The photosynthetic apparatus of the CAM plant Tillandsia flabellate and its response to water deficit

CAM plants are superior to C3 plants in drought resistance because of their peculiar photosynthesis pathway and morphological features. While those aspects have been studied for decades, little is known about the photosynthetic machinery of CAM plants. Here, we used a combination of biochemical and biophysical methods to study the photosynthetic apparatus of Tillandsia flabellate, an obligatory CAM plant. Most of the Photosystems super- and sub-complexes have properties very similar to those of Arabidopsis, with the main difference that in Tillandsia PSI-LHCI complexes bind extra LHCI. Functional measurements show that the PSI/PSII ratio is rather low compared to other plants and that the antenna size of both PSI and PSII is small. Upon 30-day water deficiency, the composition of the photosystems does not change significantly, PSII efficiency remains high and no Photosystem II photoinhibition was detected despite a reduction of non-photochemical quenching (NPQ).

Automated summary

CAM plants have a unique photosynthesis pathway and morphological features, making them more resistant to drought compared to C3 plants. However, little is known about the photosynthetic machinery of CAM plants. In this study, the photosynthetic apparatus of Tillandsia flabellate, an obligatory CAM plant, was investigated using biochemical and biophysical methods. The results showed that most of the Photosystems super- and sub-complexes have properties similar to those of Arabidopsis, with the main difference being the binding of extra LHCI in Tillandsia PSI-LHCI complexes. The functional measurements revealed that the PSI/PSII ratio was low, and the antenna size of both PSI and PSII was small. Despite a reduction in non-photochemical quenching (NPQ), no significant changes were observed in the composition of the photosystems, and PSII efficiency remained high even after 30-day water deficiency.