Ultrastructural changes of radish leaf exposed to cadmium

Cadmium (Cd²⁺) is one of the most toxic heavy metal pollutants in nature. Mesophyll cells from the leaf of radish seedlings exposed to 0.25 and 1.0 mM of CdCl₂ during 24 h exhibited structural changes of chloroplasts, mitochondria and nuclei when compared to non-treated control plants. Chloroplasts from Cd²⁺-exposed samples exhibited changes in the organelle shape, an increase in the stroma volume and a deposition of electron-dense material in the double membrane. The changes in the chloroplast membranes were not very drastic, however and reorganization of the thylakoids and stroma was observed. In contrast, the breakdown of the nuclear envelope of the plant cells treated with Cd²⁺ was very clear. The accumulation of electron-dense granules was also observed in mitochondria. No alterations were observed in the vacuoles of radish seedlings grown at different Cd²⁺ concentrations for the periods tested.     

簇生岐柄菌的超微形态学研究

为揭示网柄细胞状黏菌的超微结构特征,对簇生岐柄菌Cavendericfasciculata生活史过程中的孢子、黏变形体和柄细胞3种类型的细胞超微结构进行系统观察,并与目前仅知的3种网柄细胞状黏菌的超微结构进行比较.结果表明:簇生岐柄菌C.fasciculata的孢子、黏变形体和柄细胞内均有线粒体结构,随着细胞分化,线粒...     

Ultrastructural study of different types of callus from leaf expiants ofAesculus hippocastanum L.

Summary The cell ultrastructure in three types of callus obtained from leaf explants ofAesculus hippocastanum L. has been studied. Remarkable differences have been shown between the cells of the forerunner E₁ callus and those of the callus arising from it, according to the culture conditions.The peculiar characteristics of E₁ are the scarcity of intercellular spaces and the occurrence of autophagic vacuoles in the cells.An embryogenic friable callus (E₂) is formed in time when E₁ is maintained on solid culture medium. The E₂ cells show cytological features typical of a higher metabolic level and contain starch. Diffused middle lamella digestion leads to the detachment of small embryogenic cell aggregates consisting of vacuolated parenchymatous-like cells and small meristematic cells which may be regarded as embryoids initials.Shaking E₁ in the same liquid medium and subsequent culture on solid medium lead to the differentiation of a non-embryogenic callus (NE), whose cells are very large and highly vacuolated, devoid of starch and with organelle-rich cytoplasm. The NE callus shows a high degree of growth, but does not attain embryogenic competence in time.Abbreviations c cell - cr crystal - cw cell wall - d dictyosome - er endoplasmic reticulum - m mitochondrion - mb microbody - n nucleus - p plastid - s starch - v vacuole     

Heterogeneity in bean leaf mesophyll tissue and ion flux profiles: leaf electrophysiological characteristics correlate with the anatomical structure

It has been suggested for some time that the architectural properties of leaf venation are related to leaf functions; however, experimental evidence is scant and, when present, mainly investigates water or carbohydrate transport patterns. Transport of inorganic nutrients in relationship to leaf anatomical structure remains, to a large extent, an unexplored area in plant physiology. In this study, we correlated ion flux profiles with the anatomical structure of bean (Vicia faba L.) leaf mesophyll tissue using a non-invasive ion flux measuring technique (microelectrode ion flux estimation) and scanning electron microscopy. Quasi-periodic patterns of net H+ and K+ flux distributions were found when the mesophyll surface was scanned along the longitudinal axis with 0.1-0.2 mm increments. These patterns showed a high correlation with anatomical features of the mesophyll tissue (i.e. the distribution of vascular bundles). The observed flux profiles were not time-dependent, showed qualitative similarity in both light and dark conditions, and resulted in heterogeneous plant physiological responses. The possible physiological role of the observed findings, specifically in relation to stomatal 'patchiness' and phloem loading mechanisms, is discussed.     

