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Using isolated Pelargonium leaves parasitised by Cuscuta, we have established by means of autoradiographs that, in vivo, abscisic acid (ABA) is exported from the host leaf petiole to the attached parasite shoot. Experiments with simplified models (parasitised host stem slices, unparasitised host stem slices, isolated haustoria and parasitised host stem after removal of haustoria) showed that, in vitro, [2-14C]ABA is rapidly accumulated in haustorium tissues, and the internal/external ratio of ABA becomes greater than 1 within 45 min. The very fast ABA uptake, strongly dependent on the pH, may involve facilitated diffusion in addition to the diffusion of the undissociated acid. The high level of ABA concentration in Cuscuta, especially in haustoria, might be explained by ABA import from host tissues. In Cuscuta stem and haustoria, the hormone enhances the uptake and decreases the efflux of sucrose. In host tissues, ABA enhances phloem unloading of sucrose and decreases sucrose uptake. Thus, ABA may have a central role in the host-parasite relationship by enhancing sucrose transfer. more...

Summary In detached leaves, GA 3 and BAP exert an attractive effect on 32 P phosphate and 35 S sulphate, but not on 36 C1 chloride. At the same dose the action of GA 3 is stronger than that of BAP (200% against 150%) A comparative study has been conducted involving a pretreatment with the two hormones in order to better understand their effects both in relation to tissue absorption and also in relation to the spatial distribution of ions. Although the tissue ageing process induces a strong increase of the initial rate of absorption (twentyfold in the case of 32 P and ninefold in the case of sulphate), the absorption rate of 36 Cl is only increased twofold. Moreover a pretreatment with GA 3 increases the uptake of 32 P and 35 S (but is without effect in the case of Cl), whereas a pretreatment with BAP induces an inhibition of the absorption in the case of all three ions. Autoradiography of the tissue shows that the distribution in the fresh tissue is very rapid in the case of Cl transport, whereas the diffusion is very slow in the case of P and S. A pretreatment with the two hormones shows that the action of BAP is limited to the periphery of the disc, while the location of the GA 3 target tissues is as yet uncertain. These results confirm the specificity of the ionic response on hormone-directed transport and on changes induced by the ageing process. more...

Summary The electron microscopic observations of yellow-green and green plastids of Antirrhinum and Pelargonium demonstrate direct connections between fine structure, chlorophyll content and photo-synthetic activity. It can be shown that in young yellow-green plastids a significant decreased level of chlorophyll b is correlated with a very low amount of stacked thylakoids. A normalization of the chlorophyll a/b-ratio in the course of the development and increased greening of the plastids is connected with a preferential building of partitions. This finding supports the conception of a direct participation of chlorophyll b in the formation and maintenance of grana stacks. Young Aurea plastids accumulate only a small amount of chlorophyll, but they are photosynthetically active. Plastom mutants of the same species have an impaired photosynthesis in spite of a higher chlorophyll content (Herrmann 1971; Herrmann and Hagemann 1971). Besides of magnograna only perforated primary thylakoids are present in the mutant plastids (Knoth 1975). The Aurea plastids, however, posses always continous stromal membranes. This structurally detectable difference between both kinds of plastids is based probably on lacking or presence of chlorophyll-proteincomplex I and possibly represents the cause for a blocked or intact photosynthesis. more...

Respiration rate of foliarPelargonium discs was insensitive to ageing. The addition of BAP or GA3 to the ageing medium did not produce any effect. The presence of GA3 or BAP in the ageing medium induced an increase (27 %) or a decrease (45 %) of the phosphate uptake. The analysis of phosphorylated compound labelling showed that these two hormones decreased32P incorporation in the non-acid soluble fraction and increased32P incorporation in the acid soluble organic fraction. GA3 and BAP had little effect on the distribution of radioactivity between the different acid soluble compounds, but they increased the ATP level. These results suggest that both GA3 and BAP increase the basal metabolism, but they seem to act differently on the development of the uptake mechanism during ageing. more...

In the internodal secondary xylem of tomato (Solanum lycopersicum L. cv. Moneymaker) there are five main groups of secondary xylem elements which can be distinguished in wood macerates of basal internodes of the plant. Their top-frequency lengths are distinct: ray parenchyma cells (80 ,m); fusiform parenchyma cells and strands (250 ,m); vessel members (290 ,um); tracheids (350 ,m); and fibrous elements (590 gm), although there is overlap in length and morphology. The imperforate axial elements are strikingly diverse and morphologically intergrading, precluding ready classification according to traditional wood anatomical standards. In a novel, more appropriate, flexible categorization the variability in imperforate axial elements is depicted in a morphogram in which pit shape is plotted against cell length and cell morphology. This morphogram organizes the various elements without imposing an absolute classification. It is concluded that the appreciable variation in tomato wood samples results from developmental plasticity. The morphogram elucidates the extent and nature of element variation at the morphological level. Thus, it can be used to record developmental plasticity of wood tissues to assess interplant variation in wood tissue development, as well as intraplant plasticity. SEVERAL PAPERS on the anatomy of the tomato stem have attempted to describe the constituents of its complex secondary xylem (Venning, 1949; Thompson and Heimsch, 1964; Bonnemain, 1964). Hayward (1938) noted that the main regions of the secondary xylem consisted of large vessels and wood parenchyma, and the connecting xylem of connective and conjunctive tissue. Venning (1949) described the connective and conjunctive tissue as a kind of modified wood prosenchyma with transverse ends and thick lignified walls without pits, containing cytoplasm and a prominent nucleus. Tracheids, with prominent half-bordered or simple pits in the side and end walls, were sometimes of the dimensions of wood prosenchyma. Venning (1949) has stressed that there were no parenchymatous wood rays between the lignified elements. Thompson and Heimsch (1964) noted vessels, fibrous elements, wood rays, and noticed a lack of axial parenchyma. They described fibrous elements as elongated with pointed tips, simple pits in the thickened walls, a protoplast, and an elongated nucleus with a prominent nucleolus. Such cells were called nucleate fibers following the ' Received for publication 29 December 1987; revision accepted 9 September 1988. This research was granted by the Netherlands Organization for the Advancement of Pure Research (ZWO). Constructive criticism by Prof. P. Baas of an early draft of this paper is highly appreciated. We thank Prof. J. van Die, Ing. B. J. H. ter Welle, and an unknown referee for helpful suggestions. terminology of Arnold (1951) who proposed the term for the fibrous elements in Pelargonium zonale which retained their protoplast at maturity. In his comparison of some Solanaceae, Bonnemain (1964), shortly described the elements in maceration samples and sections of tomato stem xylem, including axial parenchyma, ray parenchyma, fibers, tracheids, and vessel members. Despite these studies on the anatomy of the tomato stem, major issues related to xylem structure remain unclear. There is no consensus on the character of xylem constituents, and presence of some elements is controversial. There are no descriptions of the dimensions of individual elements and the spatial arrangements and intercellular connections are essentially unknown. Our objective in this study was to quantify and characterize the secondary xylem elements of tomato internodes. As these elements appeared to be variable in all aspects, we designed a morphogram for a more flexible categorization. MATERIALS AND METHODS-Tomato plants (Solanum lycopersicum L. cv. Moneymaker)* were grown in sand and soil (1:1) in a greenhouse at a minimum temperature of 20 C. Stem samples for maceration were taken from internodes of a 1 m plant at a distance of 10-20 cm above the cotyledons. Excised internodes were frozen and stored at -20 C for one day. After thawing, xylem more...

42K and 14C (U)-glucose uptake by foliar discs of maize (Zea mays L.) and pelargonium (Pelargonium zonale L.) is inhibited by dimethyl sulfoxide (DMSO) at concentrations of 5 and 10%. This effect increases with the duration of the absorption and appears with varied concentrations in K or glucose. In most cases, this inhibitory effect is less with aged discs than with freshly cut discs. Besides, the DMSO (10%) enhances the exsorption of 42K by foliar discs of maize. The effects of DMSO and two osmotic agents, mannitol and polyethylene glycol 1000, on the uptake and water content of discs are compared. It seems that the effect of DMSO on the uptake is not only an osmotic effect. It may also be related to other actions of this substance in affecting an active uptake. more...

Large amounts of K+ accumulate in the multicellular trichomes in leaves of Pelargonium zonale and are retained there in the light and the dark. In guard cells, K+ accumulates in the light when stomata are open and exists from these cells in darkness when stomata close. The major site of CO2 fixation in the epidermis are the trichomes. The epidermis of P. zonale also contains potent inhibitors of phosphoenolpyruvate (PEP) carboxylase and NAD malate dehydrogenase activities. Dialysis treatment or passage through a G-25 Sephadex column does not relieve this inhibitory activity; however, boiling the crude epidermal extract of P. zonale alleviates much of the inhibition of NAD malate dehydrogenase in maize leaf extracts, suggesting that the inhibitor(s) may be protein(s). These features make the epidermis of P. zonale particularly unsuitable for studies on metabolic aspects of guard cells. more...

Summary The phenomenon of autoparasitism in the genus Cuscuta has been reported on a number of occasions. Attempts to prove the transport of radiolabelled sucrose from a host filament of Cuscuta reflexa to a parasitizing shoot of the same species were not successful. The growth of parasitizing Cuscuta stems separated from the stock culture was not stronger than the growth of isolated shoots of the same length. Light and electron microscopic pictures of cross-sections of parasitized Cuscuta stems showed an isolating layer of cells in front of the penetrating haustoria formed in the cortex of the infested shoot. This way the haustorial cells cannot reach the vascular bundles of the parasitized Cuscuta stem. In spite of the presence of haustoria, Cuscuta reflexa cannot absorb food substances autoparasitically. more...

SUMMARY A comparative investigation of techniques for the preparation of soft botanical tissue for the scanning electron microscope has been carried out using the leaves and petals of Pelargonium zonale as test specimens. Twelve different preparative procedures involving combinations of fixation, dehydration, air drying, freeze drying, critical point drying, coating methods, replicas and a temperature controlled specimen stage were tested. more...

Sedum album and Pelargonium zonale extracts do not show any peroxidase activity. Both extracts provoke a lag phase in the horse-radish peroxidase-catalyzed oxidation of guaiacol by H2O2. Preincubation of Sedum album extract with ascorbate oxidase eliminated completely the lag phase. Ascorbic acid has been identified as the substance responsible for this lag phase by reacting with a coloured intermediary product of the analytical reaction. In the Pelargonium zonale extract, the lag phase seems to be due to competitive inhibitors of peroxidase, which are of a phenolic nature. more...

Examen de quelques particularites anatomiques et morphologiques des cellules de garde de Pelargonium zonale. Reaction des stomates a la lumiere et au CO 2

SUMMARYThe ultrastructure of the tapetal cells was studied in Kalanchoe obtusa and Pelargonium zonale. In an early stage of development the most characteristic feature was the presence of many spherical bodies bounded by a single membrane and containing cytoplasmic material. These bodies were localized in dilations of the ER and in the perinuclear space. In later stages, when the pollen was mature, the tapetal cells of Pelargonium contained many « grey » bodies and their plasmalemma was in close connection with the sculptures of the pollen grains. more...

Translocation of (14)C-labelled assimilates down the petioles was studied in intact plants of Pelargonium zonale (L.) L'Hérit ex Ait. The central bundle of the petiole was dissected out and treated with solutions of various inhibitors. Whereas cytochalasin B had no effect on (14)C-translocation, a distinct and localized inhibition was caused by CCCP (10(-7) M), antimycin (5×10(-5) M), atractylate (5×10(-5) M), and valinomycin (10(-5) M) without any significant change in the proportion of [(14)C]sucrose in the translocate. The inhibition of translocation is inferred both by accumulation of (14)C distal to and a decrease in (14)C concentration basal to the treated petiolar region. If valinomycin was fed into the transpiration stream by flapping the peripheral bundles of the petioles an increased labeling of sugar phosphates occurred in the (14)C fed leaf. Plasmolysis tests indicated that whereas CCCP interfered with the semipermeability of phloem cell membranes, valinomycin had no such effect. The results with valinomycin suggest a compartmentation of potassium ions for the translocation process but are ambiguous as to whether or not a potassium pump is involved. more...

Directed Transport and Hormones — Value of Isolated Leaf as Experimental Material. Local application of aqueous phytohormonal solution (0.1 ml of various concentrations, from 50 to 0.025 mg-l−1, of IAA, 2,4-D, NAA, BAP, GA3) on isolated leaves influences the direction of ion transport. All tested hormones are efficient but the action depends upon the ionic species [positive action with 32P, 35S, 36Rb (K), but null with 45Ca or 46Cl]. The movement of ions occurs through the phloem tissue and is not a cell-to-cell transfer. Competition between different parts of the leaf is demonstrated (a) between petiole which appears to be an important attractive centre and other parts of the leaf; (b) in a depetioloted leaf, between different centres induced by different phytohormones. In this respect, GA3 appears to be the most efficient hormone in the tested material — leaves of Pelargonium zonale (L.) Aiton. The effects on directional transport are discussed in relation to other processes controlled by hormones, for instance growth, senescence, protein synthesis. A direct relation of directional transport with growth or delay of senescence may be discarded. The value of isolated leaves as simplified experimental systems is underlined by the fact that weak hormonal doses are efficient (0.025 mg.l for GA3 and 0.5 mg.1 for 2,4-D) as compared to the higher doses used in other plant systems. more...

Increasing quantities of fermented domestic waste compost resulted, in the present experiments, in a decrease in the production of Lactuca sativa (lettuce) in contrast to a yield increase for Apium graveolens (celery). The application of a calculated quantity of ion exchangers can modify the phytotoxic effect of the presence of heavy metals as well as the salt concentration of the domestic waste compost. The use of anion exchangers in the lettuce culture resulted in a considerable yield increase in comparison with the control. With regard to Chrysanthenum morifolium cv. ‘Angora’, Pelargonium zonale cv. ‘Flirt’ and Dieffenbachia perfecta, it was demonstrated that the use of a mixture of domestic waste compost and coniferous soil in a ratio of 1:3 is very useful for these ornamental plants, on the basis of comparison of results of vegetative development with the control substrate. Analysis of the vegetables cultivated with increasing quantities of domestic waste compost enriched sand-loam soil showed that the concentrations of Cu, Pb and Zn fairly quickly exceeded the normal average values. As far as pathogenesis is concerned, increasing quantities of domestic waste compost positively influenced the health index of Phaseolus vulgaris and Pisum sativum with regard to Rhizoctonia solani and Pythium ultimum. more...

Experiments on the movement of 14C-assimilates through dissected vascular bundles of Pelargonium zonale are reviewed. Potassium cyanide (KCN) applied to the central bundle causes localized, reversible blockage of transport. Both antimycin and atractylate, but not ouabain inhibit the movement of metabolites through the phloem. The proton ionophore, CCCP completely suppresses translocation at 10−7 M, however, cell membranes are damaged. Valinomycin applied to cut bundles causes serious disturbances in carbon metabolism as shown by the increased label in sugar phosphates. Cytochalasin B does not affect translocation. Limitations on conclusions drawn from inhibitor studies are discussed. more...

The investigations on the cause of the “Lent disease” of mother plants as well as cuttings ofPelargonium zonale have indicated, that these troubles are due to faulty cultural methodes combined with an infection byCorynebacterium fascians and “weakness parasites”. The bacteria cause the axillary buds to develop leafy galls on the stem under the soil level and small tumorous growths on the cortex of the stem above, the socalled corky spots. The infected plants may not wither, but galls and spots are more easily infected by pathogens than healthy plants. FrequentlyBotrytis cinerea infects these tissues and causes the black base rot. Spraying the mother plants with streptomycin (Fytostrep 60: 2.5 ml/l) and thiram (0.2%) decreased the base rot, but markedly inhibited the rooting of the cuttings. Moreover, the inocula of bothC. fascians andB. cinerea are present in such a large quantity, that full control is impossible. Reduction of losses may be achieved by improvement of cultural methods and soil disinfection. more...

Crosses were made between Pelargonium zonale, P.inquinans, P.scandans and P. stenopetalum and any interspecific hybrids obtained were selfed. The species were also selfed. Pelargonium stenopetalum was self-incompatible and cross-incompatible as the pistillate parent with the other species. As the staminate parent, P.stenopetalum was also relatively unsuccessful in interspecific crosses. Crosses between P.zonale and P.inquinans produced relatively high numbers of viable seeds and the hybrids were quite self-fertile. As indicated by the ease of crossability and hybrid self-fertility, reproductive barriers were strong between P.scandens and the other species. more...

Summary Expiants of shoot apices from varieties of Pelargonium zonale and of Pelargonium pel-tatum × Pelargonium zonale were cultured on a solid basal medium according to Murashige-Skoog supplemented with 15 % cocosmilk. The effect of NAA and 2,4-D on callus growth and differentiation was compared at a concentration of 1 ppm. In liquid medium the mass of cells in juvenile cultures were freely suspended parenchymatic single cells of abnormal size (giant cells). The diameter of cells in callus clumps was strinkingly smaller. After a shaking period of 3 month in single cells tracheary elements were formed. A great number of globular and cylindrical pitted cells and some with reticulated thickenings could be identified. This type of tracheidal cell differed from tracheids differentiated in the center of nodules in callus tissue. It is concluded that kinetin like substances favour polyploidy and the differentiation by formations of secondary wall elements. Under the described conditions callus cells from shoot apices of Pelargonium undergo two different ways of organization: 1. Formation of giant parenchymatous and tracheidal single cells without any connection with greater tissue units, 2. formation of callus clumps with small cells and tracheids in the center. more...

The ultrastructure of the generative cell of the pollen grain has been studied in two different plants: Mirabilis jalapa L., where variegation is transmitted only by the egg cell, and Pelargonium zonale AIT., where variegation can be transmitted also by the pollen grain. It was found that only in Pelargonium zonale AIT. does the male generative cell possesses a great number of proplastids. more...

Summary 1. The variety “Mrs. Pollock” of Pelargonium zonale (fig. 1) is a periclinal mesochimera of the constitution: L I green, L II yellow, L III green. Reciprocal crosses between “Mrs. Pollock” and the green variety “Trautlieb” demonstrate a biparental extranuclear inheritance of the character yellow-green. The F 1 consists of green, yellow-green variegated and yellow seedlings (Table 1). 2. In yellow-green variegated F 1-plants “mixed cells” (fig. 2) have been found containing two genetically different types of plastids, green plastids (“from Trautlieb”) and yellow plastids (from “Mrs. Pollock”). 3. The yellow cells of “Mrs. Pollock” thus represent a yellow plastid mutant (= plastom mutant). Its genetic designation is “extranuclear: gilva-1”; its symbol is en: gil-1. 4. On the other hand, crosses between the periclinal chimera „Cloth of Gold‟ (fig. 4, 5) and “Trautlieb” show, that the yellow cells of “Cloth of Gold” are heterozygous for a dominant gene mutation of the Aurea type (Table 1). 5. Leaves and shoots containing only mutant “Mrs. Pollock”-plastids are able to grow green intensely under dim light; its chlorophyll content increases up to 41 % of the control (Table 2). Under normal light conditions the leaves bleach out. (This is also true for the yellow areas of the periclinal chimera.) 6. The greenish mutant plastids have an almost normal ratio of chlorophyll a/b (Table 2). However, the absorption maximum of the long-wave form of chlorophyll a has in vivo been shifted 3-4 nm towards shorter waves (fig. 8) in comparison to wild type plastids. 7. In spite of its chlorophyll content, mutant “Mrs. Pollock”-plastids cannot perform any photosynthesis (fig. 6, 7). 8. Young yellow leaves of the gene mutant “Cloth of Gold” (yellow component) have a lower chlorophyll content than the greenish plastid mutant. Moreover, the content of chlorophyll b is very low (Table 3). Nevertheless these leaves are photosynthetically active (Table 3). The absorption maximum of the long-wave form of chlorophyll a is normal in this mutant (fig. 9). 9. In our opinion, the shift of the absorption maximum of the long-wave form of chlorophyll a is — in accordance with our results from other mutants — a general characteristic of a defect of photosynthesis. 10. The comparison of the yellow leaves of the gene mutant “Cloth of Gold” and the greenish leaves of the plastid mutant “Mrs. Pollock” demonstrates, that the whole chlorophyll content of the mutant plastids would be sufficient for photosynthesis. Therefore, the plastid mutant seems to contain a specific block, which entirely inhibits photosynthesis. 11. Experiments are in progress to characterize this plastom-specific block. more...

The petiole of Pelargonium zonale is traversed by 17 bundles, whose arrangement and form are typical for this plant. The bundles of the petiole are connected with the conducting system of the axis and with the main nerves by a system of phloem anastomoses in the leaf base and in the junction between the petiole and the leaf blade (Fig. 2). The anatomical findings were confirmed and extended by a study of the translocation of K-fluorescein and 14C. It could be shown that the metaphloem of the central petiole bundle is composed of phloem subunits, each of which is connected with the phloem of one certain main nerve only (Fig. 4). Accordingly, if fluorescein or 14CO2 is applied to one main nerve, the dye or 14C-material is translocated exclusively in a small phloem area of the central bundle. Autoradiograms of the petioles indicate that the 14C-labelled assimilates (sucrose, glucose, fructose and amino acids) are translocated exclusively in the phloem. A lateral movement of the labelled material within the petiole was not observed. The metaphloem of the central petiole bundle of Pelargonium zonale revealed a functional organization of phloem subunits. more...

Results concerning ureide biosynthesis in chlorophyll-deficient leaves of Pelargonium zonale and germinating seeds of Triticum vulgare are consistent with the concept that allantoin and allantoic acid are formed via purine intermediates. The determination of radiocarbon distribution over the carbon atoms 4, 5 and 2 and 2′ (2+8) of allantoin and allantoic acid after feeding glycine-1-14C and glycine-2-14C, definitely excludes a more direct pathway of ureide biosynthesis from simpler molecules, e.g., by condensation of glyoxylate and urea. In the plants in question a reaction cycle is operative connecting aerobic purine degradation and de novo purine synthesis by means of glyoxylate. Glyoxylate which is rapidly formed in the degradative pathway is readily introduced into purine synthesis via glycine (and serine?), and thus becomes an important link in the cyclic reaction path. As a consequence, radiocarbon from glycine-1-14C is introduced in the methylene carbon of glycine. By analogy, glycine-2-14C is transformed to glycine-1-14C. But radioactivity from glycine-2-14C is also incorporated into positions 2 and 8 (2 and 2′) of glyoxylic ureides, thus furnishing 14C-urea. As a consequence of the cyclic reaction pathway, carboxyl-labeled glycine is also introduced in the ureide carbons of allantoin and allantoic acid, thus also yielding urea-14C. The accumulation of considerable amounts of free urea observed in chlorophyll-deficient leaves of Pelargonium zonale is a result of different rates of urea and glyoxylate utilization depending on low urease activity and a rapid utilization of glyoxylate for glycine and ureide synthesis. The results are discussed in terms of the metabolism of glycine. more...

Summary The primary reactions of photosynthesis in pale green mutant plastids of the plastom mutants, en : viridis-1 of Antirrhinum majus and en : gil-1 (“Mrs. Pollock”) of Pelargonium zonale have been studied by biochemical and biophysical methods. The en : viridis-1 plastids of Antirrhinum are not able to reduce the Hill-oxydant DPIP indicating a defect in photosystem II. The measurement of DLE (delayed light emission) shows a strongly reduced activity of photosystem II. However, the activity of photosystem I is entirely normal in this mutant. In accordance with this result, the ESR-signal (electron spin resonance) assigned to P 700 is present as normal. –In the greenish en : gil-1 plastids of Pelargonium a normal, distinct DLE could be detected indicating the normal function of photosystem II. A defect in photosystem I is shown by the absence of light induced short-lived ESR-signals. The defects in mutant plastids of the plastom mutants en : viridis-1 of Antirrhinum and en : gil-1 of Pelargonium are caused by mutations of the plastid DNA. Thus, the results obtained suggest that the plastid DNA controls particular reactions in both photosystem I and photosystem II. more...

A series of experiments were conducted to investigate the effects of moving, normal and carbon dioxide-free air on the stomata within porometer cups attached to the illuminated leaves of Datura stramonium, Pelargonium zonale, Duranta plumieri and Clerodendron inerme. A marked opening stomatal response was obtained in Datura and Pelargonium on changing to carbon dioxide-free air. In general no such response was established in Duranta and Clerodendron. Indications of even an opposite closing effect were shown in the case of Duranta. The present results seem to disprove the reduction of carbon dioxide by photosynthesis as the major factor controlling the wide stomatal opening within a porometer cup. The possibility of a humidity effect is also suggested. more...

The main route of adenine degradation in chlorophyll-deficient and variegated leaves of Pelargonium zonale (Geraniaceae) may be the over-all reaction path of oxidative purine catabolism. Only part of the supplied adenine is transformed into free guanine. Part of the 8- 14 C-adenine supplied gives rise to serine- 14 C. It is suggested that the imidazole ring of adenine or a metabolically related adenine derivative is opened and C-8 is lost as a single carbon unit which is used in serine biosynthesis, giving carbon-3 atom of serine. more...

IT IS RATHER widely accepted that the accumulation of carbon dioxide from respiration in darkness and its removal in light by photosynthesis, brings about changes in the hydrogen-ion concentration in guard cells. A survey of the literature dealing with the physiology of the stomata, however, reveals that there is no general agreement among botanists in respect to how such changes in acidity influence the mechanism which causes the turgor and hence the posture of the guard cells to vary. In general, more emphasis is placed in textbooks on the "enzymatic mechanism," based on starch-sugar transformations, as supported by Kohl (1895), Darwin (1898), Lloyd (1908), lijin (1914), Loftfield (1921), Weber (1923), and Sayre (1926), but the mechanism proposed by Scarth (1926a), based on changes in the water adsorptive power of the colloidal content of the guard cells, is also frequently mentioned as being responsible for the rapid movement of the stomata. Kisselew (1925) related the stomatal movement to changes in the permeability of the guard cells, but this theory has not received much support from other investigators. In a recent publication on the effect of some environmental factors on the movement of the guard cells, Wilson (1948) considered that none of these proposed theories is adequate to account for all of the observed facts concerning the opening and closing of stomata. The present study is an attempt to determine the mechanism or mechanisms involved in the movement of the stomata. Experiments were first performed for the purpose of confirming the results of former investigators on the rate of light-induced stomatal opening, and on the pH-relations of the stomatal movement. Following this, a comparative study between the starch-sugar mechanism and the colloidal imbibition mechanism was undertaken. MATERIALS AND METHODs.-Since the writer was particularly interested in studying the relative importance of the colloidal imbibition mechanism as compared with enzymatic mechanism of stomatal behavior, it was thought desirable to include in the experiments plants which contained different amounts of colloidal material in the guard cells. A preliminary test was made with several species using the staining with neutral red as a criterion to evaluate the amount of colloidal substance in the guard cells (Scarth, 1926b; Guilliermond, 1941). As a result, zebrina (Zebrina pendula), geranium (Pelargonium zonale), and bean (Phaseolus vul more...

Summary As a consequence of a plastid mutation the white plastids en: alba-1 of the variety “Mrs. Parker” of Pelargonium zonale do not possess ribosomes, and therefore they are not able to perform plastidal protein synthesis. By means of biochemical and electron microscopic methods the question was studied, whether the mutant plastids contain DNA. The DNA of isolated wild type chloroplasts of Pelargonium zonale has a buoyant density in CsCl of 1,697 ± 0.001 g/cm 3 (fig. 1), and a melting temperature of 85°C (fig. 2). The chloroplast DNA of Pelargonium cannot be separated by buoyant density centrifugation in CsCl and melting temperature from the nuclear DNA. The base composition of both chloroplast and nuclear DNA was calculated to be 37–38% GC. However, the chloroplast DNA renatures almost completely, whereas nuclear DNA renatures only to a low extend. In the DNA of pure white mutant leaves of en: alba-1 there is no indication of the presence of any other component differing in the density (fig. 1c). The electron microscopic study of plastid DNA by means of three independent techniques gave the following results for both normal chloroplasts and mutated en: alba-1 plastids: In situ studies show an intraplastidal localization of DNA (fig. 4 b) in nucleoplasmatic areas, occupying 39.3 ± 8.2 % of total plastid capacity (fig. 4a) in the case of mutant plastids. The identity of the fibrillar structures with DNA was proved in positive DNase-tests. Spreaded DNA from osmotically disrupted plastids is associated with membranes in a consistent way. It was possible to find good visible, loop-like moleeules from wild type (fig. 8) and from the mutant plastids (fig. 6 a). Apart from this there are large “displays” of DNA with numerous membrane attachment points (fig. 7 a). Thereby the DNA has contact with the membrane either directly in polyfibrillar form or by building solid stick-like structures (fig. 7 b). A single DNA molecule from en: alba-1 plastids is presented with partially distinct diameters of its strand. This phenomenon was interpreted as a possible result of replication (fig. 6 b). Evidence for the ability for replication of en: alba-1 DNA was obtained by electron microscopic autoradiography (fig. 8). As in wild type chloroplasts, about four labelled centres are scattered over the plastid sections. DNase-treated samples do not show any specific labelling. It is discussed, whether the DNA is present in the plastid as a single molecule or as a multitude of independent molecules. more...

The stomata of Allium cepa are fully motile (Loftfield, I921) and exhibit a genuine response to light and, by inference, to changes in carbon dioxide tension (Heath, I952). They are, however, completely starch-free, as demonstrated by a number of investigators from Parkin (I899) to Heath. The former, having examined both alcohol fixed and living epidermis of some eight species of onion, including A. cepa and A. schoenoprasum, reported: 'No chloroplasts could be recognized, nor could I certainly detect any green colour in the guard cells.' He noted, however, that refractive granules were sometimes present. Heath also was unable to recognize chloroplasts in the stomata of A. cepa (var. Ebenezer) and obtained negative results with certain microchemical tests for chlorophyll (saturated KOH and the phaeophytin test: Molisch, I92I), but did not refer to the Molisch reaction (reduction of AgNO3 by chloroplasts: Molisch, I9I8). It may be noted that Sayre (I926) found that the stomatal plastids of Rumex patientia, though obviously green, did not give the microchemical tests (sic) for chlorophyll, a result he regarded as inconclusive in view of the small amount of pigment present. Apparently neither Heath nor Sayre made use of the fluorescence microscope, with which the stomatal plastids of a number of species have been found to exhibit the red fluorescence characteristic of chlorophyll. Moreover, Heath was apparently not aware that chloroplasts have been reported to occur in onion guard-cells. In I927 Linsbauer wrote of A. cepa (pp. 53I-2): 'Die Chloroplasten, 20-25 an der Zahl, liegen zumeist der Riickenwand an und sind auffallend klein und bleich. Nichtsdestoweniger geben sie die Molische Chlorophyll Reaktionen und reduzieren AgNO3.' In a footnote he added that the guard-cell chloroplasts showed typical fluorescence under the fluorescence microscope, commenting that Sayre's observations, recorded above, certainly did not apply to Allium. Again, Hofler (I939), in a study of silver nitrate reduction by guard-cell plastids, obtained positive results with A. cepa and A. schoenoprasum (cf. Parkin, above) as well as with Vicia faba, Helianthus, Tradescantia, Galium and Pelargonium zonale. Hofler and also Linsbauer (1926, for Chrysanthemum) observed that localized blackening of the plastids was accompanied by a general reduction (browning) of silver nitrate throughout the protoplast in open but not in closed stomata, suggesting an increase in reducing substances during opening of 'starch' and 'starch-free' stomata alike. Unfortunately, Hofler presented no experimental data for Allium, merely stating that the results obtained were similar to those for Vicia. It is clear, none the less, that the results of Linsbauer and Hofler are not in accord with those of Parkin and Heath. Since the point at issue has a critical bearing on stomatal more...

Summary The cultivar Pelargonium zonale ‘Freak of Nature’ is a trichimera (XYZ). The genetically different potencies of the apical layers in the leaf development are characterized as follows: L 1 : chlorophyll-intact, cells normally growing (X) L 2 : chlorophyll-defect, cells stunted growing (Y) L 3 : chlorophyll-defect, cells normally growing (Z) The observed dichimera XZZ (originated by layer-rearrangement from the trichimera XYZ) but rarely shows on the contrary to XYZ participation of green L 1 -descendants in mesophyll formation. The different behavior of X-descendants in the two chimeras is explicated by differences in the growth pressure executed by the underlaying Y- or Z-descendants. The lower growth pressure executed by Y-descendants allows periclinal divisions in the dermatogen, whereas the stronger pressure executed by the Z-descendants supresses such divisions. Two investigated variants (from Euphorbia pulcherrima ‘Eckes Rosa’ and Pelargonium zonale ‘Kleiner Liebling’) corresponded to Pelargonium zonale ‘Freak of Nature’. more...

This paper describes the second half of a series of tests of the photosynthetic theory of stomatal movement. A corollary of this theory is that any agent that inhibits photosynthesis should prevent opening or cause closure in light?unless some other action prevents this. It has been reported that this relationship does not hold either in wilting or under the action of chloroform (Wilson, 14). The effects of these factors are investigated in the present paper. As before (11), stomatal aperture was measured by means of a modified porometer method, photosynthesis by infrared absorption, and, except in a few experiments, the leaf material all belonged to the same clone of Pelargonium zonale var. Barney. more...

Searching behaviour of the larvae of Chrysopa carnea Steph. (Neur.: Chrysopidae). While searching for their prey larvae of Chrysopa carnea were hindered by the hard layer of wax of different varieties of cabbage and the strong felt-like hair of plants like Phaseolus vulgaris, Pelargonium zonale and Nicotiana tahacum. Their searching for prey remained unchecked on Beta vulgaris, Vicia faba and Brassica chinensis those being plants lacking the strong hair and wax layer. In searching for their prey the larvae preferably followed morphological guidelines such as plant stems, leaf stalks, leaf veins, leaf margins and pot edges. Aphids (Myzus persicae) on the margin or the stalk of sugar beet leaves were found within 16 hours two to three times as often as aphids on all of the leaf area. The numbers of aphids being fed-on among dispersed aphids and those in colony-type aggregation were not significantly different. Increasing the degree of starvation (up to 72 hours without food) had hardly any influence on the searching behaviour of the larvae or on the number of aphids being fed-on, but there was a positive correlation of starvation with cannibalism amongst larvae of the same age and size. Success in searching for larvae of Chrysopa carnea was dependent more on the prey-density per leaf area than on the prey-density per plant. The devoured more aphids on comparatively small plants than on bigger plants with the same number of aphids. By their activity larvae of Chrysopa carnea caused an escape-reaction-pattern (dropping and running away on the ground) among the aphids and so the original density decreased. The initial number of aphids of all ages on single leaves decreased in two hours by 21–25 %, the number of adult aphids by 33–34 °/o. The larvae fed on only 4–5 °/o of the suitable aphids. Zusammenfassung Die Larven von Chrysopa carnea wurden durch die Wachsschicht verschiedener Kohlvarietaten und durch starke, filzige Behaarung, wie sie bei Buschbohne, Pelargonien und Tabak zu finden ist, in ihrer Beutesuche behindert. Ungehindert konnten sie ihre Beute auf Zuckerrube, Ackerbohne oder Chinakohl suchen, also auf Pflanzen ohne oder mit nur schwacher Behaarung und Wachsschicht. Auf den Suchwegen folgten die Larven bevorzugt morphologischen Leitlinien und bewegten sich daher uberwiegend auf Pflanzenstengeln, Blattstielen, -randern und -adern sowie besonders auf dem Topfrand. Von Blattlausen, die am Rand oder Stiel von Zuckerrubenblattern sasen, wurden innerhalb von 16 Stunden 2–3mal so viele gefunden wie von Vergleichstieren auf der Spreite. In einer Kolonie zusammenlebende Blattlause wurden nicht haufiger vertilgt als verstreut sitzende. Zunehmender Hunger wirkte sich (bis zu 72 Stunden ohne Nahrung) anschliesend kaum auf das Suchverhalten der Larven und deren Nahrungsverbrauch aus. Der wachsende Hunger war aber positiv korreliert mit Kannibalismus zwischen Larven gleichen Alters und gleicher Grose. Der Sucherfolg der Chrysopa-Larven war weniger von der Beutemenge je Pflanze, als vielmehr von der Beutedichte auf der Blattflache abhangig. Auf kleineren Pflanzen frasen die Rauber mehr Blattlause als auf groseren trotz gleicher Blattlauszahl/Pflanze. Chrysopa-Larven bewirkten die Abwanderung von Blattlausen durch Fall und Flucht und damit eine Abnahme der ursprunglichen Blattlausdichte. Die anfangliche Blattlausmenge einzelner Blatter verringerte sich in 2 Stunden um 21–25 %, die Anzahl der Adulten um 33–44 %. Nur 4–5 % wurden vertilgt. more...

The sequence of the plastid 5S rDNA of Pelargonium zonale hort. “Roseum” is presented. In the 5′ region of this gene there is almost no homology to the Escherichia coli promoter consensus sequences. In an E. coli minicell system we have demonstrated that the plastid promoter of the 16S rDNA is active in E. coli but no separate transcript of the cloned 5S rDNA can be detected. These results provide new evidence that the plastid 5S rDNA of P. zonale and probably also of other higher plants is not transcribed as a separate unit. more...

63Ni was applied to nonsenescent source leaves and found to be transported to sink tissues in pea (Pisum sativum L.) and geranium plants (Pelargonium zonale L.). The comparative mobilities (percent tracer transported out of source leaf ÷% 86Rb transported) for 63Ni in peas was 2.12 and in geranium 0.25. The value for the phloem mobile 86Rb was 1.00. By contrast, the comparative mobility of 45Ca, which is relatively immobile in the phloem, was low (0.05 in peas, 0.00 in geranium). Interruption of the phloem pathway between source and sink leaves by steam girdling almost completely inhibited 63Ni accumulation in the sink leaves of both species. We conclude that Ni is transported from nonsenescent source leaves to sink tissues via the phloem of leguminous and nonleguminous plants. more...

We present the primary structure of a chloroplast tRNAArgACG gene of the plant, Pelargonium zonale, and its faithful expression in Xenopus oocyte nuclei. This tRNAArg gene is located 250 bp downstream of a 5S RNA gene within a cloned 5kb long ribosomal DNA segment (Fig. 1). The Pelargonium tRNAArg gene shares 97% and 86% sequence homology with tRNAArgACG genes of Spirodela oligorhiza and Euglena gracilis chloroplasts, respectively, and also extensive homology (70%) with the corresponding gene of E. coli. It lacks an intervening sequence and, like eukaryotic tRNA genes, does not code for the 3' terminal CCA nucleotides. Moreover, the chloroplast tRNAArg gene carries all the sequence elements essential for transcription by vertebrate RNA polymerase III since it is efficiently expressed in Xenopus oocyte nuclei, even in the presence of 1 microgram/ml alpha-amanitin. In Xenopus oocyte nuclei, no transcripts of the chloroplast 5S RNA gene were detected. more...

Shoot tips (0.5 mm high) of Pelargonium zonale hybrid cvs. ’Career’ and ’Fire flash’ were cultured on modified MS medium: macroelements (Murashige and Skoog 1962), microelements (Nitsch and Nitsch 1970) containing (mg 1^1) thiamine.HCl 0.4, m-inositol 200, caseine hydrolysate 1000, IAA 0.5, kinetin 10.0; (g 1-1) sucrose 30, bacto agar 6; pH 5.8. The ’Career’ did not grow on this medium, while the ’Fire flash’ did: 30% of shoots produced an organogenic callus, which was capable of being continuously subcultured. The shoots and plantlets obtained rooted well on a medium containing 0.1 mg 1-1 IAA only, and after a month they were transferred into pots. Callus cultures and in vitro formed plants, examined for Xanthomonas pelargonii and other bacteria, were found to be free of pathogens., Vegetacijske vrškove (veličine 0,5 mm) biljke Pelargonium zonale hybrid 2 sorte: ’Career’ i ’Fire flash’ kultivirali smo na modificiranom MS mediju (Makroelementi po Murashige i Skoogu 1862, mikro- elementi po Nitsch i Nitschu 1970) uz dodane slijedeće tvari: (mg 1-1) tiamina.HCl 0,4; m-inositola 200; hidrolizata kazeina 1000; 0,5 kinetina 10,0 te (g 1-1) saharoze 30 i Difco bakto-agara 6; pH 5,8. Dok sorta ’Career’ nije rasla na mediju ovog sastava, sorta ’Fire flash’ 'e na 30% eksplantata proizvela dobro rastući organogeni kalus koji se mogao supkultivirati. Izdanci i biljčice regenerirani in vitro dobro su se zakorjenjivali na osnovnom mediju uz dodatak samo 0,1 mg 1-1 IAA i u velikom postotku preživljavali presađivanje u lonce. Testiranje kalusnih kultura i in vitro regeneriranih biljaka na prisutnost bakterija Xanthomonas pelargonii i ostalih bakterija dalo je negativne rezultate. more...

The comparison of EcoRI patterns of chloroplast DNAs (ctDNAs) from five species of the genus Pelargonium and from 16 cultivars and varieties of Pelargonium zonale hort. demonstrates a remarkable inter- and intraspecific ctDNA (plastome) variation. The plastome of the P. zonale varieties could be differentiated into groups I, II and III. Reasons for this variation seem to be: occurrence of numerous spontaneous plastome mutations, intense hybridisation by gardeners and breeders, and biparental plastid inheritance.Crosses of P. zonale varieties with different ctDNA types lead to the direct evidence on the molecular level of biparental plastid inheritance and plastid sorting-out in F1-hybrids. more...