摘要:

When seedlings ofPhaseolus vulgariswere grown under controlled conditions at a light intensity of 3200 ft-c, 60% relative humidity, and at nitrogen levels of 5.25, 52.5, and 210 ppm, growth of the buds at the cotyledonary node, which served as a measure of apical dominance, showed a positive correlation with the nitrogen supply and with the soluble nitrogen content of the hypocotyl. Increasing the nitrogen supply to 420 ppm caused a proportionate increase in soluble nitrogen content but no additional bud growth response. That the growth response was limited by water supply was shown by growing plants at 420 ppm nitrogen and relative humidities of 30, 60, and 90%. Each reduction in water stress, as measured by leaf relative turgidity, caused a highly significant increase in growth of the cotyledonary buds. Under high nitrogen, low water stress conditions, bud growth was markedly inhibited by reduction of the light intensity from 3200 to 700 ft-c.These results support the concept of nutrient competition as a major factor in the mechanism of apical dominance and also suggest that conflicting reports on the effect of externally applied growth-regulating substances on lateral bud inhibition may be due partly to environmentally induced differences in nutritional status of the experimental plants.

ISSN:0008-4026    

DOI:10.1139/b73-036

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The symptoms of zinc toxicity in beans, soybeans, and corn are described. In beans and soybeans these include the deposition of a red-brown pigment in parenchyma cells of the cortex, xylem and phloem of veins, petioles, and stems. The pigment fills some parenchyma cells completely but is confined to the cell walls of others. The xylem vessel lacunae remain free of the pigment. Extensive disorganization of cortical cells is evident in veins. The pigment is suspected to be a polyphenolic substance of unknown biochemical origin.

ISSN:0008-4026    

DOI:10.1139/b73-037

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Mycoarctium ciliatumis described and illustrated as a new species and a new genus found on deer dung from Colorado, U.S.A. The small, very light brown apothecia have numerous, rigid, septate hairs. The asci are eight-spored, clavate, without an operculum, and evanescent. The ascospores have reticulate ridges and are not forcibly discharged.

ISSN:0008-4026    

DOI:10.1139/b73-038

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The genusCryptoclinePetrak is redescribed. Fourteen species are accepted, of which 10 are illustrated.Cryptocline nobile(Sacc.) Arx andC. proquinqua(Bubák and Vleugel) Arx are excluded from the genus whileRhabdogloeum hypophyllumD. E. Ellis and Gill is transferred to it.

ISSN:0008-4026    

DOI:10.1139/b73-039

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

In preliminary studies of terrestrial orchids of the Thunder Bay regionCypripedium reginaeshowed greatest promise as a species for the investigation of the effects of temperature, light, and nutrients. The orchid was grown from seed in sterile cultures on agar slopes of media consisting of various combinations of minerals, sugars, casein hydrolysate, yeast extract, potato extract, the vitamins thiamine, pantothenic acid, and pyridoxine, and the aminopurines kinetin, kinetin riboside, 6(γ,γ-dimethylallylamino)purine, and zeatin.Better germination and growth occurred at 25 °C vs. 15 °C. Germination was better in the dark than in the light. The young protocorms are adversely affected by light until a crucial stage of development is reached. Premature exposure to light, even at the low intensity of 70 lm/ft2, caused mortality.There was no germination on sterile-distilled-water agar or on mineral media alone. Mineral–sugar media produced fairly healthy plantlets; better results were obtained with sucrose, dextrose, and fructose, respectively.Cypripedium reginaewas highly intolerant of the casein hydrolysate and yeast extract supplements. Potato extract at 10% of the original concentration was very beneficial.In some cultures the presence of ammonium ions could be responsible for a marked enhancement of growth (and a slight stimulation of germination irrespective of the presence of sugar). The right nitrate/ammonium ratio may be critical. Low levels of nitrate or high levels of chloride or both hindered responses to iron supplements. Also,C. reginaemay have a low calcium requirement.The effects of the three vitamins were restricted to the leaves, causing them to broaden to natural proportions while those in the controls remained spindly. Thus,C. reginaemay be heterotrophic for those vitamins.There was no morphogenetic response to the four aminopurines. They impeded growth equally in the light as in the dark.

ISSN:0008-4026    

DOI:10.1139/b73-040

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Pythium sulcatumn. sp. was isolated from carrots with browned and forked roots grown in muck soils from Wisconsin and Florida. It is primarily distinguished by small oogonia and oospores and by antheridia which are variable in shape and frequently adorned with single or multiple transverse furrows and folds, for which the species is named. Zoospores are rarely produced; vesicles always arise from filamentous sporangia indistinguishable from vegetative hyphae. Vegetative hyphal bodies vary in shape and are outnumbered by sexual bodies on most media. Radial growth rates ofP. sulcatumon potato dextrose agar are slower than those ofP. irregulare, P. paroecandrum, andP. sylvaticumover a wide temperature range, andP. sulcatummay easily be distinguished from these species on that basis.

