Online Test — Photosynthesis and Plant Physiology in Detail
35 Questions • 15 min • Chapter MCQ
15:00
Question 1 of 35
Photosynthesis takes place inside the cell structure called the:
Nucleus
Chloroplast
Mitochondrion
Vacuole
Explanation: Chloroplasts are the sites of photosynthesis in plant cells.
Question 2 of 35
Chloroplasts appear green because they contain:
Haemoglobin
Chlorophyll
Starch
Water
Explanation: The green pigment chlorophyll gives chloroplasts their colour.
Question 3 of 35
The thick fluid inside a chloroplast is called the:
Stroma
Granum
Thylakoid
Cytoplasm
Explanation: The fluid surrounding the thylakoids is the stroma.
Question 4 of 35
A stack of thylakoids is called a:
Stroma
Granum
Membrane
Nucleus
Explanation: A stack of thylakoids is a granum (plural: grana).
Question 5 of 35
The light reactions of photosynthesis occur in the:
Stroma
Thylakoid membranes
Cell wall
Vacuole
Explanation: The light reactions take place in the thylakoid membranes (grana).
Question 6 of 35
The light reactions of photosynthesis take place in the:
Stroma
Thylakoid membranes
Nucleus
Root
Explanation: The light reactions occur in the chlorophyll-rich thylakoid membranes.
Question 7 of 35
The splitting of water by light energy is called:
Respiration
Photolysis
Transpiration
Fixation
Explanation: Photolysis is the splitting of water into hydrogen and oxygen by light.
Question 8 of 35
The gas released during the light reactions is:
Carbon dioxide
Oxygen
Nitrogen
Hydrogen
Explanation: Splitting water releases oxygen, which is given off into the air.
Question 9 of 35
Which two energy-carrying molecules are produced in the light reactions?
ATP and NADPH
Starch and sugar
Water and CO₂
Salt and sugar
Explanation: The light reactions produce ATP and NADPH.
Question 10 of 35
Most of the oxygen in Earth's atmosphere comes from:
Volcanoes
Photosynthesis in plants
Burning fuels
Rainfall
Explanation: Oxygen released by photosynthesis is the source of most atmospheric oxygen.
Question 11 of 35
The dark reactions of photosynthesis take place in the:
Thylakoid
Stroma
Nucleus
Cell wall
Explanation: The dark reactions (Calvin cycle) occur in the stroma.
Question 12 of 35
The dark reactions are so called because they:
Happen only at night
Do not need light directly
Need no chloroplast
Make oxygen
Explanation: They are named "dark" because they do not directly require light.
Question 13 of 35
The dark reactions take carbon dioxide and carry out:
Photolysis
Carbon dioxide fixation
Transpiration
Respiration
Explanation: The dark reactions fix carbon dioxide into a food molecule.
Question 14 of 35
The enzyme that fixes carbon dioxide in the Calvin cycle is:
RuBisCO
Chlorophyll
Amylase
Pepsin
Explanation: RuBisCO captures CO₂ and starts the Calvin cycle.
Question 15 of 35
The dark reactions use ATP and NADPH (from the light reactions) to make:
Glucose
Water
Oxygen
Salt
Explanation: ATP and NADPH power the building of glucose in the dark reactions.
Question 16 of 35
Which of these is NOT a main factor affecting photosynthesis?
Light intensity
CO₂ concentration
Temperature
Soil colour
Explanation: Light, CO₂, temperature and water are the main factors; soil colour is not.
Question 17 of 35
Increasing light intensity raises the rate of photosynthesis:
Forever
Up to a limit, then it levels off
Only at night
Never
Explanation: The rate rises with light up to a point, then levels off.
Question 18 of 35
Carbon dioxide is important because it is the raw material for:
The light reactions
The dark reactions (fixation)
Transpiration
Respiration only
Explanation: CO₂ is fixed in the dark reactions to build sugar.
Question 19 of 35
Photosynthesis slows in very cold conditions because cold affects the:
Enzymes
Sunlight
Colour of leaves
Roots only
Explanation: Cold slows the enzymes that control photosynthesis.
Question 20 of 35
The factor in shortest supply that controls the rate of photosynthesis is the:
Limiting factor
Raw factor
Growth factor
Light factor
Explanation: The scarcest factor, the limiting factor, controls the overall rate.
Question 21 of 35
The loss of water vapour from the aerial parts of a plant is called:
Respiration
Transpiration
Photosynthesis
Germination
Explanation: Transpiration is the loss of water as vapour, mainly from the leaves.
Question 22 of 35
Transpiration occurs mainly through tiny leaf pores called:
Stomata
Roots
Veins
Petals
Explanation: Most transpiration occurs through the stomata on the leaves.
Question 23 of 35
A stoma is opened and closed by two:
Guard cells
Root hairs
Xylem tubes
Petals
Explanation: Two guard cells border each stoma and open or close it.
Question 24 of 35
Transpiration generally increases when there is:
High humidity
Strong wind
Total darkness
Cold and calm air
Explanation: Wind carries away water vapour, increasing transpiration.
Question 25 of 35
One important benefit of transpiration is that it:
Adds weight to the plant
Helps pull water and minerals upward
Makes food
Stops growth
Explanation: Transpiration creates a pull that draws water and minerals up the plant.
Question 26 of 35
Water and dissolved minerals are carried in the plant by the:
Phloem
Xylem
Stomata
Cuticle
Explanation: The xylem carries water and minerals upward from the roots.
Question 27 of 35
Food (sugar) made in the leaves is carried by the:
Xylem
Phloem
Root hairs
Guard cells
Explanation: The phloem carries food to other parts of the plant.
Question 28 of 35
Water moves up the xylem mainly because of the pull explained by the:
Pressure-flow theory
Cohesion-tension theory
Germination theory
Cell theory
Explanation: The cohesion-tension theory explains the upward pull of water in xylem.
Question 29 of 35
The movement of food through the phloem is called:
Transpiration
Translocation
Respiration
Photolysis
Explanation: Translocation is the movement of food through the phloem.
Question 30 of 35
Compared with xylem, the direction of flow in the phloem is:
Always upward only
In different directions (source to sink)
Always downward only
Sideways only
Explanation: Phloem carries food from source to sink, so it can flow in different directions.
Question 31 of 35
Plant growth regulators are also known as plant:
Hormones
Minerals
Pigments
Enzymes only
Explanation: Plant growth regulators are natural plant hormones controlling growth.
Question 32 of 35
Which regulator causes cell elongation and bending toward light?
Auxins
Abscisic acid
Ethylene
Cytokinins
Explanation: Auxins cause cell elongation and the bending of plants toward light.
Question 33 of 35
Gibberellins mainly help in stem elongation and:
Closing stomata
Seed germination
Fruit fall
Cell death
Explanation: Gibberellins promote stem elongation and help seeds germinate.
Question 34 of 35
The regulator that inhibits growth and closes stomata is:
Auxins
Gibberellins
Abscisic acid
Cytokinins
Explanation: Abscisic acid inhibits growth and closes stomata (the "stress hormone").
Question 35 of 35
The hormone that is a gas and promotes the ripening of fruits is:
Ethylene
Auxins
Cytokinins
Gibberellins
Explanation: Ethylene is a gaseous hormone that ripens fruits.