scholarly journals Quantification of leaf-scale light energy allocation and photoprotection processes in a Mediterranean pine forest under extensive seasonal drought

2019 ◽  
Vol 39 (10) ◽  
pp. 1767-1782 ◽  
Author(s):  
Kadmiel Maseyk ◽  
Tongbao Lin ◽  
Amnon Cochavi ◽  
Amnon Schwartz ◽  
Dan Yakir
Keyword(s):  
Soil Water ◽  
Carbon Fixation ◽  
Pinus Halepensis ◽  
Electron Flow ◽  
Incident Light ◽  
Light Energy ◽  
Absolute Amount ◽  
Summer Drought ◽  
Low Carbon ◽  
Psii Efficiency

Abstract Photoprotection strategies in a Pinus halepensis Mill. forest at the dry timberline that shows sustained photosynthetic activity during 6–7 month summer drought were characterized and quantified under field conditions. Measurements of chlorophyll fluorescence, leaf-level gas exchange and pigment concentrations were made in both control and summer-irrigated plots, providing the opportunity to separate the effects of atmospheric from soil water stress on the photoprotection responses. The proportion of light energy incident on the leaf surface ultimately being used for carbon assimilation was 18% under stress-free conditions (irrigated, winter), declining to 4% under maximal stress (control, summer). Allocation of absorbed light energy to photochemistry decreased from 25 to 15% (control) and from 50% to 30% (irrigated) between winter and summer, highlighting the important role of pigment-mediated energy dissipation processes. Photorespiration or other non-assimilatory electron flow accounted for 15–20% and ~10% of incident light energy during periods of high and low carbon fixation, respectively, representing a proportional increase in photochemical energy going to photorespiration in summer but a decrease in the absolute amount of photorespiratory CO2 loss. Resilience of the leaf photochemical apparatus was expressed in the complete recovery of photosystem II (PSII) efficiency (ΦPSII) and relaxation of the xanthophyll de-epoxidation state on the diurnal cycle throughout the year, and no seasonal decrease in pre-dawn maximal PSII efficiency (Fv/Fm). The response of CO2 assimilation and photoprotection strategies to stomatal conductance and leaf water potential appeared independent of whether stress was due to atmospheric or soil water deficits across seasons and treatments. The range of protection characteristics identified provides insights into the relatively high carbon economy under these dry conditions, conditions that are predicted for extended areas in the Mediterranean and other regions due to global climate change.

scholarly journals Summer drought in Switzerland 1981‒2020: Events, trends and drivers

2021 ◽  
Author(s):  
Simon C. Scherrer ◽  
Christoph Spirig ◽  
Martin Hirschi ◽  
Felix Maurer ◽  
Sven Kotlarski
Keyword(s):  
Regional Climate Model ◽  
Soil Water ◽  
Climate Model ◽  
Potential Evapotranspiration ◽  
Meteorological Data ◽  
Regional Climate ◽  
Reanalysis Data ◽  
Summer Drought ◽  
Temperature And Precipitation ◽  
Temperature Scaling

<p>The Alpine region has recently experienced several dry summers with negative impacts on the economy, society and ecology. Here, soil water, evapotranspiration and meteorological data from several observational and model-based data sources is used to assess events, trends and drivers of summer drought in Switzerland in the period 1981‒2020. 2003 and 2018 are identified as the driest summers followed by somewhat weaker drought conditions in 2020, 2015 and 2011. We find clear evidence for an increasing summer drying in Switzerland. The observed climatic water balance (-39.2 mm/decade) and 0-1 m soil water from reanalysis (ERA5-Land: -4.7 mm/decade; ERA5: -7.2 mm/decade) show a clear tendency towards summer drying with decreasing trends in most months. Increasing evapotranspiration (potential evapotranspiration: +21.0 mm/decade; ERA5-Land actual evapotranspiration: +15.1 mm/decade) is identified as important driver which scales excellently (+4 to +7%/K) with the observed strong warming of about 2°C. An insignificant decrease in precipitation further enhanced the tendency towards drier conditions. Most simulations of the EURO-CORDEX regional climate model ensemble underestimate the changes in summer drying. They underestimate both, the observed recent summer warming and the small decrease in precipitation. The changes in temperature and precipitation are negatively correlated, i.e. simulations with stronger warming tend to show (weak) decreases in precipitation. However, most simulations and the reanalysis overestimate the correlation between temperature and precipitation and the precipitation-temperature scaling on the interannual time scale. Our results emphasize that the analysis of the regional summer drought evolution and its drivers remains challenging especially with regional climate model data but considerable uncertainties also exist in reanalysis data sets.</p>

scholarly journals The carbon fixation efficiency in biomass of Cylindrotheca closterium (Ehrenberg) Reimann & J. C. Lewin (Bacillariophyceae) under the conditions of cumulative cultivation

