Flooding of tropical forests in central Amazonia: what do the effects on the photosynthetic apparatus of trees tell us about species suitability for reforestation in extreme environments created by hydroelectric dams?

Photoinactivation of photosystem II (PSII), the light–induced loss of ability to evolve oxygen, is an inevitable event during normal photosynthesis, exacerbated by saturating light but counteracted by repair via new protein synthesis. The photoinactivation of PSII is dependent on the dosage of light: in the absence of repair, typically one PSII is photoinactivated per 10 7 photons, although the exact quantum yield of photoinactivation is modulated by a number of factors, and decreases as fewer active PSII targets are available. PSII complexes initially appear to be photoinactivated independently; however, when less than 30% functional PSII complexes remain, they seem to be protected by strongly dissipative PSII reaction centres in several plant species examined so far, a mechanism which we term ‘inactive PSII–mediated quenching‘. This mechanism appears to require a pH gradient across the photosynthetic membrane for its optimal operation. The residual fraction of functional PSII complexes may, in turn, aid in the recovery of photoinactivated PSII complexes when conditions become less severe. This mechanism may be important for the photosynthetic apparatus in extreme environments such as those experienced by over–wintering evergreen plants, desert plants exposed to drought and full sunlight and shade plants in sustained sunlight.

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The Parallel Molecular Adaptations to the Antarctic Cold Environment in Two Psychrophilic Green Algae

Genome Biology and Evolution ◽

10.1093/gbe/evz104 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1897-1908 ◽

Cited By ~ 4

Author(s):

Zhenhua Zhang ◽

Changfeng Qu ◽

Ru Yao ◽

Yuan Nie ◽

Chenjie Xu ◽

...

Keyword(s):

Molecular Evolution ◽

Positive Selection ◽

Green Algae ◽

Large Scale ◽

Extreme Environments ◽

Photosynthetic Apparatus ◽

Antioxidant Systems ◽

Significant Evidence ◽

The Antarctic ◽

Molecular Convergence

Abstract Psychrophilic green algae from independent phylogenetic lines thrive in the polar extreme environments, but the hypothesis that their psychrophilic characteristics appeared through parallel routes of molecular evolution remains untested. The recent surge of transcriptome data enables large-scale evolutionary analyses to investigate the genetic basis for the adaptations to the Antarctic extreme environment, and the identification of the selective forces that drive molecular evolution is the foundation to understand the strategies of cold adaptation. Here, we conducted transcriptome sequencing of two Antarctic psychrophilic green algae (Chlamydomonas sp. ICE-L and Tetrabaena socialis) and performed positive selection and convergent substitution analyses to investigate their molecular convergence and adaptive strategies against extreme cold conditions. Our results revealed considerable shared positively selected genes and significant evidence of molecular convergence in two Antarctic psychrophilic algae. Significant evidence of positive selection and convergent substitution were detected in genes associated with photosynthetic machinery, multiple antioxidant systems, and several crucial translation elements in Antarctic psychrophilic algae. Our study reveals that the psychrophilic algae possess more stable photosynthetic apparatus and multiple protective mechanisms and provides new clues of parallel adaptive evolution in Antarctic psychrophilic green algae.

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Isoprene emission in central Amazonia - from measurements to model estimates

10.5194/egusphere-egu2020-1618 ◽

2020 ◽

Author(s):

Eliane Gomes-Alves ◽

Tyeen Taylor ◽

Pedro Assis ◽

Giordane Martins ◽

Rodrigo Souza ◽

...

Keyword(s):

Tropical Forests ◽

Plant Traits ◽

Leaf Age ◽

Environmental Drivers ◽

Good Representation ◽

Leaf Demography ◽

Isoprene Emission ◽

Environmental Controls ◽

Central Amazonia ◽

Emission Capacity

<p>Isoprene regulates large-scale biogeochemical cycles by influencing atmospheric chemical and physical processes, and its dominant sources to the global atmosphere are the tropical forests. Although global and regional model estimates of isoprene emission have been optimized in the last decades, modeled emissions from tropical vegetation still carry high uncertainty due to a poor understanding of the biological and environmental controls on emissions. It is already known that isoprene emission quantities may vary significantly with plant traits, such as leaf phenology, and with the environment; however, current models still lack of good representation for tropical plant species due to the very few observations available. In order to create a predictive framework for the isoprene emission capacity of tropical forests, it is necessary an improved mechanistic understanding on how the magnitude of emissions varies with plant traits and the environment in such ecosystems. In this light, we aimed to quantify the isoprene emission capacity of different tree species across leaf ages, and combine these leaf measurements with long-term canopy measurements of isoprene and its biological and environmental drivers; then, use these results to better parameterize isoprene emissions estimated by MEGAN. We measured at the Amazon Tall Tower Observatory (ATTO) site, central Amazonia: (1) isoprene emission capacity at different leaf ages of 21 trees species; (2) isoprene canopy mixing ratios during six campaigns from 2013 to 2015; (3) isoprene tower flux during the dry season of 2015 (El-Ni&#241;o year); (3) environmental factors &#8211; air temperature and photosynthetic active radiation (PAR) - from 2013 to 2018; and (4) biological factors &#8211; leaf demography and phenology (tower based measurements) from 2013 to 2018. We then parameterized the leaf age algorithm of MEGAN with the measurements of isoprene emission capacity at different leaf ages and the tower-based measurements of leaf demography and phenology. Modeling estimates were later compared with measurements (canopy level) and five years of satellite-derived isoprene emission (OMI) from the ATTO domain (2013-2017). Leaf level of isoprene emission capacity showed lower values for old leaves (> 6 months) and young leaves (< 2 months), compared to mature leaves (2-6 months); and our model results suggested that this affects seasonal ecosystem isoprene emission capacity, since the demography of the different leaf age classes varied a long of the year. We will present more results on how changes in leaf demography and phenology and in temperature and PAR affect seasonal ecosystem isoprene emission, and how modeling can be improved with the optimization of the leaf age algorithm. In addition, we will present a comparison of ecosystem isoprene emission of normal years (2013, 2014, 2017 years) and anomalous years (2015 - El-Ni&#241;o; and 2016 - post El-Ni&#241;o), and discuss how a strong El-Ni&#241;o year can influence plant functional strategies that can be carried over to the consecutive year and potentially affect isoprene emission.</p>

