Combining PSII photochemistry and hydraulics improves predictions of photosynthesis and water use from mild to lethal drought.

Rising temperatures and increases in drought negatively impact the efficiency and sustainability of both agricultural and forest ecosystems. Although hydraulic limitations on photosynthesis have been extensively studied, a solid understanding of the links between whole plant hydraulics and photosynthetic processes at the cellular level under changing environmental conditions is still missing, hampering our predictive power for plant mortality. Here, we examined plant hydraulic traits and CO2 assimilation rate under progressive water limitation by implementing Photosystem II (PSII) dynamics with a whole plant process model (TREES). The photosynthetic responses to plant water status were parameterized based on measurements of chlorophyll a fluorescence, gas exchange and water potential for Brassica rapa (R500) grown in a greenhouse under fully watered to lethal drought conditions. The updated model significantly improved predictions of photosynthesis, stomatal conductance and leaf water potential. TREES with PSII knowledge predicted a larger hydraulic safety margin and a decrease in percent loss of conductivity. TREES predicted a slower decrease in leaf water potential, which agreed with measurements. Our results highlight the pressing need for incorporating PSII drought photochemistry into current process models to capture cross-scale plant water dynamics from cell to whole plant level.

Local temperature responses to actual land cover changes present significant latitudinal variability and asymmetry.

Land cover changes (LCCs) affect surface temperatures at local scale through biophysical processes. However, previous observation-based studies mainly focused on the potential effects of virtual afforestation/deforestation using the space-for-time assumption, while the actual effects of all types of realistic LCCs are underexplored. Here, we adopted the space-and-time scheme and utilized extensive high-resolution (1-km) satellite observations to perform the first such assessment. We showed that, from 2006 to 2015, the average temperature in the areas with LCCs increased by 0.08 K globally, but varied significantly across latitudes, ranging from -0.05 to 0.18 K. Cropland expansions dominated summertime cooling effects in the northern mid-latitudes, whereas forest-related LCCs caused warming effects elsewhere. These effects accounted for up to 44.6% of overall concurrent warming, suggesting that LCC influences cannot be ignored. In addition, we revealed obvious asymmetries in the actual effects, i.e., LCCs with warming effects occurred more frequently, with stronger intensities, than LCCs with cooling effects. Even for the mutual changes between two covers in the same region, warming LCCs generally had larger magnitudes than their cooling counterparts due to asymmetric changes in transition fractions and driving variables. These novel findings, derived from the assessment of actual LCCs, provide more realistic implications for land management and climate adaptation policies.

[Phase Separation of Purified Human LSM4 Protein].

Liquid-liquid phase separation of proteins occur in a number of biological processes, such as regulation of transcription, processing, and RNA maturation. Sm-like protein 4 (LSM4) is involved in multiple processes, including pre-mRNA splicing and P-bodies assembly. Before investigating the involvement of LSM4 in the separation of the two liquid phases during RNA processing or maturation, the separation of the liquid phases in an in vitro preparation of LSM4 protein should be first be detected. The mCherry-LSM4 plasmid was derived from pET30a and used to isolate mCherry-LSM4 protein from prokaryotic cells (Escherichia coli strain BL21). The mCherry LSM4 protein was purified using Ni-NTA resin. The protein was further purified by fast protein liquid chromatography. Delta-Vision wide-field fluorescence microscopy was used to observe the dynamic liquid-liquid phase separation of the LSM4 protein in vitro. Analysis of the LSM4 protein structure using the Predictor of Natural Disordered Regions database revealed that its C-terminus contains a low complexity domain. A purified preparation of full-length human LSM4 protein was obtained from E. coli. Human LSM4 was shown to provide concentration-dependent separation of liquid-liquid phases in vitro in buffer with crowding reagents. Salts in high concentration and 1,6-hexanediol block the LSM4-induced separation of the two liquid phases. In addition, in vitro fusion of LSM4 protein droplets is observed. The results suggest that full-length human LSM4 protein can undergo liquid-liquid phase separation in vitro.

Land use and land cover changes and their impacts on surface-atmosphere interactions in Brazil: A systematic review.

Major land use and land cover changes (LULCC) have taken place in Brazil, including large scale conversion of forest to agriculture. LULCC alters surface-atmosphere interactions, changing the timing and magnitude of energy fluxes, impacting the partitioning of available energy, and therefore the climate and water balance. The objective of this work was to provide a detailed analysis of how LULCC has affected surface-atmosphere interactions over the Brazilian territory, particularly focusing on impacts on precipitation (P), evapotranspiration (ET), and atmospheric humidity (h). Our systematic review yielded 61 studies, with the Amazon being the most studied biome followed by the Cerrado. P was the most analyzed variable, followed by ET. Few papers analyzed LULCC impacts on h. For the Amazon biome, decreasing dry season P and in annual ET were reported. In the Cerrado biome, decreasing P in the wet and dry seasons and decreasing dry season ET were the most common result. For the Atlantic Forest biome, increasing annual P and increasing wet season ET, likely due to reforestation, were reported. Few studies documented LULCC impacts on surface-atmosphere interactions over the Brazilian biomes Caatinga, Pantanal and Pampa. Therefore, new research is needed to assess impacts of LULCC on these biomes, including assessments of atmospheric moisture recycling, and interactions of LULCC with global climate and climate extremes including droughts.

Investigation of the climatological impacts of agricultural management and abandonment on a boreal bog in western Newfoundland, Canada.

We compared greenhouse gas (GHG) fluxes and albedo of a pristine boreal bog and an adjacent abandoned peatland pasture in western Newfoundland, Canada to estimate the magnitude of radiative forcing (RF) created by agricultural drainage and abandonment. Our results indicated that these anthropogenic activities induced a climate cooling effect (negative RF), with the magnitude of the RF caused by the albedo change comparable to that induced by altered GHGs. Although the albedo-induced RF was positive in winter and negative in summer, the summer effect dominated because of greater solar radiation received. The climate cooling effect of GHGs change was due to an increase in the carbon dioxide sink capacity and a reduction in methane emissions under lower water table levels following agricultural drainage and abandonment. Calculation of sustained-flux global warming/cooling potentials also supported this finding. Our results show that the overall increase in albedo resulting from agricultural drainage and abandonment contributes significantly to the negative RF, strengthening the cooling effect due to the changing GHG fluxes. Therefore, changes in albedo due to altered vegetation coverage and hydrology and GHG fluxes should be considered when assessing the climatic impacts from land-use change in northern peatland.