ANATOMY OF SOME LEAF GALLS OF ROSA WOODSII (ROSACEAE)

Infection of Rosa woodsii by some members of the order Hymenoptera results in neoplasmic outgrowths on the leaves. One type of outgrowth produces a spherical swelling (leaf gall) while the other has extensive hair-like proliferations (hairy gall). The anatomy and ultrastructure of these galls were examined by light microscopy and transmission electron microscopy. The leaf gall cells were considerably larger than normal cells, lacked well-developed chloroplasts and were loosely arranged with prominent intercellular spaces. Vascular bundles were scattered throughout the gall tissue. The upper three cell layers of the leaf gall tissue resembles a periderm, having many suberin lamellae. The suberin lamellae were often traversed by pores which may represent incomplete plasmodesmata. Phenolic compounds were commonly seen both in the normal and gall cells. A layer of internal cells of the hairy galls have remarkably thickened cell walls, presumably due to the deposition of cellulosic substances. Unlike leaf galls, the epidermal cells of the hairy galls were not heavily cuticularized and no periderm was found. The hair-like outgrowths present on the outer surface of these galls had a central vascular bundle. The epidermis of the outgrowths also had thickened cell walls, and trichomes occurred on the outer surface. The structural modifications brought about by the insect invasion in these two galls are compared and their roles in gall formation are discussed.     

DEVELOPMENTAL ANATOMY OF THE HORNED OAK GALL INDUCED BY CALLIRHYTIS CORNIGERA ON QUERCUS PALUSTRIS (PIN OAK)

The horned oak gall forms on twigs of Quercus palustris Muench. and is initiated when the wasp Callirhytis corrigera O.S. oviposits into the periderm or cortex of the twigs. Injury to phellogen as a consequence of oviposition results in dedifferentiation of phelloderm and underlying phloem tissue to form a wound-response phellogen. The wound-response phellogen encircles and compartmentalizes the wasp ovum and is continuous with the normal stem phellogen. This tissue arrangement forms the framework for the ensuing stages of gall development. Development of the insect larva coincides with the formation of a gall-matrix phellogen. This additional meristem is derived from locally hyperplastic stem phellogen where adjacent to the wound-response phellogen. The essentially parenchymatous, roughly spherical body of the gall, the gall matrix, is formed chiefly from derivatives of the gall-matrix and wound-response phellogens. In the immediate area of the wasp larva, the wound-response phellogen produces cells toward the larva that differentiate to form a vascularized, externally sclerified, horn-shaped chamber containing in its base the developing insect larva. The involvement of the vascular cambium is apparent during intermediate gall development stages. Vascular strands, produced transverse to the stem axis, penetrate the gall-matrix tissue and terminate near the base of the horn-like larval chamber. Vessel elements in the region of the gall that are not included in this tissue alteration often become heavily tylosed. Disruption of the vascular tissue through the galled area appears to be a primary cause of twig death.     

Root-knot development in mulberry infested with Meloidogyne incognita

Healthy mulberry roots were inoculated with second stage juveniles of the root-knot nematode, Meloidogyne incognita and the sequential anatomical changes in the root concurrent with the development of the nematode were studied with light and scanning electron microscopes. Visible anatomical changes occurred four weeks post-inoculation when the pear-shaped adult female nematodes appeared in the tissues. The infected roots lost their circular outline and increased in thickness as traumatic parenchyma was induced in the root. The stele was disorganised with reduced and deformed vascular elements. Many giant cells developed in the traumatic tissue, adjacent to the adult females. Eight weeks after the inoculation, cavities developed around the adult females by tissue disintegration, and the galls became discernable on the roots. The number and size of thegalls increased in the next three weeks, corresponding to the development of more traumatic tissues and the enlargement of the adult female nematodes. The majority of the nematodes were settled towards the gall periphery, with their posterior oriented outwards for the release of their eggs into soil by the disintegration of the outer root layers. But many were settled deep inside the gall tissue without a channel to release their eggs to soil. The inner cavities enlarged in large proportions, sometimes occupying the major volume of the gall. The conductive tissues of the root were totally disorganised or were nonexistent.     

