Ultrastructural Observations on Pinaceae Leaf Phloem I. The Spring Condition

Harris, William M.

doi:10.1111/j.1469-8137.1972.tb04824.x

Cited by 12 publications

(5 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Es liegen bislang nur einige Arbeiten iiber die Feinstruktur selbst von gesunden Koniferennadeln vor (z. B. PARAMESWARAN und LIESE 1970;PARAMESWARAN 1971;HARRIS 1971HARRIS , 1972CAMPBELL1972;CARDE1973, 1974CARDE1973, ,1978WALLES etal. 1973;CHABOT und CHABOT 1975), was eine vergleichende Bewerttuig teilweise erschwert.…”

Section: Diskussionunclassified

Feinstrukturelle Untersuchungen an Nadeln geschädigter Tannen und Fichten aus Waldschadensgebieten im Schwarzwald

Parameswaran

Fink

Líese

1985

European Journal of Forest Pathology

View full text Add to dashboard Cite

Fine structural studies on the needles of damaged fir (Abies alba Mill.) and spruce [Picea abies (L.) Karst.] trees from forest dieback areas in the Black Forest. The fine structural changes in the variously damaged needles of fir and spruee trees from forest dieback areas have been investigated with special reference to cytoplasmic organization in the vascular bundles, mesophyll tissue and cuticle. The results are compared with those available for a few plants affected both by natural and artifieial stress factors especially air pollutants.

show abstract

Section: Diskussionunclassified

Feinstrukturelle Untersuchungen an Nadeln geschädigter Tannen und Fichten aus Waldschadensgebieten im Schwarzwald

Parameswaran

Fink

Líese

1985

European Journal of Forest Pathology

View full text Add to dashboard Cite

show abstract

“…3 , which shows that groups of plasmodesmata with more or less extensive median cavities are typically combined in fields at all interfaces from mesophyll to phloem: mesophyll–endodermis-transfusion parenchyma–Strasburger cell-sieve element (Fig. 3a–e, g ; see also Parameswaran and Liese 1970 ; Boddi et al 2002 ; Carde 1974 , 1978 ; Gambles and Dengler 1982 ; Glockmann and Kollmann 1996 ; Harris 1972 ; Scholz and Bauch 1973 ; Walles 1973 ). While most plasmodesmata on the pre-phloem pathway are located in non-elevated primary pit fields, those linking Strasburger cells are located in conspicuous, dome-shaped wall thickenings (Fig.…”

Section: Branched Plasmodesmata Are Present At All Interfaces Of the mentioning

confidence: 93%

Symplasmic transport and phloem loading in gymnosperm leaves

2010

View full text Add to dashboard Cite

Despite more than 130 years of research, phloem loading is far from being understood in gymnosperms. In part this is due to the special architecture of their leaves. They differ from angiosperm leaves among others by having a transfusion tissue between bundle sheath and the axial vascular elements. This article reviews the somewhat inaccessible and/or neglected literature and identifies the key points for pre-phloem transport and loading of photoassimilates. The pre-phloem pathway of assimilates is structurally characterized by a high number of plasmodesmata between all cell types starting in the mesophyll and continuing via bundle sheath, transfusion parenchyma, Strasburger cells up to the sieve elements. Occurrence of median cavities and branching indicates that primary plasmodesmata get secondarily modified and multiplied during expansion growth. Only functional tests can elucidate whether this symplasmic pathway is indeed continuous for assimilates, and if phloem loading in gymnosperms is comparable with the symplasmic loading mode in many angiosperm trees. In contrast to angiosperms, the bundle sheath has properties of an endodermis and is equipped with Casparian strips or other wall modifications that form a domain border for any apoplasmic transport. It constitutes a key point of control for nutrient transport, where the opposing flow of mineral nutrients and photoassimilates has to be accommodated in each single cell, bringing to mind the principle of a revolving door. The review lists a number of experiments needed to elucidate the mode of phloem loading in gymnosperms.

show abstract

“…Since that time several other papers on gymnosperm phloem ultrastructure have appeared, all using the now standard doublefixation with aldehydes and osmium (Wooding, 1968;Murmanis and Evert, 1967;Harris, 1972;Campbell, 1972;Parameswaran, 1971;Evert, et ai., 1973;Behnke and Palival, 1973;Neuberger and Evert, 1974;Sauter, 1977;Sauter, et ai., 1976). These studies have shown that the various gymnosperm species have many common phloem characteristics.…”

