Light intensity-dependent changes in the photochemistry of photosystem II, cell constituents, and lipid accumulation in the Wild-type (WT) and DCMU-tolerant mutant of green alga Scenedesmus vacuolatus

Abstract

Microalgae utilize light energy for photosynthesis; however, variations in light intensities can have antagonistic and synergistic effects on its growth and cell constituents. In the present experimental study, photodynamic effects of light intensity on the growth, cell constituents, photochemistry of PS II, and lipid accumulation were studied in wild-type (WT) and DCMU-tolerant mutant strains of S. vacuolatus. Microalgal algal cells (WT and DCMU-tolerant mutant) were exposed to light intensities ranging from 10 to 100 µmol m− 2 s− 1 and cultured in a BG-11 nutrient growth medium. Overall results showed higher light intensity tolerance in the mutant strain (60 µmol m− 2 s− 1) than the WT (40 µmol m− 2 s− 1). The photosynthetic parameters derived from chlorophyll fluorescence induction kinetics (OJIP), non-photochemical quenching (NPQ), and Light curve (rETR) revealed better photosynthetic performance by the mutant strain than the WT under the high light stress. Thus, it was inferred that, unlike the WT, a better photosynthetic efficiency coupled with an improved photo-protection mechanism in the mutant strain at higher light intensities might be contributing to an enhanced level of cell constituent and lipid accumulation in the mutant strain.