摘要:

The relationship of ozone-induced foliar injury (ozone sensitivity) with several leaf characteristics including stomatal frequency, stomatal closure in the presence of ozone (O3), and trichome densities (abaxial and adaxial) was evaluated for a diverse group ofPhaseolus vulgarisL. cultivars. Differences were observed among cultivars for ozone sensitivity and leaf parameters including stomatal frequency, trichome density, and stomatal closure in the presence of O3. Although significant (P ≤ 0.05) differences among the cultivars for stomatal frequency and trichome densities existed, no consistent pattern between insensitive and sensitive cultivars was observed. Ozone-sensitive genotypes responded to 40 parts per hundred million O3with similar or greater stomatal closure than the more insensitive genotypes, indicating that stomatal closure was not a primary mechanism for O3insensitivity among the cultivars evaluated.

ISSN:0008-4026    

DOI:10.1139/b82-268

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Mesophyll protoplasts were isolated from five pea (Pisum sativum) varieties and cultured in medium 8p, modified to test the effects of varieties, leaf ages, protoplast population densities, pH, and plant hormones on relative division frequency. Protoplasts isolated from the variety Rondo had a much greater capacity for division than those from Century, Laxton's Progress, Trapper, or Afghanistan 72-HI-2. The highest division frequency occurred in protoplasts isolated from the top expanded leaf of seedlings at the three-, four-, or five-leaf stage. The maximum frequency of division was obtained using a protoplast density of 5 × 104to 1 × 105per millilitre and the 8p medium at pH 5.6 with 850 mg/L of CaCl2∙2H2O, 0.25–1.00 mg/L of 2, 4-D, and 2 mg/L of zeatin riboside. Gradually reducing the osmolality from 510 mosmol to 420 mosmol was essential to achieve a high frequency of cell divisio

ISSN:0008-4026    

DOI:10.1139/b82-269

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Phenology and anatomy of the postdormancy reproductive phase ofAbies grandisLindl, were studied. The dormant microsporangia contained compactly arranged pollen mother cells (PMC). The pollen cones broke dormancy in the 3rd week of February and soon afterwards the PMC entered meiosis. Microspore tetrads formed by the 2nd week of March. Pollen grains were shed at the five-celled stage in the 3rd week of April. The pollen grains were bisaccate and showed a triradiate mark on the proximal pole. The dormant ovulate-cone buds bore rudimentary ovuliferous scales, each with two ovular areas. Ovulate cones broke dormancy at the end of January. Megaspore mother cells differentiated by the end of February and the integument was initiated soon afterwards. A megaspore triad formed in the 2nd week of April. By the 3rd week of April, at the time of pollination, the ovule contained a free-nuclear gametophyte, and the integument had developed a stigmatic micropylar funnel. Numerous microdroplets were observed on the surface of the funnel to which pollen adhered. After pollination the funnel became infolded, enclosing the pollen grains. Pollen germination, pollen tube growth through the nucellus, and syngamy took only 3–4 days and occurred in the 3rd week of June. The female gametophyte was long and bore two or three archegonia. The proembryo consisted of four tiers of four cells each. The suspensors developed from the subterminal tier of cells. The four terminal cells formed the embryonal mass, whose proximal cells elongated and developed into a secondary suspensor. Differentiation of the root apical meristem and the cotyledons in the young embryo occurred in the 1st week of July and the embryo matured in the 3rd week of August.

ISSN:0008-4026    

DOI:10.1139/b82-270

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Carbohydrate and nitrogen budgets were studied in Jerusalem artichoke tuber explants culturedin vitroafter gamma irradiation (0 to 106 rads (1 rad = 10−2 J/kg)). A certain level of reducing sugars is reached and retained in all the explants and, in all cases, an increase of protein nitrogen is observed. The highly irradiated tissues have a very disturbed metabolism that involves in particular, amino acid leaching into the culture medium.

ISSN:0008-4026    

DOI:10.1139/b82-271

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The ultrastructural organization of the megagametophyte ofPlumbago zeylanica, which lacks synergids, was examined in chemically and physically fixed ovules after entry of the pollen tube. Similar to angiosperms with conventionally organized megagametophytes, the pollen tube enters the ovule through a micropyle, formed by the inner integument, and approaches the female gametophyte by growing between nucellar cells. Unlike other described female gametophytes, however, continued pollen tube growth results in direct penetration of the base of the egg through cell wall projections forming a filiform apparatus and is completed between the egg and central cell without disrupting either of these cells' plasma membranes. A terminal pollen tube aperture forms when the pollen tube reaches an area of strong curvature near the summit of the egg; this results in the release of two sperm cells, the vegetative nucleus, and a limited amount of pollen cytoplasm. The formerly continuous chalazal egg cell wall is locally disrupted near the tip of the pollen tube and apparently is thus modified for reception of male gametes. Discharged pollen cytoplasm rapidly degenerates between the egg and central cell, but unlike pollen tube discharge in conventionally organized megagametophytes, it is unassociated with the degeneraton of any receptor cell within the female gametophyte. Sperm nuclei are transmitted, one to the egg and the other to the central cell, to effect double fertilization by nuclear fusion with their respective female reproductive nuclei. The vegetative nucleus and discharged pollen cytoplasm degenerate between the developing embryo and endosperm during early embryogenesis. The emerging concept that the egg ofPlumbagopossesses combined egg and synergid functions is supported by the present study and suggests that the megagametophyte of this plant displays a highly specialized egg apparatus composed exclusively of a single, modified egg cell.

