摘要:

An in‐depth transmission electron microscope study of the ungerminated, unimbibed rice germ was conducted. All tissues in the germ were examined. Plastids were similar in all cells; many contained osmiophilic globules and phytoferritin, some displayed a limited thylakoid system, and all contained cytoplasmic tubular and vesicular inclusions formed by invaginations of the outer plastid membranes. Filament bundles were found in cells of the coleoptile, plumule, mesocotyl, radicle, and epiblast. Three general categories of cells could be identified in the germ based on protein body characteristics and on lipid body distribution: 1) Cells having inclusions in protein bodies and having numerous lipid bodies scattered throughout the cytoplasm; 2) Cells having or lacking protein body inclusions and possessing peripheral lipid bodies and/or having electron‐dense deposits in the lipid bodies; and 3) Cells lacking protein bodies and having peripheral lipid bodies.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb10838.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The range of variability in the taxonomic characteristics traditionally used to establish genera and species ofSphenophyllumcones is studied from specimens ofBowmanites dawsoni, B. trisporangiatus, B. bifurcatus, Litostrobus, andSphenostrobus.Taxonomic criteria examined include configuration of the cone stele, number of sporangiophores per bract, anatropous vs. orthotropous sporangium attachment, number of appendages per node, and spore morphology. Because of the large degree of variability observed, these characteristics do not appear to adequately differentiate between the generaLitostrobusandSphenostrobus, so these genera are combined underSphenostrobus.A new combination,S. iowensis, is proposed for specimens previously described asL. iowensis, L. paulus, andB. moorei.It is suggested that species currently placed in the genusBowmanitesmay represent several distinct natural genera of sphenophyllalean cones.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb10839.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The protoplast of the non‐articulated branched laticifer in the embryo and seedling ofAsclepias syriacaL. was studied at the ultrastructural level and was found to differ from that of adjacent cell types. Embryonal laticifers possess numerous vesicles with electron‐dense contents, but lack a large organized central vacuole. Plastids have few lamellae, possess phytoferritin, and accumulate small amounts of starch. Other organelles and membrane systems are similar to those in other cells. After germination, laticifers develop numerous elongated vacuoles by dilation of endoplasmic reticulum. Nuclei in laticifers within the hypocotyl of seedlings are highly lobed and possess dilated perinuclear spaces. Plastids and other organelles are similar to those observed in the protoplast of laticifers in the embryo. The latex or rubber component of the laticifer is not apparent in mature embryos of 72‐hr seedlings.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb10840.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The presence of paracytic stomata and paired guard cells on specimens presumed to beDrepanophycus spinaeformisGöppert from eastern Canada and New York State supports the conclusion of Banks and Grierson that the species is not a reliable index of Lower Devonian strata. The interpretation of stomatal morphology demonstrates that the species lived in Early, Middle, and Late Devonian time and that slender specimens are distinct from zosterophylls such asSawdoniathat had anomocytic stomata and a single guard cell. Knowledge of the stomata also permits a reinterpretation of the stomatal apparatus as first described by Lang. Siegenian specimens of the genus apparently represent the oldest occurrence of paired guard cells and of paracytic stomata.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb10841.x

出版商:Wiley    

年代:1978

数据来源: WILEY

摘要:

The ontogenetic and phylogenetic significances of the postgenital carpel fusion inCatharanthus roseuswere investigated experimentally. When one of the two carpel primordia was surgically destroyed prior to carpel fusion, the remaining carpel differentiated nevertheless; however, the tissue development on the adaxial (normally fused) carpel face appeared aberrant. Possible reasons for this modified ontogeny are discussed. The suggestion that syncarpy is phylogenetically significant because any pollen tube can potentially reach any ovule was verified inC. roseusby monitoring pollen tube growth following spatially controlled pollinations. The suture formed by the postgenital fusion was no barrier to pollen tube growth, and the pollen tubes rapidly became distributed throughout the stigmatic tissue.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb10842.x

出版商:Wiley    

年代:1978

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb10843.x

出版商:Wiley    

年代:1978

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb10844.x

出版商:Wiley    

年代:1978

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1978.tb10827.x

出版商:Wiley    

年代:1978

数据来源: WILEY