摘要:

The formation of silica cells in the sheath epidermis of wheat is described. These cells are of two types, unpaired rod-shaped cells and isodiametric cells paired with basal cork cells. When the leaves have expanded fully, the potential silica cells have reached their mature shape, with thin, usually concave outer walls. At this stage, the nucleus and cytoplasm of these cells are suddenly lost, producing apparently empty cells. After this, silica appears to accumulate and precipitate in these empty cells. Very early stages of silica accumulation could not be detected, but later, refractive granular masses of precipitated silica gel can be seen in fixed, dehydrated preparations. In aqueous mounts the accumulating silica appears as a translucent peripheral mass, surrounding vesicular contents. Further silica accumulation produces the mature, glassy silica bodies containing small vesicles which probably represent some remnant of the disintegrated cytoplasm. The young silica cells did not seem to have the low pH levels sometimes suggested as initiating silica precipitation. Enzyme localization tests did not distinguish potential silica cells from their immediate neighbors.

ISSN:0008-4026    

DOI:10.1139/b69-120

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Seasonal growth patterns and water balance of first- and second-year strobili and seeds ofPinus resinosaAit. were studied. Strobili emerged from the bud in late May or early June and grew slowly during the first season, reaching approximately 1/40 the weight of mature strobili. After a rapid period of hydration which lasted until mid-June, the weight of water in first-year strobili remained stable, but percentage of moisture decreased, primarily because of increasing dry weight. Strobili resumed growth in mid-April of the second year and grew slowly until June. Then, at about the time that fertilization of ovules occurred, dry weight increment of strobili increased greatly until a final weight of 6 to 8 g was reached early in August. However, strobili reached final size in mid-July. After mid-June, both the weight of water and percentage of moisture of second-year strobili decreased greatly, reflecting characteristic dehydration of cones during maturation. Seeds increased rapidly in dry weight after fertilization, but decreased sharply in percentage of moisture and weight of water.Continuous monitoring of strobilus diameters with dendrographs showed that, during the first year, strobili expanded slowly and showed diurnal fluctuations in diameter during periods of water stress. Second-year strobili showed three growth phases: an initial phase characterized by net diameter increment; a second phase in which no large net diameter increment took place although diurnal fluctuations regularly occurred; and a third, dehydration, phase during which time strobilus diameters decreased, accompanied by diurnal contraction and partial reexpansion.

ISSN:0008-4026    

DOI:10.1139/b69-121

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Morphological features were studied of callus tissues from carrot root, endive embryo, lettuce leaf petiole and stem, parsley and spinach leaf petiole, and navy bean and red kidney bean stem grown on solid C- or D-medium. The callus tissue of carrot, endive, lettuce leaf petiole and stem, parsley, and red kidney bean were irregularly lobed while the callus tissues of navy bean and spinach were hemispherical and somewhat flattened, respectively. The cultures of carrot and endive were firm and massive, while the calli of other species were friable. Callus cells of these seven species, examined with the phase microscope, varied in size and shape. The callus cells of carrot, lettuce leaf petiole and stem, navy bean, and red kidney bean were spherical, oval, and elongated. Endive callus tissue consisted of oval and elongated cells and that of parsley consisted of spherical and oval cells, while spinach callus usually consisted of spherical cells. Elongated cells ranged from 204 to 475 μ in length by 45 to 92 μ in width, spherical cells 62.5 to 129.8 μ in diameter, and oval cells 118 to 172.8 μ in length by 63 to 94.5 μ in width. Variations were noted in the morphology and number of cell inclusions including the nucleoli, plastids, mitochondria, and starch granules. In chlorophyllous cells, the chloroplasts were generally scattered in the cytoplasm, but in spinach it often surrounded and obscured the nucleus. Varying numbers of starch granules were seen around the nucleus and in the cytoplasm.

ISSN:0008-4026    

DOI:10.1139/b69-122

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The brief history ofAcrodictysM. B. Ellis is reviewed and two new species from rotting bark ofPopulusare described and illustrated.Acrodictys fuliginosan. sp. is characterized by non-proliferating conidiophores and obovate, shining-black conidia with three transverse and three to six longitudinal septa. InAcrodictys excentrican. sp. a succession of variably shaped shining-black conidia is formed from the long, readily proliferating conidiophores. Conidia are typically five-celled, one of the two apparently lateral pale brown inflated cells is the recurved apical conidium cell and the other is separated from the basal conidium cell by a longitudinal septum.

