摘要:

The selection conducted at L'Assomption, P.Q., from 1950 to 1963, has confirmed the very high susceptibility of the white elm (Ulmus americanaL.) to the attack ofCeratocystis ulmi(Buis.) C. Moreau and the absence of resistant strains in nature. Thermal neutrons or X-ray treatment of seeds has not appreciably modified seedlings reaction to infection, except in 4 cases out of almost 150,000 in which no symptoms were apparent before the fifth annual inoculation or more. One individual has resisted nine consecutive tests and its cuttings did not take the infection after two assays. Resulting from a mutation produced by X-rays, this vigorous clone has a normal foliage but is of a smaller size than other elms of the same age. This case of immunity in the white elm is related to that of the Asiatic species and certain European strains also of slow-growing habit and resistant.

ISSN:0008-4026    

DOI:10.1139/b65-011

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

A time sequence study of the movement of C14-assimilates at the tissue level was carried out with squash. Tissue of mature and immature petioles, stem, and hypocotyl were examined after 1-minute exposures of the primary leaf blade to C14O2. C14-Translocates were transported in the phloem from the mature leaf simultaneously toward the root and young organs of the upper plant. Rapid movement of the C14-front in the phloem was not due to gaseous diffusion of C14O2. Radial movement of C14-translocates occurred along the entire length of the phloem, ultimately supplying C14to every living cell of the plant within 2 hours of assimilation. The velocity and rate of radial movement depended on the stage of development of each plant organ. Young and rapidly expanding petioles displayed maximum velocities of about 6 cm/hour whereas older tissues showed velocities of about 1 cm/hour. These values compared favorably with those known for protoplasmic streaming but contrasted sharply with the velocity of C14conducted longitudinally in the phloem and estimated at between 250 to 300 cm/hour. Radial movement of C14-translocates appeared to occur in the form of sucrose rather than stachyose, which suggested a differential permeability of the conducting elements of the phloem toward these two sugars.

ISSN:0008-4026    

DOI:10.1139/b65-012

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

not available

ISSN:0008-4026    

DOI:10.1139/b65-013

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Heretofore Warburg's one-quantum theory of photosynthesis has seemed inconsistent with the existence of the Hill reaction. The one-quantum theory states that massive oxygen uptake and CO2release are preconditions of photosynthetic oxygen production, yet isolated chloroplasts produce oxygen at high rates apparently without consuming any oxygen or producing any CO2. Warburg has attempted to resolve the dilemma by pointing out a CO2dependence of the Hill reaction. On the basis of this observation he proposed a reinterpretation of the Hill reaction which is consistent with the one-quantum theory. The effect of CO2on isolated chloroplasts has been confirmed and some of the conditions which are necessary for the demonstration of the effect have been defined. It is not clear if CO2is actually metabolized as Warburg claims. Contrary to Warburg's model, its participation seems to be at a site remote from the photochemical act. A number of other reasons for doubting the reality of the one-quantum mechanism are presented.

ISSN:0008-4026    

DOI:10.1139/b65-014

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

In dark-adapting dividing cells ofEuglena gracilisvar.bacillaris, chloroplast lamellae gradually come apart into constituent discs which are progressively lost from the plastids. The entire process from fully formed chloroplasts containing approximately 14 lamellae, each composed of about three discs, to the proplastid (containing no internal membranes) takes about 144 hours (eight generations). Electron micrographs of the process are presented and also the kinetics of loss of discs, lamellae, and pigments. Chlorophyll is lost, at the outset, at a rate commensurate with simple dilution among chloroplasts of progeny cells. The rate of loss of discs and lamellae, however, is somewhat slower and suggests either that all chloroplasts do not divide at each cell division or that there is a continuing slow production of chloroplast membranes in the dark after pigment synthesis has stopped.In non-dividing cells, essentially no loss of structure occurs over the entire 144 hours of dark adaptation. The plastids appear to lose little or no internal structure over the entire period and never return to the proplastid condition. Chlorophylladrops to about one-third of the original value in the first 24 hours and is lost slowly from then on.The evolutionary and ecological implications of this type of control for a cell which is a facultative phototroph or organotroph are discussed.

ISSN:0008-4026    

DOI:10.1139/b65-015

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Fruit weights taken from twoF2's of 1500 plants indicated that the genesd p o s Lc dilandsufall affect fruit weight. The recessive alleles, exceptsufandLc, were associated with small fruit size. The data were analyzed to determine whether this association was the result of linkage or pleiotropic effects. The major effect occurred in theoregion, which is some 44 units from the centromere of chromosome 2. Theogene makes the genes oval or pear-shaped instead of spherical, and it is shown that when the locule wall of a spherical fruit and an oval fruit are composed of the same number of cells, the spherical fruit is always heavier. Since cell number is the inherited unit of fruit size, thenois always associated with small size. A gene controlling number of locules, which affects fruit size, is also located in this section of the chromosome. The genesdands, which are at opposite ends of the present linkage map, both appear to be linked with fruit size genes. It is suggested that these size genes lie in the hetero-chromatin which is adjacent to both ends of the linkage map. The genesdilandsuf, which were produced by radiation of the same variety, appear to have pleiotropic effects on fruit size;sufincreasing, anddildecreasing fruit size.

ISSN:0008-4026    

DOI:10.1139/b65-016

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Two new species of the genusMannia, viz.M. foreauiUdaretChandra from Kodaikanal, South India, andM. perssoniiUdaretChandra from Gangotri, Western Himalayas, along withM. indica(St.) Kachroo andM. dichotoma(Raddi) comb. nov. have been described from India. The problem of generic epithet has been discussed and it is argued to conserveManniaOpiz instead ofGrimaldiaRaddi in conformity with the recent Code of Botanical Nomenclature.

ISSN:0008-4026    

DOI:10.1139/b65-017

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Flowering of winter rye was advanced and the final leaf number reduced by red radiation (ca. 660 mμ) given to grain germinated at low temperatures for 4, 6, 8, or 9 weeks, and by far-red radiation (ca. 740 mμ) given during 3 weeks' low temperature treatment. Radiation was without effect on flowering when given during low temperature treatment continued until the grain was fully vernalized, when given during low temperature treatment of grain of spring rye, when given to grain of spring or winter rye maintained at 15 °C, and when given during thermal de-vernalization of winter rye.It is concluded that the phytochrome system is not involved in the flower-promoting effect of low temperature (vernalization) but that radiation given during low temperature treatment of germinating grain may enhance the stabilization of the vernalized condition.

ISSN:0008-4026    

DOI:10.1139/b65-018

出版商:NRC Research Press    

年代:1965

数据来源: NRC

ISSN:0008-4026    

DOI:10.1139/b65-019

出版商:NRC Research Press    

年代:1965

数据来源: NRC

ISSN:0008-4026    

DOI:10.1139/b65-020

出版商:NRC Research Press    

年代:1965

数据来源: NRC