The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Hugh D. Wilson - One of the best experts on this subject based on the ideXlab platform.
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Senna occidentalis (Introduced) 2
2011Co-Authors: Hugh D. WilsonAbstract:Senna occidentalis , Node with Pulvinus, stipules. Family Caesalpiniaceae, Subclass Rosidae. Origin: Introduced.
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Senna obtusifolia (Native) 2
2011Co-Authors: Hugh D. WilsonAbstract:Senna obtusifolia, Node with Pulvinus, stipules. Family Caesalpiniaceae, Subclass Rosidae. Origin: Native.
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Amorpha fruticosa (Native) 2
2011Co-Authors: Hugh D. WilsonAbstract:Amorpha fruticosa , Pulvinus, node. Family Fabaceae, Subclass Rosidae. Origin: Native
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Senna obtusifolia (Native) 5
2011Co-Authors: Hugh D. WilsonAbstract:Senna obtusifolia, Node with Pulvinus, stipules. Family Caesalpiniaceae, Subclass Rosidae. Origin: Native
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Senna occidentalis (Introduced) 4
2011Co-Authors: Hugh D. WilsonAbstract:Senna occidentalis , Node with Pulvinus, stipules. Family Caesalpiniaceae, Subclass Rosidae. Origin: Introduced
Michael T. Mcmanus - One of the best experts on this subject based on the ideXlab platform.
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Further examination of abscission zone cells as ethylene target cells in higher plants.
Annals of botany, 2007Co-Authors: Michael T. McmanusAbstract:BACKGROUND AND AIMS Two aspects of the competence of abscission zone cells as a specific class of hormone target cell are examined. The first is the competence of these target cells to respond to a remote stele-generated signal, and whether ethylene acts in concert with this signal to initiate abscission of the primary leaf in Phaseolus vulgaris. The second is to extend the concept of dual control of abscission cell competence. Can the concept of developmental memory that is retained by abscission cell of Phaseolus vulgaris post-separation in terms of the inductive/repressive control of beta-1,4-glucan endohydrolase (cellulase) activity exerted by ethylene/auxin be extended to the rachis abscission zone cells of Sambucus nigra? METHODS Abscission assays were performed using the leaf petiole-Pulvinus explants of P. vulgaris with the distal Pulvinus stele removed. These (-stele) explants do not separate when treated with ethylene and require a stele-generated signal from the distal Pulvinus for separation at the leaf petiole-pulvinis abscission zone. Using these explants, the role of ethylene was examined, using the ethylene action blocker, 1-methyl cyclopropene, as well as the significance of the tissue from which the stele signal originates. Further, leaf rachis abscission explants were excised from the compound leaves of S. nigra, and changes in the activity of cellulase in response to added ethylene and auxin post-separation was examined. KEY RESULTS The use of (-stele) explants has confirmed that ethylene, with the stele-generated signal, is essential for abscission. Neither ethylene alone nor the stelar signal alone is sufficient. Further, in addition to the leaf Pulvinus distal to the abscission zone, mid-rib tissue that is excised from senescent or green mid-rib tissue can also generate a competent stelar signal. Experiments with rachis abscission explants of S. nigra have shown that auxin, when added to cells post-separation can retard cellulase activity, with activity re-established with subsequent ethylene treatment. CONCLUSIONS The triggers that initiate and regulate the separation process are complex with, in bean leaves at least, the generation of a signal (or signals) from remote tissues, in concert with ethylene, a requisite part of the process. Once evoked, abscission cells maintain a developmental memory such that the induction/repression mediated by ethylene/auxin that is observed prior to separation is also retained by the cells post-separation.
