摘要:

not available

ISSN:0008-4026    

DOI:10.1139/b69-170

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Studies of cuticular modifications of leaves by the environment were conducted onDatura stramoniumL. (Blakeslee seed lot, box 8-451) to determine the degree of constancy of cuticular features when plants were subjected to different environmental conditions. This species was considered to be a highly inbred line with a high degree of genetic constancy. The plants were subjected to five environmental conditions, from xeric to very humid. Sinclair and Dunn's method (reported in 1961) of making plastic cuticular imprints was used. It was concluded that the stomatal size classes, mean stomatal size, subsidiary cell complex, pattern of stomatal development, and the type of trichome and trichome distribution pattern were consistent. Stomatal index was generally reliable, except under extreme environments where the plants probably would not have survived in nature, under competition. Stomatal frequency, epidermal cell frequency, and trichome frequency were inconsistent under the different environmental conditions. The total leaf area was so easily modified that absolute stomatal numbers described by Gupta in 1961 were not worth calculating.

ISSN:0008-4026    

DOI:10.1139/b69-171

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Noninfected cabbage callus andPlasmodiophora brassicaeinfected callus isolated from clubroot galls were maintained for over 40 successive transfers on Murashige-Skoog's medium modified to contain 0.5 mg/l of α-naphthalene acetic acid. Infected callus if transferred at 7- to 12-day intervals grew rapidly, doubling its dry weight about every 3 days, whereas noninfected callus doubled its dry weight about every 5 days. Approximately one-third of the cells in infected callus contained the parasite in various stages of its life cycle, ranging from small vegetative plasmodia to mature resting sporangia. Sporangia isolated from callus were viable and produced clubroot inoculated on cabbage seedlings. When a high percentage of the plasmodia in infected cells in any portion of a callus underwent sporogenesis, the callus growth slowed and the tissues became brown. By transferring only actively proliferating callus a high percentage of plasmodia could be maintained in the vegetative condition. Infected callus resembles closely gall tissue from natural clubroot both cytologically and chemically and thus should be a useful material for studying parasitism and the processes of hypertrophy and hyperplasia in a contaminant-free system.

ISSN:0008-4026    

DOI:10.1139/b69-172

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Six populations of apparently morphologically similar sessile-floweredTrillium(known taxonomically asT. cuneatumRaf. andT. luteum(Muhl.) Harb.) observed growing at elevations between 800 and 1700 ft in the Appalachians of western North Carolina and eastern Tennessee exhibit a wide range of variability by observation. The extent of variability was assessed by using statistical and karyotypic methods of analysis and by intraspecific cross-pollination. A correlation exists between the mean coefficient of variability and (1) the size of the population and (2) the degree of geographic isolation. The number of types of each kind of chromosome (A–E), as resolved by cold treatment, varies by one type from population to population. The homozygosity for the six populations is 85.8%, and the distribution of euchromatin is not complex. Intraspecific cross-pollination was effective among 76% of the test crosses. A review of the statistics and other morphological data indicates that the presence or absence of anthocyanins, flower scent, and the degree of geographic isolation are the three major variants among the six populations. These kinds ofTrilliumgrow sympatrically withT. grandiflorum(Michx.) Salisb.,T. simileGleason,T. erectumvar.album(Michx.) Pursh,T. flexipesRaf. (T. gleasoniFern.), andT. erectumL. The cumulative karyotype for the six stands indicates that these plants have not hybridized with any of the above species and varieties. Although these plants have been classified asT. cuneatumRaf. in some stands and asT. luteum(Muhl.) Harb. in others the data demonstrate that these six stands represent one discontinuous population of a sessile-floweredTrillium. Trillium discolorWray, although relatively rare in western North Carolina, also grows here. AlthoughT. discoloris not directly involved in this problem, its description and distinctive karyotype are included.

ISSN:0008-4026    

DOI:10.1139/b69-173

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The correlation of electrical behavior and cytoplasmic streaming in internodal cells ofChara brauniiwas studied by a voltage clamp technique. The observations were as follows. (i) Neither axial currents nor hyperpolarizing currents are adequate to stop the streaming. (ii) Below the threshold for excitation, streaming was independent of vacuolar voltage. (iii) In cells subjected to step depolarizations, streaming stoppage coincided with the peak of the resultant action current. (iv) Neither an action current nor an action potential seemed to be an essential correlate of streaming stoppage, but a sudden variation in membrane conductance was always associated with stoppage. (v) Recovery of streaming after an electrical excitation was complex and appeared to proceed most rapidly when the cell's conductance was at or near resting level. These data are consistent with the view that the mechanism responsible for streaming is strongly coupled to the plasmalemma and that it is disrupted by the variations in ionic conductance which characterize electrical excitation of the plasmalemma.

