Vascular optimality dictates plant morphology away from Leonardo's rule.

Metabolic scaling theory (MST) provides an understanding of scaling in organismal morphology. Empirical data on the apparently universal pattern of tip-to-base conduit widening across vascular plants motivate a set of generalized MST (gMST) relationships allowing for variable rates of conduit coalescence and taper and a transition between transport and diffusive domains. Our model, with coalescence limited to the distalmost part of the conductive system, reconciles previous MST-based models and extends their applicability to the entire plant. We derive an inverse relationship between stem volume taper and conduit widening, which implies that plant morphology is dictated by vascular optimality and not the assumption of constant sapwood area across all branching levels, contradicting Leonardo's rule. Thus, energy efficiency controls conduit coalescence rate, lowering the carbon cost needed to sustain the vascular network. Our model shows that as a plant grows taller, it must increase conduit widening and coalescence, which may make it more vulnerable to drought. We calculated how our gMST model implies a lower carbon cost to sustain a similar network compared to previous MST-based models. We also show that gMST predicts the cross-sectional area of vessels and their frequency along the relative length better than previous MST models for a range of plant types. We encourage further research obtaining data that would allow testing other gMST predictions that remain unconfirmed empirically, such as conduit coalescence rate in stems. The premise of energy efficiency can potentially become instrumental to our understanding of plant carbon allocation.

Standardizing Ecosystem Morphological Traits from 3D Information Sources.

3D-imaging technologies provide measurements of terrestrial and aquatic ecosystems' structure, key for biodiversity studies. However, the practical use of these observations globally faces practical challenges. First, available 3D data are geographically biased, with significant gaps in the tropics. Second, no data source provides, by itself, global coverage at a suitable temporal recurrence. Thus, global monitoring initiatives, such as assessment of essential biodiversity variables (EBVs), will necessarily have to involve the combination of disparate data sets. We propose a standardized framework of ecosystem morphological traits - height, cover, and structural complexity - that could enable monitoring of globally consistent EBVs at regional scales, by flexibly integrating different information sources - satellites, aircrafts, drones, or ground data - allowing global biodiversity targets relating to ecosystem structure to be monitored and regularly reported.

Sunflower (Helianthus annuus) variability in antioxidant enzyme defenses.

In order to investigate the existence of genetic variability in antioxidant enzyme defenses in sunflower, twelve inbred lines, six cytoplasmic male-sterile and six restorer lines, commonly used in breeding programs have been compared with respect to (a) their levels of constitutive superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2) and guaiacol-dependent peroxidase (GPX, EC 1.11.1.7), and (b) their isoenzyme polymorphism in SOD, CAT, and GPX activities. Constitutive levels of antioxidant enzymes in the 2nd leaf pair of 15-20-day-old sunflower plants showed significant differences between lines. The ranges of variation in enzyme activities of the different lines were equivalent to 34.3% (CAT), 38.2% (SOD), 59.5% (APX), 60.0% (GR), and 62.9% (GPX) of the respective maximal values. Isoenzyme profiles of CAT, GPX and SOD revealed the existence in sunflower of at least three, six and four isoforms of these enzymes, respectively. Further characterization of SOD isoenzymes revealed that no isoenzyme corresponded to a Mn-SOD, the faster moving isoform being a Cu/Zn-SOD and the remainder three Fe-SODs. Among the twelve inbred sunflower lines studied there were ample qualitative, and sometimes quantitative too, differences in isoenzyme dotation of CAT, GPX and Fe-SOD.

Acute poststreptococcal glomerulonephritis. A review of recent developments.

This revision is concerned with controversial aspects of the etiopathogenesis of acute poststreptococcal glomerulonephritis (APSGN) and with recently published clinical, serologic, immunohistologic and prognostic data. The putative nephritogenic antigens in group A streptococcus are discussed and the pathogenetic alternatives of exogenous (streptococcal) versus autologous (streptococcal-induced) immune complex (IC) disease are analyzed. The possible role of antiglobulins is reviewed in the light of the work that shows high titers of rheumatoid factor activity in the serum, as early as the first day of clinical APSGN, and glomerular-fixed anti-IgG in the biopsies of these patients. Circulating IC have been documented to be more frequent in the first week of the disease (2/3 of patients) that at a later date. Cryoglobulins are present in most cases tested in the first week, and elevation of serum IgG and IgM levels is found in over 90% of the patients. From the immunohistologic viewpoint, emphasis is made in recent work indicating IgG localization in the dermal papillae of uninvolved skin, which may be of potential diagnostic significance. Review of the published data on the prognosis of APSGN suggest that this issue is far from settled. Attention is called to the fact that the conflicting opinions may reflect different interpretations of possibly not too different data.

Kinetic properties of phenylalanine ammonia-lyase from sunflower (Helianthus annuus L.) hypocotyls.

Phenylalanine ammonia-lyase (PAL) from sunflower hypocotyls has been partially purified by selective precipitation with ammonium sulfate and molecular gel filtration on Sephacryl S-300. Kinetic assays carried out with this partially purified PAL preparation revealed that the enzyme did not show a homogeneous kinetic behaviour. The observed kinetic pattern and parameters (Km and Vmax) depended on the assay conditions used and the protein concentration added to the assay mixture. PAL displayed Michaelian or negative cooperativity kinetics. Such behaviour can be explained by the existence of an association-dissociation process of PAL-protein subunits. The presence of mono-, tri- and tetrameric forms of PAL has been assessed by molecular gel filtration on Sephacryl S-200, using different elution conditions.