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Peroxidases in the separation zone during ethylene-induced bean leaf abscission
Phytochemistry, 1994Co-Authors: Michael T. McmanusAbstract:Abstract To determine if peroxidase activity is induced specifically in the abscission zone during ethylene-induced cell separation, the spectrum of isoenzymes and activity of the enzyme in extracts from the distal Pulvinus, the Pulvinus: petiole abscission zone and the petiole of Phaseolus vulgaris leaves were compared. For the cationic isoenzymes, the onset of ethylene-induced cell separation correlated with an increase in the expression of two isoenzymes that are present in both the Pulvinus and the abscission zone. In terms of the anionic isoenzymes, two isoenzyrnes were induced at the time of ethylene-induced cell separation. Both of these are expressed preferentially in the zone, while another was induced predominantly in the petiole. No peroxidase isoenzymes could be detected that were induced specifically in the abscission zone at the time of Pulvinus separation. When total enzyme activity was compared, ethylene treatment increased the measurable activity in all tissues, although the highest was at the zone at the time of cell separation. When specific activity was compared, these differences were not as marked. Together, these results show that while peroxidase activity is induced at the abscission zone during ethylene-induced cell separation, changes in specific isoenzymes are observed both in the zone and in neighbouring (non-abscission) tissue. These changes in the spectrum of isoenzymes observed in neighbouring tissue, therefore, should not be ignored when postulating a role for peroxidase in mediating cell-cell separation at the abscission zone.
Peter B. Kaufman - One of the best experts on this subject based on the ideXlab platform.
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Cell Elongation in the Grass Pulvinus in Response to Geotropic Stimulation and Auxin Application
2016Co-Authors: P. Dayan, Frederick V. Hebard, Peter B. KaufmanAbstract:ira L. shoots show a negative geotropic response after a period of 30 rain. This response is based on cell elongation on the lower side of the leaf-sheath base (Pulvinus). Triticum aestivum L., Hordeum vul-gare L. and Secale cereale L. also show geotropic responses that are similar to those in Avena shoots. The Pulvinus is a highly specialized organ with radial symmetry and is made up of epidermal, vascular, parenchymatous and collenchymatous tissues. Stato-liths, which are confined to parenchyma cells around the vascular bundles, sediment owards the gravita-tional field within 10-15 min of geotropic stimulation. Collenchymatous cells occur as prominent bundle caps, and in Arena, they occupy about 30 % of the volume of the Pulvinus. Geotropic stimulation causes a 3- to 5-fold increase in the length of the cells on the side nearest o the center of the gravitational field. Growth can also be initiated in vertically-held pulvini by the application of indole-3-acetic acid, 1-naphtha-leneacetic acid or 2.4-dichlorophenoxyacetic acid. 2.3.5-triiodobenzoic a id interferes with growth re-sponse produced by geotropic stimulation as well as with the response caused by auxin application. Gib-berellic acid and kinetin have no visible effect on the growth of the Pulvinus. Polarization microscopy shows a unique, non-uniform stretching of the elon-gating collenchymatous cells. Nonelongated collen-chymatoug cells appear uniformally anisotropic. After geotropic "stimulation or auxin application, they ap-pear alternately anisotropic and almost isotropic. Such a pattern of cell elongation is also observed in collenchyma cells of geotropically-stimulated shoots of Rurnex acetosa L., a dicotyledon. Abbreviations: 2.4-D=2.4-dichlorophenoxyacetic id; GA3=gib-berellic acid; IAA =indole-3-acetic acid; NAA = 1-naphtha-leneacetic a id; TIBA =2.3.5-triiodobenzoic ac
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A Role for Inositol 1,4,5-Trisphosphate in Gravitropic Signaling and the Retention of Cold-Perceived Gravistimulation of Oat Shoot Pulvini
Plant physiology, 2001Co-Authors: Imara Y. Perera, Ingo Heilmann, Wendy F. Boss, Soo Chul Chang, Peter B. KaufmanAbstract:Plants sense positional changes relative to the gravity vector. To date, the signaling processes by which the perception of a gravistimulus is linked to the initiation of differential growth are poorly defined. We have investigated the role of inositol 1,4,5-trisphosphate (InsP3) in the gravitropic response of oat (Avena sativa) shoot pulvini. Within 15 s of gravistimulation, InsP3 levels increased 3-fold over vertical controls in upper and lower Pulvinus halves and fluctuated in both Pulvinus halves over the first minutes. Between 10 and 30 min of gravistimulation, InsP3 levels in the lower Pulvinus half increased 3-fold over the upper. Changes in InsP3 were confined to the Pulvinus and were not detected in internodal tissue, highlighting the importance of the Pulvinus for both graviperception and response. Inhibition of phospholipase C blocked the long-term increase in InsP3, and reduced gravitropic bending by 65%. Short-term changes in InsP3 were unimpaired by the inhibitor. Gravitropic bending of oat plants is inhibited at 4°C; however, the plants retain the information of a positional change and respond at room temperature. Both short- and long-term changes in InsP3 were present at 4°C. We propose a role for InsP3 in the establishment of tissue polarity during the gravitropic response of oat pulvini. InsP3 may be involved in the retention of cold-perceived gravistimulation by providing positional information in the pulvini prior to the redistribution of auxin.
