bluuebunny/crossref_metadata_2025 huggingface dataset:
Pollination in Geonoma macrostachys and Three Congeners, G. acaulis, G. gracilis, and G. interrupta
Authors: Listabarth Ch.
Published: February 2014

A continuous 15 month study of the floral ecology of four syntopic understorey palm species of Genoma was conducted in Amazonian Peru lowland rainforest.

The spicate inflorescences of G. macrostachys, G. acaulis and G. gracilis are strictly protandrous and the plants are functionally dioecious. Data suggest that in G. macrostachys and G. acaulis pollination is based on a mimicry system, the pistillate flowers mimicking the staminate ones in colour, shape and scent. Pollen‐collecting meliponine bees (Hymenoptera, Apidae, Meliponinae) and pollen‐feeding syrphid flies (Diptera, Syrphidae) which visit inflorescences during both sexual stages are the pollinators of G. macrostachys. Geonoma acaulis is pollinated by small pollen‐feeding weevils (Coleoptera, Curculionidae, Derelomini) that visit male and female spikes.

Additionally, in G. macrostachys another pollinator type, viz. euglossine bees (Hymenoptera, Apidae, Euglossinae), which are attracted and rewarded by both types of flowers may account for long‐distance pollination.

The palm G. gracilis shows a very distinct pollination system. Although opportunistic insect visitors are attracted to the inflorescences of this species it seems to be mainly anemophilous because pollen becomes powdery during an thesis.

The branched inflorescences of G. interrupta are also protandrous, but unlike the other species of Geonoma observed, staminate and pistillate anthesis of individual flowers are, for the most, overlapping. A broad spectrum of visitors is attracted (bees, wasps, flies, and beetles), which all may act as pollinators. Outcrossing is especially encouraged during the purely female phase at the end of the flowering cycle when there are no more staminate flowers in the inflorescence.

Effects on the reproductive biology and population structure of different pollination systems and breeding system are discussed.
The Bizarre Inflorescence of Norantea brasiliensis (Marcgraviaceae): Visits of Hovering and Perching Birds1
Authors: Sazima I. , Buzato Silvana , Sazima Marlies
Published: February 2014

The pollination biology of Norantea brasiliensis (Marcgraviaceae) was studied in the rain forest of southeastern Brazil. This plant presents bizarre, brush‐type racemous inflorescences bearing numerous flowers and extrafloral cup‐shaped nectaries. Flower anthesis is diurnal, nectar production is continuous and copious, and the sticky pollen is readily removed by visitors during the first morning hours. The ruby‐coloured inflorescences were visited by eight species of hummingbirds (Trochilidae), and 10 species of passerine birds (three Coerebidae and seven Thraupidae). Hummingbirds hovered while probing for nectar and touched flowers occasionally, whereas passerine birds perched and made contact with flowers habitually. Due to differences in flower‐visiting and general foraging behaviour, perching birds act as better pollen vectors than hovering birds. The inflorescence of Norantea brasiliensis seems well fitted for pollination by passerine birds, and the hexose‐dominated nectar supports this idea. Pollination syndrome trends within Marcgraviaceae may stem from insect‐pollinated, condensed and spike‐like inflorescences which would give rise to bird‐pollinated, brush‐type inflorescences. From the same basic condensed inflorescence, bat‐pollinated umbelliform inflorescence may be derived from bird‐pollinated, pendulous and corymb‐like inflorescences. These postulated inflorescence types are found among the extant species of Marcgraviaceae.
Polyamines and Morphogenesis ‐ Effects of Methylglyoxal‐bis(guanylhydrazone)
Authors: Féray Annie , Hourmant A. , Penot M. , Caroff J. , Cann‐Moisan Christine
Published: February 2014

The effects of methylglyoxal‐bis(guanylhydrazone) (MGBG), an inhibitor of polyamine biosynthesis were studied on tuberization and cellular polyamine content using in vitro Solanum tuberosum (cv Binjte) plants.

When MGBG was added to the culture medium, it produced a partial inhibition of the growth of stems and leaves; it totally blocked rhizogenesis and strongly stimulated tuber formation. Morphogenetic effects of MGBG were correlated to a 40 % decrease in free putrescine, spermidine, spermine content of the leaves and to a 28 % decrease in spermidine titer of the stems. In the tubers, this inhibitor did not change the free polyamine titer but increased by up to 85 % the titer of conjugated putrescine, spermidine, spermine. When the plants were grown in the dark, MGBG produced, like benzyladenine, a stimulation of the rate of tuberization and enhanced the content of conjugated polyamines in the tuber.

