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1. Resolving the contrasting leaf hydraulic adaptation of C₃ and C₄ grasses

   https://doi.org/10.1111/nph.20341  

   Baird, Alec S; Taylor, Samuel H; Pasquet‐Kok, Jessica; Vuong, Christine; Zhang, Yu; Watcharamongkol, Teera; Cochard, Hervé; Scoffoni, Christine; Edwards, Erika J; Osborne, Colin P; et al (March 2025, New Phytologist)

   Summary Grasses are exceptionally productive, yet their hydraulic adaptation is paradoxical. Among C₃grasses, a high photosynthetic rate (A_area) may depend on higher vein density (D_v) and hydraulic conductance (K_leaf). However, the higherD_vof C₄grasses suggests a hydraulic surplus, given their reduced need for highK_leafresulting from lower stomatal conductance (g_s).Combining hydraulic and photosynthetic physiological data for diverse common garden C₃and C₄species with data for 332 species from the published literature, and mechanistic modeling, we validated a framework for linkages of photosynthesis with hydraulic transport, anatomy, and adaptation to aridity.C₃and C₄grasses had similarK_leafin our common garden, but C₄grasses had higherK_leafthan C₃species in our meta‐analysis. Variation inK_leafdepended on outside‐xylem pathways. C₄grasses have highK_leaf : g_s, which modeling shows is essential to achieve their photosynthetic advantage.Across C₃grasses, higherA_areawas associated with higherK_leaf, and adaptation to aridity, whereas for C₄species, adaptation to aridity was associated with higherK_leaf : g_s. These associations are consistent with adaptation for stress avoidance.Hydraulic traits are a critical element of evolutionary and ecological success in C₃and C₄grasses and are crucial avenues for crop design and ecological forecasting. 

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2. Reduced global plant respiration due to the acclimation of leaf dark respiration coupled with photosynthesis

   https://doi.org/10.1111/nph.19355  

   Ren, Yanghang; Wang, Han; Harrison, Sandy P; Prentice, I Colin; Atkin, Owen K; Smith, Nicholas G; Mengoli, Giulia; Stefanski, Artur; Reich, Peter B (January 2024, New Phytologist)

   Summary Leaf dark respiration (R_d) acclimates to environmental changes. However, the magnitude, controls and time scales of acclimation remain unclear and are inconsistently treated in ecosystem models.We hypothesized thatR_dand Rubisco carboxylation capacity (V_cmax) at 25°C (R_d,25,V_cmax,25) are coordinated so thatR_d,25variations supportV_cmax,25at a level allowing full light use, withV_cmax,25reflecting daytime conditions (for photosynthesis), andR_d,25/V_cmax,25reflecting night‐time conditions (for starch degradation and sucrose export). We tested this hypothesis temporally using a 5‐yr warming experiment, and spatially using an extensive field‐measurement data set. We compared the results to three published alternatives:R_d,25declines linearly with daily average prior temperature;R_dat average prior night temperatures tends towards a constant value; andR_d,25/V_cmax,25is constant.Our hypothesis accounted for more variation in observedR_d,25over time (R² = 0.74) and space (R² = 0.68) than the alternatives. Night‐time temperature dominated the seasonal time‐course ofR_d, with an apparent response time scale ofc.2 wk.V_cmaxdominated the spatial patterns.Our acclimation hypothesis results in a smaller increase in globalR_din response to rising CO₂and warming than is projected by the two of three alternative hypotheses, and by current models. 

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3. Group 13 ion coordination to pyridyl breaks the reduction potential vs hydricity scaling relationship for NADH models

   https://doi.org/10.1039/d3sc03806h  

   Parsons, Leo_W T; Fettinger, James C; Berben, Louise A (December 2023, Chemical Science)

   The relationshipE_pvs. ΔG_H− correlates the applied potential (E_p) needed to drive organohydride formation with the strength of the hydride donor that is formed: hydride transfer catalysis - as in enzymes like LarA - will be more energy efficient ifE_pis shifted anodically using kinetic effect. 

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4. Crystal structure and characterization of a new one-dimensional copper(II) coordination polymer containing a 4-aminobenzoic acid ligand

   https://doi.org/10.1107/S2056989024001336  

   Gogia, Alisha; Novikov, Egor M.; Guzei, Ilia A.; Fonari, Marina S.; Timofeeva, Tatiana V. (March 2024, Acta Crystallographica Section E Crystallographic Communications)

   A Cu^IIcoordination polymer,catena-poly[[[aquacopper(II)]-bis(μ-4-aminobenzoato)-κ²N:O;κ²O:N] monohydrate], {[Cu(pABA)₂(H₂O)]·H₂O}_n(pABA =p-aminobenzoate, C₇H₄NO₂⁻), was synthesized and characterized. It exhibits a one-dimensional chain structure extended into a three-dimensional supramolecular assembly through hydrogen bonds and π–π interactions. While the twinned crystal shows a metrically orthorhombic lattice and an apparent space groupPbcm, the true symmetry is monoclinic (space groupP2/c), with disordered Cu atoms and mixed roles of water molecules (aqua ligand/crystallization water). The luminescence spectrum of the complex shows an emission at 345 nm,cf.349 nm forpABAH. 

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5. Constraining the H ₂ column densities in the diffuse interstellar medium using dust extinction and H I data

   https://doi.org/10.1051/0004-6361/202347968  

   Skalidis, R; Goldsmith, P F; Hopkins, P F; Ponnada, S B (February 2024, Astronomy & Astrophysics)

   Context. Carbon monoxide (CO) is a poor tracer of H₂in the diffuse interstellar medium (ISM), where most of the carbon is not incorporated into CO molecules, unlike the situation at higher extinctions. Aims. We present a novel, indirect method for constraining H₂column densities (N_H2) without employing CO observations. We show that previously recognized nonlinearities in the relation between the extinction,A_V(H₂), derived from dust emission and the H Icolumn density (N_H I) are due to the presence of molecular gas. Methods. We employed archival (N_H2) data, obtained from the UV spectra of stars, and calculatedA_V(H₂) toward these sight lines using 3D extinction maps. The following relation fits the data: logN_H2= 1.38742 (logA_V(H₂)⁾³− 0.05359 (logA_V(H₂)⁾²+ 0.25722 logA_V(H₂) + 20.67191. This relation is useful for constrainingN_H2in the diffuse ISM as it requires onlyN_H Iand dust extinction data, which are both easily accessible. In 95% of the cases, the estimates produced by the fitted equation have deviations of less than a factor of 3.5. We constructed aN_H2map of our Galaxy and compared it to the CO integrated intensity (W_CO) distribution. Results. We find that the average ratio (X_CO) betweenN_H2andW_COis approximately equal to 2 × 10²⁰cm⁻²(K km s⁻¹)⁻¹, consistent with previous estimates. However, we find that theX_COfactor varies by orders of magnitude on arcminute scales between the outer and the central portions of molecular clouds. For regions withN_H2≳ 10²⁰cm⁻², we estimate that the average H₂fractional abundance,f_H2= 2N_H2/(2N_H2+N_H I), is 0.25. Multiple (distinct) largely atomic clouds are likely found along high-extinction sightlines (A_V≥ 1 mag), hence limitingf_H2in these directions. Conclusions. More than 50% of the lines of sight withN_H2≥ 10²⁰cm⁻²are untraceable by CO with aJ= 1−0 sensitivity limitW_CO= 1 K km s⁻¹. 

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