Fungal diversity in galls of baldcypress trees

The baldcypress midge (Taxodiomyia cupressi and Taxodiomyia cupressiananassa) forms a gall that originates from leaf tissue. Female insects may inoculate galls with fungi during oviposition, or endophytes from the leaf tissue may grow into the gall interior. We investigated fungal diversity inside of baldcypress galls, comparing the gall communities to leaves and comparing fungal communities in galls that had successful emergence versus no emergence of midges or parasitoids. Galls of midges that successfully emerged were associated with diverse gall fungal communities, some of which were the same as the fungi found in surrounding leaves. Galls with no insect emergence were characterized by relatively low fungal diversity.     

Structure of floral galls of Byrsonima sericea (Malpighiaceae) induced by Bruggmanniella byrsonimae (Cecidomyiidae,Diptera) and their effects on host plants

Galls are anomalies in plant development from parasitic origin, and affect cellular differentiation or growth of plants. This parasite–plant interaction occurs in many environments and typically in vegetative organs of plants. The existence of galls in reproductive organs and their effects on the host plant are seldom described in the literature. In this paper, we present a novel study of galls in plants of the neotropical region. Galls of Bruggmmaniella byrsonimae develop in the flower buds of Byrsonima sericea DC. (Malpighiaceae) and affect development of the reproductive organs and the reproductive effort of these plants. The sepals and petals show hypertrophy of parenchyma tissues after differentiation, and the stamens exhibit degeneration of the sporogenic tissue. The gynoecium is not entirely developed; ovary and ovules are often absent. Changes in vascular tissues are also frequent, which may indicate high demand for nutrient resources by the new tissues initiated by the larva. We compared the amount of inflorescences, galls and fruits to evaluate possible effects on host reproduction. The results suggest that the Cecidomyiidae galls in flower organs affect fruit set and the reproductive success of B. sericea.     

Morphometric analysis of young petiole galls on the narrow-leaf cottonwood, <Emphasis Type="Italic">Populus angustifolia</Emphasis>, by the sugarbeet root aphid, <Emphasis Type="Italic">Pemphigus betae</Emphasis>

An insect-induced gall is a highly specialized structure resulting from atypical development of plant tissue induced by a reaction to the presence and activity of an insect. The insect induces a differentiation of tissues with features and functions of an ectopic organ, providing nutrition and protection to the galling insect from natural enemies and environmental stresses. In this anatomical and cytological study, we characterized how the gall-inducing aphid Pemphigus betae reshapes the leaf morphology of the narrow-leaf cottonwood Populus angustifolia to form a leaf fold gall. Young galls displayed a bend on one side of the midvein toward the center of the leaf and back to create a fold on the abaxial side of the leaf. This fold was formed abaxially by periclinal and anticlinal divisions, effectively eliminating intercellular spaces from the spongy parenchyma. Galls at this stage exhibited both cell hypertrophy and tissue hyperplasia. Cells on the adaxial surface were more numerous and smaller than cells near the abaxial surface were, creating the large fold that surrounds the insect. Mesophyll cells exhibited some features typical of nutritive cells induced by other galling insects, including conspicuous nucleolus, reduced and fragmented vacuole, smaller and degraded chloroplasts, and dense cytoplasm compared to ungalled tissue. Even though aphids feed on the contents of phloem and do not directly consume the gall tissue, they induce changes in the plant vascular system, which lead to nutrient accumulation to support the growing aphid numbers in mature galls.     

