The effect of darkness on chloroplast length of Euglena gracilis over time

  • Su Young Ahn
  • Inderpreet Basra
  • Katrina Liu
  • Prabh Sahota


Euglena gracilis is a mixotrophic algae that can gain energy through photosynthesis and phagocytosis. Previous research has extensively studied the effects of light on E. gracilis chloroplast length; however, much about the effects of darkness on chloroplast length is still unknown. Therefore, the objective of our study was to investigate whether exposure to darkness will affect chloroplast length of E. gracilis over time. We predicted that chloroplast length would decrease after being exposed to darkness with time and that chloroplast length would remain the same when exposed to light over time. To test this prediction, we exposed E. gracilis to light and dark conditions and measured the chloroplast length at three different times (0 hr, 48 hr and 72 hr). Our data was analyzed using a 2-way ANOVA test. We found that there was no statistical difference in chloroplast length when considering time independently (p = 0.1266). However, there was statistical difference in chloroplast length when exposed to darkness (p = 0.0011). We rejected the null hypothesis that the effect of time on the length of chloroplasts is the same in dark and light exposed E. gracilis (p = 0.0387). These results suggest that darkness limits thegrowth of chloroplast in E. gracilis.