NOTES ON THE BEHAVIOR OF THE HYDROID, CORYMORPHA PALMA

Corymorpha, like Porpita, exhibits a synchronous oral flexion,or "concert," of its proximal tentacles. As this is unlike thecontractile writhings of siphonophoran zooids, the concert maybe a significant character in linking the behavior of Porpitamore closely to hydroids than to siphonophores. Except for thisresponse the behavior of Corymorpha and Porpita are different.In Porpita a through-conducting system forms the only link betweententacles, whereas in Corymorpha both local and through-conductingsystems connect tentacles. Corymorpha engages in rhythmic bottom-feedingusing distal tentacles which have no homologue in Porpita. Themechanical properties of the musculo-skeletal system are differentin the two, giving tentacle motions in Corymorpha a continuousappearance, and in Porpita a spasmodic appearance. Reduced glutathione, glycine, DL-serine, L-cysteine and L-glutamicacid can elicit a feeding response in Corymorpha. Sodium thioglycollateand sucrose elicit no response. Glycine is the most effectivestimulant, ca. 5 X 10^–7 M solution being effective. L-glutamicacid gives the weakest response. The presence of chemicals alonecan be sufficient to elicit the feeding reaction in starvedanimals. In moderately well-fed animals, touch may be required.In fully fed animals both touch and chemicals may be insufficient. Parker reports that when Corymorpha is shocked electricallyon its stalk it will bend the stalk so as to apply the hydranthaccurately to the stimulated spot. The response I found wasa curling of the stalk toward the side stimulated, but not toa specific spot on the stalk. Chemical or tactile stimuli maybe necessary for final location of the stimulated site. Parkerreported that the response remained accurate even after severalcuts had been made in the stalk. I could find no evidence forthis.     

Effects of osmotic swelling on voltage-gated calcium channel currents in rat anterior pituitary cells

Decrease in extracellular osmolarity ([Os]_e) results in stimulation of hormone secretion from pituitary cells. Different mechanisms can account for this stimulation of hormone secretion. In this study we examined the possibility that hyposmolarity directly modulates voltage-gated calcium influx in pituitary cells. The effects of hyposmolarity on L-type (I_L) and T-type (I_T) calcium currents in pituitary cells were investigated by using two hyposmotic stimuli, moderate (18-22% decrease in [Os]_e) and strong (31-32% decrease in [Os]_e). Exposure to moderate hyposmotic stimuli resulted in three response types in I_L (a decrease, a biphasic effect, and an increase in I_L) and in increase in I_T. Exposure to strong hyposmotic stimuli resulted only in increases in both I_L and I_T. Similarly, in intact pituitary cells (perforated patch method), exposure to either moderate or strong hyposmotic stimuli resulted only in increases in both I_L and I_T. Thus it appears that the main effect of decrease in [Os]_e is increase in calcium channel currents. This increase was differential (I_L were more sensitive than I_T) and voltage independent. In addition, we show that these hyposmotic effects cannot be explained by activation of an anionic conductance or by an increase in cell membrane surface area. In conclusion, this study shows that hyposmotic swelling of pituitary cells can directly modulate voltage-gated calcium influx. This hyposmotic modulation of I_L and I_T may contribute to the previously reported hyposmotic stimulation of hormone secretion. The mechanisms underlying these hyposmotic effects and their possible physiological relevance are discussed. L-type channels; mechanosensitivity; somatotrophs; lactotrophs     

恒河猴皮肤干细胞的体外培养纯化与鉴定

探索恒河猴皮肤干细胞的体外培养及纯化条件,为进一步的研究奠定基础. 通过组织块培养法和消化培养法 在体外培养恒河猴表皮细胞,然后用Ⅳ型胶原吸附法吸附20 min,获得快吸附细胞. 对快吸附细胞进行克隆培养,并进行免疫细胞化学双标染色、RT PCR鉴定 β1 整合素和角蛋白15的表达,用流式细胞仪鉴定纯化前后的细胞中 β1 整合素和角蛋白15的阳性细胞比例,并通过透射电镜观察细胞的超微结构. 组织块培养法和消化培养法均可获得表皮细胞,Ⅳ型胶原纯化后的细胞胞体较小,饱满,核/浆比例大,细胞镶嵌状排列. 细胞克隆分析显示,细胞全克隆生长率高. 细胞免疫荧光显示,分选后的细胞显示 β1 整合素和角蛋白15阳性. RT PCR检查呈现 β1 整合素和角蛋白15的特异性片段. 流式细胞仪检查显示,纯化前的细胞中角蛋白15阳性细胞占总细胞中的比例为8％, β1 整合素阳性细胞的比例为10.7％;纯化后,角蛋白15阳性细胞的比例为89.4％, β1 整合素阳性细胞的比例为88.5％. 通过组织块培养法和消化培养法均可培养获得活性良好的表皮细胞,Ⅳ型胶原吸附法是一种简便、有效的皮肤干细胞分离方法,可以为进一步的眼表上皮替代重建眼表提供足量的高纯度的干细胞建立可靠的物质基础.     