2020 ◽  
Vol 5 (1) ◽  
pp. 12-19
Author(s):  
R. G. Gevorgiz ◽  
S. N. Zheleznova
Keyword(s):  
Co2 Fixation ◽  
Carbon Fixation ◽  
Utilization Efficiency ◽  
Chlorella Protothecoides ◽  
Carbonic Anhydrases ◽  
Low Carbon ◽  
Carbon Utilization ◽  
Porphyridium Purpureum ◽  
Cylindrotheca Closterium ◽  
Dry Biomass

The carbon utilization efficiency is an important characteristic of the cultivated object. Diatom Cylindrotheca closterium (Ehrenberg) Reimann & J. C. Lewin is known to use carbon from aquatic environment quite effectively, as it has many unique carbonic anhydrases and carbon transporters. However, the carbon fixation efficiency for many types of diatoms in culture is still unknown. When calculating the carbon fixation efficiency, researchers use different terminology and methods, and it leads to significant difficulties when comparing the carbon fixation efficiency in the biomass of various types of microalgae. The aims of this study are: 1) to update terms and definitions used in literature on the basis of modern concepts of carbon fixation in microalgae biomass, as well as absorption of inorganic carbon by microalgae culture; 2) to evaluate the carbon fixation efficiency in the biomass of C. closterium diatom under conditions of cumulative cultivation. C. closterium was grown at a temperature of +20 °C on a nutrient medium RS. During the cultivation, the culture was bubbled with air (1.1 L of air per 1 L of culture per minute). The air temperature at the outlet of the suspension was of +19 °C; the maximum productivity of the culture was of 1.254 g·L−1·day−1. According to the results of the CHN analysis, the proportion of carbon in C. closterium dry biomass was of 23 %. Under the conditions of cumulative cultivation in C. closterium, the carbon fixation efficiency in biomass was of 90 %. Compared with other algae species, C. closterium is characterized by a rather high CO2 fixation efficiency. For example, in green microalga Chlorella protothecoides and Ch. vulgaris, the CO2 fixation efficiency was of 20 % and 55.3 %, respectively; in cyanobacteria Spirulina sp. – of 38 %; in red microalgae Porphyridium purpureum – of 69 %. It was observed that to ensure an increase of 1 g of C. closterium dry biomass per day at a temperature of +19 °C, a minimum of 0.46 L of CO2, or 1132 L of air, should be consumed. Possibly, it is high carbon fixation efficiency, as well as low carbon fraction in C. closterium biomass, that explains the high production indices of this species. Under equal conditions of cultivation in terms of light and carbon availability, the productivity of C. closterium can exceed the productivity of other types of microalgae by 5–10 times. So, while Spirulina sp. productivity reaches 0.2 g·L−1·day−1, C. closterium productivity is of 1.254 g·L−1·day−1.

scholarly journals Photosynthesis Regulation in Response to Fluctuating Light in the Secondary Endosymbiont Alga Nannochloropsis gaditana

2019 ◽  
Vol 61 (1) ◽  
pp. 41-52 ◽  
Author(s):  
Alessandra Bellan ◽  
Francesca Bucci ◽  
Giorgio Perin ◽  
Alessandro Alboresi ◽  
Tomas Morosinotto
Keyword(s):  
Electron Transport ◽  
Electron Flow ◽  
Incident Light ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Electron Transport ◽  
Thermal Dissipation ◽  
Photochemical Quenching ◽  
Nannochloropsis Gaditana ◽  
Fluctuating Light ◽  
Light Fluctuations

Abstract In nature, photosynthetic organisms are exposed to highly dynamic environmental conditions where the excitation energy and electron flow in the photosynthetic apparatus need to be continuously modulated. Fluctuations in incident light are particularly challenging because they drive oversaturation of photosynthesis with consequent oxidative stress and photoinhibition. Plants and algae have evolved several mechanisms to modulate their photosynthetic machinery to cope with light dynamics, such as thermal dissipation of excited chlorophyll states (non-photochemical quenching, NPQ) and regulation of electron transport. The regulatory mechanisms involved in the response to light dynamics have adapted during evolution, and exploring biodiversity is a valuable strategy for expanding our understanding of their biological roles. In this work, we investigated the response to fluctuating light in Nannochloropsis gaditana, a eukaryotic microalga of the phylum Heterokonta originating from a secondary endosymbiotic event. Nannochloropsis gaditana is negatively affected by light fluctuations, leading to large reductions in growth and photosynthetic electron transport. Exposure to light fluctuations specifically damages photosystem I, likely because of the ineffective regulation of electron transport in this species. The role of NPQ, also assessed using a mutant strain specifically depleted of this response, was instead found to be minor, especially in responding to the fastest light fluctuations.

