摘要:

The effect of water stress on the mossDicranum polysetumSw. was studied in the growth chamber, and water potential (ψ) was found to vary as much as 15 atm between the tip of the plant and areas 2 to 4 cm within the cushion, which suggests that very little water is transported from the base of the stem to its tip. With an infrared gas analyzer it was determined that photosynthesis ceases at −21 to −23 atm and the moss remains dormant until it is rewetted. Upon rewetting, there is a sharp burst of respiration that doubles the normal CO2output. This burst reached its maximum level of 4 mg CO2 g−1 h−1within 15 min and was of short duration. Full photosynthetic rate was restored in 8 h.

ISSN:0008-4026    

DOI:10.1139/b75-318

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The 12S globulin fromBrassica junceaseeds has been dissociated by 6 Murea: 0.1 Mmercaptoethanol and the resultant products have been partially separated by preparative isoelectric focusing. Species that have the isoelectric points 4.75, 5.15, 5.40, 6.25, 6.70, 7.00, 7.20, 7.70, 8.30, 8.90, and 9.15 were detected. The results of poly aery lamide-gel electrophoretic analysis and the amino acid composition of the fractions suggested that the isoelectric species were distinct subunits.

ISSN:0008-4026    

DOI:10.1139/b75-319

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Fungi of the genusPhytophthorawere found to be associated with the initial stages of leaf litter decay ofRhizophora mangleL. and otherRhizophoraspecies in estuarine and coastal marine waters.Phytophthoraappears to be an important component of red-mangrove litter degradation systems throughout the tropics, which includes the Atlantic, Pacific, and Indian Oceans. The distributions ofPhytophthora vesiculaAnastasiou et Churchland and four new species ofPhytophthoraare discussed, as well as their occurrence in other tropical marine allochthonous spermatophytic leaf litter. The descriptions of the new species and varieties,Phytophthora bahamensis, P. epistomium, P. mycoparasitica, P. spinosavar.spinosa, andP. spinosavar.lobata, are presented.Pythiumwas rarely observed in the mangrove litter system, although one species,Pythium grandisporangiumsp.nov., is described.

ISSN:0008-4026    

DOI:10.1139/b75-320

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Measurements of the diffusion resistance ofOpuntiaplants that were growing in a controlled environment were made with a porometer to determine the effect of vapor pressure deficit (vpd) on the diurnal pattern of diffusion resistance. When the vpd was high during the light period and low in darkness, diffusion resistance was greater during the day than at night. However, when the vpd was low during the day, diffusion resistance was lower during the day than at night. Thus diffusion resistance ofOpuntia, at least under some conditions, is affected by the vpd of the atmosphere. This may explain the contradictory results that are reported by investigators working in different environments.

ISSN:0008-4026    

DOI:10.1139/b75-321

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Twelve Hyphomycetes that were collected on Barro Colorado Island, Canal Zone, Panama, during July 1973 are reported.Botryomonilia scheeleae, gen. & sp. nov. andUvarispora lignicolagen. & sp. nov. are described and illustrated.

ISSN:0008-4026    

DOI:10.1139/b75-322

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Buried seeds were studied in the subarctic forest east of Great Slave Lake, N.W.T., where 62 surface samples were collected in upland vegetation of different ages and compositions. No seeds germinated from any of the samples after cold treatment and exposure to warm, moist environment. Seeds were present in the soil, but most of them proved non-viable by the tetrazolium chloride test.Lack of viable buried seeds is consistent with a poleward decrease in the buried viable seed populations under forests. Possibly the gradient parallels a decrease in length of growing season and its effect on germination strategies. The lack of viable buried seeds provides a partial explanation of observed slow vegetational recovery after fire in subarctic forests.

ISSN:0008-4026    

DOI:10.1139/b75-323

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Mating tests were made with the type strains ofSporobolomyces hispanicusPeláez & Ramirez,S.odorusDerx, andS.salmonicolor(Fischer & Brebeck) Kluyver & van Niel, and with 19 additional strains. These tests show that 21 of the strains are of two, intercompatible mating types. Since the three type strains are linked by compatibility, the names that have been applied are synonymous. Additionally, since mycelial and strictly yeast-like strains are compatible, the genusProsporobolomycesNovák & Zolt appears to be unacceptable.

