Ethylene biosynthesis in Regnellidium diphyllum and Marsilea quadrifolia

The pathway of ethylene biosynthesis was examined in two lower plants, the semi-aquatic ferns Regnellidium diphyllum Lindm. and Marsilea quadrifolia L. As a positive control for the ethylene-biosynthetic pathway of higher plants, leaves of Arabidopsis thaliana (L.) Heynh. were included in each experiment. Ethylene production by Regnellidium and Marsilea was not increased by treatment of leaflets with 1-aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene in higher plants. Similarly, ethylene production was not inhibited by application of aminoethoxyvinylglycine and -aminoisobutyric acid, inhibitors of the ethylene biosynthetic enzymes ACC synthase and ACC oxidase, respectively. However, ACC was present in both ferns, as was ACC synthase. Compared to leaves of Arabidopsis, leaflets of Regnellidium and Marsilea incorporated little [¹⁴C]ACC and [¹⁴C]methionine into [¹⁴C]ethylene. From these data, it appears that the formation of ethylene in both ferns occurs mainly, if not only, via an ACC-independent route, even though the capacity to synthesize ACC is present in these lower plants.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AdoMet S-adenosyl-l-methionine - AIB -aminoisobutyric acid - AVG aminoethoxyvinylglycine This research was supported by the U.S. Department of Energy through grant No. DE-FG02-91ER20021 and, in part, by a fellowship of the National Engineering and Research Council of Canada to Jacqueline Chernys.     

Giant Stomata

The presence of abnormally large stomata on leaves of Mangiferaindica L. and Limoma acidissima L. is reported. Apart from theirsize, these stomata are indistinguishable from normal stomatapresent on these leaves, and it is likely that they functionin a similar way.     

Structure of Vessels and Tracheids of Regnellidium diphyllum Lindman (Marsileaceae)

The occurrence of vessels in the root of Regnellidium diphyllumis reported and tracheids with helical and reticulate thickeningson their walls are described. The vessels in the root are helically-thickenedand they seem to have originated from helically-thickened tracheidslike the vessel members of the primary xylem of angiosperms.In the rhizome and petiole, branched tracheids are of commonoccurrence.     

Zeta potential measurements of cell wall preparations from Regnellidium diphyllum and Nymphoides peltata

Abstract. Cell wall particles were prepared from the semi-aquatic plants Regnellidium diphyllum and Nymphoides peltata with minimum disruption to the integrity of the cell wall. The behaviour of freshly-prepared and frozen-thawed particles in a D.C. electric field was monitored with a microscope attached to video recording apparatus. From the respective particles mobility in a well-defined electric field. it was possible to determine their electrostatic potential and consequently estimate the corresponding surface charge density. Experiments were performed in media of different pH and cation concentration (ie, K⁺ Ca²⁺). A significant electronegative potential was found in cell wall preparations of both plants. Freezing and thawing further reduced the electrostatic potential for both plant species in all the media utilized for electrophoresis. A reduction of pH or an increase of the cation concentration was found to neutralize the electrostatic potential in a sigmoidal fashion. Ca²⁺ was more than 10 times more effective than K⁺ at neutralizing the apparent electrostatic potential of the cell wall preparations. Regnellidium was found to have a lower electrostatic potential than Nymphoides , although both responded in a similar manner to the various treatments. The possible relevance of the cell wall electrostatic potential, pH and [Ca²⁺] and particularly their inter-relationship is discussed for the two species of plants in terms of their differing growth responses to the ionic environment of the plant.     

Cell Expansion and Wall pH in the Fern Regnellidium diphyllum, A Plant Lacking Acidinduced Growth

Petioles of the semi-aquatic fern Regnellidium diphyllum donot show acid growth but low wall pH is a necessary conditionfor maximum rates of IAA-induced cell expansion. Measurementsof wall pH by two indirect methods indicate an unusually lowvalue, in the range pH 4 to 5. This is one to two pH units belowthat estimated for petioles of the semi-aquatic dicotyledonNymphoides peltata, a species in which IAA aand ethylene causegrowth responses very similar to those in Regnellidium but whereacid growth occurs. Having shown previously that fusicoccinenhances proton secretion in both Regnellidium and Nymphoides,we now show that although it causes a reduction in the estimatedapoplast pH to below 4·0 in Regnellidium, cell expansionis not promoted. The FC-induced reduction in pH in Nymphoidesis less and occurs more slowly, but growth is promoted significantly;when IAA and fusicoccin are present together, growth promotionis approximately additive for Nymphoides A model is proposed for Regnellidium in which equilibrium wallpH is maintained at a low value that is optimal for acid growth,the availability of acid-labile sites in the wall being thechief limitation to cell extension. We suggest that this controlmechanism may be widespread for organs without a cuticle, includingroots and the gametophytes of lower plants growing in acidicconditions. Key words: Acid growth, wall pH, fusicoccin, Regnellidium diphyllum, Nymphoides peltata     

Ethylene and auxin-induced cell growth in relation to auxin transport and metabolism and ethylene production in the semi-aquatic plant,Regnellidium diphyllum

Cell elongation in the rachis of the semiaquatic fern Regnellidium diphyllum is induced by the addition of ethylene or indoleacetic acid (IAA). Experiments with whole plants or rachis segments have shown that ethylene-induced growth requires the presence of auxin. Ethylene does not cause a modification in either endogenous auxin levels or in the extent of auxin metabolism but auxin transport is reduced. Rates of ethylene production in Regnellidium are not altered by either mechanical excitation or by the addition of auxin. A two-hormone control of cell expansion is proposed in which an initial, auxin-dependent growth event pre-conditions the cells to a further subsequent (or synchronous) ethylene-dependent growth event.Abbreviation IAA indole-3yl-acetic acid     

Flavonol glycoside production in callus cultures of Epimedium diphyllum.

Callus cultures of Epimedium diphyllum produced a large amount of epimedoside A in addition to a small amount of diphylloside B, ikarisoside C, epimedoside E, diglycosides of des-O-methylanhydroicaritin (8-gamma, gamma-dimethylallylkaempfero). Icariin, epimedins A-C, which are glycosides of anhydroicaritin, were also produced in the callus cultures. Contents of the flavonol glycosides in callus tissue were higher than those of mother plants, but the composition of each flavonol glycoside mixture in the callus cultures was different from that of the original plants. The time-course experiments showed that an inverse relationship existed between cell growth and flavonol glycoside production. Effects of hormonal factors on cell growth and flavonol glycoside production indicated that 2,4-dichlorophenoxyacetic acid was needed for the production of flavonol glycosides.     

Development of Stomata in Lactuca sativa L.

The structure of the epidermis on various parts of the plantof Lactuca sativa Linn. is described. Development of stomatais studied in young leaves and stems. Tognini (1897) has previouslymentioned that the stomata on stems of L. virosa develop froma meristemoid with four cutting faces but the present studypoints out that the meristemoid cuts off only two mesogene neighbouringcells and the two others are perigene.     

Development of Stomata in Equisetum

Hitherto published accounts of the development of stomata inEquisetum are conflicting about the sequence of divisions andabout the formation of a sub-stomatal cell from a meristemoid.The present study of the development of stomata in a speciesidentified as E. ramosissimum subspecies ramosissimum supportsthe observations of Strasburger (1867) and Pant and Mehra (1964)on the basis of sections cut in various planes through internodesof the plant.     

气孔运动中的活性氧信号

大量研究证明活性氧(ROS)在气孔运动中起信号分子的作用。保卫细胞中ROS的产生依赖于特定的酶,其中NADPH氧化酶组分RBOH已得到深入研究,并已证实其参与生物与非生物胁迫反应。植物激素包括脱落酸(ABA)、水杨酸(SA)、乙烯、生长素及细胞分裂素等,它们均通过ROS的介导来调控气孔运动。生物胁迫(如毒性细菌和真菌)也会调控气孔运动。ROS参与这些调控过程。保卫细胞中存在多层次对ROS产生及其作用的调节,抗氧化活性物质和ROS敏感蛋白(如蛋白激酶和磷酸酶)均可传递ROS信号并调节气孔运动。ROS对离子通道调节的证据也越来越多。保卫细胞由于可通过ROS整合复杂的信号途径,已成为研究植物ROS信号转导过程的良好模式系统。     

Radialstrukturen in den Stomata vonOuratea spectabilis (Mart.) Engl.

Zusammenfassung An den lebenden unbehandelten Spaltöffnungen vonOuratea spectabilis wurde eine vom Spalt ausgehende Radialstruktur beobachtet.Dieselbe läßt sich mit verschiedenen Farbstoffen darstellen und ist nicht mit einer Cuticularstreifung identisch.Es handelt sich um Ektodesmen, die infolge ihrer besonderen Eigenschaften (Größe usw.) ohne Anwendung spezieller Methoden sichtbar sind.Mit der Methode vonBancher, Hölzl undKlima läßt sich zeigen, daß aus ihnen Flüssigkeitströpfchen abgeschieden werden können.Mit dem Transpirationswasser aufgenommene Salze (Thallium und Mangan) reichern sich im Zellumen und in diesen Ektodesmen an.Sie sind offenbar die Bahnen der peristomatären Transpiration.

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Radial structures in the stomata ofOuratea Spectabilis (Mart.) Engl.

Summary In living, untreated Stomata ofOuratea spectabilis a radial structure originating in the stomatal opening was observed, which may be demonstrated by means of various stains.It is not identical with a cuticular striation.These structures are shown to be ectodesms visible without use of special methods because of their peculiar properties (size etc.).The method ofBancher, Hölzl andKlima allows to demonstrate that these ectodesms may secret fluid droplets. Salts (thallium and manganese) taken up with the transpiration stream are concentrated in the cell lumen and in the ectodesms. Obviously, the ectodesms are the pathways of peristomatal transpiration.

     

Development of Stomata in Some Cruciferae

Epidermal structure and ontogeny of stomata are described forten species or varieties of Cruciferae. The mature stomata aretypically anisocytic. Their development is of the mesogenoustrilabrate type. The spiral sequence of divisions in the meristemoidmay be clockwise or anticlockwise. Very often the neighbouringcells divide and form successive generations of stomata whichbecome arranged in groups. Some theoretical implications ofthe study are also discussed.     

Sulla cariologia di Gennaria diphylla (Link) Parl. (Coeloglossum diphyllum Fiori)

Abstract

OBSERVATIONS ON THE CARYOLOGY OF GENNARIA DIPHYLLA (LINK) PARL. (COELOGLOSSUM DIPHYLLUM FIORI) — Some caryological characters of Gennaria diphylla (Link) Parl, have been here investigated. Chromosome counts from somatic metaphases show a 34 chromosomes diploid set; the resting nuclei have been classified as half-reticulated with chromocenters (« noyaux semi-reticulé à chromocentres » according to Delay's classification); in prophases we have noticed that chromocenters often appear like prochromosomes. The chromosome number 17 (2n = 34) is new for the Ophrydinae.

The interest of this research lies in the fact that the species here dealt with has been differently classified by various Authors.     

Stomata of apple leaves cultured in vitro

Examination by scanning electron microscopy showed abaxial stomata on in vitro cultured apple (Malus pumila Mill.) leaves. With leaf ontogeny, most of these stomata appeared to lose their regulatory ability while developing wide vestibules of up to 20 m in diameter. It is proposed that these deformed stomata may be a possible cause for the excessive transpirational water loss and consequent dehydration associated with transferring plants regenerated in vitro from culture.     

Development of Stomata in some Ophioglossum Species

This paper deals with the development of stomata in vegetativeand reproductive organs of five species of Ophioglossum. Thestomata are typically hap-locheilic or perigenous from organto organ. Superimposed twin stomata, stoma with aborted guardcells and persistent stomatal initial are seen. The presentstudies support the view of foliar nature of the spike of Ophioglossum.     

Studies in Stomata of Chilli and Brinjal

Ontogeny and development of stomata in chilli (Capsicum annuumL.) and brinjal (Solanum melongena L ) are described Paracytic,anomocytic, and anisocyuc stomata are present Abnormalitiessuch as stoma with a single guard cell and degenerated stomatalcells are common. Degeneration of guard cell is traced in chilliJuxtaposed, superposed, and obliquely placed contiguous stomataare described. An incompletely differentiated menstemoid wasfound contiguous with a normal stoma Rarely a guard cell dividesto form a menstemoid. Cytoplasmic connections between the guardcells of adjacent or juxtaposed contiguous stomata are observedin chilli Extruded nucleoh in the guard cells of chilli arecommon Extruded nucleoh may enlarge The wounded epidermis ofchilli lose sinuosity of their walls and the degeneration ofguard cells is common.