Section: ·132mentioning

confidence: 99%

“…Some authors contend that plastid materials are released as a result of fixation-induced lysis (Wooding, 1968;135 Behnke, 1974;Evert, 1974, 1976). However, it has also been suggested that some plastids lose membrane integrity during differentiation and plastid contents become dispersed naturally (Srivastava and O'Brien, 1966b;Harris, 1972;Parameswaran, 1971;Gamaley, 1973;Sauter, 1977). Some investigators have related the fine fibrils seen in mature sieve cells to the fibrillar P-protein found in dicots (Murmanis and Evert, 1966;Campbell, 1972;Sauter, 1977) without recognizing their possible plastid origin.…”

Section: ·132mentioning

confidence: 99%

Morphological and cytological studies on Arceuthobium (Viscaceae) in relationship to host phloem with studies on the healthy phloem in Pinus sabiniana (Pinaceae)

Alosi¹

2000

View full text Add to dashboard Cite

Anatomical and developmental tissue relationships between Arce~thobium spp. endophytic tissues and host vascular tissues were examined by light and transmission electron microscopes. The host-parasite pairs studied were Psudotsuga menziesii/A. douglasii, Tsuga heterophylla/A. tsugense, Pinus sabiniana/A. occidentale, and P. lambertiana/A. californicum.The morphological form and growth characteristics of A. douglasii in different aged host tissues was found to be coordinated with growth and maturation of the host. It is proposed that morphological forms of Arceuthobiwn endophytic tissue be categorized as 1) primary, 2) diffuse-secondary, or 3) localized-secondary in order to semantically clarify the relationship of endophytic morphology with primary or secondary growth stages of host tissue.In localized-secondary endophytic forms, the parasite integrates with host rays to form multiseriate infected rays. At both the light and electron microscope level, parasite cells can usually be identified by their distinctive chromocentric nuclei and abundant lipid bodies or lipid ghosts. Sinker cells of Arce~thobium have unusual plastids which resemble etioplasts and which do not store starch. Sinker cells have distinctive mitochondria with unusually large nucleoid areas. They have abundant endoplasmic reticulum. Wall/plasmalemma specializations increase the membrane surface area in relation to cell volume in sinker cells.The walls of host and parasite are fused at the middle lamella common to both organisms and the organisms share a common apoplast. Pit-like regions in the fused walls of the host/parasite interface were commonly seen in light microscope studies, although such interspecific pitting is seen less than intraspecific pitting. It was determined that, whereas intraspecific pits are traversed by complete plasmodesmata, interspecific pits had no plasmatic channels, or, only half plasmodesmata on the host side of the pit. In one case a half plasmodesmata was seen on the Arceuthobiwn side of the host/parasite interface.On the basis of the electron microscope studies of the host/parasite interfaces it appears that plasmatic connections between host and parasite do not normally occur. Because of this plasmatic isolation it can be concluded that nutrient acquisition does not involve direct flow of nutrients via interspecific symplastic bridges. Therefore, photosynthate, normally housed within phloem cells, must be leaked into the common apoplast of both host and parasite before becoming available for absorption 3 into the parasite symplast. Since host and parasite lack symplastic continuity but share a common apoplast, apoplastically-mobile herbicides should be tested for their ability to accumulate in parasite tissues. 4 Cytopathological effects on the host cells were relatively mild although a significant increase in the ratio of radial to axillary vasculature was noted in infected tissue. other modifications included a tendency for increased numbers of specialized phloem parenchyma (Strasburger cells) in infected ra...

show abstract

Ultrastructural Observations on Pinaceae Leaf Phloem I. The Spring Condition

Cited by 12 publications

References 21 publications

Feinstrukturelle Untersuchungen an Nadeln geschädigter Tannen und Fichten aus Waldschadensgebieten im Schwarzwald

Feinstrukturelle Untersuchungen an Nadeln geschädigter Tannen und Fichten aus Waldschadensgebieten im Schwarzwald

Symplasmic transport and phloem loading in gymnosperm leaves

Morphological and cytological studies on Arceuthobium (Viscaceae) in relationship to host phloem with studies on the healthy phloem in Pinus sabiniana (Pinaceae)

Contact Info

Product

Resources

About