Rooting depth and plant water relations explain species distribution patterns within a sandplain landscape

2004 ◽  
Vol 31 (5) ◽  
pp. 423 ◽  
Author(s):  
Philip K. Groom
Keyword(s):  
Soil Moisture ◽  
Soil Water ◽  
Water Loss ◽  
Rooting Depth ◽  
Summer Drought ◽  
Tissue Water ◽  
Shrub Species ◽  
Water Deficits ◽  
Groundwater Levels ◽  
Water Potentials

Tree and shrub species of the Banksia woodlands on the sandplains of northern Swan Coastal Plain, Western Australia possess a range of strategies to avoid or tolerate soil water deficits during the annual summer drought. Shallow-rooted shrub species (< 1 m rooting depth) inhabit a range of locations in the landscape, from top of dune crests to wetland embankments. These are the most drought-tolerant of all sandplain species, surviving extremely low summer soil water potentials (< –7 MPa) and tissue water deficits by significantly reducing their transpirational water loss (< 0.2 mmol m–2 s–1). This is in contrast to the few shallow-rooted species restricted to low-lying or seasonally waterlogged areas which are reliant on subsurface soil moisture or groundwater to maintain their relatively high summer water use. Recent studies of water source usage of selected Banksia tree species have shown that these deep-rooted species access groundwater up to a maximum depth of 9 m depth during the summer months, or soil moisture at depth when groundwater was greater than maximum rooting depths, depending on the species. Medium- and deep-rooted (1–2 m and > 2 m, respectively) shrub species cope with the summer soil drying phase and related decrease in groundwater levels by conserving leaf water loss and incurring predawn water potentials between –1 and –4 MPa, enabling them to occur over a range of topographic positions within the sandplain landscape.

Soil water extraction by a mixed eucalypt forest during a drought period

Soil Research ◽  
1986 ◽  
Vol 24 (1) ◽  
pp. 25 ◽  
Author(s):  
T Talsma ◽  
EA Gardner
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Water Table ◽  
Unsaturated Flow ◽  
Growth Ring ◽  
Soil Water Potential ◽  
Water Extraction ◽  
Depth Interval ◽  
Summer Drought ◽  
Drought Period

Eucalypt trees growing on deep soils, with a water table at about 8 m depth, showed no apparent drought effects during the 1982-83 dry period in south-east Australia when gross precipitation was only 388 mm. At the end of the drought, soil water to 4 m depth was depleted to a soil water potential of -0.5 MPa and under these conditions unsaturated flow from the water table to the lower root zone was calculated to be 0.17 mm day-1. Water extraction over the depth interval from 0 to 6 m in the drought year was 533 mm, some 200 mm in excess of that used during a year of average rainfall. The contribution to tree water use from unsaturated flow from the water table was calculated to be small (15 mm) even in a drought year, and in most years water movement would be towards the water table to yield a deep drainage term estimated between 40 and 100 mm. Growth ring studies indicated that the lower water use, estimated at 2.6 mm day-1 during the spring-summer drought, did not affect the slowly growing E. radiata species, but reduced stem diameter growth of the faster growing E. dalrympleana and E. pauciflora species.

scholarly journals Phycobilisomes Harbor FNRL in Cyanobacteria

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Haijun Liu ◽  
Daniel A. Weisz ◽  
Mengru M. Zhang ◽  
Ming Cheng ◽  
Bojie Zhang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Energy Transfer ◽  
Electron Transport ◽  
Carbon Fixation ◽  
Close Association ◽  
Reaction Centers ◽  
Light Energy ◽  
Fine Tuning ◽  
Cyclic Electron Transport ◽  
Cross Link