These results support the hypothesis that polyamines play an important role in the morphogenesis of potato plants. The role of polyamine conjugation in tuber development is discussed.
Diurnal Pattern of Transpiration, Water Uptake and Water Budget of Succulents with Different CO2 Fixation Pathways
Authors: Flach Barbara M.‐T. , Eller B. M.
Published: February 2014

The water fluxes and the CO2 exchange of three leaf succulents, Othonna opima, Cotyledon orbiculata and Senecio medley‐woodii, with different leaf anatomy, growth form and CO2 fixation pathways (C3, CAM) were monitored with a gas exchange cuvette which was combined with a potometric system to quantify water uptake. Measurements, which are primarily valid for plants with a sufficient water supply, were made during 6 to 10 consecutive days under constant experimental conditions. Water uptake for 24 h exceeded water loss by transpiration only for a S, medley‐woodii plant with 10 expanding but only 7 mature leaves. In this case the gained water evidently is put into leaf expansion. All other plants showed balanced transpiration and water uptake rates. O. opima and C. orbiculata have a similar life form, similar water storage volumes and the same natural habitat but their diurnal water uptake patterns differ significantly. In the C3 plant O. opima water uptake increased when the transpiration increased or transpiration rates were higher than uptake rates and vice versa. On the contrary the CAM plant C. orbiculata transpired during the dark period at constant or decreasing rates but showed steadily increasing uptake rates. Senecio medley‐woodii‐ and C. orbiculata are CAM plants with similar diurnal water uptake patterns with its maximum in uptake during or towards the end of the CO2 dark fixation period. Water uptake of C. orbiculata was at its minimum at the end of the light period despite transpiration being maximal. The results were discussed considering the different CO2 fixation pathways. In the investigated CAM succulents, C. orbiculata and S. medley‐woodii, the CAM influenced water uptake throughout the whole day and not only during the CO2 dark fixation period.
Seasonal Changes in the Cambium of Trees. I. Sucrose Content in Thuja occidentalis
Authors: Krabel Doris , Bodson Monique , Eschrich W.
Published: February 2014

Cambium samples of Thuja occidentalis L. were collected at five different times, covering spring reactivation and early and late resting period, and used for sucrose determinations. Fragments of the different cell types ‐ xylem ray, cambial initials, sieve‐elements including phloem parenchyma cells, phloem ray ‐ were dissected from freeze‐dried radial sections and analyzed individually. Results show large differences in sucrose concentrations in the different cell types of the cambial layer. In addition, each cell type also shows seasonal fluctuations in sucrose content, whose amplitudes and patterns of variation appear specific for the particular cell type.
Organ‐ and Tissue‐specific Biosynthesis of Flavonoids in Seedlings of Oenothera odorata (Onagraceae)
Authors: Neumann G. , Schwemmle B.
Published: February 2014

In developing Oenothera odorata seedlings, phytochrome‐mediated accumulation of various flavonoids (mainly glycosides of cyanidin and quercetin) is detectable, subsequent to a transient induction of the key enzymes of the general phenylpropanoid metabolism, L‐phenylalanine ammonia lyase (PAL) and of flavonoid biosynthesis, chalcone synthase (CHS). Organ‐ and tissue‐specific distribution of these enzymes and of the flavonoid end products was investigated in seedlings, irradiated with continuous far‐red light.

Anthocyanins and quercetin glycosides are mainly localized in both the upper and lower epidermis of the cotyledons and to a lesser extent also in the epidermal cell layer of the hypocotyl. An obvious organ‐specific distribution was observed for the anthocyanins: cyanidin‐3,5‐O‐diglucoside accumulates in the epidermal cells of the cotyledons, whereas cyanidin‐3‐O‐glucoside is restricted to the epidermis of the hypocotyl. By contrast the pattern of quercetin glycosides is the same in the cotyledons and in the hypocotyl. The methylated flavonol aglycone 3‐0‐methylquercetin was found to be localized in the seed coat. According to this organ‐ and tissue‐specific pattern of flavonoids, immunochemical and immunohistochemical detection of PAL and CHS revealed a predominant localization of theenzymes in the epidermal layers of the cotyledons and the hypocotyl but also in the cells surrounding the vascular bundles. The role of compartmentation in regulation of flavonoid biosynthesis and putative functions of flavonoid compounds are discussed.
A Note on the Evolution of the Stamens in the Laurales, with Emphasis on the Lauraceae
Authors: Rohwer J. G.
Published: February 2014

The number of pollen sacs per anther and their position have traditionally been among the most important systematic characters in the Lauraceae. Opinions differ, however, about the evolutionary direction in these characters. This paper is intended to draw attention to little known morphological features of the stamens, in particular to transitions between disporangiate and tetrasporangiate anthers. In addition, the phylogenetic derivation of the stamen appendages is discussed. It is hypothesized that branched androecial structures may be primitive within the Laurales, if not in the angiosperms as a whole.
Nuclear and Organelle DNA Replication during Spore Germination in Bryophytes and Equisetum
Authors: Thoni Carola , Schnepf E.
Published: February 2014

In contrast to ferns, the spore nuclei of the moss, Funaria hygrometrica, are in the G2 phase. They do not incorporate the thymidine analogue BUdr before the first mitosis. When spores germinate in the presence of aphidicolin, an inhibitor of the (nuclear) DNA polymerase alpha, they give rise to two‐celled, negatively phototropic protonemata, consisting of relatively long and thin cells. Determinations of nuclear DNA content further confirm the presence of G2‐nuclei in Funaria spores. Spores of Pogonatum urnigerum and of Equisetum hyemale likewise contain G2‐nuclei, as shown by BUdr incorporation or experiments with aphidicolin, respectively. In germinating Funaria spores, the organelle DNA is synthesized very early and independent of nuclear DNA. A gradient in replication of organelle DNA is found only in the long tip cells which are formed in the presence of aphidicolin.
Regulation of NADP‐Dependent Glyceraldehyde 3‐Phosphate Dehydrogenase Activity in Spinach Chloroplasts*
Authors: Baalmann Elisabeth , Backhausen J. E. , Kitzmann C. , Scheibe Renate
Published: February 2014