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Greenhouse Gas Emissions From Hydroelectric Dams in Tropical Forests

Alternative Energy and Shale Gas Encyclopedia ◽

10.1002/9781119066354.ch42 ◽

2016 ◽

pp. 426-436 ◽

Cited By ~ 6

Author(s):

Philip M. Fearnside

Keyword(s):

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

Tropical Forests ◽

Hydroelectric Dams ◽

Gas Emissions

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Recovering from forest-to-pasture conversion: leaf decomposition in Central Amazonia, Brazil

Journal of Tropical Ecology ◽

10.1017/s0266467413000771 ◽

2013 ◽

Vol 30 (1) ◽

pp. 93-96 ◽

Cited By ~ 6

Author(s):

Leda Lorenzo ◽

Natalia Pérez-Harguindeguy ◽

Fernando Casanoves ◽

Alexandre Adalardo de Oliveira

Keyword(s):

Leaf Litter ◽

Tropical Forests ◽

Mixed Model ◽

Dry Mass ◽

Primary Forest ◽

Secondary Forests ◽

Mixed Model Approach ◽

Substrate Quality ◽

Central Amazonia ◽

Model Approach

Abstract:Land-use change in tropical forests can affect the micro-environment for decomposition under modified canopies. In turn, decomposition may have consequences for soil fertility and ecosystem sustainability. The effects of the conversion from primary forest to pastures on leaf-litter decomposition and its recovery in secondary forests 20 y after pasture abandonment were evaluated using litterbags and a general mixed model approach. Litterbags containing leaf-litter of two contrasting qualities were placed in those three ecosystems and the mass remaining after 90 d was quantified. The mass remaining was 50% lower in high- than in low-quality leaves. The effects of the decomposition environment depended on the substrate quality. Although differences among ecosystems were not significant for low-quality leaves, high-quality leaves decomposed more slowly in pastures than in forests (mean dry mass remaining was 38% in pastures, 14% in secondary and 12% in primary forest). The decomposition of common substrates did not differ among forests. Results show that the conversion of primary forest to pasture may produce conditions for slower decomposition; however, these conditions appear be restored to a great extent in 20-y-old secondary forests.

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Macroorganisation and flexibility of thylakoid membranes

Biochemical Journal ◽

10.1042/bcj20190080 ◽

2019 ◽

Vol 476 (20) ◽

pp. 2981-3018 ◽

Cited By ~ 8

Author(s):

Petar H. Lambrev ◽

Parveen Akhtar

Keyword(s):

Light Harvesting ◽

Current Knowledge ◽

Three Dimensional ◽

Photosynthetic Apparatus ◽

Dynamic Responses ◽

State Transitions ◽

Photochemical Quenching ◽

Light Harvesting Complex ◽

Complex Ii ◽

Light Harvesting Complex Ii

Abstract The light reactions of photosynthesis are hosted and regulated by the chloroplast thylakoid membrane (TM) — the central structural component of the photosynthetic apparatus of plants and algae. The two-dimensional and three-dimensional arrangement of the lipid–protein assemblies, aka macroorganisation, and its dynamic responses to the fluctuating physiological environment, aka flexibility, are the subject of this review. An emphasis is given on the information obtainable by spectroscopic approaches, especially circular dichroism (CD). We briefly summarise the current knowledge of the composition and three-dimensional architecture of the granal TMs in plants and the supramolecular organisation of Photosystem II and light-harvesting complex II therein. We next acquaint the non-specialist reader with the fundamentals of CD spectroscopy, recent advances such as anisotropic CD, and applications for studying the structure and macroorganisation of photosynthetic complexes and membranes. Special attention is given to the structural and functional flexibility of light-harvesting complex II in vitro as revealed by CD and fluorescence spectroscopy. We give an account of the dynamic changes in membrane macroorganisation associated with the light-adaptation of the photosynthetic apparatus and the regulation of the excitation energy flow by state transitions and non-photochemical quenching.

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