摘要:

Abstract:Recent observations of pollen tubes show that these tubes may grow in a pulsatory fashion (Pierson et al., 1995; Plyushch et al., 1995; Li et al., 1996; Geitmann et al., 1996a, 1996b), in which phases of fast and slow growth alternate regularly. The occurrence of pulsatory growth has been used by Geitmann and coworkers (1996b) to study factors that might control growth. Their results emphasize the role of the cell wall and secretory events in regulating pollen tube growth. Here we will briefly review recent results related to the role of exocytosis, cytoskeleton, calcium and the cell wall in pollen tube growth.

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1996.tb00582.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:The vascular system of the stem ofStylobasiumwas investigated during its primary and secondary phases with both light and electron microscopic methods. It contains collateral bundles arranged in a ring, separated by rays which undergo regular cambial growth. The phloem consists of short sieve elements connected to sieve tubes by simple sieve plates, companion cells of the same length, and phloem parenchyma cells. During their autophagy‐like differentiation and maturation, typical of all angiosperms, the sieve elements ofStylobasiumhave a peculiar feature, whereby they develop and retain form‐Pfs plastids (containing protein filaments and starch). The sieve‐element plastids of the twoStylobasiumspecies, and of some 100 species belonging to taxa of whichStylobasiumhad been considered to be a possible member, have been studied by transmission electron microscopy. With the exception of a few species with form‐Pcs plastids (containing a single small protein crystal in addition to starch), the great majority of taxa studied are characterized by S‐type sieve‐element plastids (containing starch only). The presence of form‐Pfs plastids inStylobasiumsupports its separation into the unigeneric Stylobasiaceae and the placement of this family close to other form‐Pfs or form‐Pcfs‐containing taxa. While other characters would exclude an affiliation to the Magnolianae (form‐Pfs plastids inCanella)or Caryophyllales (form‐Pfs plastids inMicrotea), an association with the form‐Pcfs families Connaraceae and Mimosaceae is positively considered and corresponds to their frequent allocation close to the Rutales and Sapindales. Within the Rutales/Sapindales the sizes of sieve‐element plastids (average diameter) range from very large (e.g. in the Julianaceae) to comparatively small (e.g. in Aceraceae) and are used to group the families. The sieve element characters of the Coriariaceae (tiny plastids with almost no starch, wide sieve plate pores, copious P‐protein) suggest their removal from Rutales/Sapindales into the neigh

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1996.tb00583.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:While the apparent mutual exclusiveness of anthocyanins and betalains in the Caryophyllales has given rise to considerable taxonomic debate, historical factors affecting the present distribution of these compounds have rarely been discussed. An understanding of pigment evolution in the order is hindered by a number of unresolved systematic issues and a lack of knowledge of the importance of anthocyanins and betalains beyond their roles in pollination and seed dispersal. The hypothesis that betalains arose in an unpigmented ancestor of the Chenopodiinae in response to selection from pollinators cannot be rejected, but scant evidence exists in favor of it. Questions persist regarding whether the most recent ancestor to the Chenopodiinae presented a pigmented floral display and whether the appropriate pollinators were present at this time to select for floral pigmentation. In view of these ambiguities and the possible non‐monophyly of the Chenopodiinae we consider some alternative scenarios and suggest potentially rewarding avenues for future research. We discuss roles for anthocyanins and betalains beyond their use as optical attractants, possible costs and benefits associated with producing each pigment type, and the possibility that they may have co‐occurred in an ancestor for some period of t

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1996.tb00584.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1996.tb00585.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:Specific inhibitors of the secretory pathway represent important tools for investigation of cell wall synthesis and tip growth in pollen tubes. Brefeldin A completely inhibits germination ofNicotiana tabacumpollen tubes at 2.2 μM. Ultrastructural investigation of pollen tube cytoplasm showed that brefeldin A caused the appearance of reticular structures and “brefeldin A compartments” containing unesterified pectins. Monensin caused inhibition of pollen tube germination at 80 nM. The drug induced swelling of the Golgi cisternae, many of which contained methyl‐esterified pectins. Cytochalasin D was effective at 1 μg/ml, the inhibition of germination being fully reversible. Application of the drug caused accumulation of secretory vesicles containing methyl‐esterified pectin around the dictyosomes. In contrast to brefeldin A and monensin, cytochalasin D caused a slowdown of cytoplasmic streaming. Monensin, but not the other drugs, caused a considerable decrease in pollen tube diameter. The characterization and quantification of the effects of the drugs on pollen tubes represents a necessary prerequisite for their application in physiologica

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1996.tb00586.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:The proton pumping ATPase in the plasma membrane ofElodea canadensisis believed to play a major role in inorganic carbon acquisition. To investigate potentially different carbon uptake strategies within the same plant, plasma membrane H+‐ATPase distribution and polar current patterns were investigated inElodealeaves and stems. Specific activity of plasma membrane H+‐ATPase in leaf microsomal fractions was tenfold higher than in stem derived microsomes. Probing western blots with a monoclonal antibody specific for plasma membrane H+‐ATPase, yielded strongly visible double bands at 100 kDa in leaf microsome preparations, whereas little antigen was detected in analogous stem microsome preparations. Using the same plasma membrane H+‐ATPase specific antibody on tissue sections, the enzyme was found almost exclusively localized at the border of cells at the lower leaf surface. A positive ion current leaving the lower leaf surface was measured, using a vibrating probe device. Part of this current entered the upper leaf surface and part of it the internodes of the stem. The experimental results support the view, thatElodealeaves have different means of inorganic carbon uptake than stem int

