To determine the ET50-light for this trial, plot the percent leaf disk floating as a function of time: From the above graph, we can interpolate that 50% of the leaf disks floated at 5.5 minutes. Therefore, the ET50-light is 5.5 minutes.

Why do you think 1 ET50 is more useful as indicator of the rate of photosynthesis or cellular respiration than ET50?

This is because the times to float are the inverse of the rate of photosynthesis. Taking the reciprocal of ET50, 1/ ET50 allows the graphic presentation to more closely express the physical phenomenon, as shown in Figure 3.

What does ET50 mean?

The ET50 is the amount of time it took 50% of the leaf disks to float, so in this case the time at which 5 disks floated. The purpose of calculating the ET50 was that the reciprocal of the ET50 (1/ET50) is the rate of photosynthesis.

How do you find net rate of photosynthesis?

Net photosynthesis may be represented by the following equation: net photosynthesis = gross photosynthesis – respiration. Net photosynthesis can also be depicted as a measure of the oxygen released or a measure of the carbon dioxide uptake.

What is the relationship between light intensity and rate of photosynthesis?

Increasing the light intensity increases the rate of photosynthesis, until some other factor – a limiting factor – becomes in short supply. At very high light intensities, photosynthesis is slowed and then inhibited, but these light intensities do not occur in nature.

How do you calculate the rate of photosynthesis in leaf discs?

To measure the rate of photosynthesis, you will replace the air in the spongy mesophyll in your leaf disks with a liquid. This will cause the leaf disks to sink. Then you will put these leaf disks in water with dissolved CO2 and measure the amount of time it takes for the leaf disks to float.

Is the rate of photosynthesis or the rate of cellular respiration higher?

The compensation point So the rate of respiration is greater than the rate of photosynthesis. So this means there is an overall excess of carbon dioxide produced during respiration.

Why does more CO2 increase the rate of photosynthesis?

Carbon dioxide and rate of photosynthesis An increase in the carbon dioxide concentration increases the rate at which carbon is incorporated into carbohydrate in the light-independent reaction, and so the rate of photosynthesis generally increases until limited by another factor.

What will happen if you remove the air from these spaces answers?

If you draw the gases out from the spaces, then the leaves will sink because they become more dense than water. If this leaf disk is placed in a solution with an alternate source of carbon dioxide in the form of bicarbonate ions, then photosynthesis can occur in a sunken leaf disk.

How is CO2 used to measure photosynthesis?

Count the number of oxygen bubbles given off by the plant in a one -minute period. This is the rate of photosynthesis at that particular concentration of CO2. The gas should be checked to prove that it is indeed oxygen – relights a glowing splint.

Article first time published on

How does light intensity and rate of photosynthesis relate to the position of the sun?

The rate of photosynthesis relies on light intensity because when sunlight is limited, so is photosynthesis. This means that in the winter (when there are less hours of sunlight) and at night (when there is no sunlight at all), there is less photosynthesis.

What is a rate of photosynthesis?

The rate of photosynthesis is a gross measure of the rate at which a plant captures radiant energy and fixes it in organic carbon compounds.

What do you mean by rate of photosynthesis?

The rate of photosynthesis is defined in terms of the rate of oxygen production either per unit mass (or area) of green plant tissues or per unit weight of total chlorophyll.

What is the optimum rate of photosynthesis?

CropWheatOptimum20 – 25°CMaximum38°CMinimum5°C

What is the independent variable in photosynthesis experiment?

Independent variable – the light intensity (how close the light is). Dependant variable – the number of oxygen bubbles given off (the rate of photosynthesis). Controlled variables – the size of the pondweed, the volume of water used and its temperature.

Why do leaf disks float?

Leaf disks float, normally. When the air spaces are replaced with water the overall density of the leaf disk increases and the disk sinks. … As photosynthesis proceeds oxygen is released into the interior of the leaf which changes the buoyancy–causing the disks to rise.

Why does sodium bicarbonate increase the rate of photosynthesis?

From this investigation, we learned that an increase in carbon dioxide allows for photosynthesis to occur at a faster rate. … The more sodium bicarbonate present, there is a greater amount of carbon dioxide present, which in result will increase the speed of photosynthesis.

What light intensity will maximize the rate of photosynthesis?

In the Gizmo, what light intensity and CO2 level do you think will maximize the rate of photosynthesis? The highest light intensity and CO2 level will maximize the rate of photosynthesis.

Is the relationship between the intensity of light and the rate of photosynthesis a direct or an inverse 5 relationship?

Direct proportion As light intensity increases the rate of photosynthesis also increases. This is because photosynthesis is an energy requiring reaction, endothermic. More light energy will increase the rate at which oxygen is given off so more bubbles of oxygen will be produced per minute.

What is light intensity?

Light intensity refers to the strength or amount of light produced by a specific lamp source. It is the measure of the wavelength-weighted power emitted by a light source.

Is the rate of photosynthesis the same as cellular respiration?

Overall, photosynthesis (oxygen production) is higher than the rate of respiration in plants during a year. Aerobic respiration continues all the time in plant cells (in light and in darkness), using up oxygen and making carbon dioxide.

What is cellular respiration vs photosynthesis?

Photosynthesis converts carbon dioxide and water into oxygen and glucose. Glucose is used as food by the plant and oxygen is a by-product. Cellular respiration converts oxygen and glucose into water and carbon dioxide.

Why is rate of respiration slower in plants?

Plants do not have special respiratory organs for exchange of gases unlike animals . … The transport of gases from one part of the plant to another is very less. Moreover there is not much need of exchange of gases in plants. So compared to animals rate of respiration is slow in plants.

How do you measure the rate of photosynthesis in a lab?

The rate of photosynthesis will be measured by counting the number of oxygen bubbles produced by the Elodea plants in each 2-minute trail. After completing a number of experiments, students and teachers will discuss their findings in relation to macro-level factors that affect ecosystem health and climate change.

What is stoma function?

The stomata control gas exchange in the leaf. Each stoma can be open or closed, depending on how turgid its guard cells are. Diffusion of carbon dioxide into the leaf for photosynthesis and oxygen and water vapour out of the leaf, is greatest when the stomata are open during the day.

Why do leaves sink in the dark?

When you put floating leaf disks in the dark, they will eventually sink. Without light energy, no photosynthesis will occur, so no more O2 gas will be produced.

Why does oxygen production stop without light?

Oxygen is needed to break the sugar into carbon dioxide, releasing energy the plants can use to stay alive. … (They use the ‘carbon’ in carbon dioxide to build the sugar molecule). Since there’s no sunlight at night, this gives the plants a way to stay alive, even when there’s no light.

What is the relationship between CO2 and photosynthesis?

Elevated [CO2] increases the availability of carbon in leaves causing greater Rubisco activity and higher rates of photosynthesis. Greater photosynthesis increases the content of non-structural carbohydrates in leaves which can lead to greater starch reserves and increased auxin biosynthesis.

How does CO2 levels affect photosynthesis?

Studies have shown that higher concentrations of atmospheric carbon dioxide affect crops in two important ways: they boost crop yields by increasing the rate of photosynthesis, which spurs growth, and they reduce the amount of water crops lose through transpiration.

What is elevated CO2?

Hypercapnia is excess carbon dioxide (CO2) buildup in your body. The condition, also described as hypercapnia, hypercarbia, or carbon dioxide retention, can cause effects such as headaches, dizziness, and fatigue, as well as serious complications such as seizures or loss of consciousness.

How does CO2 level affect oxygen production?

How does CO2 level affect oxygen production? increasing CO2 production increases oxygen production. … Greater flow of oxygen corresponds to a higher rate of photosynthesis.