Light- and electron-microscopical studies on the structure of salt glands of Tamarix aphylla L.

Cuttings of Tamarix aphylla were grown in various concentrations of NaCl. Salt glands on newly developed branches were sectioned and examined, both with the light- and with the electron-microscope. An electron-dense material appears in cuttings grown in all concentrations of NaCl at the anticlinal walls of the innermost pair of secretory cells and, to some extent, on the surface of the gland above the cuticle. In the glands of cuttings grown in high concentration of NaCl this material also appears in large quantities, not only on top of the gland but also beneath the cuticle at the region of the median anticlinal wall of the outermost pair of secretory cells. The material beneath the cuticle is connected to the electron-dense material on the outer surface of the cuticle via the secretory pores. It is suggested that this material is of pectic nature and forms a continuous system with the walls and wall protuberances of the secretory cells which are also very rich in pectic substances. As pectic substances absorb solutions easily they may enhance the transport of salt.
Many proplastids, vacuoles with simple structure and others with infolded membranes as well as numerous mitochondria were observed in the secretory cells. In the walls between the collecting cells and the innermost secretory cells there are numerous plasmodesmata with characteristically arranged membranes.     

Tubule bundle-inclusions in vacuoles of Tamarix aphylla L. mesophyll cells

Summary Vacuoles of differentiating mesophyll cells of Tamarix aphylla contain an amorphous electron-dense material in which stacks of parallel aligned striations are embedded. Cross-sections of the striations disclosed that they represent profiles of longitudinally sectioned bundles of tubules (tubule outer diameter 9.0 nm, tubule wall thickness 1.8 nm). In advanced mesophyll cell development, the amorphous vacuolar material disappears, whereas the bundles of tubules turn into bundles of double helices (double helix diameter 14.5 nm). Cytochemical treatment of mesophyll cells with the enzymes pepsin and trypsin has revealed that both the bundles of tubules/double helices and the embedding material are constituted of protein. The possible functional role of the vacuolar inclusions is discussed.     

Light Microscopical Studies on Salt Gland Development in Tamarix aphylla L

Young branches and leaves of Tamarix aphylla L. have many epidermalsalt glands, and each salt gland originates from a single protodermalcell which divides anticlinally to give rise to two equally-sizeddaughter cells. The latter further undergo two successive asynchronous,asymmetrical divisions resulting in the formation of six, denselycytoplasmic, secretory cells. In the next developmental stage,two inner, vacuolated parenchyma cells adjacent and adherentto the inner secretory cells progressively transform to whathave been termed in the literature the collecting cells of theglands. Thus, it appears at maturity that the glands consistof eight cells, and all eight cells may be directly involvedin the secretory process Tamarix aphylla L., alt gland, development     

The glands of Tamarix aphylla: a system for salt recretion or for carbon concentration?

During periods of high atmospheric humidity, twigs of Tamarix aphylla (L.) Karst. become covered by an alkaline solution. The pH of that solution fluctuates between 8.0 – 8.5 in the dark and 10.5 during the light hours. Such a solution, produced by the glands, constitutes an efficient trap for atmospheric CO₂. Upon the periodic drop in pH, much of the preabsorbed carbon may gradually be released from the solution. This enriches the immediate surroundings of the twigs with CO₂ for prolonged periods of time. The expected concentrations of CO₂, at the boundary layer between the atmosphere and the surfaces of the twigs, are over 1 000 ppm. As net photosynthesis of T. aphylla reaches maximal rates only at CO₂ concentrations of above 500 ppm, the plants may benefit from this extra source of carbon and may exploit it for maximal assimilation during the early morning hours. Thus, the "salt glands'of Tamarix , which are liable for the production of the alkaline recretum, may serve a triple purpose: (a) removal of excess salts out of the twigs, (b) provision of a cover of hygroscopic solutes that moistens the twigs and shortens the duration of transpiration, and (c) providing the plants with an environment enriched in CO₂.     

An endogenous circadian rhythm of transpiration in Tamarix aphylla

An endogenous circadian rhythm in the transpiration of Tamarix aphylla (L.) Karst. was found for plants grown in continuous light under laboratory conditions. The mean period (±SD) was 21.7±2.3 h (n = 121). No such rhythm was observed in continuous darkness, except for one small hump at the time of the first cycle. The influence of NaCl, Cd(NO₃)₂ and LiCi on the rhythmic behaviour of young T. aphylla plants was investigated. NaCl concentrations of up to 150 m M reduced the overall transpiration rates of the plants, but did not change the period of the rhythm. The amplitude and the mesor of the oscillations were inversely correlated with the NaCl concentration. A similar influence was found for Cd(NO₃)₂, but with concentrations that were approximately three orders of magnitude smaller than those of the NaCl treatments. The rhythmic behaviour of the plants was not altered by 10 m M LiCl. It is suggested that the described rhythm of transpiration may have a dual effect: (a) it might cause a partial closure of the stomates during midday hours and (b) it might serve as a possible synchronizer ("master clock") for other rhythmic phenomena in the plants.     