Temperature-sensitive loss of tumor characteristics in a tobacco crown gall strain

Summary Three independently isolated tobacco crown gall strains incited byAgrobacterium tumefaciens C58 required phytohormone (auxin and cytokinin) supplements in the basal medium to grow, at 37°C. Six other tobacco crown gall strains incited, respectively, byA. tumefaciens IIBV7, B6, CGIC, A6NC, 27 and AT4 expressed, at 37°C, the tumor characteristic of ability to grow in vitro on medium lacking phytohormones. Nopaline was not detectable in C58 tumors cultured at 37°C, but octopine was produced by B6 tumor tissues incibated at the elevated temperature. C58 tumor strains kept at 37°C for 1 week or more lost the ability to express tumor characteristics at 27°C such as tissue morphology, growth on basal medium lacking phytohormones and nopaline production. Heat-treated C58 tissues also differed from the original tumor strain in regeneration ability and phytohormone requirements of explants; i.e. explants from regenerated, heart-treated C58 tumors required both auxin and cytokinin for growth in vitro.     

DEVELOPMENTAL ANATOMY AND HISTOCHEMISTRY OF LIGHT-INDUCED CALLUS FORMATION BY DIÖON EDULE (ZAMIACEAE) SEEDLING ROOTS IN VITRO

Light exposure caused massive areas of callus to develop from primary roots of aseptically cultured Diöon edule seedlings. Callus initiation and continued growth was due to cortical cell hypertrophy and subsequent periclinal cell division. Callus initiation occurred in the subdermal cortex and developed radially and centripetally from the locus of initiation. Callus formation encompassed virtually all of the cortex, but did not incorporate any of the vascular tissues. With very large calluses, sectors of internal periderm arose between the developing callus and the remaining quiescent cells of the inner cortex. Most of the callus cells were typical, vacuolate parenchyma with cellulose walls, and large, multilobed amyloplasts. Callus also contained idioblasts with globular deposits of polyphenols. Adjacent cortical cells were typical parenchyma with peripheral cytoplasm, but contained small plastids with little starch accumulation.     

油茶叶肿病子房瘿体和叶片瘿体的形态结构特征观察

采用光学显微镜观察了油茶叶肿病子房瘿体和叶片瘿体的形态特征和组织结构特点。结果表明:(1)油茶叶肿病瘿体是油茶的幼嫩子房和幼叶被细丽外担菌感染后所导致的组织增生而成的,细丽外担菌分布于成熟子房瘿体的外表面和叶片瘿体的表面。(2)子房瘿体由受感染的雌蕊子房增殖而来,成熟后表皮层脱落。(3)子房壁分两层,外层子房壁肉质肥厚,主要由大型薄壁细胞构成,是食用的主要部分,内层子房壁为较薄的心皮层,内外两层子房壁之间具有较大的空隙;心皮内有胚珠,胚珠着生在中轴胎座上,胚珠内部中空而没有育性。(4)叶片瘿体为受感染的幼嫩叶片增殖所致,由大型薄壁细胞构成,瘿体表面具表皮层,成熟后表皮脱落。(5)在正常叶片与叶片瘿体的过渡区内有维管束相通,瘿体侧的厚度比正常叶片厚度增加3～4倍,细胞体积增大5～10倍,但瘿体细胞内无叶绿体。     

The response of resistant kiwifruit (Actinidia chinensis) to armoured scale insect (Diaspididae) feeding

The responses of five experimental genotypes and one commercial variety of kiwifruit (Actinidia chinensis) to attack by two polyphagous, congeneric armoured scale insect pests (Hemiberlesia rapax and H. lataniae) are described. H. lataniae feeding elicits a response in the bark and fruit of all but one of the experimental genotypes, leading to the development of wound periderm over a 4–5 week period, and death of the insect. The response, which differs slightly between tissue types and genotypes, consists of wound periderm formation in a bowl shape beneath and around the insect, preventing its stylet from reaching normal unmodified parenchyma tissue. Wound periderm cell walls become suberised and cells beneath the insect become filled with phenolic compounds. In some cases, cells beneath the insect become hypertrophic or undergo lysis, exhibiting characteristics of a hypersensitive-like response. The remaining genotype showed no physical change in tissue structure in response to H. lataniae feeding, and the insects survived but were substantially reduced in size. These results suggest that both physical and chemical plant resistance responses are involved. In contrast, H. rapax elicited no observable histological response from any of the genotypes and the insects developed normally on bark and fruit. Both insect species developed normally on leaf petioles and these exhibit only slight cell wall thickening in response to their feeding. This unusual plant defensive response to a sucking insect has similarities to simple types of gall formation in response to insect and pathogen attack and has characteristics of resistance gene-mediated models of plant defence.     