ISSN:0008-4026    

DOI:10.1139/b82-272

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Leaf initiation inCyclamen persicumMill. 'F-1 Rosemunde' was examined. The sigmoid pattern of initiation which was observed may be described by a modified logistic equation which is not significantly different from that used previously to describe the pattern of leaf emergence. The relationship between initiation and emergence changes during the growing season so that initially there is an increase in the number of leaves in the bud, while later there is a decrease. It is suggested that (i) leaf emergence is not necessarily an accurate indicator of leaf initiation for application of the plastochron index and (ii) the sigmoid pattern of leaf initiation is more widespread than the literature would indicate.

ISSN:0008-4026    

DOI:10.1139/b82-273

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The structural and functional properties of a cyanophytan mat in an extremely oligotrophic acidified lake were studied. The mat forms a physiological unit well adapted to acid conditions in the lake. Two to three millimetres of the uppermost stratum consists of photosynthetically active filaments ofLyngbyawith an intrusion of other benthic algae. Relatively high rates of algal primary productivity and low rates of N2fixation were recorded in the mat.

ISSN:0008-4026    

DOI:10.1139/b82-274

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The initial vesicular–arbuscular (VA) mycorrhizal development of slender wheatgrass on extracted oil-sands and subalpine coal-mine spoils, amended with either fertilizer, peat, or liquid sewage sludge, was examined. Plants were sampled at 2, 6, and 10 weeks after plant emergence and the level of infection was expressed as length of mycorrhizal root per plant and length of root which contained arbuscules, vesicles, or only hyphae. Mycorrhizal infection of slender wheatgrass on the oil sands was limited to plants on the peat-amended spoil. Infection of plants on the peat-amended oil-sands spoil was detected by 2 weeks. Plants on the subalpine spoil were infected at 2 weeks only on the peat-amended spoil. While slender wheatgrass on the control and fertilizer-amended spoil developed mycorrhizae by 6 weeks, infection was not observed in plants on the sewage-amended spoil until 10 weeks. At 10 weeks, there were no significant differences in lengths of mycorrhizal root per plant among the amendments. Increased P levels in the fertilizer- and sewage-amended subalpine spoil did not suppress VA mycorrhizal development.

ISSN:0008-4026    

DOI:10.1139/b82-275

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Vegetative terminal and axillary bud development and the time and method of cone initiation and cone bud development are described forAbies lasiocarpa(Hook.) Nutt.Cell divisions began in vegetative buds early in April. A brief period of apical enlargement was followed by bud-scale initiation for 10 weeks. Buds were initiated in the axils of some leaf primordia about the time of vegetative bud burst, 1 month after vegetative bud dormancy ended. All buds completed bud-scale initiation by the end of June, which coincided with the end of the rapid phase of lateral shoot elongation. This was followed by a 2-week period of bud differentiation, during which time few primordia were initiated, apical size increased, and apical shape and zonation changed more in reproductive than in vegetative apices. Leaf and bract initiation began by mid-July and continued until mid-October, when vegetative and seed-cone buds became dormant. Microsporophyll initiation began earlier and was nearly completed by the end of July; pollen-cone buds became dormant in mid-September.The number of cone buds is determined by the proportion of axillary bud primordia that fully developed and the pathway along which they developed. Potential seed-cone buds may become latent but more commonly differentiate into vegetative buds of low vigor. Potential pollen-cone buds frequently become latent but have not been observed to differentiate into vegetative buds. The position of the axillary bud on the shoot and of the shoot in the tree strongly influences axillary bud development inAbies.

ISSN:0008-4026    

DOI:10.1139/b82-276

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Equations presented in an earlier paper, expressing organic matter and nitrogen dynamics in decomposing hardwood leaf litter, are extended to predict nitrogen immobilization patterns in litters of varying initial lignin and nitrogen content. A continuum of immobilization rates coincides with the successional status of the six northern hardwood species examined, with early successional species exhibiting the fastest rates. By using data from the literature, similar trends were found for southeastern hardwoods. Patterns for important species from Douglas-fir forests of the Pacific Northwest are quite different and may reflect differences in nitrogen availability following disturbance.

ISSN:0008-4026    

DOI:10.1139/b82-277

出版商:NRC Research Press    

年代:1982

数据来源: NRC