摘要:

Ultrastructural examination of a green-pigmented mutant of the red algaPalmaria palmata(L.) O. Kuntze revealed unusual features of the chloroplasts. Encircling peripheral thylakoids, characteristic of the wild-type plastids and florideophyte plastids generally, were lacking. Parallel evenly spaced thylakoids occurred in groups, leaving large volumes of thylakoid-free stroma. Irregularly shaped, electron-dense inclusions with an amorphous substructure and diameters up to 3 μm occurred in some plastids. Cells of the sporeling holdfasts contained structures resembling prolamellar bodies. Attempts to induce formation of prolamellar bodies in blades by dark treatment for 5 weeks were unsuccessful. However, some plastids did develop highly corrugated thylakoids with the crests of one thylakoid apposed to the troughs of the adjacent thylakoid. Thylakoid morphology of the wild-type control was not altered by the absence of light.

ISSN:0008-4026    

DOI:10.1139/b84-153

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Increasing the period of dark storage (DS) within a uniform seed lot of lettuce(Lactuca sativaL. cv. Grand Rapids) increased the degree of secondary dormancy (skotodormancy) induced, as evidenced by a loss of sensitivity to red light (R) and growth promoters such as gibberellin A3(GA3), kinetin, thiourea, and ethylene. Differential degrees of skotodormancy were induced in lettuce seeds from three different sources (lot I < lot II < lot III). Either R or GA3significantly increased the germination of skotodormant seeds if seeds were first immersed in strongly acidic solutions (pH ≤ 3.0) and then rinsed with water. The critical factor was found to be pH, not ionic strength. Promotion of germination by R or GA3was positively related to increasing acidity, and also to the duration of DS. Sensitivity of the germination response to acid immersion varied with the seed lots, as little as 1 s being effective with some seeds. Acid treatment thus enables skotodormant seeds to recover much of their responsiveness to R and GA3. Extended DS (21 days) produced such pronounced skotodormancy (seed lot III) that acid immersion followed by usual R and GA3produced only 10% germination. Continuous R or a seed-piercing treatment produced complete germination in otherwise skotodormant seeds. Responsiveness of germination to thiourea, kinetin, and ethylene, however, was not regained by treatment with acid. The action of these three chemicals on skotodormant seeds thus seems to be dependent on an active phytochrome and GA3-sensitive system. Acid-immersion treatments appear primarily to weaken membrane barriers of the endosperm cells, with resulting increased sensitivity of seeds to R treatment and GA3penetration.

ISSN:0008-4026    

DOI:10.1139/b84-154

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Several forms of extracellular crystals have been observedin vitroon a semisynthetic culture medium. The conditions for their formation have not been determined. Their morphology and their localisation on the hyphal surface and in the culture medium have been investigated by means of scanning electron microscopy. These crystals have been identified as dehydrated calcium oxalate (Weddellite) using x-ray diffraction methods. Their high calcium content has been demonstrated with the scanning electron microprobe, by detecting the x-ray emission of calcium. The significance of calcium oxalate production by an ectomycorrhizal fungus is discussed.

ISSN:0008-4026    

DOI:10.1139/b84-155

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The inhibitors of oxidative phosphorylation antimycin A (0.5 μg/mL), oligomycin (0.01 mg/mL), and sodium azide (3 mM) eliminated energy-dependent H+efflux from isolatedAsparagusmesophyll cells. Antimycin A and oligomycin also reduced ATP levels by 60% or more. In contrast the same concentrations of inhibitors had little or no effect on respiratory O2consumption. The sequential addition of potassium cyanide to give a final concentration of 5.2 μMresulted in a 60% maximum inhibition of O2consumption. Subsequent addition of 0.2 mMdisulfiram (tetraethylthiuram disulfide), a potent inhibitor of cyanide-resistant respiration, resulted in a further reduction of the oxygen consumption rate. In the absence of cyanide, 0.2 mMdisulfiram inhibited O2consumption by 40 to 80%, depending on the suspension medium. Disulfiram had little or no effect on the ATP levels which varied between 0.7 and 2.2 nmol ATP/106cells. The results indicate that disulfiram inhibits a non-energy-conserving cyanide-resistant alternative pathway inAsparagusmesophyll cells.

ISSN:0008-4026    

DOI:10.1139/b84-156

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Pollen development has been studied by various microscopical techniques in five genic male-sterile lines and in male-fertile lines of barley (Hordeum vulgareL.). Two of the male-sterile lines (msg,,hoandmsg,,fz) exhibited apparently identical abnormalities: defective cytokinesis at the end of meiosis 1. Another male-sterile gene (msg,,fg) also appeared to cause defects at this stage; in this case nuclear restitution was incomplete. In the male-sterile linemsg,,gfa failure of the periclinal division of the inner secondary parietal layer occurred, so that a tapetal layer was not formed. Development was normal through meiosis in anthers frommsg,,fpplants until the early vacuolated microspore stage when normal sporopollenin production was inhibited.

ISSN:0008-4026    

DOI:10.1139/b84-157

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The development and function of the pollination mechanism and the optimal time for pollination are described for Sitka spruce (Picea sitchensis(Bong.) Carr.). After winter dormancy, the rudimentary integument overgrew the nucellus and formed two long micropylar arms. Soon after seed-cone buds burst, the epidermal cells on the micropylar arms secreted mucilage droplets to which pollen adhered. The ultrastructure of mucilage droplet secretion is described. After 6–8 days a pollination drop formed from the nucellus. This filled the space between the micropylar arms and picked up any pollen which adhered to the arms or landed on the pollination drop. The pollination drop was then withdrawn carrying pollen into the micropyle. The secretory cells on the micropylar arms then autolyzed and a large mucilage plug sealed the micropyle and filled the space between the withered micropylar arms. Conelets closed and became pendant. Pollen germinated and pollen tubes formed about 2 weeks after pollination ended. Conelets enclosed in pollination bags were open and receptive for about 10 days, but the optimal time for pollination was 6 to 8 days after cone buds burst. This coincided with the time of pollination-drop formation.

ISSN:0008-4026    

DOI:10.1139/b84-158

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

[3H]indoleacetic acid (AIA) was applied to the shoot tip of intact young plants of Tomato (Lycopersicum esculentumMill.) for 10, 60, or 120 min. Autoradiograms of whole plants were prepared and liquid scintillation counts of stem segments and principal root segments were performed. Chromatographic analysis showed that 66% of the radioactivity was associated with AIA after 120 min of contact with [3H]AIA. Autoradiographs of semithin and ultrathin sections were prepared after treatment by DCC (1-(3-dimethyl-aminopropyl)-3-ethylcarbodiimide hydrochloride). The quantity of label per cell and the density of label were determined for all tissues of the apical bud. The density of label was greater for meristematic cells than for differentiated cells. The observed homogeneity of label distribution in the apical meristem shows that auxin levels do not play a prominent role in distinguishing between its lateral and axial zones. The density of label was similar in the apical and in the axillary bud of leaf 4. The cells of the rib meristem, which elongate to produce pith, were more intensely labelled than the other meristematic cells. The percentage of label was calculated for each tissue in a transverse section of the stem just below the apex. The amount of auxin was greatest in the parenchyma (axial and cortical) with lesser amounts in the procambium, phloem parenchyma, and xylem parenchyma. Vessels, which had the greatest density of label, did not contain more than about 3% of total radioactivity of the stem section, while sieve tubes had only 0.5%. Pathways of auxin transport and the role of AIA in regulating meristematic activity in the apical bud are discussed.

