Soil-plant water relations, root distribution and biomass partitioning in Lupinus albus L. under drought conditions

Lupinus albus L. from different climatic origins responded toa 15 d period of water shortage during flowering by losing 50%of the total leaf canopy and gaining 55% in stem dry weight.Water deficits also led to a significant increase in the fineroot length density and a slight increase in the fine root dryweight. The latter increase was especially pronounced in thedeeper soil layers. Some marginal differences among genotypeswere observed in the responses. Stomatal closure by midday wasan early response to water deficit, giving rise to constantpredawn leaf water potentials during the first week of watershortage in spite of a decrease of 60% in the available soilwater. No osmotic regulation or adjustments of the cell wallproperties were observed in any of the lupin lines. We explainedthe maintenance of seed production in water-stressed plantsby their ability to accumulate assimilates in the shoot, whichwould be diverted to the pods during the seed filling stage. Key words: Biomass partitioning, drought, Lupinus albus, root distribution, water relations.     

Parasitic deuteromycetes from South Brazil

Summary This paper deals with four new fungi from the State of Rio Grande do Sul, Brazil.Phaeseptoria stenocalycis Batista, Upadhyay &Da Costa Netto, collected on leaves ofStenocalyx dasyblastus Bert. from Grammado,Phoma jasmino-macrospora Batista, Upadhyay &Da Costa Netto, collected on leaves ofJasminum flexicaule Vahl. from Pôrto Alegre,Melanconium argutidentis Batista, Upadhyay &Da Costa Netto, collected on leaves ofSebastiana argutidens Pex &K. Hoff from Grammado andCercospora caleifoleii Batista, Upadhyay &Da Costa Netto, collected on leaves ofCalea pinnatifida Banks from Pôrto Alegre are described here.Symptoms on the hosts and morphological characters of the fruitings and spores are described and illustrated.Publicação no 456 of IMUFP.     

Alterations in carbon and nitrogen metabolism induced by water deficit in the stems and leaves of Lupinus albus L.

Water deficit (WD) in Lupinus albus L. brings about tissue-specific responses that are dependent on stress intensity. Carbohydrate metabolism is very sensitive to changes in plant water status. Six days from withholding water (DAW), sucrose, glucose and fructose levels of the leaf blade had already increased over 5-fold, and the activities of SS and INV(A) had increased c. 1.5-2 times. From 9 DAW on, when stress intensity was more pronounced, these effects were reversed with fructose and glucose concentrations as well as INV(A) activity dropping in parallel. The stem (specifically the stele) responded to the stress intensification with striking increases in the concentration of sugars, N and S, and in the induction of thaumatin-like-protein and an increase in chitinase and peroxidase. At 13 DAW, the plants lost most of the leaves but on rewatering they fully recovered. Thus, the observed changes appear to contribute to a general mechanism of survival under drought, the stem playing a key role in that process.     

Intergeneric Coaggregation among Drinking Water Bacteria: Evidence of a Role for Acinetobacter calcoaceticus as a Bridging Bacterium

Intergeneric coaggregation of drinking water bacteria was tested. Acinetobacter calcoaceticus was found not only to autoaggregate but also to coaggregate with four of the five other isolates (Burkholderia cepacia, Methylobacterium sp., Mycobacterium mucogenicum, Sphingomonas capsulata, and Staphylococcus sp.). In its absence, no coaggregation was found. Interactions were lectin-saccharide mediated. The putative bridging function of A. calcoaceticus was evidenced by multispecies biofilm studies, through a strain exclusion process.     

Competitive interactions and partial displacement of Anastrepha obliqua by Ceratitis capitata in the occupation of host mangoes (Mangifera indica)

1. We examined the competitive interactions between a native fruit fly species (Anastrepha obliqua Macquart) and the invasive medfly (Ceratitis capitata Wiedemann) when these co-occur on a shared mango fruit host (Mangifera indica L.).
2. Using mango fruits of distinct levels of ripeness, we investigated both competition among larvae and among adult females for oviposition. We quantified competition by the numbers of eggs laid and the intensity of agonistic interactions between adult females.
3. Interactions between immature fruit flies led to reduced size and number of emerged adults of both species. These impacts were felt more acutely in the native species.
4. Interspecific competition between females led to fewer eggs laid on semi-ripe fruit by both species, which may be the result of niche overlap associated with oviposition.
5. Intraspecific interactions between A. obliqua individuals led to intense agonistic behaviour, with a concurrent decrease in number of landings on these host fruits.
6. These results suggest that the native species undergoes a partial niche displacement when facing the invasive species. A portion of the fundamental niche of A. obliqua remained unoccupied by the invading C. capitata, which may allow their coexistence under natural conditions.

     

Effect of exogenous application of gibberellic acid on color change and phenylalanine ammonia-lyase, chlorophyllase, and peroxidase activities during ripening of strawberry fruit (Fragaria x ananassa Duch.)