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Kinetic induction of oat shoot Pulvinus invertase mRNA by gravistimulation and partial cDNA cloning by the polymerase chain reaction
Plant molecular biology, 1993Co-Authors: Il Song, Nadarajah Karuppiah, Peter B. KaufmanAbstract:An asymmetric (top vs. bottom halves of pulvini) induction of invertase mRNA by gravistimulation was analyzed in oat shoot pulvini. Total RNA and poly(A)+ RNA, isolated from oat pulvini, and two oligonucleotide primers, corresponding to two conserved amino acid sequences (NDPNG and WECPD) found in invertase from other species, were used for the polymerase chain reaction (PCR). A partial length cDNA (550 bp) was obtained and characterized. A 62% nucleotide sequence homology and 58% deduced amino acid sequence homology, as compared to β-fructosidase of carrot cell wall, was found. Northern blot analysis showed that there was an obviously transient induction of invertase mRNA by gravistimulation in the oat Pulvinus system. The mRNA was rapidly induced to a maximum level at 1 h after gravistimulation treatment and gradually decreased afterwards. The mRNA level in the bottom half of the oat Pulvinus was significantly higher than that in the top half of the Pulvinus tissue. The kinetic induction of invertase mRNA was consistent with the transient accumulation of invertase activity during the graviresponse of the Pulvinus. This indicates that the expression of the invertase gene(s) could be regulated by gravistimulation at the transcriptional level. Southern blot analysis showed that there were two to three genomic DNA fragments which hybridized with the partial-length invertase cDNA.
A. Rieger - One of the best experts on this subject based on the ideXlab platform.
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Age-dependent changes of the ion content and the circadian leaf movement period in the Phaseolus Pulvinus
Journal of Biosciences, 1999Co-Authors: W. E. Mayer, B. Bok, A. RiegerAbstract:The circadian movement of the lamina of primary leaves ofPhaseolus coccineus L. depends on circadian changes of the K+, Cl- and (depending on the Cl- availability) malate content in the swelling and shrinking motor cells of the laminar Pulvinus. After sowing in soil, the laminar Pulvinus develops within about 26 days. When the leaves emerge from the soil (about 6 days after sowing) and the Pulvinus starts with the diurnal movement (about 9 days after sowing) the pulvinar dimensions are about half of those of the mature Pulvinus. The anatomical structure, however, is basically the same as in the developed Pulvinus. In soil-grown plants, the K+, Cl- and malate content as well as the period length of the circadian leaf movement rhythm change in the developing Pulvinus. In the embryo of the dry seed, the Cl- content is low (0.03 mmol g-1 DW), the K+ content, however, 22-fold higher than the Cl- content. When the leaves emerge from the soil, the pulvinar K+ and Cl- content is the same as in the whole embryo of the dry seed. In the developing Pulvinus the K+ content increases by a factor of 2 and the Cl- content by a factor of 41 in the mature Pulvinus. The pulvinar malate content increases between the 6th and 10th day from about 40 to 180Μmol g-1 DW, then decreases until the 17th day and remains thereafter on a low level (around 80 Μmol g-1 DW). These results indicate that the Cl- availability increases in the developing Pulvinus with age. It explains furthermore why in young leaves malate was found as counterion to K+ in the osmotic leaf movement motor, in older ones, however, Cl-. The circadian leaf movement starts 9 days after sowing. The period length decreases during the development of the Pulvinus from 31.3 to 28.6 h in leaves of intact soil-grown plants. In leaves which were cut from the plants and immersed with their petioles in distilled water, the age dependent decrease of the period length is also found. However, the period lengths are shorter by more than 1 h than in the leaves of intact plants. The increasing Cl- availability in the developing Pulvinus does not seem to be the cause for the age dependent shortening of the period length, because the period length in 22 days old Cl- deprived pulvini is the same as in 22 days old pulvini with a high Cl- content.
