Plant Physiology - Revision Guide Flashcards
Copy and complete these sentences. Use the words below to fill the gaps.
water chloroplasts starch photosynthesis light chlorophyll sugar(glucose)
Plant produce their own food in a process known as _______.They absorb _________energy using a green chemical called ______ which is found in ________ in the plant cells. Carbon dioxide and _______ are joined together using this energy to form ______ and oxygen. The glucose produced in photosynthesis may be converted into insoluble ______ for storage.
photosynthesis light chlorophyll chloroplasts water sugar (glucose) starch
Match the words related to photosynthesis with the right description and then copy out the correct pair.
a) Carbon dioxide gas is absorbed from the air.
* *Water** from the root moves up to the leaf through the stem.
* *Sunlight** provides energy.
* *Sugars** are made in the leaf and provide the plant with food.
* *Oxygen** is produced and released into the air.
Write word equation for the process of photosynthesis.
Carbon dioxide + water + energy from the Sun –> sugar + oxygen
Copy this diagram. Use the labels provided to complete the labelling.
A Oxygen moves out
B The epidermis is a clear protective layer that lets sunlight in
C Sugars dissolve and are taken to other parts of the plant
D Stomata (pores) let gases in and out
E Water is brought from the roots in the xylem vessel
Much of the glucose made in photosynthesis is turned into an insoluble storage compund. What is this compound?
Starch
Some plants have their energy stores scattered about their stems and leaves. Other plants, like potatoes, develop special storage organs where they keep much of their stored food to help them survive the winter.
Amt of sunlight Mass of potato
each month of the crop per plant (kg)
growing season
average 1
poor 0.5
high 1.5
One potato farmer recorded the amount of sunlight in each month that her potato crop was growing, and also recorded the average crop of potatoes she got from her plants when she harvested them. Explain her findings.
The mass of the potato crop depended on the amount of sunlight in the growing season, being
larger with more sunlight and smaller with less. Most of the mass of a potato is made of starch,
and starch is made as a direct result of photosynthesis. The amount of photosynthesis that can take place depends on the amount of sunlight available to supply the energy, so the amount of
sunlight is directly linked to the size of the potato crop.
The glucose produced during the photosynthesis is used for a number of things in the cells of the plant. List up to five different products made using the glucose produced during photosynthesis. For each product, explain how it is used in the plant cells.
Any five from
Product made How it is used in the plant cells
- **starch ** storage compound
- **cellulose ** cell walls
- **protein ** cytoplasm, enzymes
- **DNA ** genetic material, contains instructions for making new cells, etc.
- **chlorophyll ** captures light energy for photosynthesis
- **sucrose ** for transport around the body
- **amino acids ** to build up into proteins
Leaves are the plant organs that make food.
a). Copy the diagram of a section of a leaf and add the labels below:
A palisade layer
B spongy layer
C upper epidermis
D chloroplast
E stoma
F guard cell
b) Explain the function of each part you have labelled.
- The palisade layer is closely packed with lots of chloroplasts and close to the surface of the leaf so that it can capture as much light as possible for photosynthesis.
- The spongy layer consists of loosely packed cells with lots of air spaces, giving a large available surface area for gaseous exchange between the cells and the air, while the chloroplasts allow some photosynthesis to take place.
- The upper epidermis protects the cells in the leaf from damage. It is transparent so that light passes through to the palisade cells beneath.
- The chloroplast is the cell organelle that contains chlorophyll, the green pigment that captures light energy for photosynthesis.
- A stoma (plural stomata) is a pore that allows gases to diffuse into and out of the leaf.
- A guard cell controls the opening and closing of the stomata.
The diagram shows the apparatus required to demostrate photosynthesis in Elodea (Canaidan pondweed).
a) how do you know when photosynthesis is actually taking place?
b) You can use this basic apparatus to investigate the effect of light intensity on the rate of photosynthesis. What would you expect to happen if
i) you moved the light closer to the beaker containing the pondweed?
ii) you moved the light further away from the pondweed?
c) Why would you expect moving the light to have an effect on the rate of photosynthesis?
d) Which other factor might be chaning each time you move the lamp?
a) Bubbles of gas escape from the end of the stem.
b) i) More bubbles / It would bubble faster.
ii) Fewer bubbles/ It would bubble more slowly.
c) Because plants need light for photosynthesis. If they have more light, they can photosynthesise
faster, but with less light they will photosynthesise more slowly.
d) The temperature might be changing because the light gets hot.
Explain limiting factors.
A limiting factor is something that stops photosynthesis happening any faster.
The main limiting factors for photosynthesis are the intensity of the light, the concentration of carbon dioxide and the temperature.
If the temperature is too high (over 45c), the plant’s enzymes will be denatured, so the rate of photosynthesis rapidly decreases. ( see the lines on the graph level off eventually)
How do plant leaves adapt for photosynthesis and gas exchange with chloroplasts?
Plant leaves are thin and flat so as much light can be absorbed as possible, a large surface area for diffusion of gases and stomata to allow the exchange of gases between the leaf and the air, and the distances that gases need to diffuse are very short.
How do you demonstrate an experimental evidence to show that photosynthesis has taken place?
By demonstrating that starch is present in the leaf.
Kill the leaf in boiling water, then boil in ethanol, rinse in water, and test the leaf for starch using iodine solution.
How do you show photosynthesis is taking place in plants?
By the presence of oxygen, use an aquatic plant such as Canadian pondweed (Elodea) in bright light.
Capture the gas produced and analyse it to show rasied oxygen levels, or simply count the number of gas bubbles given off.
Glucose made in photosynthesis is used to make sucrose for transport, starch for storage, cellulose for cell walls, proteins and DNA, lipids as energy store in seeds, and chrolophyll.
How do you show chlorophyll is needed for photosynthesis?
Use a variegated (green and white) leaf.
This is of limited use because the products of photosynthesis could have been moved from one part of the leaf to another.
How do you show that carbon dioxide is needed for photosynthesis?
Remove carbon dioxide from the air surrounding one plant using soda lime. This is again of limited use because plant make carbon dioxide during respiration.
See the diagram below.
- Plant A is lacking in potassium and needs a potassium-rich fertiliser.
- Plant B is lacking in nitrogen and needs a nitrogen-rich fertiliser.
- Plant C is lacking in phosphate and needs a phosphate-rich fertiliser.
