The influence of summer and winter stress and water relationships on the distribution of Quercus ilex L.

Several aspects of plant-water relationships and canopy behaviour have been studied over several years in two experimental areas of Quercus ilex L. forests in the northeastern Iberian Peninsula. Water requirements, water status limits necessary for a positive carbon budget and the functional canopy behaviour in the face of abiotic stress were evaluated, in order to determine which factors influence the geographical range of these forests.The results showed that holm oak has a conservative water use, a low cuticular transpiration, a high capacity for osmotic adjustement and xerophytic characteristics in leaf morphology and canopy arrangement. More than 440 mm of annual rainfall are required for these forests to persist. Summer drought and winter cold are thus important abiotic factors limiting the distribution of Quercus ilex. In both cases, drought stress is involved.     

Current-voltage curve of electrogenic Cl− pump predicts voltage-dependent Cl− efflux inAcetabularia

Summary The current-voltage relationship of carrier-mediated, passive and active ion transport systems with one charge-carrying pathway can exactly be described by a simple reaction kinetic model. This model consists of two carrier states (one inside, one outside) and two pairs (forwards and backwards) of rate constants: a voltage-dependent one, describing the transport of charge and a voltage-insensitive one, summarizing all the other (voltage-independent) reactions. For the electrogenic Cl^– pump inAcetabularia these four rate constants have been determined from electrical measurements of the current-voltage relationship of the pump (Gradmann, Hansen & Slayman, 1981;in: Electrogenic Ion Pumps, Academic Press, New York). The unidirectional Cl^– efflux through the pump can also be calculated by the availiable reaction kinetic parameters.³⁶Cl^– efflux experiments on singleAcetabularia cells with simultaneous electrical stimulation (action potentials) and recording, demonstrate the unidirectional Cl^– efflux to depend on the membrane potential. After subtraction of an efflux portion which bypasses the pump, agreement is found between the measured flux-voltage relationship and the theoretical one as obtained from the reaction kinetic model and its parameters from the electrical data.     

Ethylene formation by germinating,Drechslera graminea — Infected barley (Hordeum sativum) grains: A simple test for fungicides

Grains of barley (Hordeum sativum L.); infected with the parasitic, systemic fungus Drechslera graminea, produce more ethylen than uninfected controls. Treatment of infected grains with mercury-free fungicides yields a differentiated suppression of the ethylene evolution 7 d after the beginning of germination. Suppression of visible symptoms (chlorotic stripes on leaves) appearing six to eight weeks after germination of infected, untreated seeds correlates with the decrease in ethylene formation after treatment with fungicides. The gaschromatographic ethylene determination thus allows for an early and reliable (significance higher than 99.9%) differentiation of fungicidal activities against the barley stripe disease.Abbreviations ACC I-aminocyclopropane-1-carbonic acid - CD critical difference     

Ornithodiplostomum ptychocheilus: migration to the brain of the fish intermediate host, Pimephales promelas.

Migration of cercariae of the diplostomatid trematode, Ornithodiplostomum ptychocheilus, to the brain of the fathead minnow, Pimephales promelas, takes place via directed, nonrandom movement. Penetration of the fish epidermis is rapid and is essentially complete by 2 hr postinfection. Migration to the central nervous system occurs almost exclusively via the general body musculature and connective tissue, although a few cercariae gain direct access to the nervous system via the eyes. Cercariae enter either the neural canal and spinal cord, or the brain via the spinal or cranial nerves and their associated foramina, although cercariae appear to remain in (on) these peripheral nerves for only a short time. Cercariae associated with cranial nerves continue to the brain. Those becoming associated with spinal nerves travel up the neural canal and (or) spinal cord to the brain. Data suggest that most arrive at the brain via the neural canal and spinal cord. Within the brain, most developing metacercariae (neascus-type) occur in the optic lobes and cerebellum. Whether this is “selective localization” or merely the result of the larger space afforded by these brain regions could not be determined.     

Aldolases of the lactic acid bacteria

Reciprocal qualitative and quantitative immunological experiments employing an anti-Pediococcus cerevisiae aldolase serum confirmed many of the interspecific relationships demonstrated previously among lactic acid bacteria with antisera prepared against the Streptococcus faecalis fructose diphosphate aldolase. The extent of immunological relatedness observed between the Lactobacillus and Pediococcus aldolases was markedly greater than that noted between Pediococcus and Streptococcus aldolases indicating that the pediococci share closer phylogenetic ties with the rod-shaped lactobacilli than with their spherical counterparts in the streptococci. In addition to confirming the existence of definitive, but distant, relationships between the lactic acid bacteria and certain gram positive nonsporeforming anaerobes, immunological cross-reactivity was also demonstrated between the pediococcal aldolases and those of Aerococcus viridans.This paper is dedicated with deepest appreciation to Prof. Roger Y. Stanier on the occasion of his 60th birthday in token of what his friendship and guidance have meant to me. — J. L.     

Ants impact the composition of the aquatic macroinvertebrate communities of a myrmecophytic tank bromeliad

In an inundated Mexican forest, 89 out of 92 myrmecophytic tank bromeliads (Aechmea bracteata) housed an associated ant colony: 13 sheltered Azteca serica, 43 Dolichoderus bispinosus, and 33 Neoponera villosa. Ant presence has a positive impact on the diversity of the aquatic macroinvertebrate communities (n = 30 bromeliads studied). A Principal Component Analysis (PCA) showed that the presence and the species of ant are not correlated to bromeliad size, quantity of water, number of wells, filtered organic matter or incident radiation. The PCA and a generalized linear model showed that the presence of Azteca serica differed from the presence of the other two ant species or no ants in its effects on the aquatic invertebrate community (more predators). Therefore, both ant presence and species of ant affect the composition of the aquatic macroinvertebrate communities in the tanks of A. bracteata, likely due to ant deposition of feces and other waste in these tanks.     