Morphogenesis of insect-induced plant galls: facts and questions

Insect-induced galls (‘galls’ hereafter) represent highly regulated growth manifestations on plants. They present unique geometrical forms, which are, usually, unknown in the normal plant system. Galls are the best examples for modified natural structures that arise solely because of messages from an alien organism - the insect. Galls develop as an extension of the host-plant phenotype. But how the physiological networks and signal-activated subsystems work in coordination in expressing galls that serve the nutritional and shelter needs of the inducing insect are unclear. In galls and bacteria-induced tumors, the basic developmental events are essentially similar. However, tightly regulated specific differentiation processes occur in galls, making them different from tumors. Moreover variations in differentiation patterns occur in galls induced by insects of different taxonomic groups. While providing an overview of the control of shape and structure in galls, this article identifies the unanswered questions in gall morphogenesis.By analyzing the recognizable steps in gall morphogenesis, viz., gall initiation, stimulus recognition in host plants, signal transduction in host plants, growth of galls, and qualitative differentiation in galls, I have indicated that the insect saliva flushed on the wounded plant site alters the subcellular environment of cells and thus places it in a state of chemical shock. This shock induces osmotic changes, which establishes the first recognizable stage in gall induction. To repair the wound and neutralize the osmotic-change induced stress, the plant responds by establishing from one to a few metaplasied cell(s). Localized metabolic changes spread, from these cells, not throughout the involved plant organ, but in a limited manner around the immediate site of insect occurrence. When the shock is of low intensity, the plant responds with the development of one or more metaplasied cell(s) and gall development starts; when the shock factor is of high intensity, the cells under the insect action die, rejecting the inducing insect, defending plant tissue. These changes dictate the new morphogenetic events. Insects feed on gall tissue continuously for a specific period (synchronizing with their life history) and therefore, the osmotic-change related stress prevails for that span of time, which in turn triggers a sequence of plant-mediated changes including synthesis of growth promotors. Osmotic stress affects electrical properties of the plasma membrane and impacts on IAA activity, which in turn, alters H⁺-transport systems. During the physical action of insect feeding, the host-cell wall breaks down, and the degenerated wall materials act as elicitors.Using galls (e.g., ‘cecidial shoots’ on leaves, modified vegetative buds) induced on species of south and south-east Asian Dipterocarpaceae by different Beesoniidae (Coccoidea) as model complexity in gall morphogenesis is discussed. Manipulatory experimental studies done on the regeneration of epiphyllous buds on Pteridium, Begonia, and a Helianthus hybrid indicate that insect-induced neoplasmic shoots that arise on the leaves of tropical Dipterocarpaceae fall into the morphogenetic regulation of leaf, yet maintaining their freedom of differentiation. Even though a gall is a part of the plant - a multicellular organism made of the same genetic material - organismal development generates a range of cell types with dictated functions fitting into of Waddington's epigenetic-landscape model. As of today, our knowledge stops here.Plants as living systems display different strategies to mitigate and neutralize stress. Although these strategies exist in their genetic constitution, they are mediated by complex molecular interactions. Plants have a flexible short-term strategy to respond to stress; organisms that can modify gene expression reversibly have an advantage in evolutionary terms, since they can avoid rearrangements and species diversification. Mechanisms of DNA methylation and histone modifications possibly regulate inheritance of stress ‘memories’. Inherited genetic traits also play a role in gall morphogenesis, followed by roles played by correlating morphogenetic factors. An articulated reconstruction of the developmental process commencing from either one or a group of metaplasied cells that gets transmitted through subsequent growth promoter-mediated cell expansion, until the commitment of the metaplastic cell and those in its neighbourhood enabling the start of ‘novel’ cell-cycle patterns, cell multiplication, programmed differentiation, and control is needed to explain symmetry - a morphogenetic phenomenon that makes the insect-induced galls distinct from the bacteria-induced tumors.     

The role of pectic composition of cell walls in the determination of the new shape-functional design in galls of Baccharis reticularia (Asteraceae)