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Compartmentation of soluble carbohydrates, of starch and of malate in motor organs (pulvini) and other parts of Phaseolus coccineus L. leaves.
Planta, 1992Co-Authors: A. Rieger, A. Lutz, Rüdiger HamppAbstract:Quantitative histochemistry was used to investigate the tissue-specific compartmentation of soluble carbohydrates (sucrose, glucose, fructose), starch and malate in the laminar Pulvinus, leaf blade and petiole of Phaselous coccineus L. at day and night positions of diurnal leaf movement. Total carbohydrate levels measured in a series of cross sections along individual pulvini of 24-d-old plants showed only small differences between the day and night positions of the respective leaf. In contrast, the level of malate changed during diurnal leaf movement, especially in the central part of a Pulvinus. The levels of glucose and fructose in the Pulvinus increased towards the transition zones between the Pulvinus and lamina, and Pulvinus and petiole, and this trend was even more pronounced for starch. By contrast, sucrose levels were highest in the Pulvinus proper. The transverse compartmentation of metabolites was studied in distinct, approx. 0.5-mm-thick tissue slices from the central part of a Pulvinus. These were dissected further into up to 14 distinct subsamples (bundle, bundle sheath, motor tissues, flanks). Irrespective of the position of the leaf (day or night), the central vascular core and the surrounding bundle sheath had high levels of sucrose (up to 500 mmol-(kg DW)−1) and low levels of glucose and fructose (below 100 mmol-(kg DW)−1), while in the cortex the situation was reversed. In the night position the level of sucrose decreased by approx. 30% in the bundle sheath and the central vascular core but not in the other sections. We thus suggest that because of the relatively small diurnal changes in their cortical pools, soluble sugars are not involved in the osmotic processes resulting in leaf movement. In contrast, pulvini from 14-d-old plants showed an interesting diurnal change in starch and malate pools in the outermost layer of the extensor. Here starch increased at night while the malate pool was lowered nearly stoichiometrically. Inverse pool sizes were found in the day position of the respective leaves. Although less significant, the opposite diurnal variation occurred in samples taken from the flexor region. We thus were able to locate areas of different carbohydrate activities in the laminar Pulvinus of P. coccineus. The central vascular core, including the bundle sheath, is involved in temporary storage of photoassimilates, and the cortical regions are responsible for osmotically driven leaf movement. The results are discussed with respect to guard-cell physiology.
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Compartmentation of soluble carbohydrates, of starch and of malate in motor organs (pulvini) and other parts
1992Co-Authors: A. Rieger, A. Lutz, Rüdiger HamppAbstract:Quantitative histochemistry was used to inves tigate the tissue-specific compartmentation of soluble carbohydrates (sucrose, glucose, fructose), starch and malate in the laminar Pulvinus, leaf blade and petiole of Phaselous coccineus L. at day and night positions of diurnal leaf movement. Total carbohydrate levels mea sured in a series of cross sections along individual pulvini of 24-d-old plants showed only small differences between the day and night positions of the respective leaf. In contrast, the level of malate changed during diurnal leaf movement, especially in the central part of a Pulvinus. The levels of glucose and fructose in the Pulvinus in creased towards the transition zones between the pul vinus and lamina, and Pulvinus and petiole, and this trend was even more pronounced for starch. By contrast, sucrose levels were highest in the Pulvinus proper. The transverse compartmentation of metabolites was studied in distinct, approx. 0.5-mm-thick tissue slices from the central part of a Pulvinus. These were dissected further into up to 14 distinct subsamples (bundle, bundle sheath, motor tissues, flanks). Irrespective of the position of the leaf (day or night), the central vascular core and the surrounding bundle sheath had high levels of sucrose (up to 500 mmol-(kg DW) ~J) and low levels of glucose and fructose (below 100 mmol-(kg DW)-1), while in the cor tex the situation was reversed. In the night position the level of sucrose decreased by approx. 30% in the bundle sheath and the central vascular core but not in the other sections. We thus suggest that because of the relatively small diurnal changes in their cortical pools, soluble sugars are not involved in the osmotic processes resulting in leaf movement. In contrast, pulvini from 14-d-old plants showed an interesting diurnal change in starch and malate pools in the outermost layer of the extensor. Here starch increased at night while the malate pool was low ered nearly stoichiometrically. Inverse pool sizes were found in the day position of the respective leaves. Al though less significant, the opposite diurnal variation occurred in samples taken from the flexor region. We thus were able to locate areas of different carbohydrate activities in the laminar Pulvinus of P. coccineus. The central vascular core, including the bundle sheath, is involved in temporary storage of photoassimilates, and the cortical regions are responsible for osmotically driven leaf movement. The results are discussed with respect to guard-cell physiology.