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1996.tb00587.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:Hydraulic conductivity (Lp) of the plasma membrane ofChara corallinawas inhibited by HgCl2maximally by about 95%. The inhibition was reversed by 2‐mercaptoethanol, reconfirming the observation obtained by Henzler and Steudle (1995). The results suggest that osmotic water transport throughCharacells occurs mostly via mercury‐sensitive water channels containing thiol groups. ZnCl2dissolved in APW (pH 5.6) also inhibited Lpby about 80% within 1–2 h, while ZnCl2dissolved in Hepes‐Tris buffer (pH 7.4) inhibited it by about 90% within several minutes. Inhibition of Lpby ZnCl2was also reversed by 2‐mercaptoethanol, suggesting that zinc acts also on thiol groups of water channel proteins. Cells from which tonoplast had been removed by ECTA were as sensitive to both HgCl2and ZnCl2(pH 7.4) as normal cells. This demonstrates that water channels sensitive to thiol reagents really exist in the plasma membrane. On the other hand, ZnCl2(pH 5.6) did not inhibit Lpof tonoplast‐free cells. This may be accounted for by assuming first that Hg‐ and Zn‐sensitive thiol groups of water channels may exist on the cytoplasmic side, and second that ZnCl2in acidic medium may exist in ionized species which can be chelated by EGTA after permeation. The polar water permeability, or the endoosmotic Lpbeing larger than the exoosmotic one, was not affected by lowering the rate of osmosis by decreasing the osmotic gradient for transcellular osmosis down to 0.02 M sorbitol. The polarity disappeared when osmotic water flow through water channels was completely inhibited by HgCl2. Thus the polarity is assumed to be intrinsic to water channels in the

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1996.tb00588.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:In stems ofRicinus communisand leaves ofKalanchoë daigremontiana, rapidly growing tumors were induced by the wild type strains ofAgrobacterium tumefaciensC58 and A281 (p35 Sgusint). Transformed cells, monitored by histochemical β‐glucuronidase (GUS) staining, showed GUS activity inK. daigremontianatumors in up to 100% of the tissue. InR. communistumors, however, GUS activity was patchy, probably due to interference ingusexpression from highly active phenolic compounds. Functionality of the sieve elements within the vascular bundles of the tumor and their connection with host stem bundles were shown by applying fluorescein to source leaves as a tracer of phloem‐mobile solutes. The transport pathway within the tumor and the mechanism of phloem unloading were investigated by iontophoretic injection of Lucifer yellow CH into sieve tubes. Apparent symplastic solute unloading into parenchyma cells was confirmed by localizing common primary pit fields by staining them with aniline blue. In spite of the evidence for symplastic unloading, the activity of acid cell wall invertase (CWI) was about tenfold higher in tumor than in the adjacent host stem tissue. These results indicate primary independence of phloem unloading of CWI in t

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1996.tb00589.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:Tumors induced by the wild‐type strain C58 ofAgrobacterium tumefaciensin hypocotyls ofRicinus communisL. were investigated structurally and functionally with respect to xylem differentiation, cuticle and stomata development, water pathway and transpiration. Clearing of tissue with lactic acid and staining with lacmoid revealed a continuation of stem xylem into differentiated bundles in the tumor. Under the influence of tumors the host xylem below the tumors increased considerably in size. Transport of negatively‐charged dyes, amido black, acid fuchsin and the fluorescent pyrenetrisulfonate demonstrated a continuous water flow through the vessels from the stem into the tumor, and up to its surface. Infrared thermography and quantitative measurements of transpiration revealed that transpiration was about 15 times and 7.5 times higher at the tumor surface in comparison to host leaves and to leaves of non‐infected plants, respectively. Leaf CO2assimilation rate remained unaffected by tumorisation. Tumor growth caused disruption of the epidermis, which did not regenerate and hence no cuticle developed to protect against water loss. Stomata located at the tumor rim hypertrophied and lost their function. Tumors are thus characterised as being structurally and functionally strong pathological water sinks on their host

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1996.tb00590.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:Hippeastrum x hortorumbulbs produce red pigments upon wounding. Analysis by TLC, HPLC, MS and NMR revealed that this pigment, which is absent in unwounded tissue, is a mixture composed of an orange‐coloured chalcone (3,2′4′‐trihydroxy‐4‐methoxychalcone) and 3 flavans (7,4′‐dihydroxy‐8‐methylflavan, 7,3′‐dihydroxy‐4′‐methoxyflavan and 7‐hydroxy‐3′‐4′‐methylenedioxyflavan). The colourless flavans can be oxidised to red‐coloured dimers or polymers. The induction of these “phytoalexins” is achieved by wounding and can be further amplified by biotic and abiotic elicitors; e.g. cell walls of yeast appeared to be a potent elicitor. Immediately after wounding or elicitation the apparent activities of phenylalanine ammonium lyase (PAL) and peroxidase, which are probably involved in the biosynthesis of the red pigments increase substantially (both enzymes are hardly measurable in unwounded tissue) and reach a transient maximum after 2 − 3d whereas pigment formation becomes visible after 2d and reaches a maximum after 9 to 12 d. Since cycloheximide inhibits the formation of the phytoalexins, ade novosynthesis of the corresponding enzymes is likely. Total phytoalexin extracts showed an inhibition of bacterial growth (e.g. ofBacillus subtilis, B. megaterium) and of feeding by polyphagous larvae of the mothSyntomis mogadorensis. These data imply that the wounding‐ and elicitor‐induced phytoalexins appear to function as de

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1996.tb00591.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY