摘要:

Changes in major cellular composition during growth have been determined for normalChlamydomonas angulosabatch cultures, napthalene-treated cultures, and cultures treated with aqueous crude oil extracts.During the exponential phase of normal growth, the cellular content of all major constituents varied in a rhythmic pattern in response to the growth rate of the cultures. The extent of initial compositional changes depended on whether the cell inoculum originated from exponential or stationary phase cultures. When cultures reached stationary phase, increases in all major constituents were observed.WhenC. angulosawas incubated in a closed system with 50% saturated naphthalene medium. pigments and total cellular carbon remained constant, total protein decreased, whereas carbohydrate and lipids increased. Immediate recovery was not observed upon transfer to an open system unless the cells were resuspended in fresh medium.WhenC. angulosawas incubated in a closed system with aqueous crude oil extract, cellular carbohydrate remained constant, total protein decreased significantly, whereas pigments, cellular total carbon, and lipids increased. On transferring to an open system, these cells recovered more readily as compared with naphthalene-treated cells.

ISSN:0008-4026    

DOI:10.1139/b77-315

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The objective of the study was to determine genetic differentiation of populations of yellow birch (Betula alleghaniensisBritton) along ecological gradients in Michigan and the Appalachian Mountains. Seeds were collected from populations in each of six physiographic regions of Michigan and in the northern and southern Appalachian Mountains. Seedlings were grown in a common garden in southeastern Michigan. First-year height of progeny, seed weight, initial germination, and germination percentage for 141 yellow birch trees in 30 populations were determined and compared.Significant differences were found among the six Michigan regions for all characters. Strong south–north clinal trends of decreasing height, increasing seed weight, earlier initial germination, and increasing total germination were revealed. Comparisons between physiographic regions showed that tall seedlings were produced by relatively light, late-germinating seeds. Within each region, however, seedlings from earlier germinating seeds tended to exhibit greater height growth. Significant differences were found among populations within a given region for specific characters. In the Appalachian Mountains, southern populations had taller progeny and lighter and poorer germinating seeds than northern populations.Regressions relating each character to 13 site variables were computed. Variation in total height and initial germination were interpreted as the result of differences in the length of the growing season associated with changes in elevation, terrain type, and aspect. Variation in seed weight was associated with differences in the length of growing season and soil moisture regimes.

ISSN:0008-4026    

DOI:10.1139/b77-316

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Mitosis and cytokinesis are examined inCryptomonassp., a member of the Cryptophyceae. The beginning of prophase is signalled by the replication of the flagellar bases which are at the anterior of the cell and a proliferation of the microtubules which run from them to the nucleus at the posterior. The microtubules continue to proliferate as the flagellar bases migrate apart and the nucleus migrates to the anterior. They dissociate from the flagellar bases and enter the nucleus as the nuclear envelope breaks down. A rectangular spindle forms and at prometaphase chromatin is scattered along the spindle. From this stage until late telophase microtubules are found attached singly to the chromatin. In metaphase the chromatin forms a solid plate penetrated by tunnels through which microtubules pass and in anaphase the chromatin separates in two masses which move toward the poles as the spindle elongates. In telophase the nuclear envelope re-forms while a number of microtubules remain between the daughter nuclei. The cytokinetic furrow forms during metaphase and constricts gradually until cytokinesis is complete at telophase. A thin ringof amorphous material is seen under the plasma membrane in the cytokinetic furrow. These results suggest that on the basis of mitotic criteria there is little similarity between the cryptophytes and either the dinoflagellates or red algae to which they have been previously linked.

ISSN:0008-4026    

DOI:10.1139/b77-317

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The subcellular organization of guard and subsidiary mother cells in sugarcane leaves was examined by electron microscopy. Guard and subsidiary mother cells assume a characteristic shape before mitosis and contain variable numbers of mitochondria, proplastids, dictyosomes, and cisternae of rough endoplasmic reticulum. In guard mother cells, the nucleus occupies a central position, whereas in subsidiary mother cells, the nucleus is located toward one end of the cell, near the guard mother cell. Microtubules are found in both guard and subsidiary mother cells and are either closely grouped to form defined preprophase bands or randomly dispersed between the nucleus and the preprophase bands. Many of the dispersed microtubules occur in close association with the nucleus in both guard and subsidiary mother cells. Possible functions for these preprophase microtubules are discussed in relation to their organization in the preprophase band, their orientation, and their distribution within guard and subsidiary mother cells.