The pectic composition of cell wall is altered during the processes of cell differentiation, plant growth, and development. These alterations may be time-dependent, and fluctuate in distinct regions of the same cell or tissue layer, due to the biotic stress caused by the activity of the gall inducer. Among the roles of the pectins in cell wall, elasticity, rigidity, porosity, and control of cell death may be crucial during gall development. Galls on Baccharis reticularia present species-specific patterns of development leading to related morphotypes where pectins were widely detected by Ruthenium red, and the pectic epitopes were labeled with specific monoclonal antibodies (LM1, LM2, LM5, LM6, JIM5, and JIM7) in distinct sites of the non-galled and the galled tissues. In the studied system B. reticularia, the epitopes for extensins were not labeled in the non-galled tissues, as well as in those of the rolling and kidney-shaped galls. The high methyl-esterified homogalacturonans (HGA) were labeled all over the tissues either of non-galled leaves or of the three gall morphotypes, while the intense labeling for arabinogalactans was obtained just in the rolling galls. The pectic composition of non-galled leaves denotes their maturity. The kidney-shaped gall was the most similar to the non-galled leaves. The pectic dynamics in the gall tissues was particularly altered in relation to low methyl-esterified HGA, which confers elasticity and expansion, as well as porosity and adhesion to cell walls, and are related to the homogenization and hypertrophy of gall cortex, and to translocation of solutes to the larval chamber. Herein, the importance of the pectic dynamics of cell walls to the new functional design established during gall development is discussed for the first time. The repetitive developmental patterns in galls are elegant models for studies on cell differentiation.     

Ant fauna associated with Microgramma squamulosa (Kaulf.) de la Sota (Polypodiaceae) fern galls

Galls are neoformed plant structures created by cell hyperplasia and hypertrophy induced by a number of organisms, especially insects. After adult insects hatch, senescent galls may remain on the host plant and be occupied by a succession of fauna, the most important and dominant being ants. This study aimed at characterizing the ant fauna successor of stem galls induced by microlepidoptera in Microgramma squamulosa (Kaulf.) de la Sota (Polypodiaceae). Four collections were carried out in the municipality of Nova Friburgo, Rio de Janeiro state, Brazil. The galls were packed in plastic bags and taken to the laboratory. Ants were euthanized and conserved in 70° GL alcohol and later identified. A total of 49 stem galls were collected and analyzed, 15 containing microlepidoptera galler larvae, one a parasitoid wasp and 33 without the microlepidoptera or parasitoid (67%). Twelve of these galls (39%) contained ants. Six ant species were recorded (Camponotus crassus, Crematogaster curvispinosa, Crematogaster sericea, Procryptocerus sampaioi, Tapinoma atriceps, and Wasmannia auropunctata), all native to Brazil. Ant occupation in M. squamulosa seems to be associated with senescent galls due to hatching of the galler insect, which leaves a hole that allows ants to colonize it, in other words, an opportunistic domatia. Senescent galls resulting from the death of galler insects do not seem to facilitate ant occupation.     

Microscopic study of the walls of galls induced by Geoica utricularia and Baizongia pistaciae in Pistacia terebinthus: a contribution to the phylogeny of Fordini

In the west of the Province of Leon (Spain), five species of gall-dwelling aphids, or greenflies, trigger the formation of different galls in Pistacia terebinthus: Forda formicaria, F. marginata, Paracletus cimiciformis, Geoica utricularia and Baizongia pistaciae. In the research presented here, a microscopic study was carried out of the wall of galls induced by the latter two species, G. utricularia and B. pistaciae. Galls induced by the first three species had already been studied previously by the same author. All the species of aphids mentioned above are included in the Eriosomatinae, Fordini. Among these, some authors further claim that it is possible to distinguish two clades: Forda and Paracletus would be included in one of these, whilst Geoica and Baizongia would be included in the other. The results of this study show that the walls of galls induced by G. utricularia and B. pistaciae present collateral vascular bundles. Specifically, there are two such vascular bundles: one distant from the chamber and the other separated from it by only a very few cells. The phloem in the latter vascular bundle is oriented towards the chamber. Furthermore, in the two galls studied, the chamber is lined with a lattice-like structure with hollows. These microscopic observations have enabled the walls of the galls studied to be differentiated from those triggered by Forda and Paracletus. These latter present a single vascular bundle, with the xylem oriented towards the chamber, whilst the surface of the chamber lining has a quilted appearance and lacks openings. This research provides data from microscopy to support the existence of two clades among the Fordini.     

