摘要:

The gametophyte growth, morphology, gametogenesis, and metabolites ofLaminaria saccharina(L.) Lamouroux were studied in different cyncentrations of nitrate and phosphate in axenic culture, using a synthetic seawater medium under optimal light and temperature conditions.Nitrate and phosphate were required for the various stages of gametophyte development and gametogenesis. Under nitrate and phosphate concentrations optimal for growth and gametogenesis, maximum quantities of DNA, RNA, protein, and carbohydrate, and low quantities of lipid were produced. Further, nutrient concentrations which gave rise to the greatest fertility also gave rise to the highest ratios of RNA/DNA and protein/RNA.Antheridial production occurred over a wider range of nitrate and phosphate concentrations than oogonial production. Further, percentage fertility was greater for the male gametophyte. This indicated that the female gametophyte was the limiting agent in sexual fusion.

ISSN:0008-4026    

DOI:10.1139/b73-106

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A closed gas exchange system was used to survey the apparent rates of photosynthesis by young wheat shoots in a wide range of O2concentrations (O2), CO2concentrations (CO2), temperatures (T), and radiant flux densities. The results are expressed graphically and by equations. The carbon dioxide compensation point (ΓH) conformed to the equation ΓH = O2e(0.0428T − 12.1). The relationship between the apparent rates of photosynthesis in the presence (PH) and absence (PL) of inhibitory concentrations of oxygen was described by the equationPH = PLkloge(CO2/ΓH) wherekwas independent of the prevailing environmental conditions and.

ISSN:0008-4026    

DOI:10.1139/b73-107

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Exudates and purified preparations of leaves infected withDaturashoestring virus (DSV) contained particles 720–750 × 16 nm. Light microscopy of DSV-infectedDatura metelleaves showed that the shoestring portions consisted mainly of midrib, with the tissues arranged as in healthy leaves, but without a lamina. Ultrathin sections of shoestring portions ofD. metelleaves, and of laminae from infected leaves ofD. metel, Nicotiana glutinosa, andN. debneyl, contained cytoplasmic lamellar inclusions as dense bands and pinwheels, in all parenchymatous tissues, and often in X-bodies. Long, rod-shaped particles were frequently arranged in regular array along the arms of the lamellar inclusions. Structures composed of ribosome-like particles were often found arranged regularly in an alternating double row in the cytoplasm. Nuclei contained tubular inclusions with an outside diameter of 35–40 nm. The classification of DSV, which is not serologically related to potato virus Y, is discussed, and it is suggested that the present practice of classifying any virus that induces formation of lamellar inclusions, regardless of size or serological relationships, in the PVY group is misleading. A proposed alternative to this practice, with a purely descriptive basis, is that all such viruses be called lamellar inclusion forming (LIF) viruses.

ISSN:0008-4026    

DOI:10.1139/b73-108

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The megaspore mother cell of sunflowerHelianthus annuusL. undergoes two meiotic divisions to form a linear tetrad of haploid megaspores. The chalazal megaspore increases in size while the other megaspores and the nucellus degenerate such that the integumentary tapetum is adjacent to the embryo sac. Mitotic divisions occur forming the coenocytic two- and four-nucleate embryo sacs and the seven- or eight-nucleate six-celled embryo sac. Electron-microscopic observations suggest that the antipodals are very active synthetically but start degenerating before fertilization. Similarly the synergids are also apparently very active synthetically before fertilization as judged by the presence of extensive regions of dilated rough endoplasmic reticulum and many Golgi bodies and associated vesicles. The egg cell is characterized by the presence of many free ribosomes and small undifferentiated plastids. The central cell contains many circular strands of rough endoplasmic reticulum, lipid droplets, and large clusters of apparently active Golgi; it is a transfer cell resulting from the presence of embryo sac wall ingrowths. The development and the possible nutritional interrelationships of the megagametophyte and surrounding tissues are discussed.

ISSN:0008-4026    

DOI:10.1139/b73-109

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The degeneration of one synergid denotes the initiation of embryo and endosperm development in the embryo sac of sunflowerHelianthus annuusL. The other synergid, the persistent synergid, is present until the late globular stage of embryogenesis. The primary endosperm nucleus divides before the zygote nucleus forming a coenocytic nuclear endosperm. When about eight endosperm nuclei are present during the early globular stage of embryogenesis, endosperm wall formation starts at the micropylar end of the embryo sac. The walls continue to grow toward the chalazal end of the embryo sac apparently as a result of the activity of Golgi located at the tips of the growing walls. Most endosperm wall formation is not associated with a mitotic spindle apparatus in sunflower. The suspensor of the embryo consists of a large basal cell during the proembryo stages, a single row of cells during the early globular stages, and at the late globular stage a double tier of cells near the radicle end of the embryo and a single row at the micropylar end of the embryo sac. Occasionally embryo development occurs in the absence of endosperm when only single fertilization has taken place. The development and nutritional implications of post-fertilization events in the sunflower embryo sac are discussed.

ISSN:0008-4026    

DOI:10.1139/b73-110

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The flower ofRanalisma humileis comparable in morphology to those of other alismads. The vascular anatomy is noteworthy. Flowers ofR. humileare provided with a major (central) vascular system supplying androecial and gynoecial vasculature and a variable amount of the sepal and petal vasculature, and a minor (peripheral) system which supplies the rest of the perianth vasculature. There is very little anastomosis between the two systems. It is suggested that the variability of perianth vascular supply reflects variability in timing of differentiation events. The occurrence of an almost independent peripheral vascular system is probably of significance in a consideration of the relationship ofRanalisma humileto other alismads.

