve tube provide this energy. A sieve tube is completely dependent on its companion cell(s)
Transpiration
the evaporation slash loss of water from the leaves through the stoma, which causes water to be drawn up the plant
Why is transpiration so important?
Evaporation of water cools plants
Water is a reactant in photosynthesis
Cells full of water support the plant
Water carries dissolved materials around the plant
Factors affecting the rate of transpiration:
Temperature
Humidity
Wind
light availability
How to measure the rate of transpiration
by using a potometer
Set up potometer in room temperature
*Position air bubble at 0mm
*Record position of bubble after 5 minutes
*Repeat steps 1-3 in other named temperature different to original
*Describe at least one control variable (such as wind, humidity, light intensity, carbon dioxide concentration
*Describe use of repeats at each temperature for reliability
How do guard cells open and close stomata?
Potassium ions diffuse into the cells which increases the concentration of the solution inside guard cells
As the gold sales on now less dilute water moves in by osmosis
The additional water leads to the guard cells swelling unevenly because the thicker inner walls are less flexible than the thinner outer walls
the stoma opens due to this uneven swelling
Light effect on the rate of transpiration
Transpiration increases in bright light because the stomata open wider to allow more carbon dioxide into the leaf for photosynthesis. More water is therefore able to evaporate.
Temperature effect on the rate of transpiration
transpiration is faster in higher temperatures Because evaporation in diffusion is faster at higher temperatures
Wind effect on the rate of transpiration
transpiration is faster in windy conditions because water vapor is removed quickly by air movement speeding up the diffusion of more water vapour out of the leaf
Humidity effect on the rate of transpiration
Transpiration is slower in humid conditions because diffusion of water vapor out of the leaf is slower if the leaf is already surrounded by moist air - less steep concentration gradient
Photosynthesis
a chemical reaction by which green plant cells produce glucose in oxygen from carbon dioxide and water using light energy
Light intensity effect on rate of photosynthesis
Without enough light a plant cannot photosynthesise very quickly even if there is plenty of water and carbon dioxide. increasing the light intensity will boost the speed of photosynthesis and then the rate will become steady as something else is a limiting factor for example temperature or carbon dioxide concentration
temperature effect on rate of photosynthesis
Increasing temperature increases rate of photosynthesis, until it reaches a certain temperature where it starts to decrease temperature. This is because the enzymes become denatured and can no longer catalyse the photosynthesis reaction.
Carbon dioxide concentration effect on rate of photosynthesis
Sometimes photosynthesis is limited by the concentration of carbon dioxide in the air. even if there is plenty of light, a plant cannot photosynthesise if there is insufficient carbon dioxide. increasing the concentration of carbon dioxide will boost the speed of photosynthesis and then the rate will become steady as something else is a limiting factor, e.g., temperature or light intensity
Use of glucose (sugars) for plants
sugars are soluble molecules that need to be transported (via veins) to the parts of the plant that need it. It can also be used as energy, to make cellulose cell walls and to make proteins for plant growth and repair.
Plants use glucose for respiration. They cannot make it at night so it is
converted into insoluble starch – this is the main energy store of a plant.
mineral ions
Mineral ions are found in low concentrations in the soil compared to inside the root hair cells, so they need to be taken in by active transport nitrates, phosphate’s, potassium and magnesium help plants grow root hair cells absorb them.
Nitrates use
used to make amino acids for protein
Phosphates use
used in respiration and to make DNA & new cell membrane
Potassium use
used in respiration, photosynthesis and to make enzymes
Magnesium use
used in photosynthesis
photosynthesis equation
