Ultrastructure and development of seedlings of the parasitic weedCuscuta japonica

2009

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The endophyte, that is, the haustorial part within the tissues of the host plant Impatiens balsamina, of the parasitic angiosperm Cuscuta japonica was studied with light and electron microscopy. The endophyte consisted mainly of vacuolated parenchymatous axial cells and elongate, superficial (epidermal) cells. Then the elongate, epidermal cells separated from each other and transformed into filamentous cells, called searching hyphae. The hyphae grew independently either intercellularly or intracellularly in the host parenchyma. The apical end of the hyphal cells was characterized by conspicuous, large nuclei with enlarged nucleoli and very dense cytoplasm with abundant organelles, suggesting that the hyphal cells penetrating host tissue were metabolically very active. Numerous osmiophilic particles and chloroplasts were noted in the hyphae. The osmiophilic particles were assumed to be associated with elongation of the growing hyphe. Plasmodemata connections between the searching hyphal cells of the parasite and the host parenchyma cells were not detected. Hyphal cells that reached the host xylem differentiated into water-conducting xylic hyphae by thickening of the secondary walls. A xylem bridge connecting the parasite and the host was confirmed from serial sections. Some hyphal cells that reached the host phloem differentiated into nutrient-conducting phloic hyphae. Phloic hyphae had a thin layer of peripheral cytoplasm with typical features of sieve-tube members in autotrophic angiosperms, i.e., parallel arrays of smooth endoplasmic reticulum, mitochondria, and plastids with starch granules. Interspecific open connections via the sieve pores of the host sieve elements and plasmodesmata of the parasite phloic hyphae were very rarely observed, indicating that the symplastic translocation of assimilate to the parasite from the host occurred.

mentioning

confidence: 99%

Structure and Development of the Endophyte in the Parasitic Angiosperm Cuscuta japonica

2009

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“…When some of those seedlings were grown for an additional 3 d in the light, the chloroplasts from their shoot subapical cells revealed crystalline inclusions with a latticed substructure within their thylakoid lumens. These inclusions in the longitudinally sectioned thylakoids corresponded to the electron-dense material previously reported from the lumens of transversely sectioned thylakoids (Lee, 2007: personal communication with Dr. Brian E. S. Gunning, Australian National University). Therefore, this current study is the first to describe two different images of thylakoid content generated from the chloroplasts of C. japonica.…”

Section: Etioplasts With Prolamellar Bodies and Electron-dense Inclusmentioning

confidence: 99%

“…1C, 2A, 3A) as a result of the light-induced conversion of etioplasts into chloroplasts. Therefore, one might suggest that the photosynthetic capability of these Cuscuta seedlings may ensure their survival until they can parasitize the host plant (Lee, 2007).…”

Section: Etioplasts With Prolamellar Bodies and Electron-dense Inclusmentioning

confidence: 99%

“…The mature embryo cells from the C. japonica contain a reserve of numerous lipid and protein bodies, as well as proplastids with a few thylakoids and phytoferritin (Lee, 2006). Furthermore, the shoot subapical cells of 3-d-old dark-grown seedlings have etioplasts with prolamellar bodies, which develop into chloroplats with thylakoids that were well organized into grana from 6-d-old seedlings grown in the light for the last 3 d (Lee, 2007). He has also found that thylakoid lumens of the chloroplasts are filled with electron-dense materials.…”

mentioning

confidence: 99%

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Ultrastructure of crystalline inclusions in the thylakoids of dodder(cuscuta japonica) plastids

2007

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The plastids from seedlings of the parasitic angiosperm Cuscuta japonica were ultrastructurally investigated. In shoot subapical cells from 3-d-old seedlings grown in the dark, the etioplasts contained prolamellar bodies and amorphous and dense inclusions. In the shoot subapical cells obtained from 6-d-old seedlings grown under light conditions for the last 3 d, the underdeveloped chloroplasts contained phytoferritin within the stroma as well as amorphous and dense inclusions that were limited by the thylakoid membranes. In the developing chloroplasts, electron-dense materials were detected within the transversely sectioned thylakoid lumens. This dense material presented two different images, depending upon the sectional plane. When transversely prepared, the materials appeared as somewhat thick, linear structures, whereas longitudinally sectioned thylakoids revealed very large crystalline inclusions. In the developed chloroplasts, the amounts of electron-dense material or crystalline inclusions were remarkably reduced in the thylakoid lumens, which were electron-translucent. Far fewer crystalline inclusions were observed in the developed chloroplasts of seedlings than in the developing chloroplasts. These results suggest that the crystalline inclusions may be temporarily reserved within the thylakoid lumens of chloroplasts in the C. japonica seedlings.

Anatomy and ultrastructure of epidermal cells in the haustorium of a parasitic flowering plant,Cuscuta japonica, during attachment to the host

2008

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Changes of epidermal cells in the haustorium of the parasitic Cuscuta japonica during its attachment to the host plant Impatiens balsamina were studied with light and electron microscopy. In the transverse sections of dodder stems not in contact with the host, epidermal cells had rounded outlines. However, when haustorial initials developed in the cortex of the parasite stem at the contact site, the epidermal cells had more dense cytoplasm and conspicuous nuclei than before, and their outline was fiat in the longitudinal section. As meristem cells developed from those initials, the epidermal cells became more elongated. When the haustorium was folly matured, the apical tips of the elongated epidermal cells at the contact site branched like toes, producing numerous projections via cell wall invaginations. This event caused spaces to form between the projections; coincidently, the surface area of the apical ends of the epidermal cells increased. The dense cytoplasm at those projections contained prominent nuclei and abundant other organelles, suggesting a active metabolism. Osmiophilic particles, releasing into the cell walls from the cytoplasm, were though to be associated with the loosening and elongating of the epidermal cell walls. Dense and homogeneous materials were secreted within the spaces between the projections. These materials could play an important role in cementing the haustorium onto the surface of the host organ.