Activation of NAD(P)‐glyceraldehyde 3‐phosphate dehydrogenase (NADP‐GAPDH, EC 1.2.1.13) can be achieved in isolated chloroplasts in the light, or in the dark upon addition of dithiothreitol (DTT) and/or 3‐phosphoglycerate plus ATP. Activation in darkened chloroplasts is only partial with DTT or 3‐phosphoglycerate plus ATP alone, but complete when both effectors are added. In the light, full activation is only achieved upon addition of ATP. The time‐course of activation appears to depend upon the actual concentration of 1,3‐bisphosphoglycerate (1,3bisPGA) inside the chloroplasts. The Ka values for 1,3bisPGA are in the same range as has been determined for the purified enzyme, namely around 20 μM for the dark form (in the absence of DTT) and around 1 μM for the light form or in the presence of DTT. In contrast, the Ka value for ATP is 1 to 2 mM for both the oxidized and the reduced enzyme forms. The observed activation of NADP‐GAPDH is strongly paralleled by an increase of 3PGA, and consequently of 1,3bisPGA in the illuminated chloroplast, while the ATP level remains constant or declines. Activation by 1,3bisPGA is accompanied by dissociation of the 600 kDa form to the 150 kDa form, while reduction alone does not induce a shift in molecular mass as documented by fast gel filtration on Superdex 200. Thus partial activation by DTT in the dark is due to an increased activity of the 600 kDa form, while the activation state in the light is the result of a partial conversion of the 600 kDa form into the more active 150 kDa form. The principle of this activation is a fast reduction of the enzyme by the ferredoxin/thioredoxin system, resulting in a lowered Kavalue for 1,3bisPGA, and thus adjusting the properties of the enzyme to the stromal 1,3bisPGA level. The occurrence of a 300 kDa oligomer mainly during inactivation has also been observed. From these results a model is constructed that describes the reversible interconversion of various activation and aggregation states of NADP‐GAPDH as observed upon light/dark transitions in isolated spinach chloroplasts.
Molecules and Morphology, Phylogenetics and Genetics
Authors: Kadereit J. W.
Published: February 2014

Various explanations can be offered for the incongruence between phylogenetic hypotheses resulting from morphological and molecular data sets. Of these, the possibility that incongruence may result from the mutation of major morphogenetic genes leading to dramatic morphological divergence unaccompanied by equivalent change of the phylogenetic marker molecule(s) used is discussed in detail. As evidence for this hypothesis, several examples for such incongruence are surveyed. It seems possible that in many cases the genetic basis of the morphological characters responsible for the incongruence found may be simple, and that the genes involved may be homologous to genes known from mutant systems.

It is suggested that: 1. the systematic documentation of incongruence between molecular and morphological phylogenies may help to assess the frequency of evolutionary change through the mutation of major morphogenetic genes, and that 2. the identification of major morphological characters distinguishing closely related taxa with mutant phenotypes known from mutant systems eventually may allow an experimental approach to the problem of evolutionary change resulting from major genes. Natural taxa suspected to be the result of such processes could be changed morphologically through transformation with the relevant genes.
A Phagomyxa‐like Endoparasite of the Centric Marine Diatom Bellerochea malleus: A Phagotrophic Plasmodiophoromycete1
Authors: Schnepf E.
Published: February 2014

In September 1993 the marine centric diatom, Bellerochea malleus (Brightwell) Heurck, collected in the Wadden Sea near List/Sylt, was parasitized by a Phagomyxa algarum‐like organism. Karling (1944) reported Phagomyxa algarum Karling in North Carolina as a parasite of the filamentous brown algae Ectocarpus and Pylaiella. The Bellerochea parasite develops an endocytoplasmic Plasmodium and incorporates host cytoplasm into a large, central digestion vacuole, by a form of phagocytosis. Later on, the Plasmodium cleaves to form a zoosporangiosorus. Each zoosporangium is surrounded by a thin wall. It releases zoospores (2.5 × 4 μm) with two unequal flagella, an anterior (4 μm long) and a posterior (8 μm long). Cystosori and cysts could not be detected. The ultrastructure of the zoosporangia and zoospores was investigated, with particular attention to the flagellar apparatus and its rearrangement during zoospore release. This process is very similar to that recorded for zoospores of the plasmodiophoromycete Polymyxa graminis Ledigham (Barr and Allan, 1982). The Bellerochea parasite is closely related to or identical with Phagomyxa algarum. The taxonomic position of Phagomyxa is discussed. In spite of its phagotrophic nutrition and the possible lack of cystosori and cysts, Phagomyxa should be regarded as a member of the Plasmodiophoromycota (or Plasmodiophorida) but not included in a separate order Phagomyxida as proposed by Cavalier‐Smith (1993a).
Chronology of Phytoparasitic Fungi Introduced to Germany and Adjacent Countries
Authors: Kreisel H. , Scholler M.
Published: February 2014

A chronologically arranged list of 59 taxa of phytoparasitic micromycetes, introduced to Germany after 1750, is presented. Another list enumerates 15 fungal taxa which have been introduced to other parts of Europe but may be expected in Germany, too. Most of the enumerated newcomers are members of the orders Pucciniales and Erysiphales. The new terms archaeomycete, neomycete, and ephemeromycete are proposed.
Chemistry, Anatomy and Morphology of Foliicolous Species ofFellhaneraandBadimia(Lichenized Ascomycotina: Lecanorales)
Authors: Lücking R. , Lumbsch H. T. , Elix J. A.
Published: February 2014