ISSN:0008-4026    

DOI:10.1139/b69-174

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

In a short-day response type ofChenopodium rubrum(ecotype 60°47′ N), light of a relatively low red/far-red ratio—but of sufficient energy to allow photosynthesis—can bring about induction of flowering when it completely replaces a single dark period interrupting continuous white light. When high-intensity white incandescent light was interrupted for less than a 24-hour period, a longer period of inductive light than darkness was required even for minimal induction. An inductive light interruption of at least 60 hours was required for 100% flower induction. The result of such forcing of the system by inductive light, as compared with the circadian rhythmic induction that occurred in darkness, was a change towards a more linear inductive response and there were indications (requiring confirmation) of oscillations of higher frequency.When seedlings were maintained continuously in optimal inductive light or in darkness, after an initial high intensity white light period, there was some flower initiation within 5 days in inductive light, but not until about 10 days in darkness, and then only when sucrose was supplied throughout darkness.There were suboptimal and (inhibitory) supraoptimal effects on induction when the R/FR ratio and (or) the energy of inductive light were decreased or increased, respectively. These results, in conjunction with the effects that were obtained when glucose and 3(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) were applied in inductive light as compared with darkness, implicate both photosynthate and phytochrome-Pfras having a positive (promotive) effect during normal inductive darkness.These findings emphasize that the important controls in photoperiodism and flowering may be quantitative rather than qualitative in character, because it can now be questioned whether there is any essential dark-requiring reaction in the induction not only of long-day but also of short-day plants.

ISSN:0008-4026    

DOI:10.1139/b69-175

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Single whorls of branches, located at different levels in the crown, were removed from 13-year-oldPinus resinosa(Ait.) trees. One-year diameter growth of the stem between whorls and below the crown, and of the leader, was used to evaluate treatment effects. Principal inferences drawn were that growth of an internode within the crown is mainly influenced by the whorl immediately above it; growth of the stem just below the crown depends heavily on all whorls; and whorl foliage does not positively influence development of either the current or previous year's leader.

ISSN:0008-4026    

DOI:10.1139/b69-176

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The morphology and chromosome number of nine species ofCirsiumof eastern North America are considered. Chromosome counts are presented for the first time forC. iowense, 2n = 18;C. lecontei, 2n = 32;C. nuttallii, 2n = 24, 28;C. repandum, 2n = 30;C. smallii, 2n = 34;C. engelmannii, 2n = 20;C. texanum, 2n = 22, 24;C. virginianum, 2n = 28. Additional chromosomes, possibly to be considered as accessories, were found inC. nuttallii,C. engelmannii, andC. texanum. These chromosomes render uncertain the number characteristic of these species. A key to the 26 native and introduced species found in Canada and the United States east of 100° west latitude is presented. The interrelationships of the eastern species and of the species of the western seriesUndulataare discussed.

ISSN:0008-4026    

DOI:10.1139/b69-177

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Seventeen isolates of the aphid-borne barley yellow dwarf virus (BYDV), collected in southern Manitoba in 1966, were transmitted from oats to oats most efficiently byRhopalosiphum padi. They were transmitted also byMacrosiphum avenaeand all but two were transmitted bySchizaphis graminumandAcyrthosiphon dirhodum. Most of these isolates were not transmitted byR. maidis.Only 3 of 25 isolates collected in 1967 were transmitted by the five species of aphids in a pattern similar to that of the isolates collected in 1966. Twenty of the remainder were transmitted with a moderate to high degree of specificity byR. maidis, R. padi, orS. graminum. Two of the latter isolates were transmitted only byS. graminum. When the transmissibility of one of the isolates, for whichS. graminumwas the most efficient vector, was examined more critically, both the relative and the specific efficiency of the three vectors varied with the age of the infection in the source plants, thoughS. graminumwas always the most efficient vector.

ISSN:0008-4026    

DOI:10.1139/b69-178

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The application site of cytokinins has a direct effect on the position of bud initiation on root segments ofOphioglossum petiolatum. Apically treated segments have buds initiated randomly along the segment while buds on basally treated segments tend to develop close to the site of cytokinin application. Buds forming on control root segments and those treated with indoleacetic acid are located randomly along the segment in both apical and basal treatments.

ISSN:0008-4026    

DOI:10.1139/b69-179

出版商:NRC Research Press    

年代:1969

数据来源: NRC