Topic 6 - Plant Structures And Their Functions Flashcards
What is photosynthesis?
An endothermic reaction that uses light energy to react CO2 and Water to produce Glucose and Oxygen.
What type of reaction is photosynthesis?
Endothermic
What are photosynthetic organisms?
Main producers of food and therefore biomass
What is the effect of temperature on photosynthesis?
As temperature increases, the rate of photosynthesis increases. However, at high temperatures, enzymes are denatured and this will decrease the rate of photosynthesis.
Effect of CO2 concentration on photosynthesis?
Carbon dioxide is one of the reactants in photosynthesis. If the concentration of carbon dioxide is increased, the rate of photosynthesis will therefore increase. At some point, another factor may become limiting and the rate of photosynthesis will become constant.
Effect of light intensity on photosynthesis?
Increasing the light intensity increases the rate of photosynthesis, until a limiting factor becomes in short supply.
How do you calculate inverse square law?
See how much the distance increases by (e.g x2)
This = 2/1.
Flip the fraction (1/2)
Square the fraction (1/2)(1/2)
This = 1/4
Divide your light intensity by 4 for your answer
How are root hair cells adapted to absorb water and mineral ions?
Have a large surface area to increase the rate of absorption. Contain lots of mitochondria, which release energy from glucose during respiration to provide the energy needed for active transport.
Explain each adaption of the leaf.
Leaves have veins to carry water into cells and carry glucose out.
Leaves are thin to allow gases to reach cells easily.
Leaves have stomata to let gases in and out.
Leaves are wide and flat to absorb as much light as possible.
What is the internal structure of the leaf?
Waxy cuticle on top, with upper epidermis directly touching it. Underneath that, the palisade layer, then the spongy layer housing the leaf vein and air spaces. At the bottom, there is the lower epidermis with a stoma and guard cells.
W
U
P
S - leaf vein + air spaces
L
S + G
Waxy cuticle
Protects the leaf and prevents excess water loss without blocking light.
What does the epidermis do?
Allows light to pass through and is thin and transparent.
Palisade layer
Column-shaped and packed with many chloroplasts. Arranged closely together so a lot of light can be absorbed.
What does spongy mesophyll contain?
Contains internal air spaces that increases the SA to V ratio for the diffusion of gases e.g CO2
What does the Vascular Bundle do?
Help transport water and sugars.
Stoma and Guard Cells
Stoma are small holes on the underside of the leaf that allow gases to diffuse in and out and to reduce water loss.
How do stomata open and close?
In day = light = photosynthesis. Stomata are open to enable gas exchange as the guard cells have taken in water by osmosis and are turgid. At night = no light = no photosynthesis, stomata close to prevent water loss from leaves, this is because the guard cells have lost water by osmosis and have become flaccid.
NPK fertiliser
Nitrogen (N) - Phosphorus (P) - Potassium (K)
Nitrate ions - use, deficiency symptoms, explanation
Use - to make proteins for growth,
Symptoms - poor growth, yellow leaves
Explanation - amino acids contain nitrogen. Amino acids are the building blocks of protein.
Phosphate ions - use, symptoms, explanation
Use - respiration, growth
Symptoms - poor root growth, discoloured leaves.
Explanation - needed to make DNA and cell membranes.
Potassium ions - use, symptoms, Explanation
Use - respiration, photosynthesis.
Symptoms - poor flower and fruit growth, discoloured leaves.
Explanation - must be present for photosynthesis and respiration enzymes to work
Magnesium ions - use, symptoms, explanation
Use - photosynthesis
Symptoms - poor growth, discoloured leaves
Explanation - chlorophyll contains Mg ions. Mg makes chlorophyll green
Minerals in soil
The concentration of minerals in the soil is very low. They dissolve in water and move around the soil in solution.
How can minerals be absorbed regarding diffusion and osmosis?
Can’t be absorbed by osmosis (movement of water) or diffusion (minerals are low concentration).
Mineral absorption (active transport)
Root hair cells have carrier molecules on their surface that pick up minerals and move them into the cell against the concentration gradient. Requires energy -> active transport.
How does water get transported around the plant?
Water travels from the soil to the roots by osmosis. Once in the roots it travels into the xylem where it will travel up the plant to the cells that need water. Xylem vessels are water proofed by lignin which stops water leaving the vessels by osmosis as it passes up the plant. This is so not all the water gets used up straight away by cells at the bottom, and therefore let some get to the top.
Translocation description
Another type of transport vessel in plants are called the phloem. The phloem transports sugar and other nutrients from the leaves, where they are produced, (in the form of Sap) to places in the plant where they are needed. This process is referred to as translocation. We say that in plants transport is always up the xylem and down the phloem.
Xylem Vessel
One-Way only
Transports water and minerals
No end walls between cells
Thick walls stiffened with lignin
Phloem Vessel
Transports water and food
Cells have end walls with perforations
Two-way flow
Xylem Summary -
Function - carries water and minerals
Structure - hollow tubes
Dead
Support - thickened with cellulose and lignin
Phloem Summary -
Function - carries dissolved sugars
Structure - tubes have sieve plates
Alive
Support - companion cells provide energy for active transport.
Definition of translocation
Movement of dissolved sugars up and down the plant through the phloem.
Definition of transpiration
Movement of water up the xylem vessel.
Factors which affect the rate of transpiration
1) Temp - the warmer it is, the faster water evaporates from the leaves
2) Humidity - the lower, the faster water evaporates.
3) Wind speed - windier, the faster moist air is taken away from the leaf surface.
4) Light intensity - transpiration is faster when the stomata are open in the light.
Potometer
Measures rate of transpiration (cm3/min)
What is a hormone?
Chemical messengers that co-ordinate systems.
What is controlled by hormones in plants?
Growth - roots and shoots, seed germination, leaf fall, disease resistance, fruit formation and ripening, flowering time, bud formation.
A tropism
Responding to a stimulus by growing towards or away from it is called a tropism.
Phototropism
A tropism caused by light
Positive tropism
A tropism towards a stimulus
Positive phototropism
Shoot tips growing upwards towards light
Negative phototropism
Roots growing downwards into dark soil
Positive geo/gravitropism
Roots growing downwards
Gravitropism
Growth towards the direction of gravity
Negative geotropism
Shoots growing upwards
Auxins effects
Auxins are produced in the shoot tip.
They have different effects depending where it is.
• In the shoots any concentration promotes growth.
• At the root, high concentration inhibits growth, small concentration promotes growth.
Why do auxins make plants bend?
The Sunlight breaks down auxins, therefore the shoot tip which has direct sunlight will have the least amount of auxins. This means the area of the plant which is shaded has a higher concentration of auxins, and so more growth occurs, this leads to lop sided growth and the plant bends towards the light
Gibberellins
Plant hormones released inside of a seed to start germination.
Uses of auxins
Rooting powder
Selective weed killers
Uses of gibberellins
germination, fruit and flower formation and the production of seedless fruit
Uses of ethene
Fruit ripening