A comparison of secondary chemistry and a variety of anatomical and morphological characters ofFellhaneraandBadimia(Pilocarpaceae) has been conducted in an effort to clarify the systematic position of both genera. Based on our results we conclude thatFellhaneraandBadimiaare closely related and separated mainly by the slightly different paraphyses, amyloid reactions of their asci, apothecial size, and the presence or absence of campylidia.Fellhanera badimioidessp.n. is described, and the following systematic changes are proposed:Badimia cateilea(Vain.) comb.n.B. lecanorina(Zahlbr.) comb.n.,B. tuckermanii(R.Sant.) comb.n. andFellhanera stanhopeae(Müll. Arg.) comb.n.
Expression of Polarity during early Development of Microspore‐derived and Zygotic Embryos of Brassica napus L. cv. Topas
Authors: Hause B. , van Veenendaal W. L. H. , Hause G. , van Lammeren A. A. M.
Published: February 2014

Microspore derived (MS‐)embryogenesis and zygotic embryogenesis of Brassica napus L. cv. Topas were investigated by light and scanning electron microscopy to reveal the expression of polarity during the transition phase from globular to heart and torpedo shape.

During the first 5 days of MS‐embryo formation, the cell wall of the former microspores remained intact and a globular mass of cells developed within. Pollen walls ruptured after 5 days of culture; embryos proceeded through heart‐shape and torpedo‐shape stages within 15 days in a way comparable to, but faster than observed during zygotic embryogenesis.

Expression of polarity in globular and elongating MS‐embryos was analyzed by detection of the distribution of activated calmodulin as well as of free cytosolic calcium by using confocal scanning laser microscopy, and by the detection of starch. Calmodulin was evenly distributed in globular embryos and only exhibited clear polar distribution in elongated embryos. Free cytosolic Ca2+ accumulated in the protoderm of globular embryos and in the central cylinder of torpedo shaped embryos, but never showed polar distribution. Accumulation of starch granules at the root poles of both sexual as well as MS‐embryos, however, indicated polar distribution before the transition from globular to heart shape stage. Since the local rupture of the pollen wall of 6‐day‐old MS‐embryos was never preceded by the decrease of starch at that site, it is likely that the rupture of the pollen wall plays an important role in the local activation of cell metabolism and thus in the determination of the polarity axis in MS‐embryos.
Influence of Drought, Rain and Artificial Irrigation on Photosynthesis, Gas Exchange and Water Relations of the Fynbos PlantProtea acaulos(L.) Reich at the End of the Dry Season
Authors: Herppich Margaretha , Herppich W. B. , VON Willert D. J.
Published: February 2014

Protea acaulos, a prostrate fynbos shrub, often experiences very low air humidity at leaf temperatures over 10°C higher than mean air temperature. We determined to what degree this particular microclimate influenced photosynthetic performance, leaf conductance and water relations of non‐irrigated and trickle‐irrigated plants. Measurements were made at the end of the dry summer season in the sand plain lowland fynbos on the west coast of South Africa. Independent of water supply, plants showed a pronounced midday depression of gas exchange. While in non‐irrigated plants leaf water potential dropped to − 2.0 MPa around noon, it never fell below −1.0 MPa in irrigated plants. On the other hand minimum pressure potential was similar in irrigated and non‐irrigated plants. The latter showed higher turgor after rain, due to osmotic acclimation, which resulted from a reduction in maximum water volume. The main osmoticum was 1,5‐anhydro‐D‐glucitol. Leaf temperature, directly or via the vapour pressure deficit between leaf and air (Δw), rather than plant water status, was the determinant of the midday depression of gas exchange. High Δw caused stomatal closure during times of saturating light, thus limiting photosynthetic CO2uptake and availability and enhancing the susceptibility for photoinhibition. This, as well as high leaf temperature per se, decreased the efficiency of photochemistry of photosystem II. Initial fluorescence remained constant until temperatures exceeded 35 °C, above which changes in fluorescence indicated both photoinhibition and heat stress. Unlike other fynbos plants,Protea acauloscould not use the improved soil water supply to increase carbon gain under hot summer condition.
Effect of Extracellular Ca2+ and Ca2+‐Antagonists on the Movement and Chemoorientation of Male Gametes of Ectocarpus siliculosus (Phaeophyceae)
Authors: Maier I. , Calenberg M.
Published: February 2014

Chemoorientation in male gametes of Ectocarpus siliculosus in response to sexual pheromones is effected by two distinct mechanisms, chemokinesis and chemoklinotaxis. These are characterized by a strongly asymmetric bending pattern of the anteriorly‐directed flagellum and transient unilateral bending of the hind flagellum, respectively. Removal of extracellular Ca2+ showed that normal flagellar movement and chemokinesis require millimolar concentrations of Ca2+ in the medium. The response to pheromones is strongly inhibited by La3+, whereas the Ca2+‐channel drugs, verapamil and nifedipine, have only little effect. Nifedipine nethertheless effectively inhibited accumulation at pheromone sources. These results are interpreted as an indication for the involvement of two pharmacologically distinct Ca2+‐channels in chemokinesis and chemoklinotaxis. The calmodulin‐antagonist, trifluoperazine, induces, at low concentrations, the same flagellar response in chemokinesis as the pheromone, the mechanism of action remaining unknown.
Subcellular Volumes and Metabolite Concentrations in Potato (Solanum tuberosum cv. Désirée) Leaves1
Authors: Leidreiter Kirsten , Kruse Anne , Heineke D. , Robinson D. G. , Heldt H.‐W.
Published: February 2014

