Serpentine leafminer (Liriomyza trifolii) on potato (Solanum tuberosum): field observations and plant photosynthetic responses to injury

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Langmuir films of an amide extracted from Piperaceae and its interaction with phospholipids

In this work, we investigate Langmuir monolayers froth an amide extracted from dried roots of Ottonia propinqua, a native Brazilian plant believed to exhibit anesthetic and hallucinogen activities. In addition to producing monolayers from the amide itself, we probe the molecular-level action of the amide on phospholipids employed as simple membrane models. The surface pressure-molecular area (pi-A) isotherms for the amide were little affected by a number of subphase conditions. Almost no changes were observed upon varying the compression speed, spreading volume onto the surface, ions in the subphase, ionic strength and the solution solvent. However, stronger effects occurred when the subphase temperature and pH were altered, as the isotherms were shifted to larger areas with increasing temperatures and decreasing pHs. These results are discussed in terms of the molecular packing adopted by the amide at the air-water interface. In the mixed films with arachidic acid, the area per molecule varied linearly with the concentration of amide, probably due to phase separation. on the other hand, in the mixed films with dipalmitoyl phosphatidyl choline (DPPC), small amounts of the amide were sufficient to change the pi-A isotherms significantly. This points to a strong molecular-level interaction, probably between the phosphate group in the zwitterion of DPPC and the nitrogen from the amidic group. (c) 2004 Elsevier B.V. All rights reserved.

Effect of calcium and magnesium silicate on the growth of the castor oil plant subjected to salinity levels

Salt stress decreases the osmotic potential of soil solution causing water stress, causing toxic effects in the plants resulting in injuries on the metabolism and nutritional disorders, thus compromising the plant growth, resulting in lower production. The calcium silicate and magnesium can perform the same function as limestone, besides providing silicon to plants, may also contribute to the resistance of plants to salt stress. Thus, the objective of this study was to evaluate the effect of calcium and magnesium silicate on the growth of the castor oil plant BRS Energia cultivated under saline conditions. This study evaluated plant height, stem diameter, number of leaves, leaf area, dry weight of shoot and root, and soil chemical characteristics. There was no interaction between factors of salinity level and of silicate level regarding the evaluated variables. There was a direct relationship between salinity levels and plant growth in height and stem diameter. The K concentration in soil were affected by salinity levels.

Cellulose degradation by Leucocoprinus gongylophorus, the fungus cultured by the leaf-cutting ant Atta sexdens rubropilosa

Leucocoprinus gongylophorus, the fungus cultured by the leaf-cutting ant Atta sexdens rubropilosa, is able to degrade efficiently cellulose, microcrystaline cellulose, carboximethylcellulose, and cellobiose. Analysis of the degradation products indicate that the fungus produce extracellular β-glucosidase, exo- and endo-glucanase. The importance of cellulose degradation to the association of fungus and ant is discussed.

Nicotiana tabacum as an experimental host for the study of plant-Xylella fastidiosa interactions

Xylella fastidiosa causes citrus variegated chlorosis (CVC). Information generated from the X. fastidiosa genome project is being used to study the underlying mechanisms responsible for pathogenicity. However, the lack of an experimental host other than citrus to study plant-X. fastidiosa interaction has been an obstacle to accelerated progress in this area. We present here results of three experiments that demonstrated that tobacco could be an important experimental host for X. fastidiosa. All tobacco plants inoculated with a citrus strain of X. fastidiosa expressed unequivocal symptoms, consisting of orange leaf lesions, approximately 2 months after injection of the pathogen. CVC symptoms were observed in citrus 3 to 6 months after inoculation. The pathogen was readily detected in symptomatic tobacco plants by polymerase chain reaction (PCR) and phase contrast microscopy. In addition, X. fastidiosa was reisolated on agar plates in 4 of 10 plants. Scanning electron microscopy analysis of cross sections of stems and petioles revealed the presence of rod shaped bacteria restricted to the xylem of inoculated plants. The cell size was within the limit typical of X. fastidiosa.

Influence of light, plant density and disinfection in spore germination of fern blechnum brasiliense desv. blechnaceae

The present assay had as objective evaluating spore germination of Blechnum brasiliense in relation to light, plant density and disinfection. The assay was carried out at Jaboticabal, Sào Paulo State, Brazil, from February, 22 to June, 30, 1996. The experimental design was randomized blocks on a factorial scheme (3x2x2), consisting of 12 treatments, three environments (shade-house, dark-house and germination camera), 2 densities (0.005 grs and 0.010 grs of spores/treatment) and presence or absence of disinfection. The leaf coverage area (130 days) and the number of days necessary to germinate were evaluated. The germination camera data were not analysed because they were insignificant; consequently, the remining data were analysed on a 2×2×2 scheme. The shade-house provided larger green covering area and a faster germination. The density of 0.0 lOg of spore/treatments presented the largest green covering area. The supply of partial light was necessary for good germination. The interaction between the environment and the density had significant effect on the green covering area.