Osamu Ueno - One of the best experts on this subject based on the ideXlab platform.
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Structure and immunocytochemical localization of photosynthetic enzymes in the lamina joint and sheath Pulvinus of the C_4 grass Arundinella hirta
Journal of Plant Research, 2013Co-Authors: Masataka Wakayama, Junichi Ohnishi, Osamu UenoAbstract:The C_4 grass Arundinella hirta exhibits a unique C_4 anatomy, with isolated Kranz cells (distinctive cells) and C_4-type expression of photosynthetic enzymes in the leaf sheath and stem as well as in the leaf blade. The border zones between these organs are pale green. Those between the leaf blade and sheath and between the sheath and stem are called the lamina joint and sheath Pulvinus, respectively, and are involved in gravity sensing. We investigated the structure and localization of C_3 and C_4 photosynthetic enzymes in these tissues. In both zones the epidermis lacked stomata. The inner tissue was composed of parenchyma cells and vascular bundles. The parenchyma cells were densely packed with small intercellular spaces and contained granal chloroplasts with large starch grains. No C_4-type cellular differentiation was recognized. Western blot analysis showed that the lamina joint and Pulvinus accumulated substantial amounts of phospho enol pyruvate carboxylase (PEPC), pyruvate,Pi dikinase (PPDK), and ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco). Immunogold electron microscopy revealed PEPC in the cytosol and both PPDK and rubisco in the chloroplasts of parenchyma cells, suggesting the occurrence of C_3 and C_4 enzymes within a single type of chlorenchyma cell. These data indicate that the lamina joint and Pulvinus have unique expression patterns of C_3 and C_4 enzymes, unlike those in C_4-type anatomy.
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structure and immunocytochemical localization of photosynthetic enzymes in the lamina joint and sheath Pulvinus of the c4 grass arundinella hirta
Journal of Plant Research, 2013Co-Authors: Masataka Wakayama, Junichi Ohnishi, Osamu UenoAbstract:The C4 grass Arundinella hirta exhibits a unique C4 anatomy, with isolated Kranz cells (distinctive cells) and C4-type expression of photosynthetic enzymes in the leaf sheath and stem as well as in the leaf blade. The border zones between these organs are pale green. Those between the leaf blade and sheath and between the sheath and stem are called the lamina joint and sheath Pulvinus, respectively, and are involved in gravity sensing. We investigated the structure and localization of C3 and C4 photosynthetic enzymes in these tissues. In both zones the epidermis lacked stomata. The inner tissue was composed of parenchyma cells and vascular bundles. The parenchyma cells were densely packed with small intercellular spaces and contained granal chloroplasts with large starch grains. No C4-type cellular differentiation was recognized. Western blot analysis showed that the lamina joint and Pulvinus accumulated substantial amounts of phosphoenolpyruvate carboxylase (PEPC), pyruvate,Pi dikinase (PPDK), and ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco). Immunogold electron microscopy revealed PEPC in the cytosol and both PPDK and rubisco in the chloroplasts of parenchyma cells, suggesting the occurrence of C3 and C4 enzymes within a single type of chlorenchyma cell. These data indicate that the lamina joint and Pulvinus have unique expression patterns of C3 and C4 enzymes, unlike those in C4-type anatomy.
