Photosynthesis, respiration etc.

Question 1

The equation of photosynthesis

Answer 1

Light
Carbon dioxide + water -»»»> Carbohyrates + oxygen
Chlorophyll

Question 2

List the environmental factors that affect the rate of photosynthesis

Answer 2

• Temperature
• Light (intensity, quality/PAR and duration)
• Carbon dioxide
• Water
• Mineral nutrients

Question 3

The law of limiting factors

Answer 3

The law of limiting factors states that the growth is controlled not by the total of resources but by the scarcest recourse of limiting factor. Whatever element is in the least supply controls the rate photosynthesis.

Question 4

How does temperature affect the rate of photosynthesis
At what temperature the photosynthesis start and stop
Does the rate increase with temperature

Answer 4

At what temperature does photosynthesis generally start, and stop? 5C to 45C (Optimum is 25-35)
Does the rate increase with the temperature? Yes, as the temperature affects the rate of photosynthesis because chemical reactions are faster as temperature rises

Question 5

How does light (intensity, quality/PAR, duration) affect photosynthesis

Answer 5

The intensity of the light varies during the year, as well as the duration; growers add artificial light to increase day length and to supplement natural light to give a higher intensity.

Light quality/PAR relates to the delivering the parts of the spectrum the plants can use (photosynthetically active) – supplementary lighting is chosen to give the most useful wavelengths.

Question 6

How does carbon dioxide affect the rate of photosynthesis

Answer 6

If the plants are in a closed spaces (i.e. greenhouse with no vents open) and the CO2 can get depleted which would slow down the photosynthesis

Question 7

How does water affect the rate of photosynthesis

Answer 7

Photosynthesis involves chemical reactions, and these need water to take place.

The stomata closes to limit evaporation which means that the CO2 cannot enter the plants

Question 8

How does mineral nutrients affect the rate of photosynthesis

Answer 8

Nutrients are the chemical elements required for the plant to function efficiently

Question 9

State the equations for aerobic and anaerobic respiration in words

Answer 9

Aerobic respirator (with oxygen) Sugars+Oxygen&raquo_space;> CO2 + Water + High yields of energy

Anaerobic respiration (without oxygen) Sugars+zymase»>Carbon dioxide + ethanol + low yields of energy

Question 10

List the factors that affect the rate of respiration

Answer 10

• Oxygen

* Temperature.

Question 11

How does a lack of oxygen affect respiration?

Answer 11

Oxygen is needed for the plants to produce higher energy yields. Lack of oxygen forces anaerobic respiration which also produces ethanol which is toxic to plants.

Question 12

What happens when the temperature falls?

Answer 12

When the temperature falls it slows downs respiration which in turn slows down growth and cell division

Question 13

Describe the significance of anaerobic and aerobic respiration in horticultural situations: 
waterlogging
propagation
produce storage
seed storage.

Answer 13

Waterlogging: Anaerobic respiration as there is not enough oxygen

Propagation: For cuttings to produce roots there needs to be an active cell division which requires a lot of energy so having higher amounts of oxygen and temperature helps the process

Produce storage: Low temperatures slow down respiration, therefore the produce stores longer

Seed storage: Seeds require warmth, moisture and oxygen to germinate, so to stop that they are kept in sealed containers

Question 14

Definition of diffusion

Answer 14

The movement of molecules of substance from high concentration to a lower concentration

Question 15

Definition of osmosis

Answer 15

the movement of water from high water concentration to a low water concentration across a semi-permeable membrane. This prevent too much minerals entering the cells

Question 16

Examples of diffusion in plants

Answer 16

Transpiration – water evaporating through stomata

Gaseous exchange - when oxygen and carbon dioxide naturally flow from higher concentration to lower

Question 17

Describe the pathway of water movement from the soil through the plant into the atmosphere.

Answer 17

• Soil water
• pathway across the root ( root hairs, osmosis across root cells, flow through root cell walls, endodermis)
• transport through xylem of stem (transpiration pull)
• pathway across leaf ( xylem in veins, osmosis across leaf cells, flow through leaf cell walls evaporation from leaf cell walls into mesophyll spaces)
• diffusion through stomata of leaf

Question 18

Definition of transpiration

Answer 18

The evaporation of water from plants, generally from the leaves, while their stomata are open for the passage of CO2 and O2 during photosynthesis

Question 19

List the factors that affect transpiration

Answer 19

• Relative humidity
• Temperature
• Wind Speed

Question 20

How do plants slow down water loss

Answer 20

• Stomatal closure

* Leaf adaptions: hairs, thick cuticle, needle leaves

Question 21

Describe the uptake and distribution of mineral nutrients in the plant

Answer 21

• nutrients from soil solution (active uptake against concentration gradient into root cells)
• transport through the plant in xylem
• distribution through phloem.

Question 22

How is the leaf held and positioned to maximize photosynthesis?

Answer 22

The shape of a leaf blade and the arrangement of leaves allow light to reach the maximum amount number and maximise photosynthesis

Question 23

How is water loss through transpiration controlled?

Answer 23

The stomata are on the underside of the leaf which is shadier side to reduce transpiration.