摘要:

Microscopic examination of semithin and ultrathin median longitudinal sections of shoot apical meristems revealed little adverse effect from the dimethyl sulfoxide treatments and the differentiation medium used. Freeze preservation was followed by storage in liquid nitrogen for 1 h. In the meristems which remained viable most of the actively growing cells were located on primordial leaf tissues and in the axillary bud and stipule meristematic areas. Growth generally resumed at many sites, and some of these were close to or in the "dome" area.

ISSN:0008-4026    

DOI:10.1139/b80-107

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

In darkness, in an inorganic liquid medium the spores ofFunaria hygrometricademonstrate a rapid increase from low to high metabolism activity with mitochondrial respiration functioning at its maximal value. The spore respiration is high during a short period of time corresponding to the transformation of the proplastids into chloroplasts. Then, the spore respiration slows down progressively. This diminution is due to a rapid decrease of the general metabolism. Under these conditions, the germination cannot take place and the spores appear to return to a quiescent state.

ISSN:0008-4026    

DOI:10.1139/b80-108

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Apple buds and developing leaves and floral parts were assessed for microbial populations by a washing procedure and scanning electron microscopy (SEM) at six stages ranging from dormancy through early tight cluster. Densities of yeasts, filamentous fungi, and bacteria associated with dormant buds were on an order of magnitude of 5 × 105propagules per gram fresh weight of tissue. Populations tended to peak as buds swelled and to diminish during subsequent developmental stages. External surfaces of buds were colonized extensively. Internal surfaces, particularly those of the peripheral scales, also supported abundant microflora. Evidence from SEM suggested that few microorganisms were associated with floral and leaf primordia. Surface sterilization was not found to be an adequate method to discriminate between external and internal bud microflora. A partial list of microorganisms included fluorescent pseudomonads,Aureobasidium pullulans, and species ofCryptococcus, Sporobolomyces, Rhodotorula, Coniothyrium, Alternaria, Phomopsis, Phoma, Epicoccum, Cladosporium, Acremonium, Fusarium, Stachybotrys, andSclerotium. These data are pertinent to the microbial ecology of the gemmisphere and to the prospective biological control of foliar pathogens.

ISSN:0008-4026    

DOI:10.1139/b80-109

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The responses of sunflower root cells to conditions of boron deficiency and to the addition of exogenous auxin were studied on the ultrastructural level. Although gross morphological effects such as inhibition of root elongation and a change in the direction of cell expansion from longitudinal to radial are similar in both auxin-treated and boron-deficient seedling roots, ultrastructural changes are different in the two treatments. An increase in cell wall thickness and a loss of membrane integrity are seen as early as 6 h in seedlings grown without boron. Auxin-treated root cells do not show this response. A role for boron may involve maintenance of membrane integrity rather than determining endogenous auxin levels.

ISSN:0008-4026    

DOI:10.1139/b80-110

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Cell walls prepared from suspension cell cultures of bean and rice in log-phase growth were used to examine the effects of endopectate lyase (PL) on the solubilization of cell wall carbohydrates and concomitant ultrastructural alterations. Cell wall preparations from both plant sources were heterogeneous and contained a range of wall types from primary walls to xylem elements with spiral, secondary wall thickenings. Marked differences in wall thickness and number of wall laminations typified both preparations.Bean cell walls were more susceptible to degradation by PL than were those of rice. Upon treatment of the former with 2.3 × 10−3units/mL of PL (1 unit released 1 μmol of unsaturated uronide/min at 30 °C from polygalacturonic acid at pH 8.5), 27% of the noncellulosic wall carbohydrate was solubilized in 1 h. This represented 50% of the PL susceptible carbohydrate in the preparation. Only 3% of the noncellulosic carbohydrate was released from rice cell walls in 1 h when treated with 115 × 10−3units of PL/mL. This accounted for 60% of the PL susceptible wall fractions. Only uronic acid, rhamnose, galactose, and arabinose were solubilized from both preparations by PL.Cell walls in the bean and rice preparations were affected differentially by the PL. Those walls with secondary thickenings did not appear to be degraded, while the distinct fibrillar appearance of both bean and rice walls tended to fade or disappear. The middle lamella tended to dissolve to varying degrees in the presence of PL. Bean walls were more severely degraded than were the rice walls and many exhibited swelling, separation of wall layers, markedly reduced staining intensity, and (or) a granular ultrastructure.This study has demonstrated that as PL acts on susceptible cell walls there are major changes evoked in cell wall structure which suggest that the rhamnogalacturonan fraction of the higher plant cell wall contributes significantly to cell wall integrity. This study also emphasizes the need for cell wall material of proven uniformity for investigations of both cell wall composition and effects of specific polysaccharide degrading enzymes on cell wall integrity. Preliminary studies indicate that tobacco pith may provide more uniform cell walls than do cell suspension cultures.