Karyotype Analysis of Hydrilla

The present paper reports the chromosome number and karyotype of the genus Hydrilla. H. verticillate was found to have 2n=16. The karyotype is 2n=16=6m+6sm+ 4st. No difference between the male and the female was found in the work. H. verticillata var. roxburghii Casp. has the somatic chromosome number 2n=24, and its karyotype is 2n= 3x=24=9m+9sm+6st. The variety may be a autotriploid. The karyotype of the genus isobviously bimodal, with No. 1-5 in the first group and 6-8 in the second group.     

Ultrastructural Study of Leaf Cells Damaged from Hg2+ and Cd2+ Pollution in Hydrilla verticillata

Hydrilla verticillata (L. f.) Royle was cultivated in water medium polluted with Hg2+and Cd2+ of different gradient concentrations for 3 days and 6 days respectively. Leaves of H. verticillata lost their green color gradually with the increasing pollutant concentration. Ultrastructural observation showed, at its early stage, dispersion of dictyosomes, disintegration after swelling of endoplasmic reticulum, swelling or vesiculation of thylakoids of chloroplasts and cristae of mitochondria and condensation of chromatin of nucleus. More serious damage was shown in the plant cells with heavier pollution, such as disappearance of ribosomes, agglutination of chromatin of nucleus, dispersion of nucleolus, disruption of nuclear membrane, disintegration of chloroplasts and mitochondria, collapse of plasmodesmata due to plasmolysis, focal dissociation of cell wall and eventually cells death. The results indicated that Hg2+ and Cd2+ might injure all the membranous and non-membranous structures of cells, though there existed different degrees of endurance of cell structures to the poison. The lethal concentration of Hg2+ to cell of H. verticillata ranged from 1 to 2 mg/L, and that of Cd2+ ranged from 2 to 3 mg/L.     

Ultrastructural characteristics of the human synoviocytes

The purpose of this study was to identify, by the scanning electron microscopy, the behaviour of the different cell types in the normal human synovial intima, in order to obtain information useful for interpreting pathological changes in the synovium. Our observations revealed that, in numerous areas of the synovial membrane (adipose or fibrous type), the synoviocytes were dispersed and the intercellular matrix, covered only by the cytoplasmic processes of cells deeply located, was in direct contact with the joint cavity. In the areolar type of the synovium the synoviocytes were more numerous; they tended to concentrate to give the appearance of a continuous tissue; but between the cells very large intercellular spaces were usually present. In this latter membrane type we identified the two main cellular types of the synoviocytes: A and B. B-synoviocytes were the predominant cell type of the synovium. These cells were characterized by long cytoplasmic processes, perpendicularly directed towards the joint cavity. Both the cellular body and the cytoplasmic processes were covered by small blebs and vesicles of various size. The A-synoviocytes were a small minority, rarely dispersed between the B-synoviocytes. They were characterized by numerous membrane infoldings which delimited intracellular canaliculi of various depth. Our ultrastructural observations demonstrated that, in normal conditions, the B-synoviocyte must be considered as a constitutive element which characterized the synovial intima, responsible for the specific structure of the interstitial tissue and for the regulation of the composition of the synovial fluid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructural characteristics of freeze-dried smooth muscle

The rapid freezing and vacuum dehydration of tissue has been employed to study the intracellular distribution of diffusible substances at the electron microscopic level. Hower, the ultrastructural detail of freeze-dried tissue is difficult to retain. Consequently, the ultrastructural preservation of freeze-dried smooth muscle has not been sufficient to permit satisfactorily definition of intracellular organelles. Therefore, determinations of the intracellular distribution of soluble ions have not been achieved in freeze-dried smooth muscle. In this study a freeze drying method is presented which provides more satisfactory definition of intracellular organelles than has been available in the past. Using this merens have been preserved. When these muscles are compared to convention preparer of surface vesicles that are observed, and the mitochondria are extremely electron opaque in the freeze-dried tissue. The smooth muscles which have been examined do not have the inherent contrast of other types of tissue nor do they contain the different types of mitochondria that have been observed in nonmuscle tissue.     