The effect of exogenously applied gibberellic acid (GA₃) on the postharvest color change of strawberry fruit was evaluated through their external color and surface color parameters. A significant delay on color evolution was observed in fruits treated with GA₃. The evolution of activities of phenylalanine ammonia-lyase (PAL), chlorophyllase, and peroxidase was also analyzed. PAL activity increased during strawberry ripening, but in fruits treated with GA₃ the increase in such activity was slower, and, probably as consequence, the development of red color was delayed. Moreover, the activity of chlorophyllase and peroxidase, enzymes possibly involved in chlorophyll metabolism, decreased during strawberry ripening. However, a delay was observed in the decrease of such activities in GA₃-treated fruits.Abbreviations PAL phenylalanine ammonia-lyase - GA₃ gibberellic acid₃ - PVPP polyvinylpolyprrolidone - CEAU chlorophyllase enzymic activity unit - PEAU peroxidase enzymic activity unit - LSD least significant difference. Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) de la República Argentina. Author for correspondence.Members of the Research Career of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) de la República Argentina.     

Membrane voltage as a dynamic platform for spatiotemporal signaling,physiological, and developmental regulation

Membrane voltage arises from the transport of ions through ion-translocating ATPases, ion-coupled transport of solutes, and ion channels, and is an integral part of the bioenergetic “currency” of the membrane. The dynamics of membrane voltage—so-called action, systemic, and variation potentials—have also led to a recognition of their contributions to signal transduction, both within cells and across tissues. Here, we review the origins of our understanding of membrane voltage and its place as a central element in regulating transport and signal transmission. We stress the importance of understanding voltage as a common intermediate that acts both as a driving force for transport—an electrical “substrate”—and as a product of charge flux across the membrane, thereby interconnecting all charge-carrying transport across the membrane. The voltage interconnection is vital to signaling via second messengers that rely on ion flux, including cytosolic free Ca²⁺, H⁺, and the synthesis of reactive oxygen species generated by integral membrane, respiratory burst oxidases. These characteristics inform on the ways in which long-distance voltage signals and voltage oscillations give rise to unique gene expression patterns and influence physiological, developmental, and adaptive responses such as systemic acquired resistance to pathogens and to insect herbivory.

Membrane voltage serves as a platform coordinating ion flux to transmit and transduce biological signals.

Advances

• The biophysics of transport that determine membrane voltage are well-described with quantitative flux equations.
• In the models of the guard cell and the giant algae Chara and Nitella these charge-transporting processes accurately describe and predict physiological behavior, including the coupling of membrane voltage oscillations with ion flux, [Ca²⁺]_i, pH, their consequences for cellular osmotic adjustments, and their spatial propagation.
• Unlike neuronal and other animal tissues, action potentials in plants are mediated by a temporal sequence of ion flux through Ca²⁺ and Cl^- channels with voltage recovery driven by ion flux through K⁺ channels. The interplay of channel-mediated ion flux and changes in H⁺-ATPase activity are likely responsible for the slower propagation of variation and systemic potentials.
• In terrestrial plants, membrane voltage transients may propagate along vascular traces, both through the parenchymal cells lining the xylem and through the phloem. Propagation of such voltage transients is associated with glutamate receptor-like channels that may contribute to plasma membrane Ca²⁺ flux and [Ca²⁺]_i elevations.
• Changes in [Ca²⁺]_i, pH, and reactive oxygen species are key mediators that translate voltage signals into physiological, developmental, and adaptive responses in plant tissues.

     

Dichloromethane as an economic alternative to chloroform in the extraction of DNA from plant tissues

Processing of large numbers smaples of plant tissue samples for molecular mapping and gene tagging requires methods that are quick, simple, and cheap, and that eventually can be automated. Organic solvents used for DNA extraction can represent a significant proportion of the overall cost. In this study we examined dichloromethane as a replacement for chloroform to be used in combination with phenol.     

Studies on the interaction between HSA and new halogenated metformin derivatives: influence of lipophilic groups in the binding ability

Abstract

In the type II diabetes mellitus, Metformin hydrochloride is recommended as a common FAD approved drug. Synthesis of novel metformin series has been widely explored, mainly due to its biological importance and to improve their pharmacokinetic profile. Generally, human serum albumin (HSA) is the main protein used to study drug viability in vitro analysis. Thus, the present study reports the synthesis of three new halogenated metformin derivatives (MFCl, MFBr and MFCF₃) and its interaction toward HSA by multiple spectroscopic techniques (UV-Vis, circular dichroism, steady-state, time-resolved and synchronous fluorescence), combined to computational methods (molecular docking and quantum chemical calculation). The interaction between each halogenated metformin derivative and HSA is spontaneous (ΔG°<0), entropically driven (ΔS°>0), moderate (K_a and K_b ≈ 10⁴ M^?1) and occurs preferentially in the subdomain IIA (close to Trp-214 residue). Molecular docking results suggested hydrogen bonding, van der Waals and hydrophobic interactions as the main binding forces. Quantum chemical calculations suggested imino groups as the most intense electrostatic negative potentials, while the positive electrostatic potential is located at the hydrogen atoms on N,N-dimethyl and the phenyl systems which can help the hydrophobic interactions.

Communicated by Ramaswamy H. Sarma