Structure of Hair Roots in Lysinema ciliatum R. Br. and its Implications for their Water Relations

The fine lateral roots ofLysinema ciliatum R. Br., an epacridfrom habitats subject to periodic drought in Western Australia,are hair roots resembling those of Ericaceae. The finest (ultimate)hair roots have a cortex consisting only of an endodermis andan exodermis. Both layers have Casparian strips on the radialwalls. The exodermis develops to state III very close to theroot tip, showing wall thickening and a suberized lamella encirclingeach cell. In many roots collected after tip-growth had ceasedand the tip had fully differentiated this suberized exodermiscompletely encircled the apex. In older hair roots the epidermiscollapses or is sloughed off leaving the suberized exodermisas the outermost layer. The very fine hair roots have a verysmall stele containing only one xylem tracheid, and phloem consistingof a single sieve element with companion cell. The very smalldiameter of the single tracheid indicates a high resistanceto water flow along the hair roots. This may tend to conservesoil moisture in the region of the hair roots, leading to improvedsurvival and prolonged function of mycorrhizas in the field. Lysinema ciliatum R. Br.; hair root; endodermis; exodermis; water; xylem     

A Possible Double Role for Brassinolide in the Reorientation of Cortical Microtubules in the Epidermal Cells of Azuki Bean Epicotyls

Brassinolide, at 10^–8M or higher, enhanced the elongationof epicotyl segments from azuki bean seedlings that was inducedby IAA, but it did not enhance the increase in fresh weightof the segments, an indication that brassinolide suppressedthe lateral expansion of the segments. The additional elongationcaused by brassinolide was completely prevented in the presenceof 10^–5 M cremart, which disrupted the cortical microtubules(MTs) in epidermal cells in the segments, and in the presenceof 10^–6M 2,6-dichlorobenzonitrile, an inhibitor of thesynthesis of cellulose. Brassinolide at 10^–7M, appliedtogether with IAA, increased the percentage of epidermal cellswith transversely oriented cortical MTs. Brassinolide appearsto enhance the longitudinal expansion and suppress the lateralexpansion of epicotyl cells by organizing cortical MTs transverselyto the cell axis and, thereby, causing the deposition of cellulosemicrofibrils in the same orientation. Brassinolide by itself, at 10^–8M or higher, induced theelongation of epicotyl segments and the elongation caused bybrassinolide was partially prevented by 10^–5M cremart,results that suggest that brassinolide regulates cell expansionvia at least two processes, an MT-dependent process and an MT-independentprocess. Brassinolide by itself increased the percentage ofepidermal cells with transversely oriented cortical MTs. Since,in azuki bean epicotyls, the percentage of cells with transverseMTs is increased only by the combination of auxin and gibberellinbut not by either alone, brassinolide applied alone seems toplay a double role, similar to that of auxin and of gibberellin,in organizing cortical MTs. (Received September 2, 1994; Accepted November 16, 1994)     

A Possible Role for Rhizobacteria in Water Treatment by Plant Roots

By accumulating Cd from solution, roots of hydroponically grown Indian mustard (Brassica juncea L.), a high biomass crop plant, were able to cause substantial reductions in the concentration of Cd in solution. The removal of Cd from solution was linearly correlated with Cd accumulation by roots. Screening of 300 different rhizobacterial isolates identified several that, when inoculated onto roots of Indian mustard, significantly enhanced the total amount of Cd removed from solution. Further investigations revealed that this enhancement was because of an overall increase in root biomass in the rhizobacterial-treated plants. Rhizobacteria were found to accumulate Cd from solution, and ultrastructural observations suggested that rhizobacteria promote the precipitation of Cd on the root surface. By precipitating Cd at the root surface, rhizobacteria reduce the amount of Cd taken up into roots, thereby protecting the plants, and in particular the roots, from the toxic effects of Cd. This reduced Cd toxicity allows for the increased proliferation of roots observed when plants are inoculated with certain rhizobacteria.     

