The Relationship Between Oil Gland and Fruit Development in Washington Navel Orange (Citrus sinensis L. Osbeck)

Changes in structure, size and number of oil glands locatedin the fruit rind were assessed in developing fruit of the WashingtonNavel orange (Citrus sinensis L. Osbeck) from pre-anthesis tofruit maturity. Initiation of oil glands was found to be restrictedto early fruit development. Glands continued to develop throughoutfruit growth, until all reached maturity by a fruit size of30 to 50 mm diameter. Mature glands continued to enlarge withfruit growth. Mature fruit had between 8 000 and 12 000 oilglands. Anatomical studies of the fruit rind were carried outusing light microscopy on samples prepared by different tissueprocessing methods. Glands were found to develop from a clusterof cells adjacent to the fruit epidermis, into a structure consistingof a central cavity surrounded by several layers of epithelialcells. All glands were joined to the fruit epidermis, irrespectiveof their stage of development. Neither lignin nor suberin waspresent in the gland. Gland cavity formation appeared to involveschizogeny. Copyright 2001 Annals of Botany Company Washington Navel orange, Citrus sinensis L. Osbeck, fruit development, secretory cavity, oil gland, image analysis, light microscopy     

Histological and Physiological Characterization of Rind Breakdown of 'Navelate' Sweet Orange

Rind breakdown of ‘Navelate’ sweet orange is characterizedby sunken colourless areas of the peel which develop into reddish-brown,dry areas partially covering the exposed portion of the maturefruit. Sudden changes in relative humidity at fruit colour breakseem to be responsible for the natural development of this disorder,which begins at the transitional zone of the flavedo-albedoand advances across the flavedo reaching the epidermis. Affectedcells have reduced amounts of cytoplasm located in a centralposition and have twisted and squashed walls, forming areasof collapsed cells amongst the healthy cells of the flavedoand albedo. Comparisons of healthy and damaged areas of affectedfruits showed no significant differences in wax morphology andcuticular thickness or permeability. Our results suggest thatan excessive loss of water from hypodermal and albedo cellsis responsible for the disorder. Copyright 2001 Annals of BotanyCompany Citrus, physiological disorder, cell collapse, rind blemish, fruit quality     

Stereological estimation of cell wall density of DR12 tomato mutant using three-dimensional confocal imaging

Background and Aims

The cellular structure of fleshy fruits is of interest to study fruit shape, size, mechanical behaviour or sensory texture. The cellular structure is usually not observed in the whole fruit but, instead, in a sample of limited size and volume. It is therefore difficult to extend measurements to the whole fruit and/or to a specific genotype, or to describe the cellular structure heterogeneity within the fruit.

Methods

An integrated method is presented to describe the cellular structure of the whole fruit from partial three-dimensional (3D) observations, involving the following steps: (1) fruit sampling, (2) 3D image acquisition and processing and (3) measurement and estimation of relevant 3D morphological parameters. This method was applied to characterize DR12 mutant and wild-type tomatoes (Solanum lycopersicum).

Key Results

The cellular structure was described using the total volume of the pericarp, the surface area of the cell walls and the ratio of cell-wall surface area to pericarp volume, referred to as the cell-wall surface density. The heterogeneity of cellular structure within the fruit was investigated by estimating variations in the cell-wall surface density with distance to the epidermis.

Conclusions

The DR12 mutant presents a greater pericarp volume and an increase of cell-wall surface density under the epidermis.     

Fatigue loading of tendon results in collagen kinking and denaturation but does not change local tissue mechanics

Fatigue loading is a primary cause of tendon degeneration, which is characterized by the disruption of collagen fibers and the appearance of abnormal (e.g., cartilaginous, fatty, calcified) tissue deposits. The formation of such abnormal deposits, which further weakens the tissue, suggests that resident tendon cells acquire an aberrant phenotype in response to fatigue damage and the resulting altered mechanical microenvironment. While fatigue loading produces clear changes in collagen organization and molecular denaturation, no data exist regarding the effect of fatigue on the local tissue mechanical properties. Therefore, the objective of this study was to identify changes in the local tissue stiffness of tendons after fatigue loading. We hypothesized that fatigue damage would reduce local tissue stiffness, particularly in areas with significant structural damage (e.g., collagen denaturation). We tested this hypothesis by identifying regions of local fatigue damage (i.e., collagen fiber kinking and molecular denaturation) via histologic imaging and by measuring the local tissue modulus within these regions via atomic force microscopy (AFM). Counter to our initial hypothesis, we found no change in the local tissue modulus as a consequence of fatigue loading, despite widespread fiber kinking and collagen denaturation. These data suggest that immediate changes in topography and tissue structure – but not local tissue mechanics – initiate the early changes in tendon cell phenotype as a consequence of fatigue loading that ultimately culminate in tendon degeneration.     

