B6 plant structure and function - Coggle Diagram
B6 plant structure and function
photosynthesis takes place in chloroplast found in plant and algae
the reaction is endothermic - needs energy and the source of this energy sunlight
the sunlight is trapped by chlorophyll in cholorplast
photosynthesis converts co2 and water into oxygen and glucose
rate of photosynthesis
the four key factors affecting rate of photosynthsesis are
light intensity - increasing light intensity increases rate of photosynthesis because more energy is provided
however, if the light intensity is increased upon a certain threshold then the rate of photosynthesis will not increase because another factor is limiting the rate of reaction
high chloryphyll concentration gives a high rate of photosynthesis
Chlorophyll is a pigment that can absorb light energy.
increasing the temperature increases the rate of photosynthesis because more energy is provided
however if the temp gets too high the enzymes used to catalyse the reaction may begin to denature
this causes ror to drop sharply till it stops altogether
carbon dioxide concentration
increasing the carbon dioxide concentration increases the rate of photosynthesis
However, above a certain threshold, further increases in the carbon dioxide concentration do not increase the rate of photosynthesis because another factor (such as light intensity) is limiting the rate of reaction.
a limiting factor is something which restricts the rate of reaction - the identtity of a limiting factor in photosynthesis depends on the conditions faced by the plant
for plants - at night - usually light intensity is the limiting factor
in warm and bright conditions , carbon dioxide is usually the limiting factor
in winter - temp is limiting factor
If plants are grown in mineral-deficient (lacking minerals) soil, they may not absorb enough minerals to produce lots of chlorophyll.
In this case, chlorophyll concentration can be the limiting factor.
Warm and bright
CO2 concentration, light levels and temperature are all at optimum values. What might be the limiting factor of rate of photosynthesis, and why?
The concentration of mineral ions in the soil is probably the limiting factor.
Chlorophyll absorbs light energy and the production of chlorophyll requires these mineral ions (especially Mg2+).
testing the rate of photosynthesis
you can easily investigate the effect of light intensity on photosynthesis by using an aquatic plant like pondweed in
to do this, change the distance between the lamp and pondweed and count the bubbles produced
in this experiment light intensity is the independant variable and the number of bubbles is the dependant variable
The rate that pond weed produces bubbles indicates the rate of photosynthesis. The bubbles released are oxygen, a waste product of photosynthesis.
the inverse square law
The light intensity is equal to 1 divided by the distance squared.
Which of the following is a reason why measuring the number of gas bubbles produced per unit time is not a completely valid experimental method for measuring the rate of photosynthesis?
not all of the gas in the bubbles is oxygen
Which of the following would increase the reliability of an experiment measuring the rate of photosynthesis?
measuring the rate of photosynthesis multiple times per experiment
Increasing the reliability of an experiment can virtually always be done by repeating an experiment, collecting values, and calculating the average of the values.
root hair cells
root hai rcells are specialised, their structure allows the plant to absorb more water they also allow the plant to take in the minerals it needs to survive
no chlorpplast as theyre located underground - no light for photosynthesis
Long prjections - root hair cells can have long projections that increase the surface area that the plant can use to absorb minerals and water
Root hair cells are adapted for taking up water and mineral ions by having a large surface area to increase the rate of absorption.
the xylem cell is used to transport water up a stem of the plant and into the leaves
xylem vessels are made up of a series of connected dead xylem cells
the end walls of the dead cells are broken to allow water to move through
Lingin strengthens the walls of xylem cells
Why are xylem cells' end walls broken?
The end walls of the dead xylem cells are broken to allow water and dissolved minerals to move through.
guard cells and stomata
stomata are gaps in the lower epidermis of leaves that facilitate the diffusion of gases including evaporated water in and out of the leaf
guard cells can open and close the stomata
closing the stomata
to close the stomata the guard cells lose water and return to a limp state
opening the stomata
the guard cells can open up the stomata by taking in lots of water causing them to swell
When water is abundant (lots available) the plant can afford to lose water, so it opens the stomata to allow gases for photosynthesis to move freely in and out of the leaf.
Why do stomata close at night?
Time of day affects the state of stomata.
At night, they close because, in the absence of sunlight, carbon dioxide is not required for photosynthesis.
At this time, their only objective is to prevent water loss.