摘要:

Undetermined P3leaf primordia of the fernOsmunda cinnamomeawere excised and grown in sterile culture, as pairs, with P12or P13primordia, primordia already irreversibly determined as leaves. Undetermined P3primordia of a pair (P3with P3or P3with P12) separated by an impervious barrier membrane (mica sheets) exhibit a tendency to develop as shoots rather than leaves. When the barrier membrane was a Millipore Filter, P3's growing with other P3's also exhibited the tendency to develop as shoots. By contrast, undetermined P3primordia of a pair (P3with P13) separated by a Millipore Filter barrier membrane exhibit the tendency to develop as leaves. These results would suggest that cell-to-cell contact is not a necessary adjunct to transmission of a leafness morphogen, and they present still further evidence in favor of a hypothesis that determination of a leaf primordium as a leaf may be under the control of more than one control center, and that one such control center is associated with certain of the older leaf primordia of a sibling series.

ISSN:0008-4026    

DOI:10.1139/b69-011

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Apical and radial growth in trunk, branches, and roots, together with needle and cone distribution, were studied in a black spruce tree 31 years old andhigh. Growth of aerial parts was summarized as follows: (1) according to years of formation (oblique summation); (2) transversely on trunk inter-nodes (horizontal summation); and (3) according to the position of the annual rings, and the branch internodes (and needles) in relation to the pith or trunk (vertical summation). Root segments were classified on the basis of their diameter and distance from the trunk. Calculated on a dry-weight basis, the trunk accounted for 37%, the branches for 24%, the roots for 21%, and the needles for 18% of the grand total of 81 kg.The tree had 7.8 million needles when sampled in the fall of 1963, one-quarter of which were formed during the last 2 years of growth. Dry weight of individual needles varied with both position and age. While needles of the same season from the lower part of the crown exceeded those from the upper part in length, the reverse was true for the individual dry-weight content.In black spruce, cone periodicity, while distinct, is not as pronounced as in white spruce. The productive capacity of one "average" needle was estimated in terms of apical growth, trunk wood, and needle and root formation.

ISSN:0008-4026    

DOI:10.1139/b69-012

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Most reports on natural hybrids betweenA. sativaandA. fatuaare not supported by definitive experimental evidence. Those authorities who have proved that natural hybrids do occur were assisted by the fact that both parents were known and occurred with the putative hybrids. The present study was conducted on samples of foundation plots from Canadian origin. Very useful characters were found in the lodicules and in the epiblasts which made it possible to detect F1hybrids with precision in seeds of cultivated oats irrespective of their external morphologic markers. A hypothesis that the epiblast of the Fatua-type is dominant over the Sativa-type in F1hybrids is set forth on the basis of the present findings. Higher frequencies of the Fatua-type epiblast were found in the samples where the lowest frequency of the Fatua-type lodicule was observed, because these samples were cultivars which had in their breeding history more crosses withA. byzantinathan the others had. The importance of the lodicule and epiblast characters as markers is reassessed, and their reliability was reevaluated in view of the similarity of characters found in the epiblast ofA. fatuaandA. byzantina, and in view of the present findings. The taxonomic status ofA. fatuaandA. sativais also discussed.

ISSN:0008-4026    

DOI:10.1139/b69-013

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The taxonomy of theTrifolium longipesNutt. complex (Leguminosae) in the western United States is reviewed. This polyploid complex consists of diploid, tetraploid, and hexaploid races having a base number ofx = 8. For the most part, each race occupies a distinct geographical area. Keys to the three species recognized in this study and to the 11 subspecies ofT. longipesin the restricted sense are provided. For each taxon a description and synonymy are given. Maps of the chromosome races and taxonomic entities are appended.

ISSN:0008-4026    

DOI:10.1139/b69-014

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The paper deals with four species of taxodiaceous woods collected from the Edmonton Formation (Upper Cretaceous, Maestrichtian) of the Drumheller area in Alberta. Two of them areTaxodioxylon gypsaceumandTaxodioxylon taxodii, the former showing remarkable resemblances with the wood of modernSequoiaand the latter withTaxodium. Both species are being reported for the first time from the Upper Cretaceous of Alberta, Western Canada. The other two species are new and are namedTaxodioxylon drumhellerenseandTaxodioxylon antiquum. T. drumhellerenseagrees particularly with the wood structure ofGlyptostrobus. The xylem ray tissue ofT. antiquumis characteristic in that the rays here are often extremely high (up to 90 cells) and locally as broad as three to four cells. Such high multiseriate rays are seldom encountered among the coniferous woods.

ISSN:0008-4026    

DOI:10.1139/b69-015

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Young vegetative plants (with 6–9 cm shoot length) ofEquisetum arvenseL. were collected from nature, washed with distilled water, and grown in plastic bottles in a defined nutrient solution with varying silicon concentrations.There was increased growth, as measured by dry weight, with increasing silicon in the nutrient solution. Plants with an adequate Si supply (40–80 mg Si/liter, replenished every 2 weeks) appeared normal and healthier than plants grown without added Si. Deficiency symptoms, such as necrosis of the branch tips, wilting or drooping of the branches, were observed in Si-deficient shoots.It was concluded that silicon is an essential element for the healthy growth ofEquisetum arvense.

