Biological Sciences Review Magazine Archive
Volume 10, 1997-1998
Number 2, November 1997
Volume 10, 1997-1998
Number 2, November 1997
This graph compares two different stages / pathways within photosynthesis, known as C4 and C3. The graph shows that at a lower concentration of CO2 the C4 route of photosynthesis is operational. C3 , the metabolic pathway for most plants, only comes into effect at 100 CO2 concentration/ppm and increases at a generally steady rate. This article was published in 1997 so next century is taken to mean after the year 2000. We can see that at 380 CO2 concentration the C4 pathway begins to plateau. However in comparison the C3 metabolic pathway only begins to plateau at the end of the graph at around 950 CO2 concentration/ppm. These will be important when considering the effect of climate change and global warming. Climate change is largely caused by gases, known as greenhouse gases, which are being emitted through a variety of ways including the thawing of permafrost and industrial agriculture. This gas accumulates and gathers at the ozone layer. One of these greenhouse gases is carbon dioxide. The levels of carbon dioxide are constantly rising as is the world population. Carbon dioxide is an important molecule for all plants as it is used in photosynthesis. Theoretically if the limiting factor to photosynthesis rate in plants was the CO2 abundance in the vicinity of the plant. Therefore an increase in carbon dioxide through emissions would be good for plant growth and may potentially produce more fruit. This ‘model’ of carbon dioxide being the limiting factor is true for C4 up until 380 CO2 concentration/ppm and for C3 up until 950 CO2 concentration/ppm. After these points, when the lines plateau both plants have an abundant supply of CO2 and we can therefore conclude that the plants are limited by another reactant of photosynthesis such as water or light. With climate change the levels of CO2 will increase meaning C3 would produce more food which would be able to cope with the growing population however plants which use metabolic pathway C4 are already at an optimum level of efficiency of photosynthesis production. Therefore it is not possible for there to be more of it without devoting more agricultural land to growing it. C4 vital plants such as maize and sugar cane. The issue with more land being made into farming is that this land must come from somewhere which could be from clearing forests which would lead to more greenhouse gases being emitted (as trees absorb carbon dioxide). This article was written for educational purposes by Dr Amanda Bamford in the School of Biological Sciences at the University of Manchester with resources being used from the University of East Anglia. I believe that this article is valid as I do not feel these contributors would have an agenda to emphasise or downplay the results of the experiment in anyway.