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Sieve Tubes (sieve + tubes)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Immunolocalization and Histocytopathological Effects of Xanthomonas arboricola pv. pruni on Naturally Infected Leaf and Fruit Tissues of Peach (Prunus persica L. Batsch)

JOURNAL OF PHYTOPATHOLOGY, Issue 6 2008
J. Aarrouf
Abstract Immunofluorescence and cytohistochemical studies have been performed to understand the host,parasite relationships in the pathosystem: peach,Xanthomonas arboricola pv. pruni (Xap). Using a commercial immunodetection kit, Xap cells were specifically identified in tissues from infected leaves and fruits. Sections from infected leaves showed that the pathogen penetrates the mesophyll via stomata and develops in the intercellular spaces where it degrades the cell wall components. This leads to cell collapse and consequently to the formation of necrotic lesions. The same events have been noted in sections from infected fruits. However, the contaminated zones of mesocarp parenchyma exhibited cell dedifferentiation and generated somatic embryo-like structures. Sections from midrib samples collected at different distances from infected lamina revealed the presence of Xap cells in the sieve tubes and xylem suggesting a systemic trafficking of the pathogen. The results are discussed in terms of cytological effects and epidemiology of Xap. [source]

Detection of Phytoplasma Infection in Rose, with Degeneration Symptoms

JOURNAL OF PHYTOPATHOLOGY, Issue 1 2001
M. Kami
In 1998 a severe disease was observed on rose cvs. ,Patina', ,Papillon' and ,Mercedes' cultivated in a commercial greenhouse in Poland. The symptoms included stunted growth, bud proliferation, leaf malformation and deficiency of flower buds. Sporadically some plants yielded flower buds transformed into big-bud structures and degenerated flowers. The presence of phytoplasma in roses with severe symptoms as well as in recovered plants and Catharanthus roseus experimentally infected by grafting and via dodder was demonstrated by nested polymerase chain reaction assay with primers pair R16F2/R2 or R16F1/R0 and R16(I)F1/R1 amplifying phytoplasma 16S rDNA fragment. The polymerase chain reaction products (1.1 kb) used for restriction fragment length polymorphism analysis after digestion with endonuclease enzymes AluI and MseI produced the same restriction profiles for all samples. The restriction profiles of phytoplasma DNA from these plants corresponded to those of an aster yellows phytoplasma reference strain. Electron microscope examination of the ultra-thin sections of the stem showed wall thickenings of many sieve tubes of the diseased roses and single phytoplasma cells within a sieve element of the phloem of experimentally infected periwinkles. This paper is the first report on aster yellows phytoplasma in rose identified at a molecular level. Detektion einer Phytoplasma-Infektion bei Rosen mit Degenerationserscheinungen Im Jahr 1998 wurde eine schwere Krankheit bei Rosen der Sorten ,Patina', ,Papillon' und ,Mercedes' festgestellt, die in einem polnischen Gewächshaus für kommerzielle Zwecke kultiviert wurden. Zu den Symptomen gehörten Kümmerwuchs, durchwachsene Knospen, Blattmißbildungen und ein Mangel an Blütenknospen. Einige wenige Pflanzen trugen übergroße Blütenknospen, die degenerierte Blüten hervorbrachten. Die Anwesenheit von Phytoplasmen in Rosen mit starken Symptomen, in erholten Pflanzen und in Catharanthus roseus, der durch Pfropfen und durch Teufelszwirn (Cuscuta) experimentell infiziert worden war, wurde mittels einer genesteten Polymerase-Kettenreaktion mit den Primerpaaren R16F2/R2 oder R16F1/R0 und R16(1)F1/R1 zur Amplifikation des Phytoplasma-16S rDNA-Fragments demonstriert. Die für die Analyse der Restriktionsfragmentlängenpolymorphismen nach Verdau mit den Endonucleasen AluI und MseI verwendeten PCR-Produkte (1,1 kb) produzierten bei allen Proben die gleichen Restriktionsprofile. Die Restriktionsprofile der Phytoplasma-DNA aus diesen Pflanzen entsprachen denjenigen eines Typenstamms eines Asternvergilbung auslösenden Phytoplasmas. Elektronenmikroskopische Untersuchungen ultradünner Schnitte des Stamms zeigten Wandverdickungen bei zahlreichen Siebröhren der erkrankten Rosen und einzelne Phytoplasmazellen innerhalb eines Siebelements des Phloems experimentell infizierter Immergrün-Pflanzen. Dies ist der erste Bericht über ein auf molekularer Ebene identifiziertes Asternvergilbungs-Phytoplasma bei Rosen. [source]

Effects of cold-girdling on flows in the transport phloem in Ricinus communis: is mass flow inhibited?

PLANT CELL & ENVIRONMENT, Issue 1 2006
ANDREAS D. PEUKE
ABSTRACT The effects of cold girdling of the transport phloem at the hypocotyl of Ricinus communis on solute and water transport were investigated. Effects on the chemical composition of saps of phloem and xylem as well as of stem tissue were studied by conventional techniques and the water flow in the phloem was investigated by NMR imaging. Cold girdling reduced the concentration of sucrose but not that of inorganic solutes or amino acids in phloem saps. The possibility that cold treatment inhibited the retrieval of sucrose into the phloem, following leaching from the sieve tubes along a chemical gradient is discussed. Leaching of other solutes did not occur, as a result of missing promoting gradients in stem tissue. Following 3 d of cold girdling, sugar concentration increased and starch was synthesized and accumulated in stem tissue above the cold girdling region and along the cold-treated phloem pathway due to leaching of sugars from the phloem. Only in the very first period of cold girdling (< 15,30 min) was mass flow inhibited, but recovered in the rest of cold treatment period to values similar to the control period before and the recovery period after the cold treatment. It is concluded that cold treatment affected phloem transport through two independent and reversible processes: (1) a permanent leaching of sucrose from the phloem stem without normal retrieval during cold treatment, and (2) a short-term inhibition of mass flow at the beginning of cold treatment, possibly involving P proteins. Possible further mechanisms for reversible inhibition of water flow are discussed. [source]

Seasonal detection of pear decline phytoplasma by nested-PCR in different pear cultivars

PLANT PATHOLOGY, Issue 4 2003
M. Garcia-Chapa
Seasonal detection of pear decline phytoplasma was studied in three pear cultivars: Bartlett, Limonera and Blanquilla. Samples from 43 infected trees were collected monthly over 2 years and analysed by nested PCR. The three cultivars each showed a different pattern of phytoplasma detection. The maximum detection rate of pear decline phytoplasma occurred in December in the three orchards, and it remained high throughout the winter months. In spring, when new buds appeared and sap was produced, the detection rate decreased. Leaf midribs, buds and stems were compared to determine which sample was more reliable for phytoplasma detection. The best indicators were stems. The presence of phytoplasma in sieve tubes during the dormant season was determined by grafting. The results suggest that phytoplasmas could overwinter in shoots, with the implication that vegetative propagation during this period could also disseminate the disease. [source]