ISSN:0008-4026    

DOI:10.1139/b80-111

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Lowbush blueberry (Vaccinium angustifoliumAit.) pericarp callus grew slowly and formed normal tetraploid roots on Nitsch's medium containingL-tryptophan and kinetin. Both growth and rooting depended on the levels of these two substances in the medium. Rooting declined but callus growth rates changed little over successive subcultures. When tryptophan was replaced by indoleacetic acid, indolebutyric acid, 2,4-dichlorophenoxyacetic acid, or naphthaleneacetic acid, callus growth rates increased but no roots formed. Tryptophan medium did not support callus growth or induce rooting unless the tryptophan was autoclaved with the rest of the medium; thus suggesting that an active substance is produced by reaction of the tryptophan with some other constitutent(s) of the medium during heating.

ISSN:0008-4026    

DOI:10.1139/b80-112

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The phenology of sexual reproduction ofPicea sitchensis(Bong.) Carr. was similar at the three sites on Vancouver Island, British Columbia, used in the study. As indicated by cell divisions, cone buds ended dormancy in early March, 2 weeks before dormancy ended in vegetative buds. Pollen mother cells underwent meiosis in mid-March and mature, saccate, four- or five-celled pollen was formed by late April. Megaspore mother cells underwent meiosis in late March and mature female gametophytes were developed by late May. Pollination occurred in late April. A pollination drop was produced by the nucellus and exuded between the two micropylar arms and pollen was drawn down into a nucellar depression where pollen germinated in late April. Fertilization occurred in early June and early stages of embryo development occurred by late June, 9 weeks after pollination. Cotyledons were initiated in late July and seed was mature by mid-August and shed during the early fall.Development of male and female gametophytes and embryos was similar to patterns shown for other species ofPicea. In this study seed set was very poor and resulted primarily from a lack of pollination. Other contributing factors were female gametophyte abortion before fertilization, embryo abortion during early development, and insect damage.

ISSN:0008-4026    

DOI:10.1139/b80-113

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The flavonoids in the leaves and stems of the 12 taxa ofSedumsectionGormaniawere determined. Two of the three compounds occur in all 12 taxa. These two are 3,7-disubstituted kaempferol and laricytrin. The third compound, a highly methylated flavone, shows variation in its occurrence, and its presence or absence serves to substantiate two evolutionary groups of taxa in sectionGormania.

ISSN:0008-4026    

DOI:10.1139/b80-114

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The eight species and one variety ofLeptostromaFr. ex Fr. hitherto described on needles ofPinusL. are examined and where possible related to anamorphs of species ofLophodermiumChev. andMelodermaDarker. Three groups of these conidiomata can be distinguished based on the depth to which they are embedded in the needles and how they open. Within each group conidiomata of individual species are often hard to identify. Each group is keyed out and illustrated.Lophodermium molitorissp. nov. andLophodermium baculiferumMayr with their respectiveLeptostromastages are described and illustrated andL. baculiferumandLeptostroma strobicolaHilitz. are neotypified. Three species ofLeptostromawhich cannot be related to anamorphs ofLophodermiumandMelodermaare excluded fromLeptostroma.

ISSN:0008-4026    

DOI:10.1139/b80-115

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The purpose of this study is to provide a contribution to the problem of organ displacement and to explain the organization of the typical inflorescence ofCornus sericeaL. Our analysis is based on anatomical and morphological data from normal and subnormal specimens.The singular nodal structure of the "normal" inflorescence ofC. sericearesults from two generalized deformations, a concaulescence and a recaulescence, appearing simultaneously. This phenomenon is particularly visible on the first pair of paracladia. These paracladia are united with the primary axis along a certain distance, and the inflorescential bracts are displaced along their axillary branches. Analysis of subnormal forms indicates that nodal deformation has a particular morphological nature which probably results from the activity of an intercalary meristem in the nodal region. In the case of the normal inflorescence, this segment cannot be considered homologous to either a node, a caulome, or a phyllome.The appendages carried by the first and sometimes by the second pair of paraclads, are appendicular organs, homologous to the foliaceous inflorescential bracts that we see on many teratological forms and in other species ofCornus.

ISSN:0008-4026    

DOI:10.1139/b80-116

出版商:NRC Research Press    

年代:1980

数据来源: NRC