A study using an O2 electrode to measure the amount of O2 produced or consumed over an amount of time with varying light intensities to determine the effect of light intensity, CO2 and diuron on the rate of photosynthesis of Spinacia oleracea.
Introduction
Photosynthesis is the process in which chloroplasts found in plants, algae and some bacteria are used to convert light energy to chemical food energy. (Reece, et al. 2012, p. 190)(Molecules, Genes & Cells Laboratory Manual 2016) .
Photosynthesis can be broken down into two parts, light dependent reactions and light independent. Light dependent reactions use light energy collected by the thylakoid to convert NADP+ and ADP to NADPH and ATP respectively (Cloot 1994, p. 23). This process is shown in figure 1. The second part of photosynthesis is also known as the Calvin cycle. In this CO2 is converted to glucose by using the energy of ATP and NADPH and it is light independent (Reece, et al. 2012, p. 192). The rate of photosynthesis can be determined using the amount of oxygen produced in an amount of time. An oxygen electrode is able to do this (Molecules, Genes & Cells Laboratory Manual 2016). Respiration is the process in which glucose is broken down by the mitochondria to obtain the energy in its bonds so that is may be used in other metabolic processes. …show more content…
Respiration occurs in all living organisms and is separate from photosynthesis (Molecules, Genes & Cells Laboratory Manual 2016). Oxygen is consumed in this process and carbon dioxide is one of the products (Reece, et al. 2012, p. 169-184).
Diuron is a herbicide that will be used in this experiment. Diuron inhibits photosynthesis as found in a study by Harrington, et al. (2005).
The hypothesis being tested is that as the light intensity is increased the rate of photosynthesis will increase.
Materials and Methods
The procedure as set out in the Molecules, Genes and Cells Laboratory Manual (2016) was followed.
A 50 mM HEPES buffer at pH 7.6 was used. The light intensity was varied from the most intense light to no light, the levels of light used were 1000, 50, 10 and 0 µmol photons m-2 s -1. After the steady rate at 0 µmol photons m-2 s -1 was recorded the light intensity was returned to maximum and Diuron was added. A short time after the amount of O2 the electrode could measure maxed out. To rectify this issue nitrogen gas was bubbled into the chamber to remove some oxygen. The chamber was once again sealed and a steady rate in the presence of Diuron was recorded. Results Figure 2 shows that as light intensity increases the rate of photosynthesis increases as a result. The figure shows that the amount of oxygen consumed decreases and the amount of oxygen produced increases as light intensity increases. The blue series shows the amount of oxygen consumed or produced and the orange series shows the true rate of photosynthesis. For both series the rate increases linearly as light is increased from 0 µmoles photons.m-2.s-1 to approx. 100 µmoles photons.m-2.s-1. As light intensity increased further the rates began to plateau. The Spinacia oleracea were exposed to zero light and the rate of oxygen consumption was determined. This is represented on the blue line as the point at zero light. The rate of respiration was then subtracted from the oxygen produced to give the true rate of photosynthesis. It was assumed the rate of respiration
Introduction
Photosynthesis is the process in which chloroplasts found in plants, algae and some bacteria are used to convert light energy to chemical food energy. (Reece, et al. 2012, p. 190)(Molecules, Genes & Cells Laboratory Manual 2016) .
Photosynthesis can be broken down into two parts, light dependent reactions and light independent. Light dependent reactions use light energy collected by the thylakoid to convert NADP+ and ADP to NADPH and ATP respectively (Cloot 1994, p. 23). This process is shown in figure 1. The second part of photosynthesis is also known as the Calvin cycle. In this CO2 is converted to glucose by using the energy of ATP and NADPH and it is light independent (Reece, et al. 2012, p. 192). The rate of photosynthesis can be determined using the amount of oxygen produced in an amount of time. An oxygen electrode is able to do this (Molecules, Genes & Cells Laboratory Manual 2016). Respiration is the process in which glucose is broken down by the mitochondria to obtain the energy in its bonds so that is may be used in other metabolic processes. …show more content…
Respiration occurs in all living organisms and is separate from photosynthesis (Molecules, Genes & Cells Laboratory Manual 2016). Oxygen is consumed in this process and carbon dioxide is one of the products (Reece, et al. 2012, p. 169-184).
Diuron is a herbicide that will be used in this experiment. Diuron inhibits photosynthesis as found in a study by Harrington, et al. (2005).
The hypothesis being tested is that as the light intensity is increased the rate of photosynthesis will increase.
Materials and Methods
The procedure as set out in the Molecules, Genes and Cells Laboratory Manual (2016) was followed.
A 50 mM HEPES buffer at pH 7.6 was used. The light intensity was varied from the most intense light to no light, the levels of light used were 1000, 50, 10 and 0 µmol photons m-2 s -1. After the steady rate at 0 µmol photons m-2 s -1 was recorded the light intensity was returned to maximum and Diuron was added. A short time after the amount of O2 the electrode could measure maxed out. To rectify this issue nitrogen gas was bubbled into the chamber to remove some oxygen. The chamber was once again sealed and a steady rate in the presence of Diuron was recorded. Results Figure 2 shows that as light intensity increases the rate of photosynthesis increases as a result. The figure shows that the amount of oxygen consumed decreases and the amount of oxygen produced increases as light intensity increases. The blue series shows the amount of oxygen consumed or produced and the orange series shows the true rate of photosynthesis. For both series the rate increases linearly as light is increased from 0 µmoles photons.m-2.s-1 to approx. 100 µmoles photons.m-2.s-1. As light intensity increased further the rates began to plateau. The Spinacia oleracea were exposed to zero light and the rate of oxygen consumption was determined. This is represented on the blue line as the point at zero light. The rate of respiration was then subtracted from the oxygen produced to give the true rate of photosynthesis. It was assumed the rate of respiration