Cellular and subcellular volumes in mature leaves of potato (Solanum tuberosum cv. Désirée) were determined stereologically from light and electron micrographs. Leaves of ten‐week‐old plants with a total leaf volume of 623 μL per mg chlorophyll (Chl) were found to be composed of 12 % epidermis, 68 % mesophyll, 5 % vascular tissue, 3 % apoplast and 16 % gas space. In the epidermal cells 97 % of the volume was occupied by the vacuole. The mesophyll cells consisted (as expressed per mg Chl) of 323 μL (76 %) vacuole, 35 μL (8 %) chloroplast stroma, 22 μL (5 %) cytosol plus nucleus and peroxisomes, and 4μL, (1 %) mitochondria. A comparison of these values with subcellular volumes previously determined for spinach and barley leaves, shows that the relative sizes of the subcellular volumes are strikingly similar. Subcellular concentrations of carbohydrates, of the phosphorylated intermediates of carbohydrate metabolism, of malate, and of amino acids have been evaluated from measurements of the corresponding subcellular metabolite contents determined using the non‐aqueous fractionation technique. Malate, glucose and fructose were found to accumulate in the vacuole, whereas the concentration of sucrose and amino acids in the cytosol were much higher than in the vacuole. The amino acid concentration in the chloroplast stroma is similar to that in the cytosol. Phosphorylated intermediates of carbohydrate metabolism are confined to the chloroplast stroma and the cytosol, confirming the validity of the fractionation method. Whereas triose phosphates and fructose‐l,6‐bisphosphate are concentrated in the stroma, the concentrations of hexose monophosphates were highest in the cytosol. Since the subcellular metabolite distribution in potato leaves reported here is very similar to that previously described for spinach and barley leaves, we conclude that it may be characteristic for mesophyll cells in general.
Quantitative Stress Responses of the V0V1‐ATPase of Higher Plants Detected by Immuno‐electron Microscopy
Authors: Ratajczak R. , Hille Angela , Mariaux J.‐B. , Lüttge U.
Published: February 2014

Immuno‐electron microscopy of negatively stained isolated tonoplast vesicles was used to quantify stress responses of the H+‐transporting tonoplast ATPase (V0V1‐ATPase; EC 3.6.1.1) of the C3/CAM intermediate Mesembryanthemum crystallinum L. and the C3 plant Hordeum vulgare L. This approach has the advantage that it relates quantitative adaptations at the level of membrane enzymes directly to membrane area and thus is independent of concomitant changes of relative amounts of other membrane proteins which may perturb conclusions when data are expressed on a tonoplast protein basis.

It was shown that in M. crystallinum the amount of V0V1‐ATPase per unit membrane area increased slightly with ageing and pronouncedly with salinity stress. In H. vulgare under salt stress there was an increase in V0V1‐ATPase amount only in the highly salt tolerant cv. California Mariout and not in the moderately tolerant cv. Carina. This corroborates conclusions from earlier work, where results were expressed on a protein basis, although this was not to be expected a priori. In all comparative ecophysiological studies using tonoplast vesicles at least some key‐point tests with the immunonegative staining technique should be included for the sake of prudence. The data obtained here via immunonegative staining of isolated tonoplast vesicles are in very close agreement with much earlier assessments of area and whole cell‐related activities given by measurements of entire isolated vacuoles and morphometric analysis, which further corroborates the suitability of the approaches.

The data presented here for the first time allow calculations of the coverage of the tonoplast surface of M. crystallinum with V0V1‐ATPase holoenzyme protein and with total tonoplast protein, i.e. 1.5 to 2.3 . 10−15 g V0V1‐ATPase per μm2 and 7.4 to 8.8 . 10−15 g protein per μm2, respectively.
Anatomical Structures of the VA Mycorrhiza in the Apocynaceae (Gentianales)
Authors: Weber H. Chr , Klahr A. , Marron‐Heimbuch M.
Published: February 2014

Roots of 19 Apocynaceae species were studied anatomically with respect to their symbiosis with VAM‐fungi. In plants collected from the field, VAM‐fungi were established in the root cortex. Also, inoculations with different Glomus species on the cultured plants are very successful in the infection and colonization of the root cortex.

After penetration of the rhizodermis, the special exodermal short cells become colonized by winding hyphae. Then, in the root cortex of many Apocynaceae species, the VAM‐fungi produce intercellular running hyphae which leads to extensive colonization of the root. Arbuscules develop on intracellular running hyphae, whereas vesicles develop mainly on intercellular hyphae. Except for some special details, this is the most common type of colonization of VAM fungi in flowering plants.

But in Amsonia tabernaemontana, Nerium oleander, and Thevetia peruviana, another type of colonization could be observed. In these species, the colonization of the hyphae within the root cortex is only possible by intracellular growth. Intercellular running hyphae in the root are lacking. Therefore, after penetration the colonization in the cortex is cluster‐like and strictly limited. Only by additional penetrations from hyphae in the soil, will roots show heavy infestations. This type of growth of the VAM fungi in the root is well known from the Gentianaceae and was explained as a structural incompatibility.