ISSN:0008-4026    

DOI:10.1139/b73-041

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Since previous studies indicated a requirement for high levels of exogenous sucrose for induction of sporogenous tissue on excised set III leaves of cinnamon fern, the initial part of this study was performed to determine which hexose moiety of sucrose would serve as the more active substrate for sporangial induction. Glucose was found to be preferentially used for sporophyll induction and resulted in more extensive development than was seen in those leaves grown on fructose. Endogenous carbohydrate levels were measured by gas–liquid chromatography. In decreasing order of quantity, freshly excised primordia contained xylans, sucrose, fructose, β-D-glucose, xylose, and α-D-glucose. In leaves cultured on medium with sucrose levels of 2, 4, 6, 8, and 10%, the highest levels of all endogenous carbohydrates studied were found in leaves grown on medium with 2% sucrose. The xylans accumulated in leaves grown on medium with all sucrose levels and the amounts present were generally above those of uncultured primordia. The xylans represented the highest quantities of the carbohydrates measured and appeared to be a major storage carbohydrate in both cultured and uncultured leaves. The concentrations of sucrose, on the other hand, generally declined and were, in all cases, below the amounts in uncultured primordia. Increasing levels of exogenous sucrose above 2% generally resulted in a decline in levels of the other internal carbohydrates afterweeks of culture, but the respective quantities were generally above those of freshly excised primordia. Enzymatic analysis failed to reveal any starch in the leaves. It is suggested that although increasing sucrose levels resulted in an increase in the growth rate, it would appear that sucrose is important in sporangial induction because of some mechanism in addition to its effect on an increasing growth rate.

ISSN:0008-4026    

DOI:10.1139/b73-042

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

White spruce seedlings containing urease were exposed to 0.16 Murea for 4 h in continuous light. Seedlings accumulated total soluble nitrogen as amides and arginine, and increased their content of bound amino acid nitrogen. In darkness, total soluble nitrogen declined and the increase of total bound amino acids was not as great as in light. In both treatments, the fate of tritiated water was examined by recovery of nonexchangeable tritium from amino acids. As urea was consumed, more tritium was recovered from seedlings in light than in darkness. In both treatments tritium followed the nitrogen of urea and was bound covalently, initially in glutamic acid, and subsequently wherever an α-keto acid was a precursor for the synthesis of the corresponding amino acid, viz. alanine and aspartic acid. In light, tritium was recovered mainly from glutamic acid, followed by glutamine, and to a lesser extent by γ-aminobutyric acid. In darkness, while glutamic acid was prominent initially, more radioactivity was recovered from γ-aminobutyric and glutamic acids compared to glutamine and to the light treatment. Glutamic acid was the main bound amino acid containing covalent tritium.The occurrence of tritium at the α-carbon of glutamic acid was supported by transfer of this tritium after decarboxylation to γ-aminobutyric acid, and by conversion of bound glutamate-3H to radioactive pyrrolidone carboxylic acid during acid hydrolysis of protein.Although urea nitrogen contributed to arginine synthesis in light, no tritium was found in arginine nor its precursors in the ornithine cycle until later, when nearly all amino acids were radioactive. This is consistent with the absence of covalent binding of tritium in ureido precursors leading to arginine biosynthesis, and supports the idea that tritium did not readily follow the carbon of urea into covalent linkage.

ISSN:0008-4026    

DOI:10.1139/b73-043

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

In early fall, the high levels of free arginine nitrogen in spruce buds were eventually replaced by proline nitrogen, and in late spring, glutamine nitrogen accumulated. In late October when levels of free proline nitrogen were high, bud primordia from terminal shoots were excised and exposed to uniformly labeled14C-L-proline and14C-L-glutamine. The main early products from14C-L-proline were Δ1-pyrroline-5-carboxylic acid, glutamic-γ-semialdehyde, and glutamic acid. Later products included glutamine, γ-aminobutyric acid, and to a much lesser extent pyrrolidone carboxylic acid, ornithine, and arginine. In protein, radioactivity was recovered from proline, glutamic acid, and hydroxyproline.Products from14C-glutamine were mainly glutamic and α-ketoglutaric acid as well as proline, γ-aminobutyric acid, alanine, and pyrrolidone carboxylic acid. In protein, glutamic acid, aspartic acid, and proline contained carbon-14. Results indicated that proline and glutamine were related by their carbon metabolism through a common path involving glutamic acid. However, the main feature of glutamine metabolism was the removal of its α-amino and the amide nitrogen to yield α-keto acids especially α-ketoglutaric acid. The occurrence of α-ketoglutaramic acid could have accounted for succinamic acid and succinimide derived from14C-L-glutamine.

ISSN:0008-4026    

DOI:10.1139/b73-044

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A gentle filtration technique is described for concentration and fixation of phytoplankters directly on Millipore membranes, followed by subsequent removal of the membrane and embedment of the cellular material in epoxy resin. The technique shows excellent preservation of cell morphology, especially of fragile algal cells (dinoflagellates, zoospores, etc.), with little loss of material, and affords permanently fixed samples for both light and electron microscopy. It is ideally suitable for handling small amounts of algal cultures and for frequent sampling of such cultures in time-sequence studies. Adaptations of the technique are described which enable (1) high proportion of flagella preservation, (2) successful concentration of algal cells from water samples of low population density, and (3) convenient preparation of samples for "freeze-etching" or histochemical studies. A further application to scanning electron microscopy is described, where the replacement of Millipore membranes by Nuclepore filters affords the differentiation of nannoplanktonic cells from non-living debris and detritus, thereby holding promise for ecological studies of natural waters.

ISSN:0008-4026    

DOI:10.1139/b73-045

出版商:NRC Research Press    

年代:1973

数据来源: NRC