ISSN:0008-4026    

DOI:10.1139/b69-123

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Chromosome numbers are reported for 12 native North American species ofSalixand one natural hybrid. The arctic speciesSalix alaxensisvar.alaxensis, S. fuscescens, S. ovalifoliavar.ovalifolia, S. phlebophylla, andS. reticulataand the boreal speciesS. arbusculoidesare diploids, 2n = 38. Tetraploid counts, 2n = 76, are reported for the arcticS. planifoliassp.pulchra. Taxa with more than one chromosome number includeS. planifoliassp.planifoliaandS. pedicellaris, each of which has tetraploid and triploid levels;S. arcticas.l., which is tetraploid in the eastern American arctic and hexaploid in the Alaska and Eurasian arctic; andS. athabascensiswith triploid, tetraploid, and hexaploid levels. Intra-population variation in chromosome number is reported forS. glaucain which tetraploids, pentaploids, and hexaploids occur in a single Alaskan population.

ISSN:0008-4026    

DOI:10.1139/b69-124

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

A comparative study of the magnitude of growth rate variation among isolates ofPhytophthora infestans(Mont.) de Bary taken from a high and a low field resistant variety of potato has shown it to be greater in the former than in the latter, even though both crops were infected by the same population of the pathogen. Competition between spores, and adaptation to the varieties, are put forward as possible alternative explanations.

ISSN:0008-4026    

DOI:10.1139/b69-125

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The cytology of the ascus initiation and the ascus development in two species of the genusChaetomidiumFuckel are described. InC. subfimeti, the initial of the ascus is the binucleate penultimate cell of the crozier, whereas inC. barbatum, in the absence of croziers, the ascus initial is a binucleate ascogenous cell. The sequential stages of ascus development (one-, two-, four-, and eight-nucleate asci) in the two species are reported. Mature ascospores are binucleate.

ISSN:0008-4026    

DOI:10.1139/b69-126

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Helminthosporal (H-al) is a phytotoxic sesquiterpenoid dialdehyde produced by the common root rot fungus,Bipolaris sorokiniana(Sacc. in Sorok.) Shoemaker. In addition to its phytotoxic properties, H-al can stimulate the synthesis of amylase and other proteins by embryoless barley seeds, having an optimum effect at a concentration of 0.1 mM. The monoacid derivative formed by air oxidation of H-al was only one-fourth as active as the dialdehyde. Helminthosporal and, particularly, the monoacid, can also inhibit the gibberellic acid (GA3) induced synthesis of amylase in barley half-seeds. The extent of inhibition was reduced when these compounds were added to half-seeds preincubated with GA3. The results of studies on the effect of H-al and its monoacid on the respiration of various plant tissues, including barley half-seeds, and on protein synthesis both in vivo and in vitro, have suggested that these substances inhibit amylase synthesis by blocking the supply of energy (ATP) in cells of the aleurone layer. Part of the inhibition may also involve the binding of the monoacid to a receptor site concerned in the mechanism of amylase induction by GA3. The hypothesis was tested that some type of relationship might exist between the inhibition of specific mitochondrial reactions and the induction of amylase synthesis. Among a wide variety of mitochondrial inhibitors only atractyligenin, amytal, and the lactone derivative of H-al could promote amylase synthesis. Amytal had high activity. The role of the mitochondrion in GA3-induced processes in the barley aleurone cell appears to warrant further investigation.

ISSN:0008-4026    

DOI:10.1139/b69-127

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

A score of pleiomerous flowers ofHyacinthus orientalisL. are described. About a quarter of these unquestionably result from synanthy. Morphology shows that, in some of the specimens, synanthy is caused by ontogenetic (postgenital) fusion. If a similar origin is admitted for certain nearly normal specimens encountered in this study, it would be another indication that the end product of synanthy may be an entity simulating a simple flower.

ISSN:0008-4026    

DOI:10.1139/b69-128

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

A 2- to 3-year-old red pine seedling was allowed to assimilate14CO2for 3 hours at 2000 ft-c and left under the same illumination for 6 days, then divided into segments and analyzed. Ethanol extracts were resolved by chromatography, insoluble residues by chemical methods. The radioactivity in various components was determined for all segments. Autoradiographs were made from stem sections at four levels.Radioactivity was found in all parts of the plant. Per unit mass of tissue, it was more or less uniformly apportioned among root, stem, and leaves, but the expanding terminal bud contained 5 times as much activity per gram of tissue. Overall, about one-third of the radioactivity was in insoluble compounds, mainly in cell wall constituents. In localities where conspicuous growth had occurred the proportion was higher. Autoradiographs of stem sections showed that14C was concentrated in newly differentiated tracheids, and was still being incorporated after 6 days. About one-third of the activity in the ethanol extract was chloroform soluble, two-thirds water soluble. In the latter fraction, activity was largely in sugars and organic acids, little in amino acids. Activity in sugars, per unit weight of tissue, was more or less uniform throughout the plant, but activity in organic acids varied greatly. It was lowest in the stem, highest in the bud, where organic acids, almost exclusively quinic and shikimic, carried 75% of the label in the ethanol and water-soluble fraction, and 23% of all the activity in the bud.

ISSN:0008-4026    

DOI:10.1139/b69-129

出版商:NRC Research Press    

年代:1969

数据来源: NRC