Transfer of nitrogen from damaged roots of white clover (Trifolium repens L.) to closely associated roots of intact perennial ryegrass (Lolium perenne L)

An experiment is described in which the magnitude of N transferred from damaged white clover roots to perennial ryegrass was determined, using ¹⁵N labelling of the grass plant. There was no effect on the growth and N-fixation of the clover plants after removing part of the root system. The ¹⁵N data suggested that N had been acquired by all grass plants, even in plants grown alone with no further N supplied after labelling. However, after quantifying the mobile and stored N pools of the grass plants it was evident that significant transfer of N from clover to grass only took place from damaged clover roots. Dilution of the atom% ¹⁵N in the roots of the grass plants grown alone, and in association with undamaged clover roots, was explained by remobilisation of N within the plant.     

The effect of root damage caused by simulated white grub attack on the growth,yield and water-use of groundnut plants

White grubs (larval scarabaeids) are now recognized as being important pests of groundnut (peanut) in many parts of the world because of their ability to damage roots. A method of simulating white grub damage to groundnut plants was developed to obtain an indication of how the feeding activity of these insects influences plant growth. The effect of root cutting and drought stress on water uptake and biomass production was evaluated, with roots being cut at three depths in the late vegetative and early podfilling stages. As groundnut plants are often grown under conditions of drought stress, the effects of which would be accentuated by root damage, this factor was introduced into the experiment. Plant water-use measurements indicated that the root systems of plants cut 30 days after emergence (DAE) and watered twice a week became fully functional again after 40 days. Pod and total biomass production were however significantly less than those of the uncut control plants, with drought stress reducing yields below the well-watered controls, particularly when cut at 10 cm below the soil surface. The root systems of plants cut 51 DAE did not regrow to any appreciable extent, and rates of plant water-use remained less than half of the uncut control plants. Over all treatments, there was a strong positive correlation between total (and pod) biomass and plant water-use. It was concluded that the phenological stage of the plant at which root damage occurred had a profound influence on the subsequent recovery in root growth and function, and ultimately on pod yield.     

Early reproduction and increased reproductive allocation in metal-adapted populations of the terrestrial isopod Porcellio scaber

Organisms inhabiting metal-contaminated areas can be stressed by metal exposure and are possibly subject to selection, resulting in increased metal tolerance and changes in growth and/or reproduction characteristics. In a previous study it was found that in the terrestrial isopod Porcellio scaber, sampled from the vicinity of a zine smelter, the body size was small and the brood size was large compared to isopods from a reference area. To assess whether these differences were due to genetic differentiation between strains, isopods collected from a reference wood, a zinc smelter area and a lead mine were cultured on non-polluted food, while growth, reproduction and metal concentrations were studied in first and second laboratory generations. The isopods from the three populations differed in age and weight at first reproduction, although there were hardly any differences in growth. The females of the mine and the smelter population started to reproduce earlier, at a lower weight, which resulted in fewer young per female. However, reproductive allocation (=wight of young relative to the weight of the mother) was higher in mine and smelter isopods. We conclude that the isopods at the metal-contaminated sites have been selected for early reproduction and increased reproductive allocation. The results indicate that populations inhabiting metal-polluted sites have probably undergone evolutionary changes. This study showed that growth and reproduction characteristics of different populations under laboratory conditions may provide information on selection processes in the field.     

再生稻褐飞虱为害损失测定和防治指标的研究

在福建,褐飞虱是再生稻的重要害虫,中进行了再生稻褐飞虱为害损失的测定,并对褐飞虱为害再生稻造成的产量损失结构进行了通径分析。根据虫量和产量损失的关系,结合现行稻谷价格,产量水平,防治费用等因素。确定允许为害损失率,同时建立了再生稻褐飞虱防治指标模型,按照防治指标模型,制定出不同产量水平的防治指标。     

Pore formation by the sea anemone cytolysin equinatoxin II in red blood cells and model lipid membranes

Summary The interaction ofActinia equina equinatoxin II (EqT-II) with human red blood cells (HRBC) and with model lipid membranes was studied. It was found that HRBC hemolysis by EqT-II is the result of a colloid-osmotic shock caused by the opening of toxin-induced ionic pores. In fact, hemolysis can be prevented by osmotic protectants of adequate size. The functional radius of the lesion was estimated to be about 1.1 nm. EqT-II increased also the permeability of calcein-loaded lipid vesicles comprised of different phospholipids. The rate of permeabilization rised when sphingomyelin was introduced into the vesicles, but it was also a function of the pH of the medium, optimum activity being between pH 8 and 9; at pH 10 the toxin became markedly less potent. From the dose-dependence of the permeabilization it was inferred that EqT-II increases membrane permeability by forming oligomeric channels comprising several copies of the cytolysin monomer. The existence of such oligomers was directly demonstrated by chemical cross-linking. Addition of EqT-II to one side of a planar lipid membrane (PLM) increases the conductivity of the film in discrete steps of defined amplitude indicating the formation of cation-selective channels. The conductance of the channel is consistent with the estimated size of the lesion formed in HRBC. High pH and sphingomyelin promoted the interaction even in this system. Chemical modification of lysine residues or carboxyl groups of this protein changed the conductance, the ion selectivity and the current-voltage characteristic of the pore, suggesting that both these groups were present in its lumen.     