ISSN:0008-4026    

DOI:10.1139/b77-318

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The long-standing problem of mixed phases in life histories of red algae was investigated by genetic techniques. Diploid tetrasporophytes ofGracilariasp. growing in culture produced functional male and female gametangia in addition to tetraspores. Sporelings resulting from fertilizations involving these gametangia were polyploid, their chromosome numbers indicating that gametes from the tetrasporophyte were diploid. The tetrasporophytes themselves were heterozygous for two genes affecting plant colour. These markers were observed to become homozygous in twin spots of recombinant tissue at the same time that gametangia were formed. All the observations are consistent with the interpretation that both gametangia and recombinant twin spots arise as a consequence of mitotic recombination. The broader implications of these observations for the Rhodophyceae are discussed.

ISSN:0008-4026    

DOI:10.1139/b77-319

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Understory relationships were examined in 12 jack pine and 11 mixed hardwood stands representing a 7- to 57-year age sequence in New Brunswick. All stands were of fire origin. Percentage cover and frequency of vascular species and major mosses and lichens were presented for each stand. Accumulation of shrub layer and herb layer biomass and distribution of N, P, K, Ca, and Mg were also examined. The biomass showed maximum values in the 10- to 20-year period after fire: it then decreased and stabilized. Contribution of the understory biomass to the total ecosystem biomass ranged from 71–88% on 13-and 16-year-old jack pine stands to 1–6% on the older stands. Nutrient accumulation generally showed a similar pattern to biomass, but some differences occurred owing to variation in nutrient concentration. In particular, shrub layer K increased dramatically on the two oldest jack pine stands; this was postulated to be due to increased dominance ofPteridium aquilinumon these stands. Understory contribution to the total aboveground nutrient pool (tree + understory + forest floor) ranged from 25 to 65% on the younger stands and 5 to 31% on the older stands.

ISSN:0008-4026    

DOI:10.1139/b77-320

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The influence of temperature on teliospore germination and basidiospore formation inGymnosporangium juniperi-virginianaewas studied in vitro. Teliospores germinated from 8 to 30 °C. Germination was first observed after 2 h from 12–28 °C but longer periods were required at lower temperatures. Promycelia formed basidiospores by 4 h from 12 to 24 °C but not until 7 h at 8 °C. Abortive germination of teliospores, without production of basidiospores, occurred from 26 to 30 °C. No germination was observed from 2 to 6 °C. Multiple regression analyses were performed and an equation relating germination of teliospores to temperature and time was formulated.

ISSN:0008-4026    

DOI:10.1139/b77-321

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Most media for the culture of plant cells contain two or more sources of nitrogen, and these appear to serve in part to balance changes in pH that occur during the growth cycle in batch cultures. Data presented in the present paper indicate that provision of an external pH control (pH-stat) makes it possible to grow cell lines initiated fromIpomoea purpureaandGlycine maxwith ammonium as the only nitrogen source. Furthermore, with ammonium hydroxide as the titrant for pH control, the level of ammonium in the medium can be kept at a selected level (combined pH-stat and ammonium-stat) thus providing a greater degree of control over nutrient concentrations during growth than has been possible heretofore.A culture ofIpomoeacells grown under pH-stat – ammonium-stat conditions was comparable in growth rate and other parameters with one grown in a medium containing both ammonium and nitrate without pH control. However, the controlled culture produced more cells per milliliter than the one without control, and these cells remained high in nitrogen (milligram per gram basis) while the nitrogen content of cells in the culture without control declined late in the growthperiod.

ISSN:0008-4026    

DOI:10.1139/b77-322

出版商:NRC Research Press    

年代:1977

数据来源: NRC