Dual trafficking of Slit3 to mitochondria and cell surface demonstrates novel localization for Slit protein

Drosophila slitis a secreted protein involved in midline patterning. Three vertebrateorthologs of the fly slit gene, Slit1, 2, and3, have been isolated. Each displays overlapping, butdistinct, patterns of expression in the developing vertebrate centralnervous system, implying conservation of function. However,vertebrate Slit genes are also expressed in nonneuronaltissues where their cellular locations and functions areunknown. In this study, we characterized the cellular distribution andprocessing of mammalian Slit3 gene product, theleast evolutionarily conserved of the vertebrate Slit genes,in kidney epithelial cells, using both cellular fractionation andimmunolabeling. Slit3, but not Slit2, was predominantly localizedwithin the mitochondria. This localization was confirmed usingimmunoelectron microscopy in cell lines and in mouse kidney proximaltubule cells. In confluent epithelial monolayers, Slit3 was alsotransported to the cell surface. However, we found no evidence of Slit3proteolytic processing similar to that seen for Slit2. We demonstratedthat Slit3 contains an NH₂-terminal mitochondriallocalization signal that can direct a reporter green fluorescentprotein to the mitochondria. The equivalent region from Slit1 cannotelicit mitochondrial targeting. We conclude that Slit3 protein istargeted to and localized at two distinct sites within epithelialcells: the mitochondria, and then, in more confluent cells, the cellsurface. Targeting to both locations is driven by specificNH₂-terminal sequences. This is the first examination ofSlit protein localization in nonneuronal cells, and this study impliesthat Slit3 has potentially unique functions not shared by other Slit proteins.

     

On assessment of prey ingestion by copepods

The consumption of photosynthetic and heterotrophic cells byan abundant calanoid copepod species feeding on natural planktoncommunities was quantified with a state-of-the-art image-analysissystem. Late copepodid stages of Eucalanus pileatus did notingest bactena, small photosynthetic and heterotrophic nanoplankton,or the abundant Ceratium spp. in quantifiable amounts Althoughdiatoms were by far the most abundant cells (in terms of POC1^–1), the copepods ingested a higher percentage of ciliatesin relation to their abundance than of diatoms and small heterotrophicdinoflagellates in the first experiment, and ingested a higherpercentage of dinoflagel lates and ciliates compared to diatomsin the second experiment Heterotrophic cells sufficiently largeto be captured were repeatedly preferred by E.pileatus overautotrophs of similar or larger size. More over, among the cellswhich could be individually perceived by this calanoid, largerones were not pre ferred over smaller cells, implying that someaspect of food quality can be as significant as prey size. Theseresults support the notion (e.g. Kleppel, Mar. Ecol Prog. Ser.,99, s183–195, 1993) that feeding by copepods will be underestimatedif ingestion of heterotrophic food organisms is not quantified.While the proposed microscope-based method is comparativelyslow (     

Arrangement of Stomata on the Leaves of Pelargonium zonale and Sedum stahlii

Stomata of Pelargonium zonale are orderly arranged on the surfaceof the lower epidermis. Inter-stomatal and Inter-trichome distancesas well as the number of sides of stomata, epidermal cells adjacentto stomata, and regular cells of the epidermis have characteristicprobability distributions. A model of epidermal developmentis constructed based upon the quantitative features of eachtype of cell. The primary restriction of the model is that stomainitials inhibit adjacent cells from becoming stoma initials. A second type of stomatal arrangement occurs in Sedum stahliiand an appropriate model for the ontogeny of epidermal cellsin this plant can also be constructed that has similar quantitativecharacteristics to those of real fields of cells. The applicationof modelling in plant morphology is discussed with respect tounderstanding ontogeny and phylogenic relationships.     