Estimating near-infrared leaf reflectance from leaf structural characteristics

The relationship between near-infrared reflectance at 800 nm (NIRR) from leaves and characteristics of leaf structure known to affect photosynthesis was investigated in 48 species of alpine angiosperms. This wavelength was selected to discriminate the effects of leaf structure vs. chemical or water content on leaf reflectance. A quantitative model was first constructed correlating NIRR with leaf structural characteristics for six species, and then validated using all 48 species. Among the structural characteristics tested in the reflectance model were leaf trichome density, the presence or absence of both leaf bicoloration and a thick leaf cuticle (>1 μm), leaf thickness, the ratio of palisade mesophyll to spongy mesophyll thickness (PM/SM), the proportion of the mesophyll occupied by intercellular air spaces (%IAS), and the ratio of mesophyll cell surface area exposed to IAS (A(mes)) per unit leaf surface area (A), or A(mes)/A. Multiple regression analysis showed that measured NIRR was highly correlated with A(mes)/A, leaf bicoloration, and the presence of a thick leaf cuticle (r = 0.93). In contrast, correlations between NIRR and leaf trichome density, leaf thickness, the PM/SM ratio, or %IAS were relatively weak (r < 0.25). A model incorporating A(mes)/A, leaf bicoloration, and cuticle thickness predicted NIRR accurately for 48 species (r = 0.43; P < 0.01) and may be useful for linking remotely sensed data to plant structure and function.     

Water balance in leaf tissue

Samples of the leaf tissue (14cm²) were placed in a plexiglass chamber which consisted of three parts. Water absorbed by the leaf tissue on one side of the sample was transported through the middle part of the sample to the opposite side and was transpirated there. The intensity of transpiration the intensity of water absorption and water saturation deficit (w.s.d.) were determined simultaneously in this tissue by gravimetry. Water balance was studied either in saturated samples of leaf tissue or in tissue where w.s.d. (10%, 20%, 30%, 40%) was established in advance. Although conditions for water absorption in leaf segments were optimal, w.s.d. originated in the saturated leaf tissue under all given external conditions (evaporation from 41.7 to 17.8 mg cm^?2 h^?1). W.s.d. which was established in advance for the most part increased during the experiment and reached even high values (more than 60%). the equilibration was reached only under conditions of low evaporation and initial w.s.d. higher than 20% in young leaves and higher than 30% in adult leaves. A positive correlation between the ratio of the intensity of water absorption to the intensity of transpiration and w.s.d. was found only under conditions of lower evaporation (17.8 and 23.2mg cm^?2h^?1). The maximal values of w.s.d. were limited in this way. Water balance was studied: 1. in leaf tissue of upper, middle and lower leaves of fodder cabbage, 2. in leaf tissue of middle leaves of young and adult plants of fodder cabbage, 3. in leaf tissue of dicots (fodder cabbage) with different vessel orientation in respect to water transport, 4. in leaf tissue of monocots (banana-tree) with water transport upright to the vessel orientation. Considerable change of water balance was observed when the water transport was prolonged by two incisions in the middle part of the sample. Results of all these experiments revealed the possibility of water stress origin even in leaf tissue sufficiently supplied with water.     

Ultrastructural findings on lipoproteins in vitro and in xanthomatous tissue.

Synopsis The application of OsO₄ plus K₃[Fe(CN)₆] as a secondary fixative following aldehyde fixation, permitted demonstration of the presence of 30–300 nm membrane-bound particles in xanthomatous tissue.With the same fixation method, isolated low density lipoprotein particles in a fibrin matrix could be observed in the transmission electron microscope in a way permitting comparison with similarly fixed tissue. However, isolated particles of very low density lipoproteins treated in the same way as low density particles had an irregular appearance and a diameter varying between 30 and 80 nm.     

Production of isoprene by leaf tissue

Isoprene production by Hamamelis virginiana L. and Quercus borealis Michx. leaves was studied. When ambient CO(2) concentrations were maintained with bicarbonate buffers, the rate of isoprene production at 125 microliters per liter of CO(2) was approximately four times that at 250 microliters per liter of CO(2). Isoprene production was drastically inhibited by 97% O(2). Dichlorodimethylphenylurea (0.1 mm), NaHSO(3) (10 mm), and alpha-hydroxy-2-pyridinemethanesulfonic acid (10 mm) inhibited isoprene production but increased the compensation point of the tissue. Isonicotinic acid hydrazide neither inhibited isoprene emission nor increased the compensation point of the tissue significantly. Inhibition of isoprene production does not seem to correlate with stomatal resistance. Isoprene was labeled by intermediates of the glycolate pathway, and similarities are noted between the biosynthesis of isoprene and that of beta-carotene.     