Distinct antimicrobial activities in aphid galls on Pistacia atlantica

Gall-formers are parasitic organisms that manipulate plant traits for their own benefit. Galls have been shown to protect their inhabitants from natural enemies such as predators and parasitoids by various chemical and mechanical means. Much less attention, however, has been given to the possibility of defense against microbial pathogens in the humid and nutrient-rich gall environment. We found that the large, cauliflower-shaped, galls induced by the aphid Slavum wertheimae on buds of Pistacia atlantica trees express antibacterial and antifungal activities distinct from those found in leaves. Antibacterial activity was especially profound against Bacillus spp (a genus of many known insect pathogen) and against Pseudomonas aeruginosa (a known plant pathogen). Antifungal activity was also demonstrated against multiple filamentous fungi. Our results provide evidence for the protective antimicrobial role of galls. This remarkable antibacterial and antifungal activity in the galls of S. wertheimae may be of agricultural and pharmaceutical value.     

Cynipid galls on oak leaves are resilient to leaf vein disruption

Journal of Plant Research - Oaks serve as host plants for numerous insects, including those forming galls. Galls induced on oaks are completely dependent on leaf resources. Many other folivores...     

扁蚜亚科昆虫虫瘿多样性研究(半翅目,蚜科)

虫瘿是蚜虫诱导植物异速生长的结果,虫瘿作为蚜虫重要的延伸特征,对蚜虫系统分类、系统发育关系、以及起源演化等研究具有非常重要的作用.而且虫瘿的形态结构、着生部位等在蚜虫的物种间存在非常丰富的多样性,是蚜虫重要的生物学特征,也是物种鉴定的重要依据之一.本文在已有标本采集记录和资料的基础上,从结瘿的植物、虫瘿着生部位、形态结构及类型等4个方面对扁蚜亚科虫瘿的多样性进行了系统研究.结果表明该亚科蚜虫大多都在原生寄主上形成虫瘿,个别属及种可在次生寄主上成瘿;虫瘿在类型上有虫瘿和伪虫瘿之别;在着生部位上,有叶片、叶脉、叶柄、小枝、粗枝等;虫瘿的形状也十分多样,有管状、袋状、球状、半球形、刺球状、纺锤形、圆锥形、分支状、香蕉束状等;在结构上既有单室、多室之分,也有开放型、封闭型之别.对于虫瘿多样性的研究,可为虫瘿演化规律的探讨提供重要信息,也是基于虫瘿进行物种鉴定的重要基础.     

Anti-insect effects of the gall wall of Baizongia pistaciae [L.], a gall-inducing aphid on Pistacia palaestina Boiss

The Enemy hypothesis is a theoretical framework for understanding the adaptive nature of galls induced in host plants by insects. Contrary to other gall inducing insects, like Cynipids or sawflies, this hypothesis has not been studied for the gall aphids on pistachio trees in the Middle East. Galls on plants are supposed to protect their inducers from other organisms, including herbivores feeding on the host plant and possibly feeding on the gall tissue. Assuming that among aphid enemies there are numerous insects which have to perforate the gall wall to access the aphids inside, determining whether the gall wall has anti-insect properties should be one of the first steps in dealing with this hypothesis. In the present research using Baizongia pistaciae [L.], an aphid that creates perfectly closed galls in Pistacia palaestina Boiss, laboratory experiments were first conducted on a herbivore, the stored grain pest, Tribolium castaneum Herbst, to assess chemical anti-insect activities of the gall tissue, and an effort was made to understand why these properties do not harm the aphids inside the gall. Addition of fresh gall tissue to food reduced the population growth of flour beetles. Non-polar organic extracts had contact toxicity for larvae of these insects, and an impact on the feeding preferences of the adults. These results indicate chemical anti-insect activities of the gall tissue. The research also reveals that the permeability of the gall wall to non-polar volatile compounds is important to the survival of the aphids inside the gall cavity. These findings do not allow us to reject the Enemy hypothesis in the gall-inducing aphids/Pistacia trees interactions.     

Structure and development of ‘witches' broom’ galls in reproductive organs of Byrsonima sericea (Malpighiaceae) and their effects on host plants

Galls are anomalies in plant development of parasitic origin that affect the cellular differentiation or growth and represent a remarkable plant–parasite interaction. Byrsonima sericea DC. (Malpighiaceae) is a super host of several different types of gall in both vegetative and reproductive organs. The existence of galls in reproductive organs and their effects on the host plant are seldom described in the literature. In this paper, we present a novel study of galls in plants of the Neotropical region: the ‘witches' broom’ galls developed in floral structures of B. sericea. The unaffected inflorescences are characterised by a single indeterminate main axis with spirally arranged flower buds. The flower buds developed five unaffected brownish hairy sepals and five pairs of elliptical yellow elaiophores, five yellow fringed petals, 10 stamens and a pistil with superior tricarpellar and trilocular ovary. The affected inflorescences showed changes in architecture, with branches arising from the main axis and flower buds. The flower buds exhibited several morphological and anatomical changes. The sepals, petals and carpels converted into leaf‐like structures after differentiation. Stamens exhibited degeneration of the sporogenous tissue and structures containing hyphae and spores. The gynoecium did not develop, forming a central meristematic region, from which emerges the new inflorescence. In this work, we discuss the several changes in development of reproductive structures caused by witches' broom galls and their effects on reproductive success of the host plants.     

Host range and host preference of a flea weevil, Orchestes hustachei, parasitizing aphid galls

Although larvae of flea weevils (Curculioninae: Rhamphini) have been known to be leaf miners, larvae of the rhamphine weevil Orchestes hustachei have been found in aphid galls of four Tetraneura species on Ulmus davidiana and in galls of Paracolopha morissoni on Zelkova serrata. This study clarified the feeding habits of O. hustachei larvae and evaluated gall selection by ovipositing females to test the hypothesis of host race formation on their hosts, Tetraneura and Paracolopha galls. When weevil larvae were placed in half‐cut galls, they always fed on aphids rather than on gall tissue. When given gall tissue only, all larvae failed to reach adulthood. The number of aphids surviving in a parasitized gall decreased significantly with the development of the weevil larvae. These results suggest that O. hustachei larvae use aphids as their major food source. In the field, ovipositing females did not discern between four Tetraneura species on U. davidiana, in spite of a large difference in suitability as food. Paracolopha morrisoni was introduced into Hokkaido approximately 100 years ago, together with the host plant Z. serrata. It is probable that P. morrisoni has recently come to be used as a host by O. hustachei in Hokkaido. Host choice experiments using Tetraneura sp. O and P. morrisoni galls indicated that female weevils from Z. serrata preferred P. morrisoni to Tetraneura sp. O galls, while females from U. davidiana selected the two types of gall randomly. On Z. serrata, female weevils selected larger P. morrisoni galls, while on U. davidiana, females did not show a preference for gall size. These results suggest that a host shift to P. morrisoni galls may have led to an initial stage of host race formation between the weevil population using Tetraneura galls on U. davidiana, and that using P. morrisoni galls on Z. serrata.     

Characterisation of the effects of leaf galls of Clusiamyia nitida (Cecidomyiidae) on Clusia lanceolata Cambess. (Clusiaceae): Anatomical aspects and chemical analysis of essential oil

Galls develop in different plant organs and are induced by the activity of various organisms. Some studies have investigated the ecological interactions between species of Clusia and gall-inducing insects. The goal of our study is to characterise changes in leaf anatomy caused by the activity of gall insects in Clusia lanceolata. Additionally, we also investigated the chemical composition of volatile compounds of normal leaves and those with galls to detect possible effects on the host plants. For anatomical studies, we used botanical material fixed in FAA₅₀. Transversal sections of the leaf blade were obtained from samples of leaves located on the third and fourth nodes from both male and female individuals. Material was studied from both sexes both with unaffected leaves and leaves containing galls. Fresh leaves of C. lanceolata were used for the extraction of volatile compounds, which were submitted to stem distillation using a modified Clevenger apparatus determining the oil yields subsequently (w/w). The unaffected leaves of female and male individuals of C. lanceolata exhibit similar anatomical structures. However, galls on leaves of both sexes show anatomical differences. The activity of the gall insect Clusiamyia nitida induces several changes in the foliar anatomy and the distribution of metabolic compounds in new tissues during gall development. However, the larvae are not able to induce significant changes in the volatile compounds of inflected leaves from male and female individuals.     

