B4 - Limiting Factors

What is photosynthesis?

A process where plants use light energy to convert carbon dioxide and water into glucose and oxygen.

What type of reaction is photosynthesis?

An endothermic reaction.

What are the 4 main factors that affect the rate of photosynthesis?

Light intensity, carbon dioxide concentration, temperature, and chlorophyll level.

What is a limiting factor in photosynthesis?

A factor that is in short supply and prevents photosynthesis from happening at its fastest possible rate.

How does light intensity affect the rate of photosynthesis?

Increasing light intensity increases the rate up to a point, after which another factor becomes limiting.

What happens to the rate of photosynthesis when light is no longer the limiting factor?

The rate levels off and does not increase any further with more light.

What does a rising rate of photosynthesis with increasing CO₂ levels indicate?

Carbon dioxide concentration was the limiting factor.

What happens when increasing CO₂ no longer affects the rate of photosynthesis?

CO₂ is no longer the limiting factor; something else is.

What happens to photosynthesis if temperature is increased moderately?

The rate increases as enzyme activity increases.

What happens to photosynthesis if the temperature gets too high?

Enzymes denature and the rate of photosynthesis falls.

How does temperature act as a limiting factor?

If too low, enzymes work slowly; if too high, enzymes denature.

What is the role of chlorophyll in photosynthesis?

Chlorophyll absorbs light energy needed for photosynthesis.

What happens if a plant has less chlorophyll?

The plant traps less light energy and the rate of photosynthesis decreases.

What is the shape of the graph for light intensity vs rate of photosynthesis?

Initially increases steeply, then levels off when light is no longer limiting.

What is the shape of the graph for CO₂ concentration vs rate of photosynthesis?

Increases, then plateaus when CO₂ is no longer limiting.

What is the shape of the graph for temperature vs rate of photosynthesis?

Rises with temperature, then drops sharply when enzymes denature.

How can graphs help identify the limiting factor?

If increasing one factor increases the rate, that factor was limiting; if no change, it was not limiting.

Why do farmers use greenhouses?

To control conditions and increase the rate of photosynthesis to maximise crop yield.

What 3 main conditions do farmers control in greenhouses?

Light, temperature, and carbon dioxide concentration.

Why do farmers use artificial lights in greenhouses?

To increase light intensity and allow photosynthesis to occur beyond natural daylight hours.

Why do farmers heat greenhouses?

To maintain the optimal temperature for enzyme activity in photosynthesis.

How do farmers increase CO₂ levels in greenhouses?

By adding carbon dioxide directly or using oil burners which produce CO₂.

What are oil burners used for in greenhouses?

To provide both heat and carbon dioxide at the same time.

What must farmers consider when controlling conditions in greenhouses?

The cost of lighting, heating, and CO₂ must be balanced against the increased crop yield (profit).

Why does increasing photosynthesis benefit farmers?

It increases the yield of crops, which can improve profits.

Why do gardeners and farmers aim to remove limiting factors?

To ensure that the rate of photosynthesis is as fast as possible for maximum growth.

What is the economic goal of managing greenhouse conditions?

To maximise crop yield while minimising unnecessary costs.

What is meant by "optimal conditions" in a greenhouse?

The best combination of light, CO₂, and temperature to maximise photosynthesis without wasting resources.