Endosymbiosis in Hydra and the Evolution of Internal Defense System

Certain species of Chlorella have exploited an intracellularhabitat and occur naturally as cytobionts in Hydra viridissima.The algae evoke phagocytosis by Hydra digestive cells and aresequestered in individual phagosomes that migrate to the baseof the host cells and resist fusion with lysosomes. The abilityto resist digestion is closely correlated with release of extracellularcarbohydrate (maltose) by the algae. The established populationof algae grows at an average rate equal to or greater than thatof the host and a constant population density is maintained.The host regulates algal population density by expelling ordigesting excess algae, or by controlling algal cell division.The control mechanism is unknown but can be breached by additionof inorganic ions to the Hydra culture medium with the resultthat the algae overgrow the Hydra. The Hydra-Chlorella symbiosis is probably mutually beneficial,but conditions such as prolonged darkness (with or without feeding)can reduce the competitive fitness of the host since this conditionresults in heterotrophy by the algae at the expense of selectedhost substrates. The evolution of selective permeability toorganic substrates is a major feature of the successful colonizationof the intracellular habitat by symbiotic Chlorella.     

Potassium Involvement in Stomatal Movements of Paphiopedilum

There are conflicting reports about whether guard cells of Paphiopedilumspp. accumulate K during stomatal opening. In this study X-raymicroprobe analysis and histochemical staining for K indicatedthat K accumulated in guard cells in leaves of Paphiopedilumspp. when stomata opened. Additionally, stomatal opening inepidermal strips of P. harrisseanum could only be induced inan MES buffered KC1 medium. Element analysis ofP. harrisseanumepidermis also indicated substantial levels of K, Na and Cawithin the tissue. We conclude that K is involved in the stomatal movements ofPaphiopedilum. Key words: K⁺ transport, Paphiopedilum, Stomatal movements     

Ecological Consequences of Altering the Timing Mechanism for Metamorphosis in Anural Ascidians

SYNOPSIS. In the present study the timing of metamorphosis inan anural ascidian, Molgula pacifica, was compared to metamorphosisin a urodele species Boltenia villosa. Metamorphosis in M. pacificawas triggered at a fixed time in development (32–36 hoursafter fertilization), just prior to hatching. In contrast, metamorphosiswas triggered in B. villosa after the hatched larvae respondedto substrate cues. The timing of metamorphosisin B. villosawas often delayed for up to four days, whereas delays in M.pacifica were not observed. An antibody, termed Epi-3, was foundto cross-react exclusively with epidermal cells in both species.The binding of FITC-labelled Epi-3 was very low prior to metamorphosisand then it increased dramatically after metamorphosis was triggered.The cytoplasm of ampulla tip cells and the tunic immediatelysurrounding each ampulla showed the highest levels of Epi-3fluorescence. The histological and ultrastructural featuresof the ampulla cells suggest that Epi-3 antibody recognizesgranules localized in the apical cytoplasm. How the evolution of an internal "clock" mechanism responsiblefor initiating metamorphosis may be beneficial to anural speciesis discussed. One possibility is that the anural type of timingmechanism reduces mortality rates during this critical phaseof its life cycle.     

美洲大蠊中枢DUM神经元的分离和电压门控Na+电流的记录

【目的】建立美洲大蠊Periplaneta americana中枢神经系统背侧不成对中间神经元（dorsal unpaired median neurons, DUM neurons）的分离方法和DUM神经元电生理实验模型。【方法】IA型胶原酶法消化美洲大蠊末端腹神经节, 机械吹打得到DUM神经元细胞, 运用膜片钳技术记录DUM神经元细胞电压门控Na+电流。【结果】分离得到的DUM神经元细胞状态良好, 具有DUN神经元典型的梨状形态和表面特征。以膜片钳全细胞方式记录到的Na+电流符合钠通道电流特征。【结论】IA型胶原酶消化得到美洲大蠊DUM神经元细胞的方法可靠, 能稳定地记录到Na+电流。本文描述的方法为昆虫神经细胞的电生理机制研究提供一个可用的实验模型。     

Regulation of ET-1 biosynthesis in cerebral microvascular endothelial cells by vasoactive agents and PKC