1H Nuclear Magnetic Resonance Spectroscopy Study of Cerebral Glutamate in an Ex Vivo Brain Preparation of Guinea Pig

Abstract: Cerebral glutamate was monitored in a superfused cerebral cortical preparation by ¹H NMR spectroscopy using a semiselective spin-echo sequence N -acetyl aspartate (NAA) as an internal concentration reference. During controlled metabolic conditions, the cerebral ¹H NMR-detected glutamate-to-NAA ratio was ∼ 20–30% lower than expected from the ratio of neutralized perchloric acid extracts of the preparations. Inhibition of respiration in the presence of glucose did not change the ¹H NMR glutamate-to-NAA ratio in brain slice preparation. In contrast, either complete depletion of ATP during cyanide poisoning together with 0 m M glucose, anoxia in the absence of glucose, or treatment with nigericin or with a protonophore, carbonyl cyanide- m -fluorophenylhydrazone, increased ¹H NMR-detected glutamate/NAA in the cerebral preparations without a change in the relative and absolute concentration ratios determined from the tissue acid extracts. Spin-spin relaxation times of glutamate and NAA peaks in anoxic slices were 749 ± 89 and 729 ± 94 ms, respectively, and thus, the portion of glutamate that could not be detected by ¹H NMR was quantified in absolute terms. It was calculated that an increase in the glutamate-to-NAA ratio from 0.55 ± 0.02 to 0.67 ± 0.02 during aglycemic anoxia corresponded to some 6 mmol/kg of tissue dry weight of glutamate from the total concentration of 28 mmol/kg dry weight. It is suggested that this 22% of total glutamate pool is present in a noncytoplasmic compartment during controlled metabolic state.     

Fine structure of aphid stylet routes in plant tissues in correlation with EPG signals

Abstract. Plant penetration by Aphis fabae (Scopoli) was recorded by the electrical penetration graph (EPG) technique and followed by stylectomy during wave-forms that were suspected of indicating sieve element punctures. The severed stylets in the plant tissue were subsequently processed for transmission electron microscopy (TEM) and sectioned either transverse or longitudinal to the stylets. Two completely serially sectioned probes from the epidermis to the phloem were reconstructed.
In one probe the stylet pathway went to a sieve element and showed many empty branches of salivary sheath material. Breaks in cell walls filled with sheath material demonstrated that the majority of cells bordering the track had been punctured, which supports earlier evidence from EPGs. All types of cells showed punctures and the highest number was found inside the vascular bundle. Very few cells died, which would appear to be important for virus transmission, and in others cellular reactions remained limited to some callose formation. The route of the stylets was intercellular and passed through the secondary wall material. The role of pectinase in intercellular penetration, and previous evidence for intracellular tracks are discussed. Most sieve elements had been punctured but only one was eventually accepted. Thus, reaching a sieve element in a host plant does not automatically imply its acceptance though the reason remains unclear. Gelation of phloem proteins was shown in the stylet canal.
In a second probe, plant cytological and morphological correlations with the EPG were emphasized. Probes by other aphid-plant combinations showed great similarity.     

Morphological and biological characteristics of the Korean population of Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae), an invasive insect pest of conifer cones

In this study, we investigated the morphological and biological characteristics of a serious insect pest of conifer cones, the western conifer seed bug (WCSB), Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae), in Korea. WCSB adults shared external morphology with overseas populations, including zig-zag fascia on the coria, dilation of the hind tibiae, and color pattern on the abdominal dorsum. The average body length and width of WCSB adults were 17.20 and 4.85 mm, respectively, in males and 19.05 and 5.55 mm in females. The average body weights were 111.27 and 169.89 mg in adult males and females, respectively. On average, eggs were 2.12 mm long and 1.17 mm wide. The average body lengths of the first- to fifth-instar nymphs were 3.07, 4.76, 8.77, 13.56, and 15.53 mm, respectively. For biological characteristics, developmental durations of the egg and five nymphal instar stages were 8.6, 3.7, 7.6, 5.8, 5.8, and 9.1 days, respectively, in laboratory conditions. Nymphal mortality was 47.5% in total. The average life expectancy of WCSB adults was 58.2 and 63.9 days in males and females, respectively. Oviposition of the adult females started 23.4 days after emergence, and the total number of eggs laid by a single adult female was 68.6 on average. The results of this study offer basic morphological and biological information that can be used to design an effective control strategy to manage the WCSB population in Korea.     

Damage to living trees contributes to almost half of the biomass losses in tropical forests

Accurate estimates of forest biomass stocks and fluxes are needed to quantify global carbon budgets and assess the response of forests to climate change. However, most forest inventories consider tree mortality as the only aboveground biomass (AGB) loss without accounting for losses via damage to living trees: branchfall, trunk breakage, and wood decay. Here, we use ~151,000 annual records of tree survival and structural completeness to compare AGB loss via damage to living trees to total AGB loss (mortality + damage) in seven tropical forests widely distributed across environmental conditions. We find that 42% (3.62 Mg ha⁻¹ year⁻¹; 95% confidence interval [CI] 2.36–5.25) of total AGB loss (8.72 Mg ha⁻¹ year⁻¹; CI 5.57–12.86) is due to damage to living trees. Total AGB loss was highly variable among forests, but these differences were mainly caused by site variability in damage-related AGB losses rather than by mortality-related AGB losses. We show that conventional forest inventories overestimate stand-level AGB stocks by 4% (1%–17% range across forests) because assume structurally complete trees, underestimate total AGB loss by 29% (6%–57% range across forests) due to overlooked damage-related AGB losses, and overestimate AGB loss via mortality by 22% (7%–80% range across forests) because of the assumption that trees are undamaged before dying. Our results indicate that forest carbon fluxes are higher than previously thought. Damage on living trees is an underappreciated component of the forest carbon cycle that is likely to become even more important as the frequency and severity of forest disturbances increase.