Effect of light intensity on Chlamydomonas reinhardtii growth rate

Abstract

The effect of light intensity on the growth rate of Chlamydomonas reinhardtii was explored. The null hypothesis stated that an increase in light intensity will either decrease or have no effect on C. reinhardtii growth rate, and the alternative hypothesis tested for this study was that an increase in light intensity will increase C. reinhardtii growth rate. Three replicates of C. reinhardtii solution were grown under three different light intensities: high (4660 Lux), control (2380 Lux) and low (1330 Lux). Cell growth was monitored for two weeks by taking samples from each treatment and counting the amount of cells using a haemocytometer. The obtained results for this experiment showed that compared to the control growth rate (18.6207 cells/day ± 7.2430), low light intensity had a decreased growth rate (12.8572 cells/day ± 5.7973) while high light intensity also had a relatively small decrease in growth rate (16.2760 cells/day ± 1.8620). The calculated p-value was 0.48, which indicates that no significant difference. It is suspected that the lower results in a high intensity were due to a process called non-photochemical quenching, or NPQ. In conclusion, we failed to reject the null hypothesis and could not provide support for the alternate hypothesis.