Endothelin-1(ET-1) is the most potent vasoconstrictor agent known. ET-1 is elevatedin the cerebrospinal fluid following hemorrhage and brain injury andcan compromise cerebral microvascular homeostasis. The modulation ofET-1 production by cerebral microvascular endothelial cells and themechanism by which such changes take place are very important in ourunderstanding of the pathological roles of ET-1. In the present study,we investigated the effects of vasoconstrictor agents that can bereleased from hemolyzed blood, cAMP-dependent dilators, and the role ofprotein kinase C (PKC) in the regulation of ET-1 production by pigletcerebral microvascular endothelial cells in culture. ET-1 was measured by RIA. 1) Cerebral microvascularendothelial cells synthesize and release ET-1 into the media;2) 5-hydroxytryptamine (5-HT), lysophosphatidic acid (LPA), thromboxane analog U-46619, fetal bovineserum (20%), and phorbol 12-myristate 13-acetate significantly increase ET-1 production; 3) basaland vasoconstrictor agent-induced increases in ET-1 production byendothelial cells may be mediated via PKC;4) cAMP-dependent vasodilatorsattenuate the basal production of ET-1 by cerebral microvessels; and5) pretreatment of endothelial cellswith a higher concentration of LPA, U-46619, or 5-HT counterbalances the cAMP-dependent dilator agent-induced reduction in basal ET-1 production. Therefore, by-products of hemolyzed blood can stimulate theproduction of ET-1 by a PKC-mediated mechanism. cAMP-dependent dilatorscan attenuate the vasoconstrictor agent-induced elevation in ET-1production. These results suggest that cerebral microvascular homeostasis could be compromised by effects of interactions among vasoactive agents released during conditions injurious to the brain andthey may further the understanding of potential contributions ofhemolyzed blood clots to subarachnoid hemorrhage-induced vasospasm.     

Morphogenetic Movements and Fate Maps of Vertebrates

SYNOPSIS. Fate maps are totally lacking for hagfishes, rays,holocephals, dipnoi, holostei and mammals, and for all excepttwo of the thirty or so orders of the huge teleost assemblage.Important errors have been found in earlier studies of the movementsby closer control of marking techniques, but there are stillmajor elements in the literature that remain unconfirmed. Recentstudies on Salmo, Xenopus and chick suggest that a wider samplingof major vertebrate groups will uncover more unsuspected variationsin this phase of embryology. Experimental results on the chondrosteansturgeon Acipenser are here compared and contrasted with thoseon Salmo and Xenopus. Though chondrostei and teleosts had arelatively recent common ancestry, the morphogenetic movementsand fate map of Acipenser give no hint as to how the uniquelyteleostean behavior could have arisen. Instead the experimentshave shown in new elaborate detail how close the early developmentof Acipenser is to that of modern amphibia, closer to Xenopusthan to Rana, closer to anura than to urodeles. The search forunity in the field of comparative morphogenetic movements isplagued by lack of breadth in the sample of vertebrates hithertostudied but also by a vocabulary too much loaded with ancienthomological thinking. It is pointed out that when a group ofmovements, all called invagination—or all called epiboly,is studied closely it can be discovered that they may be doingquite different things, controlled by different environmentalfactors. General theory of this part of embryology requiresthe bringing together of the knowledge of cellular movementsfrom in vitro and non-embryonic systems with the knowledge ofthe full variety of normal patterns of morphogenetic movementsin the vertebrates. Before this can be accomplished, we willneed a precise knowledge of what the cells are actually doingin all the sectors of these patterned movements, and in allthe major patterns that the phylum has produced.     

Neurosecretion and Molting in Some Parasitic Nematodes

The adult female of Ascaris lumbricoides possesses a numberof nerve cells containing material which stains with paraldehyde-fuchsin.Among others, most of the primary sensory cells in the lipsare fuchsinophilic. Ascaris does not survive outside its host,so that it is impossible to ascribe a function to these cells. Phocanema decipiens possesses similar cells in the dorsal andventral ganglia which exhibit a cycle of secretion correlatedwith the burst of cytological activity which accompanies thedeposition of the new cuticle. Ligation experiments have demonstratedthat a new cuticle can be deposited in the absence of theseneurosecretory cells. Our most recent experiments suggest thatthe neurosecretory cells may control the release of leucineaminopeptidase in the excretory gland, a substance which isthought to be responsible for ecdysis.     

Direct Somatic Embryogenesis in Roots of Cichorium: Is Callose an Early Marker?

