摘要:

The ratio of ray and ray cell initials to fusiform initials of the vascular cambium relative to radial growth rate as reflected in the secondary xylem was studied in stems ofAcer saccharumMarsh. Ray initials increased in size as they aged, slowly when growth rate was low, rapidly when it was high, but there was little fluctuation in the number of rays per unit of tangential area; as the cambium increased in circumference, the older, larger rays diverged and new small rays arose in intervening areas, thus maintaining a uniform unit area population independent of growth rate. However, since ray size increased rapidly when growth rate was high, the unit area population of ray cells rose abruptly with accelerating growth rate: the relative volume of xylem ray tissue rose from 8.6 to 12.7% of the total xylem volume when annual ring width increased from 1 to 7 mm. When fast growth was not maintained, the unit area population of ray cells declined slowly as the large rays diverged.

ISSN:0008-4026    

DOI:10.1139/b77-293

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The nature of the association between the basidiomycetous mycobiont and the blue-green phycobiont in two species of the tropical basidiolichenDictyonemawas investigated using Nomarski light optics and scanning and transmission electron microscopy. Although members of this family may exhibit either a homoiomerous or heteromerous type of thallus organization, the fungus–alga relationship at the cellular level is remarkably consistent.Scytonemafilaments are intimately associated with appressorial hyphae of the mycobiont and with extensive intracellular hyphae, which appear to be unrelated to the basidiomycetous fungal symbiont. This is the first report of a lichen displaying an apparent dual fungal symbiosis with the algal host. Association with the intracellular fungus produces no discernible damage to the phycobiont and apparently does not interfere with the symbiosis involving the basidiomycetous fungus.

ISSN:0008-4026    

DOI:10.1139/b77-294

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Pollen-cone buds differentiated in the fall but meiosis and pollen development did not occur until the next spring. Pollen cones resumed development in mid-April, meiosis occurred in mid-May and pollination about 1 month later. Mature four-celled pollen entered the micropyle by means of a pollination drop and germinated on the nucellus about 1 month after pollination. Pollen tubes grew part way through the nucellus and became dormant in late summer before male gametes formed.Seed-cone buds differentiated in the spring from distal axillary apices which were initiated in the long-shoot terminal buds in the fall. Apices resumed development in early April and bracts and ovuliferous scales were initiated from mid-April until early June. Meiosis of the megaspore mother cell occurred in early July and the functional megaspore underwent free nuclear division until late August when the seed cones became dormant. Ovule and pollen-tube development resumed in early April. Free nuclear division occurred in the female gametophyte until early May when cell walls formed and three to five archegonia differentiated. Two male gametes formed in each pollen tube before it reached the archegonium. Fertilization occurred in early June. Simple polyembryony was rare but cleavage polyembryony was a regular feature. Early embryo development was rapid and easily distinguishable embryos were present by mid-July. Embryos and seeds were mature by early September when seeds were normally shed.The reproductive phenology and morphology ofPinus monticolais similar to other soft pines. Stages in the reproductive cycle are noted where abortion of cones or ovules or adverse weather conditions may result in a poor cone crop or poor seed set.

ISSN:0008-4026    

DOI:10.1139/b77-295

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The tempo of water efflux from singleFagus grandifolialeaves has been measured. The resistance to pressure-driven water efflux has been measured for normal leaves,Rs, and for leaves in which extracellular mesophyll spaces are infiltrated with water,Rs*. The ratioRs*/Rsis about 0.4. The resistance to water flow through the xylem,Rx, was also measured and found to be a small part ofRs, i.e.,Rx/Rs = 0.08. The activation energies for water efflux from normal and infiltrated leaves are both about 26 ± 4 kJ/mol.After an analysis of our data, we conclude that the membrane hydraulic conductivity ofF. grandifolialeaves is roughly 10−6 cm s−1 bar−1(1 bar = 100 kPa) and that water travels the shortest path between the cell sap and the nearest xylem vessel, flowing in and out of mesophyll cells through the areas in contact between adjacent cells along the pathway.

ISSN:0008-4026    

DOI:10.1139/b77-296

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

An historically important collection of 330 hepatics collected by John Macoun, the Canadian naturalist–explorer, in southwestern British Columbia has recently been examined and annotated. Since Macoun's specimens have long been cited in the hepaticological literature, a knowledge of the limitations of the data from his identifications and packet labels becomes important. Problems were encountered in regard to species identification, multiple labels on a single packet, multiple collections in a single packet, and incorrect or vague information on habitat and location. A most important single collection of John Macoun, the type specimen ofCololejeunea macounii, is discussed in terms of recent hepaticologial findings in southwestern British Columbia. A list of 73 species identified in Macoun's collection is presented.