Ultrastructural cytochemistry of biogenic amines in nervous tissue: methodologic improvements.

A new fixation method has been developed for localizing biogenic amines in nervous tissue. The method is a modification of the chromaffin reaction in which all fixation steps are buffered with mixtures of sodium chromate and potassium dichromate. In this way the fixation and cytochemical reaction are carried out almost simultaneously. Using the rat vas deferens as a model tissue, it was found that the preservation of electron dense (chromaffin) cores in the vesicles of adrenergic nerve terminals depended on several factors: a short primary fixation using low concentrations of aldehydes, the presence of the chromate/dichromate buffer during all fixation steps and, finally, a long incubation period in a slightly acidic (pH 6.0) solution of this buffer before postfixation in osmium tetroxide. Using this method it was possible to identify not only small and large dense-cored vesicles as storage sites for amines but also a tubular reticulum (neuronal endoplasmic reticulum), the latter especially in nerve terminals of mesenteric arteries and iris. Biogenic amines were also visualized in sympathetic ganglion cells and in the central nervous system e.g., supraependymal nerve terminals, tissues that up to now proved the most difficult in terms of amine localization. In all the tissues examined the cytochemical reaction was highly selective and present in well preserved tissue, which is a significant advance over previously available techniques. It therefore offers new opportunities for further studies on the role of biogenic amines as neurotransmitters.     

Ultrastructural features of flavonoid accumulation in leaf cells ofChrysosplenium americanum

Summary The intracellular localization of partially O-methylated flavonol glucosides was studied inChrysosplenium americanum leaves using caffeine as stabilizing and visualizing reagent. Electron microscopic observations and chromatographic data indicated that intracellular flavonoids were found to accumulate mainly within the walls of epidermal and mesophyll cells. Various membrane profiles and associated vesicles appeared to be involved in the packaging and channelling of the electron-dense material towards the cell wall. There was no evidence to suggest the participation of chloroplasts in these processes. The significance of flavonoid accumulation in cell walls was discussed in relation to the nature of these compounds and their possible ecophysiological role in this plant.Abbreviations ER endoplasmic reticulum - HPLC high-performance liquid chromatography - TLC thin-layer chromatography     

遮荫条件下草莓的光合持性变化

对宝交早生和硕丰两个草莓品种遮荫处理后测定其光合特性变化结果表明,遮荫处理使两个草莓品种叶片光合速率显著降低,分别下降了20％和47％,而表观量子效率分别提高了13％和8％,叶片中叶绿素含量升高而可溶性蛋白含量显著降低,光系统II电子传递活笥（PSII活性）分别下降了22．5％和53．7％,1,5二磷酸核酮糖羧化酶（Rubisco)活性分别低了19．6％和35．3％,进一步讨论了草莓光饱和速率下降的生理基础。     

黑藻对水体和沉积物理化性质的改善和营养元素的去除作用

通过人工模拟实验,研究了不同种植密度(50、100和150株/ m2)的黑藻(Hydrilla verticillata)对富营养湖泊水体和沉积物理化性质的改善和营养元素的去除作用。结果表明：种植黑藻能显著提高水体溶解氧(DO)和沉积物的氧化还原电位(Eh), DO由3.95mg/L提高到10.42mg/L;沉积物Eh提高了58.6-109.4mV。黑藻的生长有效地降低了水体和沉积物中的氮、磷含量,水体中TP降低了38.9%-57.1%;NH4+-N的含量降低了90.2%; 沉积物中TN的含量比试验前中期降低了70.0%。50、100和150株/ m2 三个种植密度间对水质和沉积物的改善效果差异不明显,说明当单位面积生物量达到一定程度后改善效果也趋于饱和,故在富营养湖泊的植被恢复中种植密度不宜过大。