Direct somatic embryogenesis can be obtained from epidermaland cortical cells in roots from in vitro Cichorium plantlets.The first embryogenic cells are seen after six days of culturein darkness, at 35 °C, in a liquid medium supplemented withNAA (1 x 10^–7 M), 6-dimethylallyl-amino-purine (2·5x 10^–6 M), sucrose (0.03 M) and glutamine (1·7x 10^–3 M). Embryogenic cells undergo first a linear andthen a globular segmentation, with increasing cytoplasmic density.These cells and young embryoids show aniline blue fluorescence.SEM allows the same microglobular pattern to be seen on thesurface of young embryoids and on young microspores of Cichoriumused as controls. In this root system, callose deposition seemsto be an early marker in somatic embryogenesis. Somatic embryogenesis, callose, Cichorium     

A Behavioral Assay for Mechanosensation of MARCM-based Clones in Drosophila melanogaster

Because of the structural and functional homology to the hair cells of the mammalian inner ear, the neurons that innervate the Drosophila external sense organs provide an excellent model system for the study of mechanosensation. This protocol describes a simple touch behavior in fruit flies which can be used to identify mutations that interfere with mechanosensation. The tactile stimulation of a macrochaete bristle on the thorax of flies elicits a grooming reflex from either the first or third leg. Mutations that interfere with mechanotransduction (such as NOMPC), or with other aspects of the reflex arc, can inhibit the grooming response. A traditional screen of adult behaviors would have missed mutants that have essential roles during development. Instead, this protocol combines the touch screen with mosaic analysis with a repressible cell marker (MARCM) to allow for only limited regions of homozygous mutant cells to be generated and marked by the expression of green fluorescent protein (GFP). By testing MARCM clones for abnormal behavioral responses, it is possible to screen a collection of lethal p-element mutations to search for new genes involved in mechanosensation that would have been missed by more traditional methods.     

Comparison of intestinal folate carrier clone expressed in IEC-6 cells and in Xenopus oocytes

We recently identified a cDNA clone frommouse small intestine, which appears to be involved in folate transportwhen expressed in Xenopus oocytes. Theopen reading frame of this clone is identical to that of the reducedfolate carrier (RFC) (K. H. Dixon, B. C. Lanpher, J. Chiu, K. Kelley,and K. H. Cowan. J. Biol. Chem. 269: 17-20,1994). The characteristics of this cDNA clone [previously referred toas intestinal folate carrier 1 (IFC-1)] expressed inXenopus oocytes, however, were foundto be different from the characteristics of folate transport in nativesmall intestinal epithelial cells. To further study these differences,we determined the characteristics of RFC when expressed in anintestinal epithelial cell line, IEC-6, and compared the findings toits characteristics when expressed inXenopus oocytes. RFC was stablytransfected into IEC-6 cells by electroporation; its cRNA wasmicroinjected into Xenopus oocytes.Northern blot analysis of poly(A)⁺RNA from IEC-6 cells stably transfected with RFC cDNA (IEC-6/RFC) showed a twofold increase in RFC mRNA levels over controls. Similarly, uptake of folic acid and 5-methyltetrahydrofolate (5-MTHF) by IEC-6/RFCwas found to be fourfold higher than uptake in control sublines. Thisincrease in folic acid and 5-MTHF uptake was inhibited by treatingIEC-6/RFC cells with cholesterol-modified antisense DNAoligonucleotides. The increase in uptake was found to be mainly mediated through an increase in the maximal velocity(V_max) of theuptake process [the apparent Michaelis-Menten constant(K_m) alsochanged (range was 0.31 to 1.56 µM), but no specific trend wasseen]. In both IEC-6/RFC and control sublines, the uptake of bothfolic acid and 5-MTHF displayed 1)pH dependency, with a higher uptake at acidic pH 5.5 compared with pH7.5, and 2) inhibition to the sameextent by both reduced and oxidized folate derivatives. Thesecharacteristics are very similar to those seen in native intestinalepithelial cells. In contrast, RFC expressed inXenopus oocytes showed1) higher uptake at neutral andalkaline pH 7.5 compared with acidic pH 5.5 and2) higher sensitivity to reducedcompared with oxidized folate derivatives. Results of these studiesdemonstrate that the characteristics of RFC vary depending on the cellsystem in which it is expressed. Furthermore, the results may suggestthe involvement of cell- or tissue-specific posttranslationalmodification(s) and/or the existence of an auxiliary proteinthat may account for the differences in the characteristics of theintestinal RFC when expressed inXenopus oocytes compared with whenexpressed in intestinal epithelial cells.