ISSN:0008-4026    

DOI:10.1139/b75-324

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Thin sections of developing, fully expanded, and germinating chlamydospores ofPhytophthora cinnamomiwere studied by electron microscopy. Expanding chlamydospores had thin walls and contained nuclei, mitochondria, dictyosomes, rough endoplasmic reticulum, lipid-like bodies, peripheral vesicles, and small vacuoles with dense, spherical inclusions. Small vesicles, about 200 nm in diameter, were occasionally observed underlying the plasmalemma.In fully expanded chlamydospores, structures that are necessary for zoosporogenesis, i.e. exit pores, flagella, and cleavage vesicles, were not present. The vacuoles with dense, spherical inclusions constituted a large proportion of fully expanded chlamydospores and had usually fused to form a large central vacuole. The walls of two-week-old chlamydospores were similar in density to sporangial walls and were non-layered.Chlamydospore germination was direct, i.e. by the production of germ tubes with numerous vesicles at the tips which ruptured through the chlamydospore wall. A germination wall was formedde novobeneath the chlamydospore wall and extended with the germ tube to form the germ tube wall.The distinguishing ultrastructural characteristics between chlamydospores and sporangia, aged sporangia, oogonia, and oospores ofPhytophthoraare discussed.

ISSN:0008-4026    

DOI:10.1139/b75-325

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

InStipa elmeriPiper & Brodie ex Scribn., the pollen tube enters at the filiform apparatus of the degenerated synergid. The degenerated synergid has electron-dense cytoplasm in which organelles are not discernible. All other cells of the mature megagametophyte have nuclei, endoplasmic reticulum, plastids, mitochondria, dictyosomes, and vacuoles. Starch is found in the persistent synergid (in minute quantities), egg, and central cell. Lipids occur in the persistent synergid, central cell, and antipodals. The filiform apparatuses of the two synergids are hypothesized to perform different functions. In the degenerated synergid, the filiform apparatus serves to increase the surface area of the plasma membrane and thereby to offer a large area for pollen-tube-growth-directing compounds to diffuse out of the synergid. In the persistent synergid, the filiform apparatus is part of a suite of features which indicate that the persistent synergid is involved in the transference of materials into the megagametophyte. Another possible function of the persistent synergid is to aid in establishing the polarity of the egg. The pollen grain and tube have distinctive polysaccharide spheres that serve to delimit the pollen tube cytoplasm after discharge into the degenerated synergid. Associated with the degenerated synergid are bodies of dense materials as seen under electron microscopy, and bodies of RNA and protein as determined histochemically. These are probably the same thing and come from the degenerating synergid. The antipodals are the most cytologically active cells of the megagametophyte. They have some features which are characteristic of transfer cells and possibly function in the transference of materials into the megagametophyte. Other studies (Brink and Cooper 1944) have indicated that grass antipodals are involved in the control of endosperm development. The active cytoplasm of the antipodals may reflect the synthesis or transference of growth-controlling substances.

ISSN:0008-4026    

DOI:10.1139/b75-326

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The variation in the relative amounts of the terpenes of the mature and young leaves, buds, and twigs of blue spruce was investigated during a full year. As with the spruces that were investigated previously, large changes were recorded only in the buds and in the young leaves after bud burst. The variations that were recorded in the latter for santene, tricyclene, camphene, camphor, bornyl acetate, and limonene were similar to those that were found in white spruce, but those of car-β-ene, α-pinene, and β-pinene differed. Several quantitative differences in the oil of the winter buds were also recorded. The variation of β-pinene correlated negatively with that of sabinene, γ-terpinene, and terpinolene. A transient diterpene alcohol of the geranylgeraniol type was found in the buds and young twigs during spring. The seasonal variation of the terpenes of the twig oil was smaller than the twig-to-twig variation within a tree. The implications for chemosystematic studies are discussed.

ISSN:0008-4026    

DOI:10.1139/b75-327

出版商:NRC Research Press    

年代:1975

数据来源: NRC