GENOTYPIC VARIATION AND INTEGRATION IN HISTOLOGICAL FEATURES OF THE GOLDENROD BALL GALL

The herb Solidago altissima (Compositae) forms a gall when attacked by the fly Eurosta solidaginis (Diptera: Tephritidae). We performed an experiment to determine how histological features of gall morphology contribute to previously observed genetic variation in gall diameter. Galls induced on 10 replicated plant clones were sectioned, and their internal tissues and cells measured. Four concentric tissue zones were identified, including a cytoplasmically rich tissue lining the insect's central chamber, and a cytoplasmically poor cortex. As expected, outer gall diameter differed among clones, with a broad sense heritability of 0.29. However, clonal differences for component tissue thicknesses were found for only two of the zones; cortex thickness showed the greater genotypic variation, with a broad sense heritability of 0.30. Path analysis was used to examine the contribution of the zone thicknesses, vascular supply and cell sizes to outer gall diameter at the phenotypic, genotypic and environmental-developmental levels. These showed that cortex thickness was the single greatest determinant of gall size. At the phenotypic level, the single most important determinant of cortex thickness was the number of cortical cells, whereas the amount of cortical vascularization was second in importance. But, at the genotypic level of analysis, vascularization was the single most important determinant of genotypic differences in gall size. The larger the gall, the greater the protection to the inducing insect. Since the bulk of the gall consists of large, cytoplasmically poor cells, the insect gains protection while imposing a small cost on the plant.     

Symplastic and apoplastic sugar contents in gall tissues and callus of the sumac (Rhus chinensis MILL.)

To elucidate the role of cell wall in interaction with gall-inducing organisms, symplastic and apoplastic sugar contents in different shapes of gall tissue of the sumac (Rhus chinensis Mill.) were compared with those of the callus. The gall tissues with vascular cylinders, intercellular spaces and callus were fractionated into symplastic [methanol (MeOH), hot water (HW), and starch] fractions and apoplastic [pectin, hemicellulose, trifluoroacetic acid (TFA)-soluble, and cellulose] fractions. Symplastic sugar content of gall tissues was higher than that of callus. In apoplastic (cell wall) fractions, the cellulose content of gall tissues was lower than that of callus, due to large amount of pectin with high ratio of uronic acid (UA) and hemicellulose with low ratio of UA. Analysis of neutral sugar component of the hemicellulosic, TFA-soluble fraction showed that arabinose (side chain) and galactose (backbone) of arabinogalactan were rich in gall tissues and callus. The gall tissues had higher glucose and lower xylose contents than the callus. These results suggest that the structure of cell wall polysaccharides of gall changed during its development with an increase in symplastic sugar contents. The feeding activities occuring in gall by the gall-inducers were discussed.     

Patterns of cell elongation in the determination of the final shape in galls of Baccharopelma dracunculifoliae (Psyllidae) on Baccharis dracunculifolia DC (Asteraceae)