The Role of the Epidermal Cells in the Stomatal Movements

The water deficit of the leaves, the osmotic values of the stomatal cells and epidermal cells at incipiment plasmolysis, as well as the width of the stomatal apparatus and pore opening, were measured every hour from 6-17 o'clock under natural environmental conditions. During the noon hours, the intensity of light in clear weather ranged from 40,000-55,000 lux in the open position, and from 15,000-20,000 lux in the shade. The temperature was usually 15–20°C. The experimental object was Vicia Faba growing in a field, both plants freely rooted and plants in pots buried in the soil. The experiments resulted in the following observations and conclusions: 1. When leaves are exposed to strong light, the osmotic value at incipient plasmolysis changes not only in the guard cells, but also in the epidermal cells. If the epidermal cells' osmotic value rises, water is sucked from the guard cells and their uptake of water by suction is decreased, which promotes closure and counteracts opening, respectively. If the value falls, the effect is the reverse. The guard cells react passively to these epidermal changes. The passive stomatal movement eliciteed in this way has therefore been denoted as “osmopassive”, in contrast to the long known passive movement caused by a change in turgor of the epidermal cells, and which has therefore been denoted as “turgorpasslve”. The osmopassive component of stomatal closure has an earlier and more rapid onset than the hydroactive closing reaction, which consists of a decrease in the guard cells' osmotic value. Stomatat closure often starts with the osmopassive rapid process, and is completed and stabilized by the hydroactive process. It has not been possible to determine whether the osmopassive closing reaction is identical with the rapid reaction previously described, and interpreted as of adenoid nature, and tlius belonging to the active group. 2. The osmotic potential of the guard cells - i.e., the difference between the osmotic value of guard cells and epidermal cells at incipient plasmolysis - is, therefore, formed not only by a cbange in the osmotic value of the former cells, but also by a cbange in that of the latter. 3. Although the pore width runs largely parallel to the osmotic value of the guard cells, there is greater agreement between pore width and osmotic potential. When the water deficit of the leaf exceeds a certain threshold value, potential and stomatal width start to decrease. Closure is completed when the fall in potential approaches the zero value. If the water deficit subsequently continues to increase, the potential becomes negative and the stomata remain closed. 4. The stomatal movements are regulated by physiological processes which form two kinds of equilibrium between increase and decrease of the osmotic potential of the guard cells, i.e. the osmopassive increase - osmopassive decrease and the photoactive increase - hydroactive decrease. These equilibria complement each other in rate and stability. The osmopassive processes start rapidly and as soon as the deficit cbanges; hydroactive closure and sometimes also photoactive opening, are, on the contrary, time-consuming. When the water deficit is suboptimal, turgorpassive opening and closing are superadded, but only in those cases in which the osmotic potential of the guard cetls is positive.     

Cytological Analysis of Seedling Roots, Transformed Root Cultures and Roots Regenerated from Callus of Swainsona galegifolia (Andr.) R. Br.

The stability of chromosome number was investigated in culturesof roots from Swainsona galegifolia. Roots from germinated seedsor plants grown in vitro when cultured in liquid medium howed90% or more cells with the diploid number of 2n = 32. The remainingcells showed aneuploidy mostly below 32. The stability of chromosomenumbers was not affected by transformation with Agrobacteriumrhizogenes although when roots were transformed with A. rhizogenesLB 9042 the range of chromosome numbers in the few aneuploidcells present was higher than in roots for which strain A4 wasused. In contrast, roots regenerated from callus had only 15%of cells with 2n = 32 and showed a modal number of 18. Six rootcultures established from individual roots regenerated fromcallus showed a wide variation in number (8–83). Fivecultures had a modal number around 18, the sixth, a modal numberof 39 which is above the diploid number. The implication ofthe results for the production of secondary metabolites fromroot culture is discussed. Key words: Agrobacterium rhizogenes, callus cultures, chromosome number, root cultures, Swainsona galegifolia     

