Journal
JOURNAL OF PLANT PHYSIOLOGY
Volume 170, Issue 2, Pages 129-135Publisher
ELSEVIER GMBH
DOI: 10.1016/j.jplph.2012.09.019
Keywords
High light; NADP-MDH; NADP-ME; PSII photochemistry; Starch degradation
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Funding
- [633/N-COST/09/2010/0]
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In the halophytic plant Mesembryanthemum crystallinum salinity or drought can change the mode of photosynthesis from C-3 to crassulacean acid metabolism (CAM). These two stress factors are linked to oxidative stress, however, the induction of CAM by oxidative stress per se is not straightforward. Treatment with high light (HL) did not lead to the induction of CAM, as documented by a low night/day difference in malate level and a low expression of the CAM-related form of phosphoenolcarboxylase (Ppc1), despite causing some oxidative damage (elevated MDA level, malondialdehyde). In contrast to the action of high salinity (0.4M NaCl), HL treatment did not activate neither the cytosolic NADP-malic enzyme nor the chloroplastic form of NADP-dependent malate dehydrogenase (NADP-MDH). In plastids of HL-treated plants a huge amount of starch was accumulated. This was associated with a weak stimulation of hydrolytic and phosphorolytic starch-degrading enzymes, in contrast to their strong up-regulation under high salinity. It is concluded that HL alone is not able to activate starch degradation necessary for CAM performance. Moreover, in the absence of salinity in C-3 M. crystallinum plants an age-dependent increase in energy dissipation from PSII was documented under high irradiance, as illustrated by non-photochemical quenching (NPQ). Obtained data suggest that in this halophytic species several photoprotective strategies are strictly salinity-dependent. (C) 2012 Elsevier GmbH. All rights reserved.
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