摘要:

A small fraction of individual cellulose microfibrils in plant cell walls show appreciable bending along a portion of their length in a plane tangential to the cell surface. Segments of such curved microfibrils from transverse sections ofAvenacoleoptile epidermal or parenchyma cells do not straighten when they are freed from the constraints imposed by adjacent microfibrils, amorphous cell wall constituents, or the embedding medium. The curvature of these segments is not affected by immersion in cold water for 30 minutes, in hot water for 10 minutes, or in steam at 100° for 10 minutes. The results indicate that there is no elastic deformation of bent cellulose microfibrils in dried plant cell walls. The curvature of the microfibrils in the absence of elastic deformation suggests either (a) that cellulose microfibrils may be synthesized in a bent strain-free condition or (b) that cellulose microfibrils are synthesized in a straight form, followed by elastic deformation with subsequent release of strain by recrystallization on drying.

ISSN:0008-4026    

DOI:10.1139/b65-036

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

The number of spikelets on the differentiating inflorescence and the ear at anthesis was highest at high light intensities and at low temperatures. The length of the developing inflorescence and the ear, the height of the main stem, and the total plant dry weight at the time of anthesis were also greatest under these conditions.These results are related to differential effects of temperature and light intensity on the rates and duration of apical elongation, morphological development of the ear, and spikelet formation.

ISSN:0008-4026    

DOI:10.1139/b65-037

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

The morphological variability of the early stages in the development of the Plasmodium is recorded. In all stages a semblance of the formerly anterior extremity of the diploid swarmcell may be recognized in the young plasmodium. Observations indicate that the planogametes and the amoeboid plasmodial cells are photophobic and that the aphanoplasmodium, characteristically found in the Stemonitaceae, appears during a stage in plasmodial growth. In microculture the hyphoid plasmodial stage disintegrates into protoplasmic spherules.

ISSN:0008-4026    

DOI:10.1139/b65-038

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

A collection of the allotetraploidAnemone stylosaNelson from Heliotrope Mts., Gunnison, Utah, was successfully crossed withA. multifidaPoir. (tetraploid) and the diploidsA. ripariaFern.,A. virginianaL.,A. silvestrisL., andA. pavoninaLam. The karyotype ofA. stylosaresembles that ofA. multifidaexcept for modifications of chromosome VII in the “large set” and chromosome IV in the “small set”. Meiotic analysis inA. stylosa×A. multifidahybrids indicates that these modifications are due to a chromosome interchange and that this is the only detectable chromosome rearrangement between the two species.Analysis of the crosses with the diploids corroborates these conclusions and suggests that the donor of the “large-chromosome” set ofA. stylosahad theA. ripariakaryotype rather than theA. virginianaone.A. stylosamay have originated as a variant ofA. multifidain which an interchange became established homozygously.

ISSN:0008-4026    

DOI:10.1139/b65-039

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

All 24 varieties of barley tested were found susceptible to both a celery-infecting strain (CAYV) and a non-celery-infecting strain (NAYV) of aster yellows virus transmitted byMacrosteles fascifrons(Stål). Percentage of infection varied among varieties and between virus strains. There was no apparent correlation between degree of susceptibility and barley type, length of incubation period in the plant, or percentage survival of insects on varieties. Symptoms were generally slower to appear for NAYV than for CAYV. Of 3080 seeds harvested from infected plants, 2697 germinated but none of the resulting plants developed aster yellows symptoms. The symptoms produced on diseased plants are discussed and illustrated.

ISSN:0008-4026    

DOI:10.1139/b65-040

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Physiological studies ofLindra thalassiaeOrpurtet al., a scolecosporous pyrenomycete infecting leaves of turtle grass (Thalassia testudinumKönig), have demonstrated the stimulating effect of leaf tissue on fungal reproduction. The fungus does not sporulate on wood under field and laboratory conditions. In contrast,Thalassialeaves are an ineffective substrate for reproduction by various lignicolous marine Ascomycetes common in Biscayne Bay, Florida.L.thalassiaeshows a euryhaline growth response in the mycelial stage, but requires higher concentrations of seawater for maximal reproduction. Thiamine and biotin, in conjunction with gas-sterilized leaf sections, support fungal reproduction. The vitamin combination can be replaced by additions of natural plant materials to culture media. It has been shown that maturation of the reproductive structure rather than vegetative growth alone is a more valid criterion for differentiation of physiological characteristics ofL. thalassiaeand lignicolous species.

ISSN:0008-4026    

DOI:10.1139/b65-041

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Modern pollen content has been examined in 10 surface samples from the Nichicun Lake area, southwest of Schefferville, Quebec, and from three other localities in the same region. The pollen assemblages obtained reflect with fair reliability the regional characteristics of the northern boreal forest. Long-distance wind transport over several hundred miles is indicated by the presence of occasional ragweed and hardwood pollen grains from south of the boreal forest region. A morphological study of the black spruce pollen found indicates a rather wide range of variability, greater than that found in the pollen of black spruce south of this region.

ISSN:0008-4026    

DOI:10.1139/b65-042

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Diploids of four species of desmids were produced in culture. Morphological and cytological evidence of their diploidy is presented. A possible tetraploid was also detected. It is suggested that diploidy also occurs in nature. The taxonomic position of various forms of diploids with respect to the haploid forms is discussed.

ISSN:0008-4026    

DOI:10.1139/b65-043

出版商:NRC Research Press    

年代:1965

数据来源: NRC