摘要:

Variation in long‐continued cultures ofHaplopappus gracilisandDaucus carotahas been investigated. A strain of carrot tissue was isolated that grew with a compact habit, in contrast to the highly friable habit of the parent strain. Its dividing cells were arranged quite differently than in the parent strain. Earlier work had shown thatHaplopappuscultures could be reversibly altered in their pigmentation and form, by changing the culture medium. This was confirmed, and it was further shown that pronounced changes in nitrogenous compounds also occurred in response to factors in the medium. However, strains ofHaplopappuswere isolated which differed persistently from the parent strain, even when they were maintained under the same conditions. The variant strains, grown in the same medium, showed differences in their content of nitrogenous compounds. Stock cultures also changed spontaneously with time with respect to their content of nitrogenous substances. Acriflavine, at low concentration, inhibited the growth and formation of colonicsbycells plated on nutrient agar, but, by prolonged exposure to sublethal amounts of the drug, resistant strains were isolated. Certain of the spontaneous variant strains were found to differ from each other and from the parent strain in their chromosome complements in ways that are described and to which the observed changes in morphology and metabolism of the cultures may be attributed. The variations that may occur in the free cells in culture are contrasted with the greater uniformity of the cells as they exist in the plant body.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06703.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Some homokaryotic isolates ofVerticillium albo‐atrum(microsclerotial form) vary radically in colony appearance even when temperature, lighting, humidity and medium content are held constant. This variation is so great that it may easily be mistaken for hereditary variation. The environmental factors which control the variation are differences in shape of medium on which the colonies grow and presence or absence of otherVerticilliumcolonies. The cause of the variation appears to be a diffusible substance whichVerticilliumitself produces.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06704.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Plants of 5 species were acclimated for periods of not less than 3 weeks in a desert and subalpine environment. Subsequent measurements of photosynthesis over a range of temperatures indicated both rate modifications and shifts in temperatures of optimal photosynthesis. Plants of all species acclimated in the coldest environment were more efficient in terms of percentage of maximum photosynthetic activity at colder temperatures. Conversely, plants acclimated in the desert environment were more efficient at warmer temperatures.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06705.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

To determine to what extent higher plants can metabolize mannitol‐C14, it was introduced into 26 species belonging to 17 families. Fifteen species respired mannitol as measured by the evolution of C14O2. In several species, includingFraxinus americanaandSyringa vulgaris,mannitol was respired at rates comparable to those of fructose and glucose. In others, includingAvena sativa,mannitol was respired only slightly. A lag period in the production of C14O2from mannitol‐C14, which does not occur after offering glucose‐C14or fructose‐C14, was considered to be due to a slow penetration of mannitol to the site of its metabolism. The first step in the dissimilation of mannitol was shown to be its oxidation to fructose, possibly via phosphorylated intermediates. Mannitol was not found to be a constituent of polysaccharides ofSyringa vulgaris.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06706.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Two new endocommensal fungi belonging to the Genistellaceae (Harpellales) were isolated in pure culture from the hindguts of Diptera larvae:Smittium culesitaefrom the mosquitoCulesita impatiens,on a 10% brain‐heart infusion, andS. simuliifrom the black flySimulium argus,on a potato dextrose‐yeast extract medium. Both species appear to have no unusual nutritional or cultural requirements and can grow on synthetic media and a variety of extract media, as can also the other 4 existent isolates ofSmittium (Rubetella).Identical isolation methods proved unsuccessful for culturing various other genera of Harpellales and Eccrinales, with the exception of anEnterobryussp. (from the fiddler crabUca crenulata)which survived several generations before ceasing to grow. The genusRubetellaTuzet&Manier is discarded in favor ofSmittiumPoisson, for reasons discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06707.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Relationships of the putativeRuelliaspecies,R. caroliniensis, R. ciliosa, R. heteromorpha,andR. succulentawere analyzed by population sampling, investigation of chromosome numbers, garden transplants, and hybridization experiments. Character data from 25 local, Florida populations and from transplants were evaluated. Some interfertility of these “taxa” was demonstrated, as was some interfertility with other species occurring in the eastern United States. Chromosome numbers aren= 17 and 2n= 34. The effect of different breeding systems on population structure is discussed. Total evidence suggests that the 4 “taxa” in question be considered ecological races of a single species widespread in the eastern United States, namelyR. caroliniensis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06708.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

The kinetics of the effects of inductive photomorphogenically active light on etiolated peas have been studied by means of time‐lapse photography. The effects noted include: (1) A light‐induced decrease in the rate of stem elongation, beginning about 6 hr after the light treatment, and ending about 18 hr later. (2) A light‐induced opening of the apical hook, beginning ca. 2–5 hr after light treatment, and reaching its peak rate ca. 6 hr later. (3) A light‐stimulated circumnutation, starting usually about 15–22 hr after the light, and resulting in a decreased period of oscillation (from ca. 86 to ca. 76 min) and an increased amplitude (from 15° total angular displacement to about 40°). (4) A promotion of terminal bud growth, known from previous work to start at about 4 hr after irradiation and to reach a peak about 12 hr later. (5) A “bobbing” movement of the apex, apparently involving reversible hook and stem oscillations, which appears to be of endogenous origin and insensitive to light. These data furnish a kinetic background against which proposed biochemical mechanisms of de‐etiolation can be assessed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06709.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Dormant seeds of ponderosa pine(Pinus ponderosa)were stratified and then planted in the greenhouse. Changes occurring in the shoot apex during germination and growth of the seedlings were observed and are described. Cell divisions in germinating embryos are first noted on the flanks of the apex near the cotyledons. From these loci, mitotic reactivation proceeds up the flanks of the apex and inward toward cells of the rib meristem. Cells are dividing actively in all regions of the shoot apex of seedlings 12 days after planting, but no cytohistological zonation is evident due to differences in staining intensity and in cell and nuclear size. In 64‐day‐old seedlings the mitotic rate is reduced and the characteristic zonation of pine apices begins to appear. Zonation is even more evident in older seedlings. These observations are discussed in relation to the concept of initials and to theories concerning factors which regulate growth in the shoot apex.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06710.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

In liquid inorganic axenic cultures ofChlorococcum echinozygotumcontaining 20 ppm CaCl2, which was optimal for growth, motile cells were released in abundance; gametic fusion occurred commonly and the resulting zygospores reached a maximum of 31% of the total cell population. In a Sr‐replaeement medium, less growth, not quite equivalent to that with 5 ppm CaCl2, occurred, and more than 99% of the cells were non‐motile vegetative cells. Old Sr‐replacement cultures contained much‐enlarged vegetative cells which, upon transfer to fresh Sr‐medium, produced entrapped motile cells equivalent in number to those produced and released upon transfer to fresh Ca‐medium. Release of these entrapped cells, after their production in Sr, was induced in 4 hr by transferring them to Ca (25 ppm CaCl2).

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06711.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Photosynthetic and respiratory rates were studied inCetraria islandica, C. nivalis,andCladonia rangiferinain the alpine zone of Mt. Washington, New Hampshire. Measurements were made in the field using an infrared gas analyzer; light, temperature, and thallus water content were varied. In all species, considerable reduction in photosynthesis and respiration occurred with drying, more rapidly in photosynthesis than respiration. Optimal photosynthetic rates in all 3 species occurred at 15–20 C with light levels of 1,600 ft‐c. Light compensation points ranged from 200 to 350 ft‐c. Optimal respiratory rates were attained at 15 C in the 2 species ofCetrariaand at 20 C inCladonia.The data indicate that these wide‐ranging, arctic‐alpine and arctic‐temperate lichens on Mt. Washington are quite well adapted to a moist, foggy environment with cool temperatures and low light levels, conditions which predominate in summer.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06712.x

出版商:Wiley    

年代:1964

数据来源: WILEY