ABSTRACT Cyanobacterial phycobilisomes (PBSs) are photosynthetic antenna complexes that harvest light energy and supply it to two reaction centers (RCs) where photochemistry starts. PBSs can be classified into two types, depending on the presence of allophycocyanin (APC): CpcG-PBS and CpcL-PBS. Because the accurate protein composition of CpcL-PBS remains unclear, we describe here its isolation and characterization from the cyanobacterium Synechocystis sp. strain 6803. We found that ferredoxin-NADP+ oxidoreductase (or FNRL), an enzyme involved in both cyclic electron transport and the terminal step of the electron transport chain in oxygenic photosynthesis, is tightly associated with CpcL-PBS as well as with CpcG-PBS. Room temperature and low-temperature fluorescence analyses show a red-shifted emission at 669 nm in CpcL-PBS as a terminal energy emitter without APC. SDS-PAGE and quantitative mass spectrometry reveal an increased content of FNRL and CpcC2, a rod linker protein, in CpcL-PBS compared to that of CpcG-PBS rods, indicative of an elongated CpcL-PBS rod length and its potential functional differences from CpcG-PBS. Furthermore, we combined isotope-encoded cross-linking mass spectrometry with computational protein structure predictions and structural modeling to produce an FNRL-PBS binding model that is supported by two cross-links between K69 of FNRL and the N terminus of CpcB, one component in PBS, in both CpcG-PBS and CpcL-PBS (cross-link 1), and between the N termini of FNRL and CpcB (cross-link 2). Our data provide a novel functional assembly form of phycobiliproteins and a molecular-level description of the close association of FNRL with phycocyanin in both CpcG-PBS and CpcL-PBS. IMPORTANCE Cyanobacterial light-harvesting complex PBSs are essential for photochemistry in light reactions and for balancing energy flow to carbon fixation in the form of ATP and NADPH. We isolated a new type of PBS without an allophycocyanin core (i.e., CpcL-PBS). CpcL-PBS contains both a spectral red-shifted chromophore, enabling efficient energy transfer to chlorophyll molecules in the reaction centers, and an increased FNRL content with various rod lengths. Identification of a close association of FNRL with both CpcG-PBS and CpcL-PBS brings new insight to its regulatory role for fine-tuning light energy transfer and carbon fixation through both noncyclic and cyclic electron transport.

scholarly journals A Genome-Scale Metabolic Model of Thalassiosira pseudonana CCMP 1335 for a Systems-Level Understanding of Its Metabolism and Biotechnological Potential

2020 ◽  
Vol 8 (9) ◽  
pp. 1396
Author(s):  
Ahmad Ahmad ◽  
Archana Tiwari ◽  
Shireesh Srivastava
Keyword(s):  
Carbon Fixation ◽  
Electron Flow ◽  
Single Gene ◽  
Metabolic Model ◽  
Thalassiosira Pseudonana ◽  
Marine Diatom ◽  
Omega 3 ◽  
Biotechnological Potential ◽  
A Genome ◽  
Genome Scale

Thalassiosira pseudonana is a transformable and biotechnologically promising model diatom with an ability to synthesise nutraceuticals such as fucoxanthin and store a significant amount of polyglucans and lipids including omega-3 fatty acids. While it was the first diatom to be sequenced, a systems-level analysis of its metabolism has not been done yet. This work presents first comprehensive, compartmentalized, and functional genome-scale metabolic model of the marine diatom Thalassiosira pseudonana CCMP 1335, which we have termed iThaps987. The model includes 987 genes, 2477 reactions, and 2456 metabolites. Comparison with the model of another diatom Phaeodactylum tricornutum revealed presence of 183 unique enzymes (belonging primarily to amino acid, carbohydrate, and lipid metabolism) in iThaps987. Model simulations showed a typical C3-type photosynthetic carbon fixation and suggested a preference of violaxanthin–diadinoxanthin pathway over violaxanthin–neoxanthin pathway for the production of fucoxanthin. Linear electron flow was found be active and cyclic electron flow was inactive under normal phototrophic conditions (unlike green algae and plants), validating the model predictions with previous reports. Investigation of the model for the potential of Thalassiosira pseudonana CCMP 1335 to produce other industrially useful compounds suggest iso-butanol as a foreign compound that can be synthesized by a single-gene addition. This work provides novel insights about the metabolism and potential of the organism and will be helpful to further investigate its metabolism and devise metabolic engineering strategies for the production of various compounds.