In Catharanthus roseus, Pachypodium lamerei, and Trachelospermum jasminoides, intermediate stages of both types of colonization could be described. The results are discussed in the search for possible stimulants for structural incompatibility.
The Effect of Photoinhibition on Photosynthetic Oxygen Production in the Brown Alga Dictyota dichotoma
Authors: Hanelt D. , Uhrmacher S. , Nultsch W.
Published: February 2014

Photoinhibition of photosynthesis in the brown alga, Dictyota dichotoma, was studied with a PAM fluorometer (Walz, Effeltrich, Germany) and a homemade oxygen measuring device. As a measure of fluorescence, Fv/Fm, and for the photosynthetic yield, ΔF/Fm', were used. Oxygen measurements show clearly that the observed degree, as well as the time course, of photoinhibition depends on the fluence rate of the light used to measure changes of the production rate. After photoinhibition of photosynthesis the depression of oxygen production caused by non‐saturating fluence rates was generally much more pronounced than that caused by saturating or nearly saturating fluence rates. At minimal photoinhibition the initial slope and the convexity of the fluence rate‐response curve of oxygen evolution decrease, whereas the level of light saturation decreases only after strong photoinhibition. Nevertheless, at different degrees of photoinhibition, changes in the degree of the upper bending of the fluence rate‐response curve of oxygen production are also linearly correlated to changes in the fluorescence ratios (Fv/Fm and ΔF/Fm'). The action spectrum of photoinhibition, calculated on the basis of changes of Fv/Fm, indicates that the reaction center of PS I is not involved in photoinhibition. The lower effectiveness of blue light in comparison to effects of green and red light may be due to chloroplast displacement, as in the so‐called strong light position, the light absorbed by the thalli in vivo is decreased.
How Indicative are Changes in Major Metabolites for Freezing Tolerance of Wheat?
Authors: Stuiver C. E. E. , De Kok L. J. , Clement J. M. A. M. , Kuiper P. J. C.
Published: February 2014

Relative growth rate of winter wheat at low temperature (day/night, 4/2 °C) was about 0.02 g g−1 fresh weight day−1. There was a substantial increase in dry matter content of shoots and roots, especially during the first week of low temperature exposure, which for the greater part could be attributed to an accumulation of soluble sugars and starch. The freezing tolerance (LT50) of the leaf tissue gradually increased with 6 °C during the 6 weeks exposure, whereas freezing tolerance of roots was hardly affected. Upon low temperature exposure there was an increase in the content of water‐soluble non‐protein thiols (mainly glutathione), soluble sugars, starch, amino acids and total nitrogen in both shoots and roots. The most substantial increases in the content of thiols, sugars and amino acids already occurred within hours or a few days after the onset of the exposure. The nitrate content in shoots showed a rapid and strong decrease during low temperature exposure, however, in roots its content remained unaffected. It is proposed that the observed rapid increases in the content of various metabolites at low temperature are primarily due to an altered balance in their synthesis and their consumption in growth. There was no direct relation between increases in the content of the various metabolites and the degree of freezing tolerance of the tissue.
In vitro Reconstitution of Epicuticular Wax Crystals: Formation of Tubular Aggregates by Long‐Chain Secondary Alkanediols
Authors: Jetter R. , Riederer M.
Published: February 2014

Cuticles of several plant species are covered by tubular wax aggregates that are known to consist mainly of (S)‐nonacosan‐10‐ol. The present work addresses the question whether minor wax components may additionally contribute to these tubules. Thin layer chromatography was used to prepare secondary alkanediol fractions from leaf cuticular waxes of Nelumbo nucifera and Thalictrum flavum, containing nonacosane‐3,10‐diol, nonacosane‐4,10‐diol, nonacosane‐5,10‐diol, nonacosane‐7,10‐diol, nonacosane‐9,10‐diol and nonacosane‐10,13‐diol. From organic solutions all these compounds crystallized in tubular shapes. Possible crystal structures of relevant alkanediol isomers are proposed, in analogy to the lattice geometries of comparable aliphatic compounds. The resulting structural model shows that nonacosan‐10‐ol and various secondary alkanediols may join in metastable mixed crystals. According to the structural model proposed the admixture of alkanediols to nonacosan‐10‐ol aggregates should enhance the stability of their tubular habit.
Branch Roots of Zea. V. Structural Features that may Influence Water and Nutrient Transport
Authors: Wang X. L. , McCully M. E. , Canny M. J.
Published: February 2014

First‐order branch roots of field‐grown Zea mays L. were examined by optical and electron microscopy. They were small‐scale versions of nodal roots except for the usual retention of a live epidermis throughout their length. The Casparian strips and suberized lamellae of hypodermis and endodermis developed closer to the root tip than reported for main roots (in the zone 0.5 to 5.5 cm from the tip for the hypodermis, and 0.5 to 4 cm for the endodermis), in branches retaining an apical meristem. The hydrophobic deposits were in place to the distal ends of determinate branches. All hydrophobic deposits were fully formed before the late metaxylem elements were mature. Gaps in the suberized lamellae of both hypodermis and endodermis may permit apoplastic diffusion of solutes through these layers. Pit frequency in the outer tangential walls of the hypodermis and endodermis was 0.3 per 100 μm2, and 0.6 to 0.7 per 100 μm2, respectively, in both branch and main roots. Numbers of plasmodesmata per pit in the branches were 60 and 30 in the hypodermis and endodermis, respectively. Water fluxes from published data were used to calculated the possible flux through plasmodesmata on a symplastic path. Values up to 0.2 pl h−1 for the hypodermis and twice this for the endodermis were obtained.
An Assemblage of Hummingbird‐pollinated Flowers in a Montane Forest in Southeastern Brazil
Authors: Sazima I. , Buzato Silvana , Sazima Marlies
Published: February 2014