Cell redifferentiation, division, and elongation are recurrent processes, which occur during gall development, and are dependent on the cellulose microfibrils reorientation. We hypothesized that changes in the microfibrils orientation from non-galled tissues to galled ones occur and determine the final gall shape. This determination is caused by a new tissue zonation, its hyperplasia, and relative cell hypertrophy. The impact of the insect’s activity on these patterns of cell development was herein tested in Baccharopelma dracunculifoliae—Baccharis dracunculifolia system. In this system, the microfibrils are oriented perpendicularly to the longest cell axis in elongated cells and randomly in isodiametric ones, either in non-galled or in galled tissues. The isodiametric cells of the abaxial epidermis in non-galled tissues divided and elongated periclinally, forming the outer gall epidermis. The anticlinally elongated cells of the abaxial palisade layer and the isodiametric cells of the spongy parenchyma originated the gall outer cortex with hypertrophied and periclinally elongated cells. The anticlinally elongated cells of the adaxial palisade layer originated the inner cortex with hypertrophied and periclinally elongated cells in young and mature galls and isodiametric cells in senescent galls. The isodiametric cells of the adaxial epidermis elongated periclinally in the inner gall epidermis. The current investigation demonstrates the role of cellulose microfibril reorientation for gall development. Once many factors other than this reorientation act on gall development, it should be interesting to check the possible relationship of the new cell elongation patterns with the pectic composition of the cell walls.     

Regeneration of tobacco plants from crown gall tumors

Summary Tissue culture methods have been developed for regeneration of normal appearing tobacco plants from bacteria-free crown gall strains incited byAgrobacterium tumefaciens C58, IIBV7, B6, CGIC, A6NC, 27, and AT4. Regenerants fall into two categories depending on the properties of tissues from these plants. The first type of regenerant was obtained from tumors incited byA. tumefaciens C58 and it retained the potential for expression of tumor characteristics such as a nonrequirement for phytohormones (auxin and cytokinin) by explants in vitro and the presence of detectable concentrations of nopaline. Normal appearing plants obtained from C58 tumors had much lower concentrations of nopaline than the corresponding tumor tissue (130 versus 1700 μg per g dry wt) indicating a parallel repression of abnormal growth and nopaline concentrations in regenerants. The second type of regenerant was obtained from tumors incited by the otherA. tumefaciens strains and was characterized by requirements for phytohormones by explants in vitro and the apparent lack of octopine or nopaline in regenerant tissues.     

Comparative histopathology of chromomycosis and cladosporiosis in the experiment

Conclusions 1. The reaction of the brain tissue and skin in cladosporiosis and chromomycosis (as well as in some other fungal affections) is in many respects similar and is manifested by the formation of microabscesses, containing giant cells, with phagocytized elements of the causative agents. The fungus contained in the cells at the late phase of the experiment retains its viability, which may be the cause of the dissemination of the process when the reactivity of the organism is lowered.2. The course of cladosporiosis of the brain is characterized by the absence of visible changes of the nerve cells even near the growth of the fungus. The observed edematous changes of neurons in the area of the infiltrations are connected with the foci of the purulent liquefaction of the brain tissue.3. The tissue form both in chromomycosis and cladosporiosis is a stage of the fungus development independent of the organ which it affects (skin, brain).4. The predominating involvement of the brain byCladosporium trichoides may be partly due to tis quicker development in the tissue of the skin as compared toHormodendron pedrosoi and to its ability to germinate through the walls of the blood vessesls, resulting in the penetration into their lumen and hematogenic dissemination.5. Under the conditions of the increased content of glucocorticoids in the organism, the macrophagic and giant cell reaction of the tissues is regularly inhibited, the formation of collagens is disturbed, which results in the generalization of the mycotic process.     

Observation by SEM of the attachment ofAgrobacterium tumefaciens to the surface of vinca,asparagus and rice cells

Transformation of vinca cells was performed by the co-cultivation of cell-wall regenerated vinca protoplasts withAgrobacterium tumefaciens. Using thisin vitro and single cell system, attachment of the bacteria to the surface of vinca cells was observed by scanning electron microscopy (SEM). Figures of the bacteria polarly binding to the plant cell wall were often observed. AsEscherichia coli does not attach to the plant cells at all, the observed attachment ofA. tumefaciens is suggested as a characteristic feature in crown gall induction. Even though no evidence of transformation was obtained by the co-cultivation methods, a similar attachment was observed in the cell-wall regenerated protoplasts of rice. The bacteria also attached to the surface of isolated mesophyll cells of asparagus and root hairs of rice. From these observation, we concluded that the attachment is not the limiting step of crown gall induction byA. tumefaciens in monocotyledonous plants. Extracellular fibrils like pili were observed with a few strains of A.tumefaciens for the first time. These fibrils were observed regardless of their ability of attachment and infectivity.     