Could the Extended Phenotype Extend to the Cellular and Subcellular Levels in Insect-Induced Galls?

Neo-ontogenesis of plant galls involves redifferentiation of host plant tissues to express new phenotypes, when new cell properties are established via structural-functional remodeling. Herein, Psidium cattleianum leaves and Nothotrioza cattleiani galls are analyzed by developmental anatomy, cytometry and immunocytochemistry of cell walls. We address hypothesis-driven questions concerning the organogenesis of globoid galls in the association of P. cattleianum - N. cattleianum, and P. myrtoides - N. myrtoidis. These double co-generic systems represent good models for comparing final gall shapes and cell lineages functionalities under the perspective of convergent plant-dependent or divergent insect-induced characteristics. Gall induction, and growth and development are similar in both galls, but homologous cell lineages exhibit divergent degrees of cell hypertrophy and directions of elongation. Median cortical cells in P. cattleianum galls hypertrophy the most, while in P. myrtoides galls there is a centrifugal gradient of cell hypertrophy. Cortical cells in P. cattleianum galls tend to anisotropy, while P. myrtoidis galls have isotropically hypertrophied cells. Immunocytochemistry evidences the chemical identity and functional traits of cell lineages: epidermal cells walls have homogalacturonans (HGAs) and galactans, which confer rigidity to sites of enhanced cell division; oil gland cell walls have arabinogalactan proteins (AGPs) that help avoiding cell death; and parenchyma cell walls have HGAs, galactans and arabinans, which confer porosity. Variations in such chemical identities are related to specific sites of hypertrophy. Even though the double co-generic models have the same macroscopic phenotype, the globoid morphotype, current analyses indicate that the extended phenotype of N. cattleiani is substantiated by cellular and subcellular specificities.     

A new Asphondylia species (Diptera: Cecidomyiidae) and a eulophid wasp (Hymenoptera) inducing similar galls on leaf buds of Schoepfia jasminodora (Schoepfiaceae), with reference to their ecological traits and a description of the new gall midge

Different gall inducers belonging to distinct insect orders are rarely known to induce similarly shaped galls on the same host plant organs. We report that Asphondylia tojoi Elsayed & Tokuda sp. nov. (Diptera: Cecidomyiidae) and Ceratoneura sp. (Hymenoptera: Eulophidae) induce galls on leaf buds of Schoepfia jasminodora Sieb. et Zucc. (Schoepfiaceae). We describe the gall midge species as new to science and report a phylogenetic analysis for known Japanese Asphondylia species. We also describe life histories of the two species, based on monthly surveys during 2015–2017: although both species are multivoltine, A. tojoi overwinters as first instars in galls, whereas Ceratoneura sp. possibly does so as adults outside the galls. In addition, the internal structure of galls differed between the two species. Galls containing A. tojoi consist of a single chamber with inner walls clearly covered with whitish fungal mycelia after the gall midges develop into second instars. Those containing the Ceratoneura sp. have multiple chambers with hard black inner walls. Although some eulophids are known to be inquilines of galls induced by Asphondylia species, we consider that the Ceratoneura sp. is probably a true gall inducer because of the different gall structure and absence of fungal mycelia in their galls. This is the first report detailing the annual life history of a Ceratoneura species. Asphondylia tojoi represents the first example of monophagous Asphondylia species with a multivoltine life history on a deciduous tree.     

Developmental anatomy and immunocytochemistry reveal the neo-ontogenesis of the leaf tissues of Psidium myrtoides (Myrtaceae) towards the globoid galls of Nothotrioza myrtoidis (Triozidae)

Key message

The temporal balance between hyperplasia and hypertrophy, and the new functions of different cell lineages led to cell transformations in a centrifugal gradient that determines the gall globoid shape.