Relationships between ornithophilous flowers and hummingbirds have been little studied in southern South America, where hummingbird species richness is low. We studied an ornithophilous flower assemblage and the hummingbird pollinators in a montane forest in southeastern Brazil. Twenty‐three native hummingbird‐pollinated plant species in 21 genera and 14 families were observed. Bromeliaceae, Fabaceae, Gesneriaceae, and Lobeliaceae are represented by more than one species within the assemblage. Flower shapes vary from narrow tube to bowl‐shape, but tubular flowers prevail. The variety of flower shapes and sizes results in diverse pollen placement on the body parts of hummingbird visitors, although pollen is deposited mostly on the bill. Sugar concentration in nectar averages 22.1%, and nectar volume per flower averages 16.9 μl. The plant populations bloom for one month to year‐round, and their flowering approaches the steady‐state pattern. Four flower subsets may be defined within the assemblage, each subset related to the bill size and foraging habits of the most frequent bird visitor. Of the six species of hummingbirds recorded at the study site, four are common and largely resident. The four hummingbirds differ in bill size, body mass, and favoured foraging sites, attributes which reflect their favoured flower subsets. One hermit and one trochiline hummingbird share most of the flower species they use, these two birds being the major pollinators within the flower assemblage. This montane forest community may be viewed as medium‐rich in ornithophilous flower species and poor in hummingbird species.
Expression of Chalcone Synthase Genes in Coleoptiles and Primary Leaves of Secale cereale L. after Induction by UV Radiation: Evidence for a UV‐Protective Role of the Coleoptile*
Authors: Haussühl Kirsten , Rohde W. , Weissenböck G.
Published: February 2014

Four chalcone synthase (CHS; EC 2.3.1.74) clones from rye were isolated and characterized. Two of these clones were used for analysis of CHS gene activities in response to ultraviolet and visible radiation in the coleoptile and the primary leaf of the rye seedling. The time‐dependence of CHS gene activation and the spatial distribution of CHS were studied by investigation of enzyme activities and CHS mRNA levels, including in situ RNA hybridization. In the primary leaf strong induction of CHS gene activity was localized in the epidermal layers and only marginally found in the mesophyll. The coleoptile showed an even higher response to UV irradiation, but CHS gene activity was evenly distributed throughout the tissues. It is suggested that, in addition to its function as a mechanical protection for the primary leaf during seed germination and seedling emergence through the soil, the coleoptile may also protect the emerging seedling from harmful radiation.
Photosynthetic Fluorescence Induction and Oxygen Production in Corallinacean Algae Measured on Site
Authors: Häder D.‐P. , Herrmann Heike , Schäfer J. , Santas R.
Published: February 2014

Photoinhibition of photosynthesis was measured in two Mediterranean Corallinaceae, Jania rubens and Corallina mediterranea, using pulse‐amplitude modulation (PAM) fluorescence and oxygen production on site. Both algae were found to be adapted to low irradiances of solar radiation and easily inhibited by exposure to excessive radiation. Both algae were impaired even in their natural habitat under overhanging rocks which protected them from direct solar radiation, except for a few hours in the early morning. Recovery from photoinhibition of both the photosynthetic quantum yield, defined as Fv′/Fm′, and oxygen production took several hours and was not complete. Judging from both parameters indicated above, Jania seems to be even more sensitive than Corallina, even though the former alga was found in more exposed habitats.
Characteristics of Hg‐ and Zn‐sensitive Water Channels in the Plasma Membrane of Chara Cells*
Authors: Tazawa M. , Asai K. , Iwasaki N.
Published: February 2014

Hydraulic conductivity (Lp) of the plasma membrane of Chara corallina was inhibited by HgCl2 maximally 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 through Chara cells occurs mostly via mercury‐sensitive water channels containing thiol groups. ZnCl2 dissolved in APW (pH 5.6) also inhibited Lp by about 80% within 1–2 h, while ZnCl2 dissolved in Hepes‐Tris buffer (pH 7.4) inhibited it by about 90% within several minutes. Inhibition of Lp by ZnCl2 was 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 HgCl2 and 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 Lp of 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 ZnCl2 in acidic medium may exist in ionized species which can be chelated by EGTA after permeation. The polar water permeability, or the endoosmotic Lp being 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 plasma membrane.
Wounding‐ and Elicitor‐induced Formation of Coloured Chalcones and Flavans (as Phytoalexins) in Hippeastrum x hortorum*
Authors: Wink M. , Lehmann P.
Published: February 2014