ISSN:0008-4026    

DOI:10.1139/b69-016

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The vegetative apex was a low dome consisting of two layers of tunica surmounting a very small corpus. Foliar primordia originated as periclines in the flanks of T2. The transition apex became first a steep cone and then a hemisphere. All floral primordia—the two bracts, the two sepals, the several whorls of petals, the several whorls of stamens, and the carpels—originated in the manner of leaves, as periclines in T2on the flanks of the apex. All appendages, including carpels, were therefore lateral. In the early transition, the apex had a brief stage in which there were three tunica layers, but the inner one was lost with the onset of the sepals. The bracts and the first sepal continued the normal positions of primordia for the vegetative phyllotaxy of 3/8, but with the second sepal, this phyllotaxy was lost, and petals, stamens, and carpels were produced in whorls. While leaves, bracts, sepals, and petals were produced in acropetal sequence, stamens were produced in basipetal sequence, and carpels appeared simultaneously. After carpels were formed, the rest of the floral apex underwent a brief period of expansion growth, achieving a diameter comparable to that of a shoot apex, but its substance was eventually incorporated into the carpel margins, which later produced the ovules. This agrees with the determinate nature of the floral apex. During the development of the first series of floral organs, the floral apex underwent continued increase in area, finally achieving a diameter several times that of the vegetative shoot apex. Its size and form were such that they were compared to those of some inflorescence apices. After development of the first series of floral organs, the subjacent tissues to the floral meristem underwent divisions and elongation at right angles to the axis, causing at first a flattening of the meristem, and eventually a cup-shaped form, with the carpels attached in the bottom of a bowl. The mature flower was thus perigynous, but this development arose quite differently from the perigyny as it is known from ontogenetic studies in the Rosaceae.

ISSN:0008-4026    

DOI:10.1139/b69-017

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Temperature and relative humidity regimes in the stump habitat ofFomes annosuswere characterized in a red pine plantation in Pennsylvania. Data were taken automatically at 2-h intervals around several stumps. A portion of these data from several periods of the year is presented.The measurement of temperature at four levels (soil, litter, stump-top, and ambient at 2-ft above the litter) around stumps showed that important differences existed among the separate levels at one stump, as well as among identical levels at separate stumps.Relative humidity, measured at two levels (sporophore locations and 2 ft above the litter) around stumps indicated that (i) a greater diurnal fluctuation and a generally lower relative humidity occurred at the 2-ft level, although few differences among stumps existed at this level; and (ii) the relative humidity at sporophore locations was comparatively high and varied with the position of the sporophore location on the stump, i.e., relative humidity adjacent to sporophores below the litter or in shaded niches was higher than those exposed to ambient conditions.Root and adjacent soil temperatures, measured at several levels beneath stumps, were similar for any one period except near the soil surface. Generally, the temperatures of the roots and soil increased with depth during outgoing radiation periods. However, the trend for incoming radiation periods varied with season, e.g., temperatures increased with depth in January and March and decreased with depth in July and October.The nature of these differences in fungus microclimate in the stump habitat varied with season, time of day, proximity of the soil surface, and the interaction of stand climate and vegetation. These differences indicate that temperature and relative humidity data intended for use in studies relating climatic factors and fungus activity should be measured as close to the site of interaction as possible.

ISSN:0008-4026    

DOI:10.1139/b69-018

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

New morphological details of the monosulcoid form generaChasmatosporites, Marsupipollenites, andOvalipollisare given. Systematic descriptions include emendations ofChasmatosporites, Ovalipollis, and several species assigned to these genera. Possible phylogenetic relationships and paleobotanical affinities are discussed.

ISSN:0008-4026    

DOI:10.1139/b69-019

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Suggestions for more meaningful collection, processing, and interpretation of temperature data are offered. Our suggestions are based upon characteristics of the organism under study. Research on plant–temperature interactions is reviewed and another approach is illustrated.Temperature data, collected near shoots and roots of Douglas-fir (Pseudotsuga menziesii(Mirb.) Franco) seedlings in different field situations, were assembled from computer-processed temperature traces. From laboratory studies in which day and night air and soil temperatures were controlled, potential seedling growth each day during a growing season was assessed. Then, by summation, a physiological index, expressed in equivalent units, was calculated to relate the possible effect of the field temperatures to plant distribution. This index was used to interpret the effect of temperature on the distribution of vegetation and patterns of leaf initiation in the field. The importance of interactions with the other environmental factors of moisture, chemicals, light, and mechanical forces is mentioned.

ISSN:0008-4026    

DOI:10.1139/b69-020

出版商:NRC Research Press    

年代:1969

数据来源: NRC