Non-Specific Interaction between Ants (Hymenoptera; Formicidae) and Fruits of Syagrus romanzoffiana (Arecaceae) in an Area of the Brazilian Atlantic Forest

On the forest floor of a fragment of the Atlantic Forest which is considered to be in a stage of recuperation, located in southeastern Brazil, we recorded 54 species of ants interacting with the fruits of Syagrus romanzoffiana (Arecaceae). Myrmicinae was the subfamily which was the richest in species, followed by Ponerinae, Formicinae, Ecitoninae, Dolichoderinae, Pseudomyrmecinae and Cerapachyinae. The fruits of S. romanzoffiana can be classified according to whether or not they are preyed by the squirrel Sciurus ingrami, and the ant fauna that visits the fruits has an average similarity. Regarding diversity, the data suggest that there is no significant difference between ant assemblages at preyed and non-preyed-upon fruit falls. The results also indicate that there is no specific interaction between the ant fauna that visits the fruits of S. romanzoffiana, as it consists largely of species with omnivorous feeding habits.

The influence of fruit morphology and habitat structure on ant-seed interactions: A study with artificial fruits

Artificial fruits designed to simulate lipid-rich non-myrecochorous diaspores were used to test for the effect of fruit morphology and habitat structure on ant-seed interactions in an Atlantic Forest site in SE Brazil. The outcome of the interaction (i.e., if the fruit was removed, cleaned by ants on the spot or had no interaction with ants) and the time of ant response were the investigated variables. Models simulating drupes and arilate diaspores were used to test for morphological effects and four habitat attributes (litter depth, number of logs, number of trees, and percentage of bromeliad coverage on the forest floor), likely to be correlated with the ant diversity and abundance in the study site, were measured to test for the effect of habitat structure. The proportion of fruits removed or cleaned did not differ between the two morphological models. Sites in which fruits were cleaned had more trees than those in which no interaction occurred. This may be a result of the foraging behavior of arboreal ants that frequently descend to the forest floor to exploit fleshy diaspores. Sites in which model removal occurred had lower litter depth than both those in which models were cleaned and those in which no interaction occurred. A negative correlation was observed between litter depth and ant response time. Accumulation of leaf litter at a given point may have constrained the movements of large ants in general, and ponerine ants (that are important seed removers) in particular. We conclude that that local pattern in litter depth and tree density influence the frequency and outcome of interactions between ants and non-myrmecochorous, fleshy diaspores.

Toxicity of sesame extracts to leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Extracts of different sesame plant (Sesamum indicum, Linnaeus) organs were tested through ingestion and contact experiments to investigate their toxicity to Atta sexdens rubropilosa (Forel) workers. Dichloromethane extracts of seeds were toxic to the leaf-cutting ants and the factor responsible for the toxicity does not show seasonal occurrence.

Toxicity of sesame seed to leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Extracts of the ripe seeds of the sesame plant (Sesamum indicum, Linnaeus) were tested through contact experiments to investigate their toxicity to Atta sexdens rubropilosa workers. Dichloromethane extract of seeds was toxic to the ants and the factor responsible for this effect was distributed through the ethyl acetate fraction. This fraction was divided into four sub fractions composed of: A) triglycerides, B) monoglycerides + diglycerides + triglycerides, C) diglycerides + sesamoline + sesamine and D) sesamine. However, when these sub fractions were separated, no toxicity was observed. Therefore, in order to determine why the activity was lost, the concentration of each sub fraction was duplicated, and the possible combinations among them were also tested. We concluded that the toxicity to the ants is due mainly to a mixture of triglycerides, and sesamoline or the combination of sesamoline + sesamine can be a synergistic factor in this fraction.

Ant-tended hemiptera in Amazonian myrmecophytes: Patterns of abundance and implications for mutualism function (Hymenoptera: Formicidae)

We assessed how the abundance of ant-tended Hemiptera associated with two Amazonian myrmecophytes, Tococa bullifera and Maieta guianensis, varied as a function of resident ant species. We collected five species or morpho-species of adult hemiptera in the domatia of M. guianensis, with four of these species also found in Tococa bullifera. Maieta guianensis plants inhabited by Crematogaster laevis had over four-fold more hemiptera in them than plants inhabited by Pheidole minutula. In contrast, the density of hemiptera in Tococa bullifera domatia was independent of the species of ant resident. For each of the two ant species inhabiting Maieta guianensis, there was a positive and significant relationship between the abundance of hemiptera and workers inhabiting a plant. This relationship was also significant and positive for the Tococa bullifera plants inhabited by C. laevis. However, there was no relationship between Azteca worker and hemipteran density, although there was a trend towards a positive relationship. Our results indicate that hemipteran abundance can vary significantly between different myrmecophyte species, but that the nature of this relationship is mediated by the identity of the ant associate. Because hemipterans are herbivores, the costs and benefits of different ant partners to the host plant may vary in ways that are often overlooked.