     

Analysis of In Vivo Protein Synthesis and Histological Studies of Haustorial Formation in Root Cultures of Witch weed (Striga asiatica L Kuntze)

We recently described an in vitro approach that uses root culturesto study haustorial formation in Striga asiatica. Previous studieshave used haustoria formed on intact radicles of Striga seedlings.In vitro cultured roots formed haustoria that appeared morphologicallysimilar to those formed by Striga radicles, but were 5–10-foldlarger. In this study, we provide biochemical and histologicalevidence to support further the similarity of root culture haustoriato haustoria formed on radicles of seedlings. We examined invivo protein synthesis during haustorial development on rootcultures and radicles by 2-D PAGE. Four proteins increased inabundance in both root cultures and radicles after 6 h of haustorialinduction. All four proteins appeared transiently in root culturesand radicles, being more abundant at 6 h, and less abundantafter 24 h of haustorial induction. Only three of the four haustorial-specificproteins were more abundant in root cultures after 2 h of haustorialinduction; all four had decreased in abundance after 12 h ofhaustorial induction. Using light microscopic analysis we comparedthe ontogeny of root culture haustoria to that of haustoriaon radicles. These studies revealed that root culture haustoriaundergo developmental changes similar to those reported forradicle haustoria such as early expansion of cortical cells,the emergence of haustorial hairs from epidermal cells, andthe development of densely staining cells at the haustorialapex. In addition, these changes occurred within a similar time-frameand sequence in root culture and radicle haustoria. Finally,root culture haustoria were found to be capable of attachingto sorghum host roots. Key words: Striga asiatica L., Kuntze, haustoria, root cultures, proteins, histology, 2D-PAGE     

Immuno-flow cytometric identification and enumeration of the ichthyotoxic dinoflagellate Gyrodinium aureolum Hulburt in artificially mixed algal populations

Flow cytometric identification and enumeration of Gyrodiniumaureolum Hulburt (Dinophyceae) were performed in artiticiallymixed algal populations using direct immunofluorescence. Calibrationof the flow cytometer, performed with a mixed algal populationspiked with immuno-fluorescently labelled G.aureolum cells,showed that selection of target cells after analysis on greenand orange fluorescence can be done with a recovery of 91.8%[coefficient of variation (CV) = 0.09]. Other selection methodswere less good, with 67.4% (CV = 0.16) and 58.4% (CV = 0.43)recovery based on green and red fluorescence or green fluorescenceand perpendicular light scattering. For mixed algal populationsspiked with unlabelled G.aureolum cells, the quantificationof target cells was quite good (recovery of 76.7%; CV = 0.20).The percentage of total cell loss was high (58.0–92.0%),but this was caused mostly by loss of species smaller in sizethan G.aureolum. Estimates of the relative contribution of G.aureolumin labelled samples were therefore often far too high, but detectionand quantification were not affected. The methodological underestimation(23.3%) was partly caused by gating on green and orange fluorescence(inaccuracy 8.2%).     

The Anatomy of Root Initiation in Cuttings of Griselinia littoralis and Griselinia lucida

The initiation of root primordia in Griselinia littoralis andG. lucida occurred a few millimeters above the cut base. Inall cases the first cellular event was the activation of specificregions of the cambium which were associated with traces fromleaves which themselves were particularly vigorous root-formersif detached. In cuttings from seedlings, the first cells cutoff continued to divide and gave rise to root primordia in situ,whereas those from mature plants produced files of six to 22rows of cells and it was only when the cells first cut off hadbeen displaced outwards towards the fibre caps that the cambiumstopped dividing. Primordium development may then occur at theadvancing front, possibly as a result of a stimulus originatingfrom damaged cells. Thus the same cells were involved in organizedprimordium formation both in seedling and mature cutting, butthe location differed. The reduced rooting and the long lag phase in cuttings frommature plants of G. lucida may be due to the presence of a completering of fibres. This does not seem to present a mechanical barrierto emergence - since elongating primordia can force throughthe ring - nor can it affect the receipt of any root-inducingstimulus by the target cells since it is considered that thisarrives via the vascular tissues. However, evidence suggeststhat it is the initial phase of cambial activation which isprevented in cuttings from mature plants. This suggested eitherthat the initial stimulus was less effective or that the targetcells were less responsive than those of seedlings, which havevery few fibres, or of mature G. littoralis, which only hasfibm associated with the vascular bundles. Griselinia littoralis Raoul Choix, Griselinia licida Forst. f. Prodr., adventitious roots, cuttings, primordium initiation and location