根瘤形成过程中豆科植物根毛和根外层传递细胞的诱发

对7种豆科植物接种根瘤菌后根部的形态和内部结构进行了研究.结果表明:根瘤菌可诱发根瘤形成部位根段的根毛增生、形变和根外层传递细胞的发育.根外层传递细胞发生在根毛伸长形变时期,一直可持续到根瘤形成,传递细胞壁内突发育过程是先由根表皮细胞外切向壁一侧细胞质膜向细胞质内陷形成囊状壁傍体,次生细胞壁物质在初生壁上沉积并逐渐充满囊状体,最终形成传递细胞典型的壁内突结构.根瘤形成过程中根外层传递细胞的诱发与培养方式(水培、固培)没有直接关系.在不接菌的对照苗的根段内未发现壁内突结构,研究证明豆科植物根外层传递细胞的形成是由根瘤菌诱导所致.     

云南厚壳桂属一新种

瘤果厚壳桂新种CryptocaryarolletiiWangetH.Zhu,sp.nov.SpeciesproximaC.maculataeH.W.Li,sedfructumajore,2.5cmdiam,nervislateralibusutrinsecus4~6differtaC.haihanensiMerr.fructugloboso,paniculaexpansa,multifloradiffert.Arbor,usquead20malalRamuliinjuventnte...     

A Possible Role of R Plasmids in Bacterial Permeability for β-Lactam Antibiotics

Four strains of clinical isolates of Serratia marcescens (13039, 13090, 13093, 14093) harboring R plasmids were highly resistant to ampicillin (ABPC) and cephaloridine (CER). With elimination of R plasmids from these strains by acriflavine treatment, ABPC-resistance levels of these strains were markedly reduced. Reduction of CER-resistance levels was also demonstrated in strains 13039 and 13093, but not in strains 13090 and 14093. The permeability of the former strains for CER was also decreased, but not in the latter strains. At the same time, β-lactamase activity of these strains also almost completely disappeared when the R plasmids were eliminated. By broth matings with these strains, the recipient strains of S. marcescens 13031 (rif), Escherichia coli K-12 (rif), and E. coli 15046 (rif) all acquired a high permeability barrier against CER with inheritance of the R plasmids from strains 13039 and 13093, but not from strains 13090 and 14093. The transconjugant of strain 13031 that inherited R plasmid 13093 was resistant not only to CER but also to cefazolin, cephalothin, and cephalexin. Its permeability to these antibiotics was significantly lower than that of the original strain. This fact suggests the possibility that the R plasmid from strain 13093 may be involved not only in production of β-lactamases, but also in regulation of bacterial permeability for cephalosporins.     

A Possible Role for Taurine in Osmoregulation Within the Brain

Intracranial microdialysis was used to measure changes in extracellular amino acids within the rat brain during local osmotic alteration of the extracellular microenvironment or during systemic water intoxication. Increased cellular hydration produced by either of these methods was accompanied by a marked increase in extracellular taurine levels without affecting the other amino acids measured. With local osmotic alteration, this increase was osmolarity dependent and reversible. The specificity, sensitivity, and reversibility of the increase in extracellular taurine strongly suggest a functional role in osmoregulation in the brain under normal as well as pathological conditions.     

Transfer Cells in Roots of Phaseolus coccineus: Ultrastructure and Possible Function in Exclusion of Sodium from the Shoot

A study was made of ultrastructural aspects and ion distributionin roots of Phaseolus coccineus as affected by NaCl and Na₂SO₄salinity. In the proximal region of the root, xylem parenchymacells are differentiated as transfer cells with well developedwall protuberances adjacent to the half-bordered pits of thevessels. The cytoplasm of these transfer cells contains cisternaeof rough endoplasmic reticulum, the number of which was increasedgreatly when the plants were grown in the presence of NaCl orNa₂SO₄. The cisternae of the endoplasmic reticulum are oftenassociated closely with the plasmalemma and interconnected withit by fibrillar bridges. Wall protuberances occur also in the exodermis and epidermisof the more apical region of the root. Their function is stillunknown. P. coccineus excludes Na, but not Cl, from the leaves by retainingit particularly in the proximal region of the root. X-ray microanalysisof unfixed, frozen, hydrated specimens revealed that the transfercell-type xylem parenchyma cells in salt-treated roots accumulatedNa relative to both the adjoining xylem vessels and the corticalcells and showed very high Na/K and Na/Cl ratios. It is suggestedthat the xylem parenchyma cells can reabsorb Na from the vessels,probably in exchange for K, and that Na exclusion from the shootis at least partly mediated by this process. The implicationof this for regulation of salt transport in salt sensitive glycophytesis discussed.     

