TRANSIENT PHOTOSYNTHETIC RESPONSES OF NITROGEN-DEPRIVED PETALONIA FASCIA AND LAMINARIA SACCHARINA (PHAEOPHYTA) TO AMMONIUM RESUPPLY

Plant growth response to γ-irradiation includes stimulating or inhibitory effects depending on plant species, dose applied, stage of ontogeny and other factors. Previous studies showed that responses to irradiation could depend on ABA accumulation and signaling. To elucidate the role of ABA in growth and photosynthetic responses to irradiation, lines Col-8, abi3-8 and aba3 -1 of Arabidopsis thaliana were used. Seeds were γ-irradiated using 60Co in the dose range 50-150 Gy. It was revealed that the dose of 150 Gy affected germination parameters of aba3 -1 and Col-8 lines, while abi3-8 line was the most resistant to the studied doses and even showed faster germination at early hours after γ-irradiation at 50 Gy. These results suggest that susceptibility to ABA is probably more important for growth response to γ-irradiation than ABA synthesis. The photosynthetic functioning of 16-day-old plants mainly was not disturbed by γ-irradiation of seeds, and no indication of photosystem II photoinhibition was noticed, revealing the robustness of the photosynthetic system of A. thaliana. Glutathione peroxidase activity and ABA concentrations in plant tissues were not affected in the studied dose range. These results contribute to the understanding of germination and photosynthesis fine-tuning and of mechanisms of plant tolerance to ionizing radiation.

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Morphological bases of phytoplankton energy management and physiological responses unveiled by 3D subcellular imaging

Nature Communications ◽

10.1038/s41467-021-21314-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Clarisse Uwizeye ◽

Johan Decelle ◽

Pierre-Henri Jouneau ◽

Serena Flori ◽

Benoit Gallet ◽

...

Keyword(s):

Energy Management ◽

Morphometric Analysis ◽

Physiological Responses ◽

High Light ◽

Phytoplankton Diversity ◽

Eukaryotic Phytoplankton ◽

Evolutionarily Conserved ◽

Photosynthetic Responses ◽

Photosynthesis And Respiration ◽

Subcellular Imaging

AbstractEukaryotic phytoplankton have a small global biomass but play major roles in primary production and climate. Despite improved understanding of phytoplankton diversity and evolution, we largely ignore the cellular bases of their environmental plasticity. By comparative 3D morphometric analysis across seven distant phytoplankton taxa, we observe constant volume occupancy by the main organelles and preserved volumetric ratios between plastids and mitochondria. We hypothesise that phytoplankton subcellular topology is modulated by energy-management constraints. Consistent with this, shifting the diatom Phaeodactylum from low to high light enhances photosynthesis and respiration, increases cell-volume occupancy by mitochondria and the plastid CO2-fixing pyrenoid, and boosts plastid-mitochondria contacts. Changes in organelle architectures and interactions also accompany Nannochloropsis acclimation to different trophic lifestyles, along with respiratory and photosynthetic responses. By revealing evolutionarily-conserved topologies of energy-managing organelles, and their role in phytoplankton acclimation, this work deciphers phytoplankton responses at subcellular scales.

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