ISSN:0008-4026    

DOI:10.1139/b73-111

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The development of the foliage leaf bearing axes inRanalisma humile(Kunth.) Hutch. andHydrocleis nymphoidesBuch. is similar in that both show sympodial development, each branch of the sympodium terminating in an inflorescence; inButomus umbellatusL. the inflorescence is lateral and the vegetative axis is monopodial.Inflorescences ofRanalismacan adopt a horizontally growing pseudostolon form in which floral meristems are formed but abort at an early stage; there is no basic difference between the organ complements of the pseudostolon and the erect inflorescence.Inflorescences ofHydrocleisandRanalismahave similar developmental patterns. In both, the main axis terminates in a floral primordium while a large bud is developed in the axil of the first of two bracts below the flower. The lateral bud inHydrocleisdevelops into a sympodial bud complex consisting of flowers, a vegetative bud, and an inflorescence branch which repeats the pattern of development; inRanalismathe lateral bud gives rise only to a vegetative bud and an inflorescence branch.Ranalismaappears to possess a reduced form of the kind of inflorescence development found inHydrocleis.The inflorescence ofButomusalso terminates in a flower. It has three bracts, each subtending a set of multiple axillary buds. Each individual bud develops into a sympodially arranged set of flowers.Previously proposed isolation ofButomusfrom other Butomaceae and Alismataceae is further emphasized by developmental data.Ranalismaprovides a connecting link between Alismataceae and the Butomaceae excludingButomus(i.e. the Limnocharitaceae of some authors).

ISSN:0008-4026    

DOI:10.1139/b73-112

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Light-grown seedlings of 88 species of legumes were examined for anthocyanins. No red pigmentation developed in 22 species. In nearly all the 66 pigmented species, the red color was subepidermally located. Pigment determination of 40 species showed cyanidin glycosides to be the most common. In five of seven species ofPhaseolusand the closely relatedGlycine max, however, malvidin glucoside was predominant. In four of five species ofViciaas well as in two species ofPhaseolus, delphinidin glycosides were the major pigments.

ISSN:0008-4026    

DOI:10.1139/b73-113

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The portion of theCastillejasecondary haustorium external to host tissues was investigated at the light- and electron-microscopic levels. One or more haustoria may be present along a single lateral root; however, primary roots ofCastillejamay also have haustoria. A localized development of root hairs usually precedes haustorial formation. The first sign of haustorial formation is the swelling of root cortical cells which gives rise to a nearly spherical structure. Eventually, the haustorial epidermis is obliterated at the contact surface between parasite and host. The upper haustorium has a complex internal structure consisting of several distinct cell zones. The pericycle gives rise to a parenchymatous zone of cells adjacent to the plate xylem. Later, collenchyma differentiates in the center or core of the haustorium and is surrounded by a cortical zone of parenchyma cells. This is the first report of collenchyma tissue in a haustorium of any parasite. Thus, a matureCastillejahaustorium consists of a plate xylem zone, an adjacent parenchymatous zone, a centrally located collenchyma zone, and a peripheral cortical zone. The endophyte is initiated from hypodermal parenchymatous cells located between the collenchyma core and the haustorial surface. Lipid is abundant in the young endophyte and paramural bodies are common in many cells. Strands of vessel members differentiate at random and are sheathed by thin-walled densely cytoplasmic cells. Vessel members occur within the collenchyma zone as well, and frequently contain starch and other coarsely granular materials. No phloem was found in the upper haustorium ofCastilleja. The upper haustorium ofCastillejaand of other members of the Scrophulariaceae are compared.

ISSN:0008-4026    

DOI:10.1139/b73-114

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The portion of theCastillejahaustorium within the host, the endophyte, was examined at the light-and electron-microscopic levels. The endophyte consists of a stalk of lipid-containing cells and digitate cells at its tip. Vessels run the length of the endophyte. There is a harmonious meshing between host cortical cells and those of the endophyte flank, suggesting that penetration is accomplished, in part, by cell dissolution. Crushing of cells also occurs during endophyte invasion as host phloem tissues are severely buckled and cell walls are greatly folded. Some features of digitate cells include dense cytoplasm, an abundance of endoplasmic reticulum, lateral walls that are thickened as well as those on the side adjacent to the host, and an ability to conform to the contours of host tissues. Often digitate cells are divided by very thin walls that are hardly visible under the light microscope. It is suggested that the thick cell walls may function as "free space" in the absorption of materials from the host. Within the endophyte, vessels differentiate and may contain either a finely granular, dark-staining material or a more coarsely granular, light-staining material. The particles of the latter have irregular shapes. Although granular materials are thus carried by some vessels, cells resembling the structurally intermediate "phloeotracheids" were not seen. Connections through the cell wall were not observed between parasite and host; however, within the endophyte plasmodesmata were highly branched and often contained median nodules. Transfer-like cells which have irregularly thickened walls occurred in the endophyte. Host tissues next to digitate cells appeared to be in a degraded state. Invaginations of the plasmalemma were common and small flattened vesicles were formed in some host cells from the disrupted tonoplast. In several instances, the cytoplasm had receded from the host cell wall and a "beaded" material was present in both vacuoles and large vesicles. The host cell wall at times had a very loose fibrillar appearance. Some host tracheids were occluded with a dense and dark-staining material. The xylem strands of the parasite are connected to the host xylem either by cell wall dissolution or by actual penetration of a digitate cell into a host xylary cell. The penetrating cell subsequently differentiates into a vessel member. A summary and general discussion are given to relate the two portions of the haustorium, the upper haustorium and the endophyte. The mass of new information gained in this study leads us to encourage the application of plastic embedding and sectioning techniques to further light-microscope studies on haustoria.

ISSN:0008-4026    

DOI:10.1139/b73-115

出版商:NRC Research Press    

年代:1973

数据来源: NRC