京津冀城市群区域产业协同的政策格局及评价

产业协同发展是京津冀区域协同发展的三个重点领域之一,科学合理的产业协同政策是加快实现这一发展目标的重要保障。通过对京津冀城市群区域产业协同政策事件的系统梳理,从区域、省际和城际3个尺度解读了产业协同政策的格局及其演进过程,并从新区域主义的管治视角进行了评价。研究认为:(1)京津冀产业协同发展进入了快速发展的机遇期,协同政策极大地推动了区域内跨地产业合作和城市间产业联系,有助于提高城市群整体竞争力;(2)不同空间尺度的产业协同政策关注的重点、发展的方向、演化的特征不同,当前城市间的产业协同政策与区域协同发展目标的关系不明确,产业协同对生态环境的改善尚不显著,亟需加强研究和统筹协调;(3)受城市行政区等级关系和竞争关系的影响,京津冀产业协同政策与市场调节无法实现高度契合统一,与新区域主义的管治理念并不相符,影响科学合理协同政策的制定与实施。研究对当前京津冀区域产业协同发展推进及其政策制定有重要的参考意义。     

StructureActivity Relationships of Antimicrobial Gallic Acid Derivatives from Pomegranate and Acacia Fruit Extracts against Potato Bacterial Wilt Pathogen

Bacterial wilts of potato, tomato, pepper, and or eggplant caused by Ralstonia solanacearum are among the most serious plant diseases worldwide. In this study, the issue of developing bactericidal agents from natural sources against R. solanacearum derived from plant extracts was addressed. Extracts prepared from 25 plant species with antiseptic relevance in Egyptian folk medicine were screened for their antimicrobial properties against the potato pathogen R. solancearum by using the disc‐zone inhibition assay and microtitre plate dilution method. Plants exhibiting notable antimicrobial activities against the tested pathogen include extracts from Acacia arabica and Punica granatum. Bioactivity‐guided fractionation of A. arabica and P. granatum resulted in the isolation of bioactive compounds 3,5‐dihydroxy‐4‐methoxybenzoic acid and gallic acid, in addition to epicatechin. All isolates displayed significant antimicrobial activities against R. solanacearum (MIC values 0.5–9 mg/ml), with 3,5‐dihydroxy‐4‐methoxybenzoic acid being the most effective one with a MIC value of 0.47 mg/ml. We further performed a structure–activity relationship (SAR) study for the inhibition of R. solanacearum growth by ten natural, structurally related benzoic acids.     

A dynamic, architectural plant model simulating resource-dependent growth

BACKGROUND AND AIMS: Physiological and architectural plant models have originally been developed for different purposes and therefore have little in common, thus making combined applications difficult. There is, however, an increasing demand for crop models that simulate the genetic and resource-dependent variability of plant geometry and architecture, because man is increasingly able to transform plant production systems through combined genetic and environmental engineering. MODEL: GREENLAB is presented, a mathematical plant model that simulates interactions between plant structure and function. Dual-scale automaton is used to simulate plant organogenesis from germination to maturity on the basis of organogenetic growth cycles that have constant thermal time. Plant fresh biomass production is computed from transpiration, assuming transpiration efficiency to be constant and atmospheric demand to be the driving force, under non-limiting water supply. The fresh biomass is then distributed among expanding organs according to their relative demand. Demand for organ growth is estimated from allometric relationships (e.g. leaf surface to weight ratios) and kinetics of potential growth rate for each organ type. These are obtained through parameter optimization against empirical, morphological data sets by running the model in inverted mode. Potential growth rates are then used as estimates of relative sink strength in the model. These and other 'hidden' plant parameters are calibrated using the non-linear, least-square method. KEY RESULTS AND CONCLUSIONS: The model reproduced accurately the dynamics of plant growth, architecture and geometry of various annual and woody plants, enabling 3D visualization. It was also able to simulate the variability of leaf size on the plant and compensatory growth following pruning, as a result of internal competition for resources. The potential of the model's underlying concepts to predict the plant's phenotypic plasticity is discussed.     

Evolutionary relationships in thePodalyrieae andLiparieae (Fabaceae) based on morphological, cytological, and chemical evidence

Taxonomic relationships amongst the genera of the southern African tribesPodalyrieae andLiparieae are discussed. Data gained from morphological, cytological and chemical investigations are analyzed cladistically to determine relationships. The genusCadia (tribeSophoreae) is included in the investigation to establish whether it should be transferred to thePodalyrieae. The results clearly indicate that thePodalyrieae andLiparieae are monophyletic and that they should be united, but thatHypocalyptus andCadia should be excluded. Within the monophyletic group, there are two distinct subclades each supported by three apomorphies. The results also show that there is a strong sister relationship betweenAmphithalea andCoelidium. In the taxonomic treatment theLiparieae are placed into synonymy under thePodalyrieae and two subtribes are recognized. A key to the genera in the tribe is given, followed by a synopsis of the genera.