Chromosome Number of Tamarix L.

The chromosome number of thirteen species of Tamarix L. in China is reported in this paper. All of them have the same number (2n=24) and most of them are reported for the first time except T. hispida, whose chromosome number is the same as previously reported.     

Physiology and ecologic relevance of salt secretion by the salt gland of Glaux maritima L.

Summary The effects of salinity in the root medium, time, and relative humidity on the salt secretion of Glaux maritima were investigated. Both in the greenhouse and in the field increasing salinity stimulated sodium and chloride secretion, whereas the essential elements potassium, calcium, and magnesium remained at low secretion levels, which might be interpreted as efficient mineral economy. The low secretion level of potassium is remarkable, because growing on a nutrient solution containing 6 mM potassium, the concentration of the plant sap increases to 150 mM K⁺ and the secreted quantity amounts to only 2 m mol l^-1 plant sap 24 h^-1.Attempts were made to establish the secretion rate. The maximum secretion rate calculated may be 80 pEq NaCl cm^-2 s^-1, but for long periods (days) the secretion rate will be lower. Measurement of salt secretion unavoidably leads to removal of secreted salt. Salt was removed by rinsing with distilled water, which artificially accelerates the secretion process or parts of it by diffusion of salt from the cuticle cavity or secretory cells. At increasing salinities the amount of secreted ions showed a fivefold increase, whereas the osmotic potential of the plant sap was raised only twofold, indicating the importance of secretion as a rapid regulation mechanism with regard to the salt economy.     

Enhanced dissipation of polycyclic aromatic hydrocarbons in the rhizosphere of the Athel tamarisk (Tamarix aphylla L. Karst.) grown in saline-alkaline soils of the former lake Texcoco

Remediation of polycyclic aromatic hydrocarbons (PAHs) contaminated alkaline saline soil with phreatophyte or "water loving plants" was investigated by spiking soil from the former lake Texcoco with 100 mg phenanthrene (Phen) kg(-1) soil, 120 mg anthracene (Ant)kg(-1) soil and 45 mg benzo(a)pyrene (BaP) kg(-1) soil and vegetating it with Athel tamarisk (Tamarix aphylla L Karst.). The growth of the Athel tamarisk was not affected by the PAHs. In soil cultivated with Athel tamarisk, the leaching of PAHs to the 32-34 cm layer decreased 2-fold compared to the uncultivated soil. The BaP concentration decreased to 39% of the initial concentration at a distance smaller than 3 cm from the roots and to 45% at a distance larger than 3cm, but 59% remained in unvegetated soil after 240 days. Dissipation of Ant and Phen decreased with depth, but not BaP. The biodegradation of PAHs was affected by their chemical properties and increased in the presence of T. aphylla, but decreased with depth.     

Ultrastructural features of the pineal gland in normal and light deprived golden hamsters

Summary Although current physiological findings imply that the mammalian pineal organ liberates an antigonadal agent, microscopic examinations of this organ have afforded little information regarding the possible storage and release of such a substance. Since it is known that light deprivation for six weeks results in pineal-induced atrophy of certain reproductive organs in adult golden hamsters, one might expect that any morphological manifestations of this activity in the pineal organ would be enhanced in hamsters which had heen deprived of light for that length of time. A comparison at the ultrastructural level of pineal glands from normal and experimentally blinded hamsters revealed that pineal cells from the blinded animals exhibited a greater number of vesicles and contained complex membranous whorls. The possible significance of the vesicles and lamellar whorls is discussed in terms of similar structures found in other tissues.A feature common to pineal tissue of both the normal and experimental hamsters was the apparent cellular segregation of two morphologically distinct types of mitochondria. Pinealocytes containing small, cristaform mitochondria were designated as P1 cells; those containing larger mitochondria characterized by a dense, plexiform array of cristae were designated as P2 cells.Supported by A. D. Williams 3558, Medical College of Virginia, and National Institutes of Health 5FI-GM-31, 981-02.The author is grateful to Dr. Hugo R. Seibel of the Department of Anatomy at the Medical College of Virginia for assistance with the surgical procedures employed in this study.     

