Effect of light wavelength on chloroplast length in cultured Euglena gracilis

Abstract

The objective of our study was to determine whether exposing Euglena gracilis to different wavelengths of light affected their mean chloroplast length. Euglena cultures were incubated in culture tubes surrounded by coloured acetate paper, black plastic, or transparent acetate paper in order to manipulate the wavelengths of light the organisms were exposed to. In total, there were 5 different light treatments: red, green, blue, normal light, and no light. Samples were fixed and chloroplast lengths were measured using a compound microscope at 1000X magnification. A one-way ANOVA test returned an F statistic of F_{(4, 10)} = 3.169 and a p-value of 0.0633. We failed to reject the null hypothesis and conclude that the mean chloroplast length of Euglena cultured under different wavelengths of light does not differ. However, we did notice a trend: the no light treatment had a lower mean chloroplast length in comparison to the red, blue, green and the normal light treatments. This may indicate that the absence of light could be correlated with a decrease in chloroplast length. Understanding the ability of E. gracilis to change its chloroplast parameters due to changes in external environmental light conditions is important to further understand the physiological processes that underlie these organellular changes.