Ethephon application induces symptoms of fruit tissue degeneration in watermelon

Vegetable Research Division, NHRI, 475 Imok-dong, Jangan-gu, Suwon, Gyeonggi-do, 440-706, Republic of Korea Flesh tissue degeneration (called blood-black heart; BBH) of watermelon (Citrullus vulgaris S.) is occasionally observed in Korea. Fruits with BBH have lower quality, a dark-red flesh, and reduced firmness of the rind, often producing an unpleasant flavor. Although causal factors are thought to be undesirable soil moisture conditions, e.g., drought or water-logging, temperature extremes, or virus infection, the mechanism for this physiological disorder is not clearly understood. It is possible that ethylene gas (C₂H₄) is involved in degrading the cell walls. To determine such an implication for ethylene in the occurrence of BBH, we foliar-applied various concentrations of ethephon (100, 200, 400, 800, or 1000 mg L^-1) to watermelon plants at 5 or 10 d prior to harvesting, then monitored the development of this disorder in their fruits. At 400 mg L^-1 or higher, quality was diminished and the fruit had softer rind tissues. About 25% of the fruits harvested at that level exhibited BBH versus 100% of the fruits exposed to 800 or 1000 mg L^-1 ethephon. Concomitant with the onset of BBH, those affected fruits produced elevated amounts of ethylene gas during the 4-d measurement period. Therefore, a high incidence of BBH may well be related to this increased ethylene production, which can be triggered by both unfavorable environmental conditions and inappropriate cultural practices.     

西瓜种质资源主要植物学性状的遗传多样性及相关性分析

以我国西瓜、甜瓜种质资源中期库内1200份西瓜种质为材料,对果实重量、果肉颜色、中心糖、种子千粒重等12项主要植物学性状进行遗传多样性和相关性分析。多样性分析结果表明:我国西瓜资源12项植物学性状多样性指数平均值为1.70,种子千粒重多样性指数最大为2.37,果实形状多样性指数最小为1.02,其中果皮底色、果皮覆纹颜色、果肉颜色、果实重量、果实中心糖、种子千粒重性状数据分布较为分散。数量性状变异系数平均值为31.8,变异幅度均比其平均值大1～3倍。相关性分析结果表明:果实形状和果形指数、果肉颜色和果实中心糖、果肉颜色和种子千粒重、果皮厚度和硬度4对性状相关性极显著。种子千粒重和果实中心糖、果实重量和果皮厚度、果实重量和果皮硬度、覆纹颜色和形状4对性状相关性显著。     

Tissue-specific biomass recalcitrance in corn stover pretreated with liquid hot-water: SEM imaging (part 2)

In the first part of our work, we combined compositional analysis, pretreatment and enzyme hydrolysis for fractionated pith, rind, and leaf tissues from a hybrid stay-green corn, in order to identify the role of structural characteristics on enzyme hydrolysis of cell walls. Hydrolysis experiments coupled with chemical analysis of the different fractions of corn stover showed significant differences in cell wall structure before and after liquid hot water pretreatment. The extent of enzyme hydrolysis followed the sequence rind < leaves < pith with 90% conversion of cellulose to glucose in 24 h in the best cases. Since similar lignin contents remained after liquid hot water pretreatment of leaves, rind, and pith, our results indicated that the amount of lignin alone is not sufficient to explain the different enzymatic hydrolysis characteristics of the fractions. While the role of structural characteristics on enzyme hydrolysis of cell walls is measured as described in part I, the SEM images presented in this part II of our work show that sugar yields from enzymatic hydrolysis of corn fractions correlate with changes in plant cell wall structure both before and after liquid hot water pretreatment.     

Indole-3-acetic acid, ethylene, and abscisic acid metabolism in developing muskmelon (Cucumis melo L.) fruit