柽柳泌盐腺结构、功能及分泌机制研究进展

柽柳属中多数种是典型的泌盐性盐生植物,泌盐腺在调节体内离子平衡,维持渗透压稳定,提高植物的耐盐性等方面发挥重要作用。系统总结了柽柳泌盐腺研究成果,对泌盐腺的结构、功能及泌盐机制进行了论述。     

Ultrastructural and histochemical observations on spermathecal gland of Dytiscus marginalis L. (Coleoptera)

Summary Histochemical studies have been carried out on the composition of feltwork and tubule in the spermathecal gland cells of Dytiscus marginalis L.These extracellular structures represent the secretion-collecting apparatus of the cells of the spermathecal gland, through which the secretion passes externally into the lumen of the spermatheca.The presence of a particular protein, resilin, also called arthropod elastin, at the level of the tubule and the feltwork, and of neutral polysaccharides present only in the feltwork have been demonstrated.Special consideration is given to the silver-methenamine reaction, the results of which have been interpreted in terms of the amino-acid composition of resilin itself.The behavior of this reaction, as a function of the type of fixation solution employed, is also discussed.     

Ultrastructural,cyto- and biochemical observations during turnover of plasma membrane in duck salt gland

Summary The mechanism of plasma membrane turnover was investigated using the duckling salt gland as a model system. Feeding fresh water to saltstressed ducklings results in a decrease in the Na, K-ATPase in salt gland to nonstressed levels in about 7 days, as measured by ATP hydrolysis and ³H-ouabain binding. Electron micrographs reveal that this is accompanied by a decrease in plasma membrane infoldings on the basal and lateral borders of gland secretory cells. Simultaneously there is an increase in filamentous material and a rise in acid phosphatase and peptidase activities in these cells. Cytochemistry shows that the acid phosphatase activity is mostly associated with the basal or basolateral regions of secretory cells. These observations could indicate that the removal of plasma membrane components is accomplished by internalization and digestion within the secretory cells.     

Ultrastructural features of spermatocytes and spermatozoids in the fern Phyllitis scolopendrium (L.) Newm. subsp. scolopendrium

Phyllitis scolopendrium Newm. subsp. scolo-pendrium spermatozoids are cells 10 μm long in the form of spirals with about four turns. Their chromatin is partly honeycomb-shaped and partly highly condensed. The nuclear envelope over the latter has a regular, thin intermembrane space crossed by fibers that are probably involved in connecting the chromatin with elements of the microtubular ribbon. The cytoplasm is traversed by long cistern-shaped folds of the plasma membrane, believed to be involved in a late process of cell simplification through segregation and detachment of parts of the cytoplasm. The spermatozoids are embedded in 1–1.5 μm thick amorphous electron-transparent material containing cellulose fibrils. These fibrils are considered a network connected to the original spermatocyte wall and elements of elastic support for the amorphous material. The different polysaccharide composition of the inner and outer parts of the walls causes changes in the size and shape of the ring cells, so that the spermatozoids are pushed against and past the cap cell. The gametes are released through limited laceration of the cap cell. The laceration is due to the generally weak substructure of the cell wall. A light microscope sequence of spermatozoid release and scanning electron microscope features of newly released spermatozoids are shown. Received: 24 November 1999 / Revision accepted: 29 December 1999     

Lectotypification of Buxbaumia aphylla Hedw. and B. aphylla var. viridis DC. (Buxbaumiaceae)

Abstract

The two species of Buxbaumia Hedw. known to occur in Europe were both originally discovered on this continent and were the earliest in the genus (as presently delimited) to be described. Already widely known, Buxbaumia aphylla Hedw., was validated by Johannes Hedwig in 1801, whereas B. viridis (DC.) Moug. & Nestl. was initially described as a variety of B. aphylla by Augustin Pyramus de Candolle in 1815. After two centuries in the bryological literature, these taxa are herein effectively typified. Lectotypes for the names B. aphylla and B. viridis are designated based on original herbarium sheets from the Hedwig-Schwägrichen and De Candolle collections in G.     

Morphological and Anatomical Observations of Clasping Leaves of Tamarix L.

This paper deals with some morphological and anatomical adaptabilities of clasping leaves of 13 species of Tamarix L. in China. These xeromorphic leaves posses some conspicuous characteristics as follows: 1 ) The ratio of the leaf surface area to its volume is low; 2) The numerous, small stomata are deeply sinked in the surface of the epidermis; 3) The palisade tissue is only found in the abaxial part and the spongy tissue in the adaxial part, which are quite different from most of the dorsivcntral leaves; 4) The upper epidermis of these leaves is extended a different degree into the epidermis of stem. These characteristics may be considered as an expression of xeric habits resulting from desert adaption.     

无叶假木贼和盐爪爪提取物的抗菌活性

无叶假木贼和盐爪爪地上部分乙醇提取物、不同溶剂萃取部分对供试病原细菌和真菌均表现出较好的抑制作用,其乙酸乙酯萃取部分和正丁醇萃取部分的抗菌活性明显强于石油醚萃取部分和水部分。结果表明,无叶假木贼中抗菌活性成分主要为极性中等的化合物,且很可能是具弱碱性、易与酸成盐的生物碱类。盐爪爪中抗菌活性成分同样为极性中等的化合物。