A Role for Neuropilins in the Interaction between Schwann Cells and Meningeal Cells

In their natural habitat, the peripheral nerve, Schwann cells (SCs) form nicely aligned pathways (also known as the bands of Büngner) that guide regenerating axons to their targets. Schwann cells that are implanted in the lesioned spinal cord fail to align in pathways that could support axon growth but form cellular clusters that exhibit only limited intermingling with the astrocytes and meningeal cells (MCs) that are present in the neural scar. The formation of cell clusters can be studied in co-cultures of SCs and MCs. In these co-cultures SCs form cluster-like non-overlapping cell aggregates with well-defined boundaries. There are several indications that neuropilins (NRPs) play an important role in MC-induced SC aggregation. Both SCs and MCs express NRP1 and NRP2 and SCs express the NRP ligands Sema3B, C and E while MCs express Sema3A, C, E and F. We now demonstrate that in SC-MC co-cultures, siRNA mediated knockdown of NRP2 in SCs decreased the formation of SC clusters while these SCs maintained their capacity to align in bands of Büngner-like columnar arrays. Unexpectedly, knockdown of NRP1 expression resulted in a significant increase in SC aggregation. These results suggest that a reduction in NRP2 expression may enhance the capacity of implanted SCs to interact with MCs that invade a neural scar formed after a lesion of the spinal cord.     

一种同步观察喜树碱与菌根丛枝结构的方法

本文介绍一种用激光共聚焦扫描显微镜同步观察喜树碱、丛枝茵根及其结构的方法.喜树丛枝茵根经甘油浸润和明胶包埋后制成切片,再经酸性品红染色后在激光共聚焦扫描显微镜下观察.波长488mm处激发光下可获得清晰的丛枝茵根透射图像.364 nm处激发光下可获得喜树碱的荧光图像,通过两图像的叠加,在喜树丛枝菌根中得到喜树碱的定位图像.用此方法初步研究了喜树丛枝茼根的喜树碱分布.     

A Simple Method for Purification of Vestibular Hair Cells and Non-Sensory Cells,and Application for Proteomic Analysis

Mechanosensitive hair cells and supporting cells comprise the sensory epithelia of the inner ear. The paucity of both cell types has hampered molecular and cell biological studies, which often require large quantities of purified cells. Here, we report a strategy allowing the enrichment of relatively pure populations of vestibular hair cells and non-sensory cells including supporting cells. We utilized specific uptake of fluorescent styryl dyes for labeling of hair cells. Enzymatic isolation and flow cytometry was used to generate pure populations of sensory hair cells and non-sensory cells. We applied mass spectrometry to perform a qualitative high-resolution analysis of the proteomic makeup of both the hair cell and non-sensory cell populations. Our conservative analysis identified more than 600 proteins with a false discovery rate of <3% at the protein level and <1% at the peptide level. Analysis of proteins exclusively detected in either population revealed 64 proteins that were specific to hair cells and 103 proteins that were only detectable in non-sensory cells. Statistical analyses extended these groups by 53 proteins that are strongly upregulated in hair cells versus non-sensory cells and vice versa by 68 proteins. Our results demonstrate that enzymatic dissociation of styryl dye-labeled sensory hair cells and non-sensory cells is a valid method to generate pure enough cell populations for flow cytometry and subsequent molecular analyses.     

