Limiting factors in photosynthesis

NASA (the National Aeronautics and Space Administration) is investigating how to grow plants on space stations. As part of their investigation, NASA scientists looked at the effect of using different types of lamp on the rate of photosynthesis in spinach plants.

Explain why the scientists expected a link between rate of photosynthesis and biomass produced.

The scientists measured the rate of photosynthesis and the biomass produced for different types of lamp. The table shows their results.

Plot a bar graph to show the biomass produced for each type of lamp.

Suggest why the rate of photosynthesis and the biomass produced do not follow a similar pattern.

Suggest which lamp would be best for a spinach grower to use in his glasshouse.

Name three factors, other than light, that would affect the rate of photosynthesis.

Suggest why NASA is investigating how to grow plants in space stations.

The diagram shows a food chain.

How many consumers are shown in this food chain?

What term describes the trophic level of the snake?

Light is an abiotic (non-living) factor that affects the growth of maize.

Explain the role of light in helping the growth of maize.

Scientists measured the average (mean) daily increase in mass of maize in a square metre of a field in two different regions of the world. They also measured the daily light energy available in a square centimetre of each of the two regions. The table shows their results.

The scientists expected that the same light energy would produce the same average daily increase in mass of maize in each region of the world. However, the results show that the average daily increase in mass of maize produced in the UK was less than they expected. Calculate the average daily increase in mass the scientists expected to be produced in the UK.

average increase in mass =_........

The scientists concluded that factors other than light must be limiting the growth of maize in the UK. Name two other abiotic factors that could limit the growth of maize.

Give three reasons why not all of the energy available in the maize is transferred to the snake.

The amount of light falling on plant leaves is an abiotic (non-living) factor that affects photosynthesis.

Give the balanced chemical equation for photosynthesis.

The leaves of plants that live in the shade (low light) are different to the leaves of plants that live in full sunlight.

Suggest why leaves from plants that live in the shade are darker green than leaves from plants that live in full sunlight.

Explain why leaves from plants that live in the shade are thinner than leaves from plants that live in full sunlight.

The rate of photosynthesis changes during the day.

Explain the factors that affect the rate of photosynthesis in the early morning.

Explain the factors that affect the rate of photosynthesis in the early afternoon.

Describe how you could compare the rate of photosynthesis in two different plant species.

A student investigates the effect of carbon dioxide concentration on the rate of photosynthesis in a water plant. The graph shows the student’s results.

Put an X on the graph to show where carbon dioxide limits the rate of photosynthesis.

Write the word equation for photosynthesis.

The student’s method allows her to make a valid and reliable comparison of the rate of photosynthesis at different carbon dioxide concentrations.

Give the independent variable in her investigation.

Suggest a variable the student needs to control in her investigation.

Explain how the student could make sure her results are reliable.

Plants obtain their nutrition by photosynthesis.

Write the balanced chemical symbol equation for photosynthesis.

Explain how the rate of photosynthesis is affected by changes to abiotic (non-living) factors throughout the day.

Explain how very high temperatures might reduce the growth of plants.

Scientists want to compare the growth of the same species of plant in three different areas. The graph shows the biomass of the plants in each area in g per m² each year for a period of 20 years.

The table shows the increase in biomass in each area in g per m² per year for the 20-year period for areas A and B.

Calculate the increase in biomass in g per m² per year for area C Show your working.

Increase in biomass =_........ g per m² per year

After 20 years, the plants in area A had a greater biomass than those in area B.

Explain how abiotic (non-living) factors could cause this difference.

Explain how biotic (living) factors could cause this difference.

The scientists wanted to find out how efficient plants in area A were at converting light energy and using it to make biomass. The scientists knew the following information: the increase in biomass for the plant growth in area A is 115 g per m² per year one gram of the plants in area A contains 22 kJ of energy the amount of light energy available in area A is 3 200 000 kJ per m² per year The formula for calculating the percentage energy transfer efficiency is

Use this information to calculate the percentage energy transfer efficiency of the plants in area A. Show your working.

Energy transfer efficiency =_........

The table describes four different geographical regions. It also gives the amount of energy converted into plant biomass each year in each region.

Plot a bar graph on the grid to show the amount of energy converted into plant biomass each year in each region.

The amount of energy converted into plant biomass each year depends on the effect that abiotic (non-living) factors have on the rate of photosynthesis. Carbon dioxide is one of these abiotic factors. Name three other abiotic factors likely to affect the rate of photosynthesis.

Regions C and D have the same climate. Plants grown in region D have more energy converted into plant biomass than plants grown in region C. One reason for this is the use of selective breeding to produce high yielding crops.

Suggest two other reasons for more energy being converted into plant biomass in region D.

What is meant by the term selective breeding ?

Describe how you could use a quadrat to estimate the plant biomass in one of the regions.

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow. Japanese knotweed: a space invader Invasive species are one of the biggest threats to wildlife and plants worldwide. The Department for Environment, Food and Rural Affairs (DEFRA) is introducing new measures that will ban the sale of some of the most dangerous foreign species in the UK. DEFRA is attempting to prevent a problem before it happens. The majority of invader species are plants. Of the most recent count of 2 721 non-native species, 1 798 were plants. Over £1.5 billion has been spent removing a single plant species, the Japanese knotweed. Japanese knotweed was first introduced as a garden plant. Japanese knotweed causes problems as it lacks natural predators in the UK and is very difficult to remove completely. Also, the vegetation of the knotweed is so dense, that other plants cannot grow through it. The fast-growing plant can grow up to 4 metres tall and is so strong it can break through paving stones and tarmac.

Japanese knotweed has a large network of underground stems (rhizomes). These rhizomes have to be killed if the plant is to be completely removed. The rhizomes might also be described as ‘underground runners’. All above-ground portions of the plant need to be controlled repeatedly for several years in order to weaken and kill the entire patch. Digging up the rhizomes is a common solution where the land is to be developed, as this is quicker than the use of herbicides. Scientists have looked at the weed’s natural predators with the aim of finding one that feeds on Japanese knotweed and little else. After testing the predators on 90 different UK plant species, including plants closely related to Japanese knotweed, they discovered that the insect, Aphalara itadori, was the best control agent. It keeps the weed under control in its native Japan by feeding on the sap in the transport tissue in the leaves, which reduces the growth of the plants. The introduction of Aphalara itadori would be the first time that biological control has been used in Europe to fight a weed.

Suggest what is meant by the term invasive species (line 1).

Calculate the percentage of invasive species in the UK that are plants (lines 6 and 7). Show your working.

Give one reason why Japanese knotweed has spread so successfully in the UK.

Suggest why the dense growth of the Japanese knotweed reduces the growth of other plants (line 11).

The use of Aphalara itadori to feed on Japanese knotweed is an example of biological control. Describe another example of biological control.

Name the transport tissue in the leaves that contains sap (line 25).

Suggest why the plant growth is reduced when insects feed on the plant sap (lines 24 and 25).

Why is it important that the insect ‘feeds on Japanese knotweed and little else’ (line 21)?