Acclimation response of photosynthetic apparatus of Norway spruce to different growth light intensity

Václav Karlickýa,b, Irena Kurasováa,b, Zuzana Materováa, Karolína Kotalováa, Michal Štrocha,b, Vladimír Špundaa,b
a Faculty of Science, University of Ostrava, 30. dubna 22, 701 03 Ostrava 1, Czech Republic; b Global Change Research Institute CAS, Belidla 986/4a, 603 00 Brno, Czech Republic

Recently, specific features of Norway spruce photosynthetic apparatus, different from typical land plants, were found: (i) absence of lhcb3 and lhcb6 in light-harvesting complexes of photosystem II (PSII) [1], resulting in different PSII supercomplex structure [1] and PSII macro-organization [2]; (ii) possible presence of both PsbS and Lhcsr-like proteins that could be involved in non-photochemical quenching (NPQ) [1]. Thus these facts indicate that spruce can utilize different strategies of light acclimation and different mechanism of NPQ compared to other land plants. In this work, we have focused on long-term response of photosynthetic apparatus of spruce to different growth light intensity.

Norway spruce seedlings were grown from seeds in a growth chamber at 100 μmol photons m-2 s-1 (17 days). Afterwards parts of seedlings were acclimated to low (LL, 20 μmol photons m-2 s-1) and high (HL, 800 μmol photons m-2 s-1) lights for 10 days, whereas control plants continued to grow under original (normal) light (NL).

The Chl a/b ratio increased under HL indicating a reduction of the antenna size [3]. The increased Car/Chl ratio in HL seedlings in comparison with LL and NL ones was particularly due to relative increase of lutein and VAZ pool (together with permanent accumulation of deepoxidized xanthophylls anteraxanthin and zeaxanthin in darkness). Since acclimation response of carotenoid composition to HL in spruce differs from Arabidopsis (more pronounced increase of VAZ pool size and slight changes of lutein content [3]), a role of lutein in NPQ in spruce is discussed.

Circular dichroism spectra of isolated thylakoid membranes demonstrated reduced macro-organisation of the pigment-protein complexes in the thylakoid membranes under higher light intensities (HL seedlings revealed almost none psi-type circular dichroism signal). Therefore, acclimation mechanism in response to pigment-protein complexes composition and their macro-organization is also discussed.

Acknowledgements

This work was supported by Grant Agency of the Czech Republic No. 13-28093S/P50.

References

[1] R. Kouril, L. Nosek, J. Bartoš, E.J. Boekema, P. Ilík, New Phytol. 2016, 210, 808-14.
[2] V. Karlický, I. Kurasová, B. Ptácková, K. Vecerová, O. Urban, V. Špunda, Photosynth. Res. 2016, Online First.
[3] L.W. Bielczynski, G. Schansker, R. Croce, Front. Plant Sci. 2016, 7, 105.