Hormonal metabolism associated with fruit development in muskmelon was investigated by measuring IAA, ABA, and ACC levels in several tissues at various stages of development. In addition, levels of conjugated IAA and ABA were determined in the same tissues. Ethylene production, which is believed to signal the ripening and senescence of mature fruit, was also measured. Ethylene production was highest in the outer tissue near the rind and gradually declined during maturation, except for a dramatic increase in all fruit tissues at the climacteric. In contrast to ethylene production, ACC levels increased during maturation and remained equal throughout the fruit until the climacteric, when levels in the outer tissues increased nearly 5-fold over levels in the inner tissues. The consistent presence of ACC indicates that ACC oxidase rather than the availability of ACC regulates ethylene production in developing fruits. ABA and ABA esters generally declined during maturation, however an increase in ABA esters associated with the outer mesocarp tissue was observed in fully mature, climacteric fruit. IAA and IAA conjugates were only found in the outer tissue near the rind, and their levels remained low until the fruit was fully mature and entering the climacteric. At that time, increased levels of conjugates were detected. The late burst of hormonal metabolism in the outer mesocarp tissue appeared to signal its degeneration and the deterioration that typically occurs in ripening fruit. The tissue-specific conjugation of IAA and ABA, in addition to the production of climacteric ethylene, may represent part of the signaling mechanism initiating ripening and eventual deterioration of tissues in muskmelon fruits.Abbreviations ABA abscisic acid - ACC 1-aminocylopropane-1-carboxylic acid - DAP days after pollination - IAA indole-3-acetic acid     

Photodynamic assistance increases the efficiency of the process of microinjection in animal cells

A microinjection process is described that involves the photodynamically-assisted puncture of an animal cell membrane by means of a brief and partial degeneration resulting from cell membrane damage. The ratio of dye-injected rat pheochromocytoma cells that became detached three and six days after photodynamically-assisted microinjection was 9%; however, it was 83% when a conventional mechanical microinjection process was used.     

Epidermal focussing and the light microenvironment within leaves of Medicago sativa

The light microenvironment within leaves of Medicago sativa L. cv. Armor was related to the anatomy of the epidermis. Leaf epidermal cells had a convex shape and appeared to act as lenses that focussed light within the upper region of the palisade. In leaves irradiated with collimated light, epidermal focussing was demonstrated by ray tracing, photomicrography and fiber optic probe measurements, where lens signatures were observed. No relationship was observed between the location of focal spots within the palisade and chloroplast positioning. Epidermal focussing could be largely eliminated by irradiating leaves with diffuse light or by coating their surface with a thin layer of mineral oil that closely matched the refractive index of the cell walls. Measurement of variable chlorophyll fluorescence after elimination of epidermal focussing on the adaxial leaf surface caused a 19 and 11% decrease in the initial fluorescence level (F₀) and maximum fluorescence (F_max), respectively, whereas similar measurements from the abaxial surface were twice as large. These results suggest that some of the chloroplasts within the leaf may be adapted to local high-light conditions created by the epidermis.     

Regulation of tomato fruit growth by epidermal cell wall enzymes

Water relations of tomato fruit and the epidermal and pericarp activities of the putative cell wall loosening and tightening enzymes Xyloglucan endotransglycosylase (XET) and peroxidase were investigated, to determine whether tomato fruit growth is principally regulated in the epidermis or pericarp. Analysis of the fruit water relations and observation of the pattern of expansion of tomato fruit slices in vitro , has shown that the pericarp exerts tissue pressure on the epidermis in tomato fruit, suggesting that the rate of growth of tomato fruit is determined by the physical properties of the epidermal cell walls. The epidermal activities of XET and peroxidase were assayed throughout fruit development. Temporal changes in these enzyme activities were found to correspond well with putative cell wall loosening and stiffening during fruit development. XET activity was found to be proportional to the relative expansion rate of the fruit until growth ceased, and a peroxidase activity weakly bound to the epidermal cell wall appeared shortly before cessation of fruit expansion. No equivalent peroxidase activity was detected in pericarp tissue of any age. It is therefore plausible that the expansion of tomato fruit is regulated by the combined action of these enzyme activities in the fruit epidermis.     

The First Stages of Pre-harvest 'Peel Pitting' Development in 'Encore' Mandarin. An Histological and Ultrastructural Study

‘Peel pitting’ in the flavedo (the coloured epicarp)of ‘Encore’ mandarin arises as chlorotic spots.These spots correspond to parenchymal flattening and collapseof a variable number of sub-epidermal cell layers, which increasein parallel with the epidermis, extending between apparentlyhealthy zones. The first signs of cellular damage are associatedwith internal membrane disorganization of the plastids. Greatvesiculation of the cytoplasm occurs, followed by degradationof cytoplasmic membranes and accumulation of abundant osmiophilicmaterial, yielding amorphous and dense masses. The disorderstarted by September. Spotting was only observed on the outerside of the fruit and on portions of the rind most exposed toexternal factors. Radiation and high temperature of the rindover long periods may induce localized dehydration, plasmolysisand cell collapse.Copyright 1999 Annals of Botany Company Citrus, ‘Encore’ mandarin, pre-harvest pitting, peel disorder, histology, ultrastructure.     