Possible Role of Nitric Oxide in Catecholamine Secretion by Chromaffin Cells in the Presence and Absence of Cultured Endothelial Cells

Abstract: We studied the effect of cultured endothelial cells on the secretion of catecholamines by cultured bovine chromaffin cells. Chromaffin cell catecholamine secretion was stimulated by either boluses of potassium (K⁺) or the nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium (DMPP). Endothelial cells inhibited the catecholamine release and stimulatory effects of K⁺ and DMPP. This inhibition increased with time, and in 25 min the initial stimulated secretory response (100%) to 30 m M K⁺ or 25 μ M DMPP dropped to 45 ± 3% and 53.5 ± 2.3%, respectively. This endothelial cell-induced inhibition was blocked by the nitric oxide synthase inhibitors N -nitro- l -arginine methyl ester ( l -NAME) and N -monoethyl- l -arginine ( l -NMMA), and by the guanylate cyclase inhibitor methylene blue, indicating that the l -arginine/nitric oxide/ cyclic GMP pathway is involved in this endothelial cell-chromaffin cell interaction. In the absence of endothelial cells, incubation of chromaffin cells with l -NAME, l -NMMA, or methylene blue also augmented the secretagogue-induced catecholamine secretion, indicating that nitric oxide from chromaffin cells could be implicated in an autoinhibitory process of catecholamine release. These results provide indirect evidence for the presence of nitric oxide synthase in bovine adrenomedullary chromaffin cells. Our results show that there is an autoinhibitory mechanism of catecholamine release in chromaffin cells and that an additional level of inhibition is observed when cultured vascular endothelial cells are present. These two inhibitory processes may have different origins, but they appear to converge into a common pathway, the l -arginine/nitric oxide synthase/guanylate cyclase pathway.     

Ultrastructural Localization of ATPase Activity in the Cells of the Apical Meristem Zone,Elongation Zone and Root Hair Zone of Tomato Roots

A comparative study on the cytochemical localization of adenosine triphosphatase (ATPase) activity reaction in the cells of the apical meristem zone, elongation zone and root hair zone of tomato roots was carried out by electron microscopic observations of lead phosphate precipitation. The following experimental results have been obtained: In the meristematic cells of tomato roots, the heavy lead phosphate deposits indicating a very high activity of ATPase were localized at plasmalemma, plasmodesmata, endoplasmic reticulum, Golgi bodies, nucleoli and chromatin (Figs. 1—2). The reaction products of ATPase activity were also observed at some sites of ground cytoplasm and cell wall, but they were not found in little vacuoles and on tonoplast. In the cells of elongation zone, the ATPase activity at plasmalemma and plasmodesmata was as high as that in the meristematic cells of root tip, while the ATPase activity at nucleoli, chromatin, endoplasmic reticulum and Golgi bodies was markedly lowered. On the other hand, the high ATPase activity was produced on the tonoplast of the developing and enlarging vacuoles (Fig. 3). In the cells of root hair zone, the high ATPase activity was shown at plasmalemma, tonoplast and intercellular spaces, but the ATPase activity at nucleoli, chromatin and endoplasmic reticulum was wholly inactivated. (Figs. 4—7). The above results indicate that the ATPase activity with membranes and organelles is altered when the functions of cells and organelles change. Therefore, it is evident that the ATPase activity may be closely related to many physiological functions.     

天麻属——广东省兰科植物一新记录属(英文)

报道广东兰科植物一新记录属——天麻属(Gastrodia R.Br.),提供北插天天麻(G.peichatieniana S.S.Ying)的详细形态描述及照片,该种原记录仅分布于中国台湾。     

A Possible Explanation for the Variable Frequencies of Cancer Stem Cells in Tumors

A controversy surrounds the frequency of cancer stem cells (CSCs) in solid tumors. Initial studies indicated that these cells had a frequency ranging from to of the total cells. Recent studies have shown that this does not always seem to be the case. Some of these studies have indicated a frequency of . In this paper we propose a stochastic model that is able to capture this potential variability in the frequency of CSCs among the various type of tumors. Considerations regarding the heterogeneity of the tumor cells and its consequences are included. Possible effects on conventional treatments in clinical practice are also described. The model results suggest that traditional attempts to combat cancer cells with rapid cycling can be very stimulating for the cancer stem cell populations.