Transport processes in stimulated and non-stimulated leaves of Mimosa pudica

Summary Using energy-dispersive X-ray microanalysis, the concentrations of ions, especially potassium and chlorine, were determined in different tissues of primary and tertiary pulvini of Mimosa pudica. It was shown that stimulating the leaf was followed by ion displacements which were most striking in the outer extensor cells, resulting in turgor loss. Since Ca concentration remains relatively constant in cell walls of collapsed cells, the changes of K concentration are best described by the K:Ca ratio. After stimulation the K:Ca ratio dropped in the outer extensor of the primary pulvinus from 775.3 to 2.37 in the cytoplasm, and from 542.2 to 9.25 in the cell wall. Changes in chlorine content were less striking in the primary pulvinus. The KCl ratios in some cases were lower than 1.0, which indicates that Cl content can increase, while K content is diminished. In the non-stimulated tertiary pulvini the outer extensor cells show high concentrations of Cl, but much lower Cl concentrations were found after stimulation. In contrast to the primary pulvinus the K content of the tertiary pulvini is very low. In the vascular tissues of both primary and tertiary pulvini stimulation is followed by a release of K and Cl out of the sieve element cytoplasm into the apoplast. K then appears accumulated in the cell walls of the collenchymatous tissue. These displacements lead to the assumption that the collenchymatous apoplast temporarily functions as a reservoir for K and to a lesser extent for Cl. With regard to the mechanism of leaf movement after stimulation, the accumulation of ions in the apoplast seems to be initiated by the decrease of water potential triggered by an apoplastic accumulation of unloaded sucrose (Fromm and Eschrich 1988a). The resulting turgor release in the outer extensor is accompanied by an efflux of ions.Supported by the Deutsche Forschungsgemeinschaft     

An analytical model of memristors in plants

The memristor, a resistor with memory, was postulated by Chua in 1971 and the first solid-state memristor was built in 2008. Recently, we found memristors in vivo in plants. Here we propose a simple analytical model of 2 types of memristors that can be found within plants. The electrostimulation of plants by bipolar periodic waves induces electrical responses in the Aloe vera and Mimosa pudica with fingerprints of memristors. Memristive properties of the Aloe vera and Mimosa pudica are linked to the properties of voltage gated K⁺ ion channels. The potassium channel blocker TEACl transform plant memristors to conventional resistors. The analytical model of a memristor with a capacitor connected in parallel exhibits different characteristic behavior at low and high frequency of applied voltage, which is the same as experimental data obtained by cyclic voltammetry in vivo.     

Host specificity and biology ofHeteropsylla spinulosa [Hom.: Psyllidae] introduced into Australia and Western Samoa for the biological control ofMimosa invisa

The biology and host specificity of the psyllidHeteropsylla spinulosa Muddiman, Hodkinson & Hollis collected fromMimosa invisa Von Martius, was studied in Brazil and in Australia. Oviposition was recorded on 19 of 100 plant species tested but nymphs died without feeding, except onM. invisa. H. spinulosa was shown to be specific toM. invisa and was subsequently released and established in Australia and Western Samoa.      

Isolation and properties of a lectin from the seeds ofMimosa invisa L.

A lectin has been purified from the seeds ofMimosa invisa L. by gel filtration and preparative Polyacrylamide gel electrophoresis. The purified lectin was homogeneous as judged by analytical Polyacrylamide gel electrophoresis, immunodiffusion and Immunoelectrophoresis. The apparent molecular weight is 100,000; the protein is a tetramer with two types of subunits (molecular weight 35,000 and 15,000). The lectin is a glycoprotein with approximately 21% carbohydrate and interacts with Sephadex and concanavalin A-Sepharose. It agglutinates erthrocytes non-specifically, does not agglutinate leucocytes and is not mitogenic, agglutinates Mimosa-nodulatingRhizobium and is a panagglutinin; the agglutination is not inhibited by several simple sugars. It is thermo-stable and has no metal ions.     

Some observations on the present distribution and conservation of Alouatta and Ateles in Southern Mexico

Some information on the past and present distribution of Alouatta and Ateles in southern Mexico and on the impact of habitat destruction on their future existence is presented. Three surveys of primate populations and forest habitats were carried out between 1981 and 1983 in southeastern Mexico. Rapid destruction of the forest is reducing the number of forested areas where Alouatta and Ateles can exist and co-occur. Illegal hunting of the two primates also contributes to their rapid decline. Alouatta and Ateles live a precarious existence in a few large and small islands of forest, and efforts are needed to set aside some of these areas as reserves so that their future survival is ensured.     

IAA-induced hyperpolarization of the membrane potential in isolated cells fromMimosa pulvinus

Upon treatment with 10⁻⁴ M IAA the membrane potential of an isolated cell from the main pulvinus, ofMimosa pudica L. depolarized by about 6 mV in 2–5 min, but later it gradually hyperpolarized by about 30 mV. The membrane potential of a motor cell in the main pulvinar tissue hyperpolarized by about 80 mV 1 hr after application of 10⁻⁴ M IAA.     

The effect of manual defoliation and Macaria pallidata (Geometridae) herbivory on Mimosa pigra: Implications for biological control

Trials were conducted to test the effects of artificial defoliation and defoliation by Macaria pallidata (Warren) (Geometridae) larvae on the invasive weed Mimosa pigra L. Herbivory is generally thought to be detrimental to plant fitness but it is well documented that many plants can increase growth rates or reproduction to compensate for damage. The compensatory ability of an invasive plant has implications for the potential success of defoliating biocontrol agents. Mimosa compensated for 25% manual defoliation, but at 50% and 100% defoliation levels plants suffered a significant reduction in growth rate, height, stem diameter, and biomass. Defoliation by one cohort of macaria larvae, at densities of eight larvae per plant, significantly reduced growth rates and plant height after 1 week. There were no differences between the effects of macaria larvae and manually simulated defoliation. These results suggest that defoliating biocontrol agents can have a valuable role in mimosa control programs.     

Chloride ion efflux during an action potential in the main pulvinus ofMimosa pudica

The shortening, action potential and Cl⁻-efflux of the excised lower half cortex in the main pulvinus ofMimosa pudica were simultaneously recorded. The mean values±(S.E.) for Cl⁻-efflux and shortening were 183±18 picomoles/mg fresh weight/impulse and 87.0±2.2 μm, respectively.