ISSN:0008-4026    

DOI:10.1139/b84-159

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The dorsiventral shoot system ofPellionia daveauana(Godefr.) N.E. Br. is characterized by opposite pairs of dimorphic leaves. The small dorsal leaves differ from the large ventral leaves by having a reduced leaf blade, fewer tissue layers in the epidermis and mesophyll, a reduced vascular system and significantly smaller cell size in all tissue layers. The observations reported here document the developmental basis of these morphological and histological differences. Although both dorsal and ventral leaves appear to be initiated simultaneously, the volume of the ventral leaf primordium is greater than that of the dorsal leaf primordium and growth in length occurs over a longer time period. Early plate meristem activity results in the elaboration of the ventral leaf blade, while plate meristem activity is lacking in dorsal leaves. During ventral leaf expansion periclinal divisions in adaxial and abaxial protoderm and ground meristem give rise to multiple epidermis and new mesophyll layers, respectively. Similar periclinal divisions in dorsal leaves occur at an earlier developmental stage and are restricted in extent. Measurements of cell dimensions show that cell enlargement also ceases at an early developmental stage in dorsal leaves. Development of the ventral leaf is characterized by a relatively long period of cell division and enlargement. In contrast, early cessation of cell division and precocious cell maturation result in the distinctive structural features of the dorsal leaf blade.

ISSN:0008-4026    

DOI:10.1139/b84-160

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A classification is given for those Chytridiomycetes with monocentric and eucarpic growth forms, endogenous sporangium development, and multipapilliated sporangiathat are now known in culture. These belong to six genera which are classified on unique ultrastructural characteristics of the zoospore; however, for convenience of routinely distinguishing these genera, a key is given based on characters detectable by light microscopy. Eight species are described forSpizellomyces, which includeS.punctatus(Koch) D. Barr;S. plurigibbosus(D. Barr) comb, nov.;S.kniepii(Gaertner) comb, nov.;S.palustris(Gaertner) comb. nov.;S.acuminatus(D. Barr) comb. nov.;S.dolichospermussp. nov.;S.lactosolyticussp. nov.; andS.pseudodichotomussp. nov. There are two species inGaertneriomyces:G.semiglobiferus(Uebelmesser) D. Barr andG.tenuissp. nov.Triparticalcar arcticum(D. Barr) D. Barr andKochiomyces dichotomus(Umphlett) D. Barr are monotypic genera. Criteria for classifying these fungi in culture are discussed.RhizophydiumandKarlingiaare included in the generic key but are not treated at the specific level. This new classification is intended strictly for cultures and neither augments nor replaces earlier and more classical systems.

ISSN:0008-4026    

DOI:10.1139/b84-161

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The principal cytological features and their variations are described in zoospores of 38 isolates belonging to seven species ofSpizellomyces. This genus is distinguished from others in the Spizellomycetaceae by the orientation of the microtubules and the position of the nucleus relative to the kinetosome in the zoospore. Microtubules run apparently at random into the cytoplasm from a microtubule-organizing center (spur) on one side of the kinetosome. The nucleus is anteriorly or centrally positioned with a heel-like process extending to near the proximal face of the kinetosome, or it can be posteriorly positioned and elongate with one end close to the kinetosome. Differences between species are reflected by the position and shape of the nucleus, the extent of the endoplasmic reticulum which in some species circumscribes lipid globules, the presence or absence of an apparent connection by fibrillar material between the kinetosome and a nonfunctional centriole, and the morphology of the microtubule-organizing center. The zoospores ofSpizellomyces punctatus(Koch) D. Barr,S.plurigibbosus(D. Barr) D. Barr, andS.palustris(Gaertner) D. Barr are cytologically similar, but those ofS.acuminatus(D. Barr) D. Barr,S.dolichospermusD. Barr,S.lactosolyticusD. Barr andS.pseudodichotomus(Umphlett) D. Barr each have one or more distinctive characteristic.Spizellomyces dolichospermusandS.pseudodichotomusalso have some cytological characteristics in common with the genusKochiomyces.

ISSN:0008-4026    

DOI:10.1139/b84-162

出版商:NRC Research Press    

年代:1984

数据来源: NRC