摘要:

Seasonal colonization patterns of vesicular-arbuscular mycorrhizal fungi at four sites were monitored in the roots of winter wheat through the October to August growing season, as were a variety of environmental factors which might influence these patterns. Fall colonization was observed at the two sites which were the most highly colonized at all five harvests. The other two sites were not colonized until late spring and never attained high levels of colonization. Soil phosphorus, soil moisture, and plant physiology were shown to be most highly correlated with these patterns, while temperature was not believed to be an important factor.Key words: endomycorrhiza,Glomus,Sclerocystis,Acaulospora,Scutellospora.

ISSN:0008-4026    

DOI:10.1139/b91-011

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A new system was designed that permits examination of long distance transport of water and nutrients through mycorrhizal hyphae without the architectural, nutritional, and physiological differences associated with comparing mycorrhizal and non-mycorrhizal plants. The "rhizobox" system consists of a rectangular box with a chamber where mycorrhizal plants are grown and an outer chamber where hyphae proliferate. The two chambers are separated by root-excluding screens and an air gap. Two slightly different experiments examined hyphal transport. The first experiment demonstrated the difficulties of comparing water use by mycorrhizal and nonmycorrhizal plants because of dissimilarities in plant architecture. The second experiment avoided the problem by comparing intact mycorrhizal plants with plants where hyphae passing to the outer chamber were severed. In the outer chamber, a 5 mM solution of RbCl was injected. Intact mycorrhizal plants transpired 35% more water than plants with severed hyphae in 16 h. The source of transpired water was the outer chamber, as suggested by lower soil moisture in the outer chamber and a higher Rb content in intact plants. This demonstrates an active role in water and nutrient transport by mycorrhizal hyphae, since plants were of a similar nature except for hyphal access to the outer chamber.Key words: water transport, mycorrhizal plants, rhizobox system, nutrient transport, hyphae.

ISSN:0008-4026    

DOI:10.1139/b91-012

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Recently identified conditions forin vitroperithecia formation made it possible to demonstrate the existence of previously suggested heterothallism inPhaeosphaeria nodorum. Of the 28 possible pairwise crosses between the eight cultures derived from the spores of a single ascus, 9 were fertile, whereas none of the cultures ever produced fertile perithecia on their own. This result is smaller than the one obtained in classical bipolar heterothallism and suggests the existence of another incompatibility mechanism. The growth and the colour of mycelia derived from eight single ascospores from the same ascus seem to cosegregate with the factor for heterothallism. The formation of microspores in colonies from single ascospores indicates that they may play a role in the formation of perithecia. Used for fertilization, these microspores showed that they were able to bring the complementary nucleus, thus enabling the differentiation of perithecia. However, they are able to germinate and do not behave strictly as spermatia.Key words:Phaeosphaeria,Leptosphaeria nodorum, heterothallism, microspores.

ISSN:0008-4026    

DOI:10.1139/b91-013

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Little information has been available to justify the species status of the rare TurkmenianMedicago sinskiaeUljan. recognized by Uljanova in 1964. The holotype and plants raised from its seeds were examined, the chromosome number was determined, and a numerical taxonomic comparison was made ofM.sinskiaeand the other 12 species ofMedicagosectionSpirocarpossubsectionPachyspirae. It was found thatM.sinskiaeis well separated from the most closely related species ofMedicagoand deserves recognition at the rank of species.Key words:Medicago sinskiae, Leguminoseae, alfalfa, taxonomy.

ISSN:0008-4026    

DOI:10.1139/b91-014

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Lycorine stimulates budding inCryptococcus terreus. In lycorine-treated cultures, there is an increase in dry weight and even more in the number of cells.Cryptococcus dimennaeis not affected by lycorine. The filtered medium of lycorine-treated cultures ofC.terreusstimulates the growth ofC.dimennae. The possibility thatC.terreusis able to degrade lycorine and that a degradation product is able to stimulate budding inC.terreusandC.dimennaeis discussed. Scanning electron microscopy analysis shows that cells in lycorine-treated cultures ofC.terreusare round and smaller than those of the control. Similar differences are found inC.dimennaecells cultured in the filtered medium ofC.terreus, whereas they appear identical if directly cultured either with or without lycorine.Key words: lycorine, yeasts,Cryptococcus.