井冈山地区18种唇形科植物果实形状及表面微形态特征研究

采用扫描电镜方法对井冈山地区18种唇形科植物的果实形状与表面微形态特征进行观察比较。结果表明：18种唇形科植物果实形状多样,可分为矩圆形、圆形、卵形、三棱形、球形和椭圆形6类;外果皮表面细胞形状为4~6边形、不规则形和细胞形状不可见;依据外果皮表面凸起度可分为平滑型、凹陷型和凸起型3类;外果皮表面蜡质纹饰复杂多样,有平滑无纹饰、负网状纹饰、网状纹饰兼具疣状或瘤状凸起和网状纹饰兼具次级条纹4类;外果皮表面附属结构主要包括表皮毛和丝状结构,并具有或多或少的鳞片状或颗粒状分泌物。18种唇形科植物果实形状和外果皮表面微形态特征均表现出丰富的多样性,可为唇形科属间和种间亲缘关系研究提供重要的分类学依据。     

High resolution shadowing of Mycobacterium leprae

Metal shadow casting techniques for transmission electron microscopic examination was used to determine the morphological characteristics of Mycobacterium leprae in untreated and treated patients. This technique is used to visualize bacterial surface structures by thermal evaporation of platinum alloys under moderate vacuum. This method gives a high contrast image at relatively low resolution and is useful for correlating micro-morphology quantitatively to early therapeutic effects of anti-leprosy drugs. Using these techniques in untreated cases, the surface structures of M. leprae were uniformly filled with relatively homogenous protoplasm surrounded by a cell wall. Most of the bacilli had thick cell walls with prominent banded and fibrous structures on the surface of the cell body. The cell wall was not detached in any of the solid bacilli in untreated cases. The bacilli varied in size and some of them were swollen in their mid-portion. Some bacilli were very short and completely filled with cytoplasm; therefore, these short bacilli were counted as solid bacilli in electron microscopic morphological index (EM-MI) determination. During treatment, mainly the cytoplasms of the bacilli were affected, and degeneration was observed. Ultrastructurally, the cytoplasm was shrunken and detached from the cell wall indicating mild degeneration. After moderate degeneration, the cytoplasm appeared fragmented. In advanced degeneration, all structures except the cell walls collapsed completely and no fibrous or band structures were visible on the surfaces of the cell walls. Therefore, these bacilli were counted as non-solid bacilli for EM-MI determination. This study shows that transmission electron shadowing gives more accurate counts than standard light microscopy of intact M. leprae bacilli in patient specimens.     

High resolution shadowing of Mycobacterium leprae

Metal shadow casting techniques for transmission electron microscopic examination was used to determine the morphological characteristics of Mycobacterium leprae in untreated and treated patients. This technique is used to visualize bacterial surface structures by thermal evaporation of platinum alloys under moderate vacuum. This method gives a high contrast image at relatively low resolution and is useful for correlating micro-morphology quantitatively to early therapeutic effects of anti-leprosy drugs. Using these techniques in untreated cases, the surface structures of M. leprae were uniformly filled with relatively homogenous protoplasm surrounded by a cell wall. Most of the bacilli had thick cell walls with prominent banded and fibrous structures on the surface of the cell body. The cell wall was not detached in any of the solid bacilli in untreated cases. The bacilli varied in size and some of them were swollen in their mid-portion. Some bacilli were very short and completely filled with cytoplasm; therefore, these short bacilli were counted as solid bacilli in electron microscopic morphological index (EM-MI) determination. During treatment, mainly the cytoplasms of the bacilli were affected, and degeneration was observed. Ultrastructurally, the cytoplasm was shrunken and detached from the cell wall indicating mild degeneration. After moderate degeneration, the cytoplasm appeared fragmented. In advanced degeneration, all structures except the cell walls collapsed completely and no fibrous or band structures were visible on the surfaces of the cell walls. Therefore, these bacilli were counted as non-solid bacilli for EM-MI determination. This study shows that transmission electron shadowing gives more accurate counts than standard light microscopy of intact M. leprae bacilli in patient specimens.     