The effects of mulch (Olea europea and Pinus halepensis) on burned soils: A preliminary study in Adriatic coast (Croatia)

2020 ◽  
Author(s):  
Domina Delač ◽  
Paulo Pereira ◽  
Ivica Kisić
Keyword(s):  
Soil Properties ◽  
Soil Ph ◽  
Pinus Halepensis ◽  
Control Treatment ◽  
Summer Drought ◽  
Significant Difference ◽  
Adriatic Coast ◽  
Olea Europea ◽  
Preliminary Study ◽  
And Control

&lt;p&gt;&lt;strong&gt;The effects of mulch (&lt;em&gt;Olea europea&lt;/em&gt; and &lt;em&gt;Pinus halepensis&lt;/em&gt;) on burned soils: A preliminary study in Adriatic coast (Croatia)&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Delac, Domina&lt;sup&gt;1*&lt;/sup&gt;; Pereira, Paulo&lt;sup&gt;2*&lt;/sup&gt;; Kisic, Ivica&lt;sup&gt;1&lt;/sup&gt;&lt;/p&gt;&lt;p&gt;&lt;sup&gt;1&lt;/sup&gt;University of Zagreb, Faculty of Agriculture, Department of General Agronomy, Svetosimunska cesta 25, 10000 Zagreb, Croatia. (*[email protected])&lt;/p&gt;&lt;p&gt;&lt;sup&gt;2&lt;/sup&gt;Mykolas Romeris University, Environmental Management Laboratory, Ateitis street 20, LT-08303, Vilnius, Lithuania (*[email protected])&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;In the recent decades the frequency and intensity of summer drought periods is increasing in Adriatic coast. These changes in climate increase the vulnerability to wildfires. Wildfires can change soil physical and chemical properties. However, these effects can be mitigated by mulching. The aim of this work is to study the effects of mulch (&lt;em&gt;Olea europea&lt;/em&gt; and &lt;em&gt;Pinus halepensis&lt;/em&gt;) on fire affected soils. The wildfire occurred on 28 July 2019 and affected an area of about 900 ha in Dalmatia, near Adriatic Coast (43&amp;#176;45'06.0&quot;N 15&amp;#176;56'02.9&quot;E with an elevation of 105 m a.s.l.). &amp;#160;The mean annual temperature is 15.8 &amp;#176;C, and the annual precipitation is 800 mm. It was affected agricultural land with dominant culture &lt;em&gt;Olea europea&lt;/em&gt; and abandoned grassing where dominates &lt;em&gt;Pinus halepensis&lt;/em&gt;. Soils are classified as &lt;em&gt;calcocambisols&lt;/em&gt;. Twenty-five days after the fire, two plots (5 treatments per plot) were established and covered with &lt;em&gt;Olea europea&lt;/em&gt; and &lt;em&gt;Pinus halepensis&lt;/em&gt; mulch. A control plot was established as well. Soil were sampled (0 &amp;#8211; 5 cm), twenty- days after fire (August, 2019), before mulch application, and then 3 months after fire (November, 2019). A total of 15 samples were collected per treatment (45 each sampling date). The soil properties analysed were soil pH, soil organic matter (SOM), mean weight diameter (MWD) to express aggregate stability, and soil water repellency (SWR) measured with water drop penetration time method (WDPT) in different fractions (2 &amp;#8211; 1 mm; 1 &amp;#8211; 0.5 mm, 0.5 &amp;#8211; 0.25 mm, and &lt;0.25 mm). Soil pH was not significantly different among sampling dates and treatments. SOM was significantly different among sampling dates for &lt;em&gt;Olea europeae&lt;/em&gt; treatment and control. &lt;em&gt;Olea europeae&lt;/em&gt; treatment had a significantly higher SOM then &lt;em&gt;Pinus halepensis&lt;/em&gt; and control treatment. MWD was significantly higher within &lt;em&gt;Olea europeae&lt;/em&gt; treatment. Within &lt;em&gt;Pinus halepensis&lt;/em&gt; and control treatment no significant difference was observed. The soil was classified as slightly water repellent (5 &amp;#8211; 60 seconds) in &lt;em&gt;Olea europeae&lt;/em&gt; soil finer fraction (0.5 &amp;#8211; 0.25 mm and &lt;0.25) in both sampling dates. In &lt;em&gt;Pinus halepensis&lt;/em&gt; treatments and control, soil was wettable (&lt;5 seconds), and no significant difference was observed among sampling date. Future sampling and analysis will be conducted during one year to estimate the effect of &lt;em&gt;Olea europeae&lt;/em&gt; and &lt;em&gt;Pinus halepensis&lt;/em&gt; mulch on soil properties.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords: &lt;/strong&gt;Wildfire, &lt;em&gt;Olea europeae&lt;/em&gt;&lt;strong&gt;, &lt;/strong&gt;&lt;em&gt;Pinus halepensis&lt;/em&gt;, mulch.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgments&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;This work was supported by Croatian Science Foundation through the project &quot;Influence of Summer Fire on Soil and Water Quality&amp;#8221; (IP-01-2018-1645).&lt;/p&gt;

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