ISSN:0008-4026    

DOI:10.1139/b91-015

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Root architecture of five warm-season and five cool-season grasses was compared. The cool-season grasses had significantly more primary and secondary roots than warm-season grasses, and the diameter of primary, secondary, and tertiary roots of cool-season grasses was significantly smaller than that of warm-season grasses. Soil microorganisms, mycorrhizae, and P fertilization did not affect root number or diameter of the cool-season grasses; root number of warm-season grasses did respond to mycorrhizae and P fertilization, but not soil microorganisms. Specific root length of cool-season grasses was not altered by mycorrhizae, soil microbes, or P fertilization, and was significantly greater than that of warm-season grasses, particularly those inoculated with mycorrhizae. Topological analysis of root architecture revealed that mycorrhizal symbiosis inhibited root branching in warm-season grasses but had no effect on rooting strategy of cool-season grasses. In contrast, P fertilization did not substantially alter root branching in warm- or cool-season grasses. Apparently, root architecture of the mycorrhizal-dependent warm-season grasses is quite plastic, allowing energy expenditure for root development to be conserved; the root architecture of the less mycorrhizal-dependent cool-season grasses appears to be fixed and does not alter to accommodate the symbiosis.Key words: topology, rooting strategy, C3, C4.

ISSN:0008-4026    

DOI:10.1139/b91-016

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Propagules ofPseudoaegerita matsushimae, an aero-aquatic hyphomycetous fungus commonly occurring on the surface of woodland ponds, were shown to germinate readily on moist surfaces. After an initial latency period of approximately 3 h during which less than 5% germination occurred, the ensuing 2–3 h saw 97% of all propagules germinate. This figure did not increase after 16 and 24 h. Using this information as a control, germinability was tested in many situations that simulated the application of pesticides and also their carriers. Oil emulsions or emulsifiable oil concentrates containing surfactants were up to 30% more toxic than mineral oils which did not contain such additives. The surfactant itself (Tween 80) did not significantly inhibit germination. Our initial studies indicated that aromatic carriers such as xylene or turpentine are highly toxic toPseudoaegerita matsushimaepropagules, whereas aliphatic carriers such as kerosene produce no significant reduction of germination.Key words: aero-aquatic fungus, pesticide carriers, aliphatic hydrocarbons, aromatic hydrocarbons, environmental impact.

ISSN:0008-4026    

DOI:10.1139/b91-017

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

InMarsilea quadrifolia, lateral roots arise from modified single cells of the endodermis located opposite the protoxylem poles within the meristematic region of the parent root. The initial cell divides in four specific planes to establish a fivecelled lateral root primordium, with a tetrahedral apical cell in the centre and the oldest merophytes and the root cap along the sides. The cells of the merophyte divide in a precise pattern to give rise to the cells of the cortex, endodermis, pericycle, and vascular tissues of the emerging lateral root. Although the construction of the parent root is more complicated than that of lateral roots, patterns of cell division and tissue formation are similar in both types of roots, with the various tissues being arranged in similar positions in relation to the central axis. Vascular connection between the lateral root primordium and the parent root is derived from the pericycle cells lying between the former and the protoxylem members of the latter. It is proposed that the central axis of the root is not only a geometric centre, but also a physiological centre which determines the fate of the different cell types.Key words: lateral root initiation,Marsilea quadrifolia, root histogenesis.

ISSN:0008-4026    

DOI:10.1139/b91-018

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Tubular structures were observed in the developing plastids of the meristematic regions of spinach, beet, and turnip leaves. These structures were located near the plastid periphery, were frequently in contact with the plastid envelope and (or) the internal plastic membranes, usually had a near-perpendicular orientation with their associated membranes, and were decorated with a distinct striated coating. Based on the high degree of structural similarity, it was suggested that these tubules represent a unique class of plastid inclusions with a common specialized function. A detailed examination of the spinach plastids provided evidence that the tubules are membranous structures and that the tubular lumen is confluent with that of the plastid envelope and also some internal plastidial compartments. It was also shown that the membranes of the tubules differed from the other plastidial membranes in that they were thinner and only lightly stained by osmium – potassium ferrocyanide postfixation.Key words: tubular, structures, developing, plastids, dicots.

ISSN:0008-4026    

DOI:10.1139/b91-019

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The distribution of silicon in the leaf epidermis of cucumber (Cucumis sativusL.) grown in hydroponic nutrient solutions supplemented with soluble silicates was examined using scanning electron microscopy and energy dispersive x-ray analysis. Silicon was found primarily in cells surrounding the bases of the trichome hairs. During infection bySphaerotheca fuliginea(Schlecht.:Fr.) Poll., areas of host cell wall adjacent to the germinating hyphae showed altered surface morphology and high concentrations of silicon. Measurements of total hyphal length per colony showed the fungal colonies grown on silicate-treated plants were significantly smaller than fungal colonies grown on control plants. In the early stages of infection, the presence of high silicon surrounding colonies was correlated with lower fungal growth.Key words: silicon, x-ray analysis, hydroponics,Cucumis sativus,Sphaerotheca fuliginea.

ISSN:0008-4026    

DOI:10.1139/b91-020

出版商:NRC Research Press    

年代:1991

数据来源: NRC