ISSN:0008-4026    

DOI:10.1139/b77-297

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Ascocarps ofL. nitensDarker develop in the spring on fallen needles ofPinus strobusL. The ascocarp initial is a compact stroma located between host epidermis and cuticle. Most of this stroma becomes elevated to form the clypeus, while the portion remaining in contact with the epidermis constitutes the incipient hypothecium. As the latter develops, paraphyses originate from the superficial hypothecial cells. Ascogenous elements arise from the bases of certain paraphyses. Occasionally, a paraphysis may give rise directly to an ascus but more frequently to a limited system of ascogenous elements. A number of such systems, similarly produced at various points over the whole hypothecial surface, collectively comprise the hymenium. Any given ascogenous system contains many nuclear pairs. The latter are interpreted as dikaryons because they occur in association with croziers and nuclear quartets, both of which are indicative of conjugate division.

ISSN:0008-4026    

DOI:10.1139/b77-298

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The seed ofOrobanche aegyptiaca(Orobanchaceae) is very small and contains a subglobose embryo which has not differentiated into radicle, hypocotyl, cotyledons, and plumule. Seeds were aseptically cultured to study germination and the morphogenesis of the embryo. In response to the composition of the medium, the embryo displayed either a monopolar organization or a bipolar organization of the seedling. Medium supplemented either with coconut milk (20% v/v) or yeast extract (5000 ppm) resulted in a monopolar seedling development where the roots and shoot originated from the morphological radicular pole of the embryo. The bipolar pattern of seedling development occurred in response to auxin (0.1 ppm), cytokinin (0.5–10 ppm), gibberellin (1–30 ppm), and strigol (0.01 μg). In bipolar development, the shoot originated from the plumular pole and the roots from the radicular pole of the embryo.

ISSN:0008-4026    

DOI:10.1139/b77-299

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Pollen grain size and exine ornamentation were examined in 13 species ofAvenaL. (Poaceae), including six A-genome diploids, four tetraploids, and three hexaploids. A cultivated species was represented at each ploidy level. It was found that both pollen size and exine sculpturing patterns showed some correlation with the cytogenetic, morphological, and biochemical evidence which has been used in elucidating the taxonomic relationships within both the A-genome diploids and the hexaploids. However, the pollen data shed less light on relationships within the tetraploids and on relationships between the different ploidy levels. It was observed that the cultivated species at each ploidy level tended to have larger pollen grains and a more complex mode of exine process patterning than their wild relatives. Possible explanations were discussed.

ISSN:0008-4026    

DOI:10.1139/b77-300

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Two methods were used to separate heme and apoenzyme from the holoenzyme of peroxidase (EC 1.11.1.7) isolated from medium of cultured peanut cells. Apoenzyme prepared by either method lacked peroxidase activity but possessed indole acetic acid (IAA) oxidase and poly phenol oxidase (PPO) (EC 1.14.18.1) activity. When the holoenzyme was reconstituted with heme and apoenzyme, peroxidase activity was restored. The studies on the active site revealed that PPO and IAA oxidase share the same active site on the apoenzyme.

ISSN:0008-4026    

DOI:10.1139/b77-301

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Organogenesis of the male reproductive structures ofMyrica pilulifera, Gale, andComptoniais compared. InM. pilulifera, which has a compound inflorescence, one to three stamens form in the axils of second-order bracts of the partial inflorescence. InGaleandComptonia, which do not have compound inflorescences, four stamens arise simultaneously on the flank of the apex of the second-order axis. It is concluded that this defines a floral condition for the family. A model is proposed which explains the probable development of the floral condition from the inflorescence state more adequately than existing floral concepts. Hence, speculation of the phylogenetic status of this family is avoided. Similarly, it is not necessary to debate notions of an angiospermous archetype. Recent knowledge of the family is collated from various disciplines such as taxonomy, anatomy, and palaeobotany to provide a framework for assessing the significance of the discussion of the ‘flower’ vs. ‘inflorescence’ problem.

ISSN:0008-4026    

DOI:10.1139/b77-302

出版商:NRC Research Press    

年代:1977

数据来源: NRC