Photoacclimation in Eutrema salsugineum

Abstract

Eutrema salsugineum is an extremophilic model plant for stress tolerance studies. This study aimed to characterize the photoacclimation mechanisms of the Shandong and Yukon ecotypes of Eutrema under two growth irradiance regimes low- (LL) and high-light (HL). The experimental tools and techniques included physical measurements, pigment extractions and CO2- and light-response curves to assess photoacclimation. The two ecotypes showed minor differences in the growth kinetics experiment across the light regimes utilized. Under LL the two ecotypes exhibited a similar performance in terms of growth with a slightly higher growth rate of the Yukon ecotype. When plants were grown under HL conditions growth was similar in both ecotypes for the first weeks, after that point the Shandong ecotype appears to grow at a faster rate compared to Yukon. The photosynthetic pigment analyses showed that the Shandong ecotype does not modify chlorophyll (Chl) a:b ratio as a photoacclimation mechanism in response to HL growth irradiance. This inability to modify pigment composition might make this ecotype prone to photoinhibition as observed in the results of this study. Conversely, the Yukon ecotype modifies its Chl a:b ratio in response to growth at a higher irradiance conferring this ecotype a higher tolerance to photoinhibition due to a photoacclimation of the light harvesting chlorophyll-proteins as a response to the increased growth irradiance. The gas exchange measurements showed a contrasting response of these two ecotypes. The Shandong ecotype exhibits higher rates of photosynthesis than Yukon when plants were grown under HL. It appears that Shandong is suppressing photorespiration as a photoacclimation mechanism to HL. The findings of this study confirm that these two ecotypes have different photoacclimation mechanisms to HL.