BIOL1911-Concepts in Biology

Data-analysis Assignment 

To complete this assignment you are required to construct four separate properly formatted graphs and interpret their content to answer three questions related to photosynthesis 

The following data were obtained by measuring the rate of photosynthesis “P” as leaves were exposed to varying light levels of different colour. Photosynthesis in these experiments was measured as the amount of carbon dioxide (CO2) absorbed by a certain surface area of leaf per unit of time (hence the unit of measurement for the rate of photosynthesis, or “P”, is μmol/m2 /s). The experiment was conducted four times, each time with a filter that changed the colour of the light (light is measured as an amount of light per unit area per unit time, so light also has the unit μmol/m2 /s). Measurements of photosynthetic rate (P) were taken each time the light intensity was increased by 200μmol/m2 /s. Construct a graph for the data obtained from each experiment. 

*Note: the independent variable (x-axis) is what the experimenter manipulates in the experiment; the dependent variable (y-axis) is what the experimenter measures* 

Table 1. Photosynthetic rate (P) (μmol/m2 /s) of a tomato leaf (Lycopersicon esculentum) exposed to increasing light intensities (μmol/m2 /s) using different colour filters (white, red, green, and blue). 

Questions:

1. How do the different colours of light affect the rate of photosynthesis? In your answer please make reference to light intensities and photosynthetic rates from the data in Table 1 and in your graphs (provide units).

2. Do the results of these experiments make sense based on what you know about how photosynthetic pigments absorb light of various colours? In your answer, describe how photosynthetic pigments absorb different colours of light and make reference to data from Table 1 and your graphs (provide units).

3. In these experiments, photosynthetic rate (P) describes how much carbon dioxide is absorbed by a known area of leaf in a given amount of time. Can you explain why there is a negative photosynthetic rate when there is no light exposed to the leaf? In other words, what is happening in the leaf’s cells that would result in a net release of carbon dioxide when the leaf is in the dark?