Structure of the skin of an air-breathing mudskipper, Periophthalmus magnuspinnatus

The epidermis of the mudskipper Periophthalmus magnuspinnatus consisted of three layers: the outermost layer, middle layer and stratum germinativum. Extensive vascular capillary networks were present near the superficial layer of epidermis and outermost layer. The diffusion distance between the vascular capillaries and the surface of epidermis was c . 1.5 ± 0.9μm. The middle layer consisted of small or voluminous cells swollen by epidermal cells. Due to the swollen cells, the thickness of the epidermis increased and the epidermis appeared web-like. The swollen cells contained tonofilaments, lucent contents and desmosomes. Fine blood capillaries were also discernible in this layer. Well-developed lymphatic spaces containing lymphocytes existed in the stratum germinativum. Numerous blood capillaries were present under the basement membrane. The dermis consisted of a stratum laxum and stratum compactum, and there was a definite area with acid mucopolysaccharides and a small scale in the stratum laxum. The skin had an epidermal pigment cell, dendritic melanophores (-cytes) containing melanin granules within their cytoplasm, and two kinds of dermal pigment cells, melanophores and colourless pigments containing reflecting platelets.     

Early degranulation of human neutrophils: immunocytochemical studies of surface and intracellular phagocytic events.

Degranulation of azurophil and specific granules after phagocytic challenge with E. coli for 5 sec to 10 min was investigated in the human polymorphonuclear neutrophil (PMN). PMN were stained simultaneously with fluorescein and rhodamine-labeled monospecific antisera to myeloperoxidase (MPO) and lactoferrin (LF) to identify azurophil and specific granules, respectively, within single cells. Fixation was designed to preserve or disrupt differential permeability of cell membrane to fluorescent conjugates in order to study granule translocation. Within 5 sec after phagocytic challenge, MPO and LF appeared on the cell surface coating the bacteria as granule contents leaked from the incompletely formed phagolysosomes. The phagocytic cup, shown by scanning electron microscopy as large and circular, appeared by immunofluorescent markers to be outlined by curvilinear staining for both granule markers, and was always coincident with bacterial localization. MPO and LF appeared singly or simultaneously on the cell surface, suggesting that degranulation to the surface was random. Sequential phagocytic events were demonstrated by comparing staining intensities for each granule marker on the surface and intracellularly within single cells. LF sometimes appeared on the cell surface independent of the nascent phagosome, suggesting that perturbation of the cell membrane by bacteria may cause some specific granule extrusion not limited to the phagosome. These results imply that bacteria make contact with granule-associated anti-microbial substances within 5 sec after phagocytosis is initiated and that free communication of granule constituents occurs between the newly forming phagolysosome and the extracellular space.     

Role of Ca<Superscript>2+</Superscript> and calmodulin in on-tree oleocellosis tolerance of Newhall navel orange

Previous studies have shown that spraying calcium on the canopy can significantly reduce the incidence of on-tree oleocellosis (OTO). However, the OTO regulation with calcium spraying has not been reported clearly. Therefore, the physiologic mechanism of spraying Ca(NO₃)₂ and calmodulin (CaM) inhibitors (trifluoperazine-TFP) on the canopy of 8-year-old Newhall navel orange on Lichi16-6 trifoliata (P. trifoliate) including the ratio (RO) and degree of OTO (DO) have been studied under high summer temperature. The results showed that exogenous Ca(NO₃)₂ treatment significantly decreased DO value by increase in CaM content of leaves, peroxidase (POD) activity in leaves, and fruit peels. However, TFP treatment significantly decreased CaM content in leaves, SOD and CAT activity in fruit peels, while the POD activity in fruit peels significantly increased, and the formation of Ca(NO₃)₂-induced DO tolerance in citrus fruits was weakened by TFP treatment. Exogenous Ca(NO₃)₂ treatment increased stomatal conductance (Gs) and transpiration rate (Tr), and decreased the daily range of rind oil release pressure (△RORP) significantly. However, TFP treatment had no significant influence on transpiration rate (Tr) and △RORP. The results were consistent with the RO of different treatments. These results confirm that Ca²⁺ and CaM regulate DO value, and the RO of OTO was mainly related to the regulation of △RORP through water metabolism.     

The essential oil secretory structures of Prostanthera ovalifolia (Lamiaceae)

The structure of the essential oil secretory tissues of Prostanthera ovalifolia R.Br was investigated using bright- and dark-field optical microscopy, and scanning and transmission electron microscopy. The leaves of P. ovalifolia have glandular trichomes of the peltate type common to many Lamiaceae species. The trichomes consist of a basal cell embedded in the epidermis, a stalk cell with heavily cutinized walls and a 16-celled secretory head, but they differ from those of many previously reported Lamiaceae species in their morphological form defined by the elevated cuticle. The sub-cuticular space contains a mixture of lipid and aqueous phases. Secretory cells have dense cytoplasm with many leucoplasts present. Volatile terpenoids are eliminated from the cytoplasm into the sub-cuticular space, the site of essential oil accumulation, via granulocrine secretion.