MULTINUCLEATE GIANT CELL FORMATION IN A PACHYPSYLLA GALL ON CELTIS

Dundon , Thomas R. (Saint Louis U., Saint Louis, Mo.) Multinucleate giant cell formation in a Pachypsylla gall on Celtis . Amer. Jour. Bot. 49(7): 800–805. Illus. 1962.—Cytological antecedents of the multinucleate giant cell in gall tissue of Pachypsylla mamma on leaves of hackberry, Celtis occidentalis, have been presented. The nymph's stylet punctured the epidermis and terminated in a single mesophyll cell where it remained fixed until a multinucleate giant cell formed there. An intracellular cytoplasmic reaction occurred at the tip of the stylet which was attributable either to the secretory or the sucking activity of the nymph. The walls of cells surrounding the tip of the stylet gradually became less distinct as demonstrated by a decreasing affinity for cellulose stain. Later, cellulolytic effects were easily visible as large breaches formed in the walls of cells grouped around the stylet. The cellulolytic process spread centrifugally from the tip of the stylet until complete dissolution of all but the outermost walls of 6–8 cells was accomplished, leaving a typically shaped multinucleate giant cell. In one instance, nuclei from adjacent cells were observed partially drawn through apertures in the cell walls into the protoplast of an incompletely formed giant cell containing the stylet. This nuclear movement was attributed to a centripetal flow of plant juice caused by the sucking activities of the nymph. These findings do not support an earlier theory that the multinucleate giant cell was a product of plant growth, namely, enlargement of a single mesophyll cell and multiple karyokinesis or amitosis.     

Ice formation and tissue response in apple twigs

Abstract. The response of apple twig tissue to a freezing stress was examined using a combination of low temperature scanning electron microscopy and freeze substitution techniques. Bark and wood tissues responded differently. In the bark, large extracellular ice crystals were observed in the cortex. The adjacent cortical cells collapsed and a large reduction in cell volume was observed. The extent of cell collapse throughout the bark was not uniform. Cells in the periderm, phloem and cambium exhibited little change in cell volume compared to cortical cells. Large extracellular ice crystals were not observed in the xylem or pith tissues. The xylem ray parenchyma and pith cells did not collapse in response to a freezing stress, but retained their original shape. The pattern of ice formation and cell response was not observed to change with season or the level of cold acclimation. This study supported the concept that bark and xylem tissues exhibit contrasting freezing behaviour. The observations were consistent with the idea that water in bark freezes extracellularly while water in xylem ray parenchyma and pith cells may supercool to temperatures approaching –40 °C prior to freezing intracellularly.     

The protein content of tissues in cynipid galls (Hymenoptera: Cynipidae): Similarities between cynipid galls and seeds

Cynipid galls are examples of induced plant development, where the gall inducer is in control of cell differentiation and morphogenesis of a new plant organ. This study concentrates on the tissues of the larval chamber common to all cynipid galls. The protein content of the inner gall tissue was compared to that of non‐gall plant tissues. We investigated three oak and two rose galls and their respective host plants. Total protein signatures of inner gall tissues were different from those of non‐gall plant tissues, and among the five galls. N‐terminal sequences were obtained for two abundant proteins from the inner gall tissues of D. spinosa and A. quercuscalicis, which were common to all galls, at 62 and 43 kDa. Database queries suggest the 62 kDa protein to be homologous to a protein disulphide isomerase (PDI), and the 43 kDa protein to be homologous to NAD‐dependent formate dehydrogenase (FDH). A naturally biotinylated protein was detected at 33 kDa during Western analyses with streptavidin. Western analyses revealed the presence of the biotinylated protein and PDI in the inner gall tissues of all five galls, while FDH was only detected in A. quercuscalicis and A. fecundator. PDI was also common to all non‐gall tissues, while FDH was not detected in non‐gall tissues, and the biotinylated protein was only detected in seeds. The proteins identified in the inner gall tissue suggest that (a) inner gall tissues in some galls are under respiratory stress, and (b) cynipid gall formation might involve the ectopic expression of seed‐specific proteins.     