Hippeastrum x hortorum bulbs 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, a de novo synthesis of the corresponding enzymes is likely. Total phytoalexin extracts showed an inhibition of bacterial growth (e.g. of Bacillus subtilis, B. megaterium) and of feeding by polyphagous larvae of the moth Syntomis mogadorensis. These data imply that the wounding‐ and elicitor‐induced phytoalexins appear to function as defence compounds against microorganisms and herbivores.
Gaertnera and Pagamea: Genera Within the Psychotrieae or Constituting the Tribe Gaertnereae? A Wood Anatomical and Palynological Approach
Authors: Jansen S. , Robbrecht E. , Beeckman H. , Smets E.
Published: February 2014

The possible alliance between Gaertnera and Pagamea (Rubiaceae‐Rubioideae), two genera from the Old and New World, respectively, is investigated on the basis of wood anatomy and pollen morphology. Nowadays, the main point of discussion about the taxonomic position of these genera is whether they belong to the Psychotrieae or constitute a tribe Gaertnereae characterised by their secondarily superior ovary and sheathing stipules. Both the wood and pollen of the genus pair are found to show specific features absent in other genera of the Psychotrieae, e.g. parenchyma bands in the xylem and endexine thickenings on the polar sites of the pollen apertures. Nevertheless Gaertnera and Pagamea share many other characters with the Psychotrieae. Wood and pollen convincingly demonstrate the very close affinity of the two genera. The sister pair differs in so many features from other Psychotrieae, that Gaertnera and Pagamea should constitute at least a subtribe Gaertnerinae, formally recognized here. The general lack of profound studies on the affinities within the very large tribe Psychotrieae makes further comments on the taxonomic relationships of the Gaertnerinae difficult.
Effects of Local Variations in Soil Moisture on Hydrophobic Deposits and Dye Diffusion in Corn Roots
Authors: Watt M. , VAN DER Weele C. M. , McCully M. E. , Canny M. J.
Published: February 2014

The effects of local soil water content (SWC) alone on the development of hydrophobic deposits and on diffusivity of root tissues were studied in primary roots of maize seedlings whose top regions were growing at a constant rate in damp soil. Corn primary roots were grown through 30 cm‐profiles of soil with pre‐set dry (8% SWC), or wet (23% SWC), middle layers, and moist (15% SWC) top and bottom layers. When the root tissues in the soil of variable SWC were maturing (approximately 17% of the total root length), the tips of the roots were in damp soil several centimeters away and growing at the rate characteristic of this environment. Histochemistry and fluorescence microscopy on root sections of similar age showed that in these roots local SWC had no effect on hypodermal and endodermal suberization: both had equally developed Casparian bands and suberized lamellae. However, local SWC did alter the hydrophobic deposits in the walls of the epidermis; they increase in dry soil. To study tissue diffusivity, root portions from dry or wet soil were divided in the transverse direction, and half was dipped in sulphorhodamine G (SRG), sectioned, and observed with fluorescence optics. The other half was studied with a cryo‐scanning electron microscope to observe the contents of the cortical intercellular spaces. The rate of SRG diffusion in a portion of root from dry or wet soil was independent of local SWC but was positively correlated with numbers of fluid‐filled intercellular spaces. The implications of these observations for the movements of ions through the root cortex are discussed.
Morphology, Anatomy and Histochemistry of Fagus grandifolia Ehrh. (North American Beech) Ectomycorrhizas
Authors: Herr D. G. , Peterson R. L.
Published: February 2014

Abstract: Five distinct ectomycorrhizal morphotypes were recognized on root systems of Fagus grandifolia collected in a maple‐beech woodlot. Three morphotypes showed extensive root branching whereas two had limited root branching. One morphotype, a bright orange, smooth type, was studied in detail anatomically. A compact mantle with few emanating extraradical hyphae covered the root apex of each mycorrhizal lateral. A Hartig net extended around epidermal and hypodermal cells. Roots were mostly diarch and a single‐layered endodermis and a biseriate hypodermis with the inner hypodermis having suberized walls were present in all specimens examined. The mantle, and to a lesser extent the Hartig net, stored lipids, polysaccharides and proteins.
Stimulation of Plastidogenesis Induced by 5‐Azacytidine in Euglena gracilis Klebs
Authors: Pancaldi Simonetta , Bonora A. , Gualandri Rita , Muzzoli Mariavittoria , Fasulo Maria Palmira
Published: February 2014

When etiolated Euglena gracilis was treated with 10 mM 5‐azacytidine (5‐azaC), an inhibitor of DNA methylation, stimulation of plastidogenesis in both dark and light conditions was observed. The phenomenon occurred in 10–15% of the cells possibly due to the asynchronicity of the cultures. The main features of this sub‐population, as evaluated by electron and fluorescence microscopy, were the following: 1. the presence in darkness of differentiating proplastids that were red fluorescent under UV, positive to TCNBT cytochemical reaction (specific for PSII) and negative to DAB (specific for PSI); 2. the acceleration of proplastid differentiation during the first 20–30 h of illumination; 3. the occurrence in both culture conditions of concentric lamellar bodies (LBS). These structures were considered to be proplastids blocked in the first step of evolution, since they emitted a red fluorescence, were contained within compartments limited by a triple‐layered envelope, were reactive to TCNBT in darkness and to both TCNBT and DAB in light conditions. Even if the action mechanism of 5‐azaC on plastidogenesis in Euglena remains to be defined, the induced stimulatory effect on plastid differentiation pointed to a relationship between DNA methylation and plastid development. Furthermore, the presence of LBS opens the possibility of studying early aspects of plastid development in Euglena.