Ant fauna (Hymenoptera: Formicidae) in Magnoliophyta native to the Atlantic forest

The aim of the study was to analyze the preferences of ant species visiting the trunks of eight species of Magnoliophyta, belonging to the families Fabaceae, Arecaceae, Myrtaceae, Melastomataceae and Euphorbiaceae, located in a fragment of the Atlantic Forest in southeastern Brazil. A total of 101 ant species, belonging to eight subfamilies and 32 genera, were sampled during the 12-month collection period. Close to 30% of the ant species can be considered arboreal, and the others are species that nest in the ground and use trees only for foraging, which can be occasional, as in the case of the Ecitoninae sampled in Arecaceae and Euphorbiaceae. Pachycondyla mesonotalis was the only species collected on all the Magnoliophyta, whereas Camponotus rufipes, Acromyrmex niger and Crematogaster spp., were found on 87.5% of the trees analyzed. No strong similarities were found, using the Jaccard Index, among plant species in the same family of Magnoliophyta based on the visiting ants, except for the Euphorbiaceae species. This result is probably related to the presence of extra-floral nectar, which is very attractive to ants and characteristic of this family.

The role of multiple partners in a digestive mutualism with a protocarnivorous plant

Background and aimsThe protocarnivorous plant Paepalanthus bromelioides (Eriocaulaceae) is similar to bromeliads in that this plant has a rosette-like structure that allows rainwater to accumulate in leaf axils (i.e. phytotelmata). Although the rosettes of P. bromelioides are commonly inhabited by predators (e.g. spiders), their roots are wrapped by a cylindrical termite mound that grows beneath the rosette. In this study it is predicted that these plants can derive nutrients from recycling processes carried out by termites and from predation events that take place inside the rosette. It is also predicted that bacteria living in phytotelmata can accelerate nutrient cycling derived from predators.MethodsThe predictions were tested by surveying plants and animals, and also by performing field experiments in rocky fields from Serra do Cipó, Brazil, using natural abundance and enriched isotopes of 15N. Laboratory bioassays were also conducted to test proteolytic activities of bacteria from P. bromelioides rosettes.Key ResultsAnalyses of 15N in natural nitrogen abundances showed that the isotopic signature of P. bromelioides is similar to that of carnivorous plants and higher than that of non-carnivorous plants in the study area. Linear mixing models showed that predatory activities on the rosettes (i.e. spider faeces and prey carcass) resulted in overall nitrogen contributions of 26·5 % (a top-down flux). Although nitrogen flux was not detected from termites to plants via decomposition of labelled cardboard, the data on 15N in natural nitrogen abundance indicated that 67 % of nitrogen from P. bromelioides is derived from termites (a bottom-up flux). Bacteria did not affect nutrient cycling or nitrogen uptake from prey carcasses and spider faeces.ConclusionsThe results suggest that P. bromelioides derive nitrogen from associated predators and termites, despite differences in nitrogen cycling velocities, which seem to have been higher in nitrogen derived from predators (leaves) than from termites (roots). This is the first study that demonstrates partitioning effects from multiple partners in a digestion-based mutualism. Despite most of the nitrogen being absorbed through their roots (via termites), P. bromelioides has all the attributes necessary to be considered as a carnivorous plant in the context of digestive mutualism. © 2012 The Author. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.

A metabolic pathway assembled by enzyme selection may support herbivory of leaf-cutter ants on plant starch

Mutualistic associations shape the evolution in different organism groups. The association between the leaf-cutter ant Atta sexdens and the basidiomycete fungus Leucoagaricus gongylophorus has enabled them to degrade starch from plant material generating glucose, which is a major food source for both mutualists. Starch degradation is promoted by enzymes contained in the fecal fluid that ants deposit on the fungus culture in cut leaves inside the nests. To understand the dynamics of starch degradation in ant nests, we purified and characterized starch degrading enzymes from the ant fecal fluid and from laboratory cultures of L. gongylophorus and found that the ants intestine positively selects fungal α-amylase and a maltase likely produced by the ants, as a negative selection is imposed to fungal maltase and ant α-amylases. Selected enzymes are more resistant to catabolic repression by glucose and proposed to structure a metabolic pathway in which the fungal α-amylase initiates starch catalysis to generate byproducts which are sequentially degraded by the maltase to produce glucose. The pathway is responsible for effective degradation of starch and proposed to represent a major evolutionary innovation enabling efficient starch assimilation from plant material by leaf-cutters. © 2013 Elsevier Ltd.

Foraging of psilocybe basidiocarps by the leafcutting ant acromyrmex lobicornis in Santa Fé, Argentina

Background It is generally accepted that material collected by leaf-cutting ants of the genus Acromyrmex consists solely of plant matter, which is used in the nest as substrate for a symbiotic fungus providing nutrition to the ants. There is only one previous report of any leaf-cutting ant foraging directly on fungal basidiocarps. Findings Basidiocarps of Psilocybe coprophila growing on cow dung were actively collected by workers of Acromyrmex lobicornis in Santa Fé province, Argentina. During this behaviour the ants displayed typical signals of recognition and continuously recruited other foragers to the task. Basidiocarps of different stages of maturity were being transported into the nest by particular groups of workers, while other workers collected plant material. Conclusions The collection of mature basidiocarps with viable spores by leaf-cutting ants in nature adds substance to theories relating to the origin of fungiculture in these highly specialized social insects. © 2013 Masiulionis et al.