Abstract

Plant galls develop by the redifferentiation of new cell types originated from those of the host plants, with new functional and structural designs related to the composition of cell walls and cell contents. Variations in cell wall composition have just started to be explored with the perspective of gall development, and are herein related to the histochemical gradients previously detected on Psidium myrtoides galls. Young and mature leaves of P. myrtoides and galls of Nothotrioza myrtoidis at different developmental stages were analysed using anatomical, cytometrical and immunocytochemical approaches. The gall parenchyma presents transformations in the size and shape of the cells in distinct tissue layers, and variations of pectin and protein domains in cell walls. The temporal balance between tissue hyperplasia and cell hypertrophy, and the new functions of different cell lineages led to cell transformations in a centrifugal gradient, which determines the globoid shape of the gall. The distribution of cell wall epitopes affected cell wall flexibility and rigidity, towards gall maturation. By senescence, it provided functional stability for the outer cortical parenchyma. The detection of the demethylesterified homogalacturonans (HGAs) denoted the activity of the pectin methylesterases (PMEs) during the senescent phase, and was a novel time-based detection linked to the increased rigidity of the cell walls, and to the gall opening. Current investigation firstly reports the influence of immunocytochemistry of plant cell walls over the development of leaf tissues, determining their neo-ontogenesis towards a new phenotype, i.e., the globoid gall morphotype.     

Phenylalanine ammonia-lyase activity in suspension cultures of Ulmus pumila and U. campestris treated with spores of Ceratocystis ulmi

Summary Cell suspension cultures of a Ceratocystis ulmi-resistant (Ulmus pumila) and a -susceptible elm (U.campestris) were established from leaf callus tissue. Treatment of cultures with spores of C.ulmi induced a large increase in the activity of phenylalanine ammonialyase, only in the cells of the resistant species U.pumila with a maximum after 24 h. Inoculated U.pumila cells also excreted a red unidentified chemical into the culture medium. Neither responses were induced in inoculated U.campestris cultures. The results are discussed in relation to the development of the elm cell culture system as a model for studying the differential biochemical mechanisms of disease resistance in elms.     

The number of cecidomyiid insect galls affects the photosynthesis of Machilus thunbergii host leaves

Previous studies of the impacts of galls on host leaf photosynthesis do not suggest any general trends, with a reported range of effects from negative to positive. In this study, photosynthetic characteristics such as chlorophyll fluorescence (Fv/Fm), photosynthetic capacity, and stomata conductance were determined in two types of fruit-like galls (red ovoid and green obovate galls) induced by Daphnephila taiwanensis and Daphnephila sueyenae, respectively, in order to investigate whether the number of galls affects the photosynthesis of galled leaves of Machilus thunbergii. In 2008, chlorophyll fluorescence and photosynthetic capacity were negatively correlated with gall numbers, non-significantly and significantly, respectively, whereas stomata conductance was positively but non-significantly correlated with gall numbers. In 2009, photosynthesis capacity and stomata conductance were negatively, but non-significantly, correlated with gall numbers. Results imply that photosynthesis in M. thunbergii leaves is slightly affected by the number of cecidomyiid insect galls, and that the higher the gall number, the greater the negative effect that galls have on host leaf photosynthesis and subsequent infection.     

Morphological and Histochemical Changes Occurring during the Life-span of Root-tip Galls on Lolium perenne Induced by Longidorus elongatus

The RNA and protein content of perennial ryegrass root-tip galls induced by Longidorus elongatus were measured from transverse sections and the morphology described. Galls progressed through five distinct stages and were viable for only 10-12 days at 18 C, after which they collapsed and became necrotic. In the initial stage hypertrophy occurred and cells contained enlarged nuclei and nucleoli, a greater proportion of cytoplasm, and increased concentrations of protein. This was followed by hyperplasia; cells divided to give two or four daughter cells, accompanied by a proportionate reduction in volumes of cytoplasm, nuclei, and nucleoli and reduced concentrations of RNA and protein. The third stage was secondary hypertrophy with enlarged, amoeboid nuclei and nucleoli and a significant increase in concentration of RNA and protein. In the final two stages, as feeding by L. elongatus progressively removed cell contents, most cells were devoid of inclusions and galls collapsed and were invaded by soil bacteria. This ordered development and exploitation of galls suggests that L. elongatus may have two phases in its feeding.