Penetration of the Periderm of Red Raspberry Canes by Leptosphaeria coniothyrium

Umwounded raspberry canes were inoculated with Leptosphaeria coniothyrium. After penetration of the epidermis the fungus invaded the cortex readily. The accumulation of mycelium in this tissue lead to a partial digestion of the middle lamellae of the outermost cork layer within the polyderm. The fungus penetrated this single cell barrier through the openings between the separated cells and colonized the phelloid tissue between the first and second cork layer. After vigorous growth in this non-suberized tissue the fungus penetrated the second cork barrier in the same way as the first layer. This mode of penetration was repeated until the fungus had spread beyond the periderm and into the vascular tissues. The invasion process occurred rather slowly and was enhanced by weakening of the canes by defoliation at the time of inoculation.     

An electron microscope study of sunflower crown gall tumor

Summary The inception and developmental phases of sunflower (Helianthus annuus) crown gall tumor growth induced byAgrobacterium tumefaciens were studied submicroscopically. Bacteria were found only in the inception phase. Chloroplasts from tumor cells of both phases showed several kinds of structural variation. Other cytoplasmic organelles remained more or less normal.This investigation was supported in part by an American Cancer Society Institutional Grant.     

Redifferentiation of leaflet tissues during midrib gall development in Copaifera langsdorffii (Fabaceae)

The tree Copaifera langsdorffii is a superhost for galling herbivores. This plant species has great morphogenetic potential, and responds differently to the stimuli of more than 20 gall-inducing insects. Among these, an undescribed species of Cecidomyiidae induces a midrib gall in which a radial cecidogenetic field is generated and the leaflet tissues redifferentiate. Our objectives were to assess the amplitude of this cecidogenetic field, in which the leaflet tissues were influenced by the feeding action of the cecidomyiid; how the final gall shape was generated; and if tissue redifferentiation conferred any adaptive value on the galling herbivore. Leaflet morphogenesis followed the pattern described in the literature for simple leaves, resulting in a mesophytic arrangement. Tissue redifferentiation due to gall formation revealed that in a midrib gall, abaxial epidermal cells divided to enlarge the gall; spongy parenchyma cells originated the storage tissue, secretory structures, and vascular bundles; palisade parenchyma cells became homogeneous; and adaxial epidermis originated the nutritive tissue. Cell elongation, a necessary step towards cell redifferentiation, is triggered by an increase in water transport to the gall site and vacuole pressure due to neoformed xylem bundles. The generation of the final shape of the midrib gall involved repetitive histological steps in response to the amplitude of the cecidogenetic field. The largest impact of the cecidomyiid feeding action occurred in gall tissues redifferentiated from protoderm and adaxial ground meristem, which provided advantages to the gall maker of the C. langsdorffii midrib gall in terms of nutritional value, microenvironment, and protection against natural enemies.     

矩镰荚苜蓿地下茎次生结构异常发育的解剖学研究

矩镰荚苜蓿是中国特有植物,分布于青藏高原东缘,具有发达的地下扩展茎。为探明矩镰荚苜蓿地下茎异常发育与高原气候适应的关系,该研究采用常规石蜡切片法对地下茎初生结构与次生结构进行解剖观察。结果表明：(1)与初生结构相比,矩镰荚苜蓿地下茎次生结构发育不均衡,仅有少量维管束正常发育,木质部发达。(2)地下茎次生生长会产生内、外两种周皮,外周皮由靠近韧皮部的内皮层细胞形成,内周皮由靠近木质部的髓细胞形成,内、外周皮形成后取代了表皮和初生结构中的主要薄壁组织,形成了较复杂的新防护系统。(3)外周皮向内隘缩或内周皮向外延伸都会引起地下茎的分裂,但暂未观察到两种分裂方式同时发生。研究认为,矩镰荚苜蓿地下茎形成内、外周皮与异常分裂,可以增强对干旱和寒冷胁迫的抵御能力,是矩镰荚苜蓿对青藏高原寒旱环境的适应策略。