摘要:

A study of the demography of the needles and the growth pattern of Corsican pine is presented in relation to other studies of foliage dynamics. The construction of life tables is explained and applied to populations of Corsican pine needles. Needles from different trees as well as from different parts of trees had different survivorship. Leader needles had a much lower survivorship than all other needles. The frequency distribution of shoot lengths was log-normal, with the leader as the longest shoot. Climatic variations, tree age, apical dominance, and growth pattern appeared to be some of the factors involved in needle survivorship. Possible causes of needle senescence are considered with respect to an "activity schedule" derived from the work of other authors.

ISSN:0008-4026    

DOI:10.1139/b82-013

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Shoots ofScirpus maritimusvar.paludosussprout from overwintered tubers in May. Stem growth is rapid and within 2–3 weeks lateral rhizomes extend outwards and produce tillers with new tubers at their bases. By August up to four new shoots are produced in a rhizome–shoot series. All aboveground biomass is dead by late October but tubers overwinter to develop the following growing season. The ratio of below- to above-ground biomass of the rhizome–shoot series increased from 0.20 to 0.76 from early to late summer. The ratio of below- to above-ground biomass of individual stems was highest at the youngest end of the rhizome–shoot series.Stem density and inflorescence and total biomass were monitored at three sites over three growing seasons. The sites had large fluctuations in salinity in response to changes in water depth. Among all sites, maximum stem density reached 380 stems/m2by late July, slightly before the maximum standing crop of 625 g/m2was attained. At one site, changes in water levels and salinity increased the peak aboveground standing crop 22-fold (from 27 to 600 g/m2) from 1978 to 1979. A mathematical equation predicting the seasonal aboveground standing crop ofS. maritimuswas developed using water depth and conductivity as predictor variables.

ISSN:0008-4026    

DOI:10.1139/b82-014

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

A pure preparation of isolated mesophyll cells and a preparation of minor veins heavily contaminated with mesophyll and epidermal tissue were obtained from leaf strips ofCucurbita pepoby enzymatic digestion. The preparations were incubated for 10 min in sodium [14C]bicarbonate in the light to determine their ability to synthesize the major translocated sugar stachyose and its precursor galactinol. Stachyose, galactinol, sucrose, and hexoses accounted for ca. 0.5, 2.5, 55, and 30% respectively of the total14C in the neutral sugar fraction in both preparations. The close similarity was believed due to the heavy contamination of the minor vein preparation with mesophyll tissue. Intact leaf tissue incubated under similar conditions incorporated an approximately equal amount of14C into the sugar fraction but with a highly dissimilar distribution. Stachyose, galactinol, sucrose, and hexose accounted for up to 50, 20, 13, and 0.2% respectively of the total14C activity. Plasmolysis of intact tissue caused a more than 50% decrease in the14C incorporation into stachyose and galactinol and a large increase into sucrose and particularly hexoses. The enzymes synthesizing galactinol and stachyose were extracted from the mesophyll preparation but their specific activities on a total chlorophyll basis were 10-fold lower than when extracted from intact tissue. It was concluded that the procedure for isolating free cells, while not affecting sucrose synthesis, was highly detrimental to the synthesis of galactinol and stachyose, and that synthesis of the latter two compounds was most probably confined to the mesophyll.

ISSN:0008-4026    

DOI:10.1139/b82-015

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Paradiplosis tumifexinduces a simple, single-chambered, prosoplasmic gall on the adaxial surface of current-year needles of balsam fir. Proliferating and enlarged mesophyll cells surround the immature larva except for an ostiolar opening on the adaxial surface. The vascular bundle is not affected by gall formation, but the cells lining the resin ducts are altered. As the gall matures the epidermis and one or two layers of underlying mesophyll cells become lignified. Concentrations of starch granules are retained in gall cells after starch has been dissipated in tissues beyond the gall and in nongalled needles. Host damage occurs when galled needles dry and abscise prematurely.

ISSN:0008-4026    

DOI:10.1139/b82-016

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The embryology ofSwertia minorKnobl. (Gentianinae Gentianaceae) was studied. Features of its development are tetrasporangiate anthers, dicotyledonous type sporangial wall formation, glandular anther tapetum and its dual origin, simultaneous cytokinesis in microsporocytes, tricolporate two-celled pollen, unilocular ovary, forked parietal placentae, tenuinucellar unitegmic anatropous ovules,Polygonum-type megagametogenesis, persistent multiple multinucleate highly enlarged haustorial antipodal cells, nuclear endosperm, Solanad type embryo development, and multiseriate suspensor. Embryological features of taxonomic significance in the Gentianinae are compiled in a review of the pertinent data on the subtribe.

ISSN:0008-4026    

DOI:10.1139/b82-017

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The time course of early infection events inGlycine maxfollowing inoculation withRhizobium japonicumis described. Bacteria became attached to epidermal cells and root hairs within minutes of inoculation. Marked root hair curling occurred within 12 h. Infection thread formation was visible at the light microscope level of resolution about 24 h after inoculation. Infections were observed in short, tightly curled root hairs. These root hairs had not yet emerged at the time of inoculation. Infection threads appeared to originate in pockets formed by contact of the cell wall of the curled root hair with itself. Infection threads in the hairs were multiple and (or) branched. By 48 h, the infection thread(s) had progressed to the base of the root hair but had not yet penetrated into the cortex. Increases in cortical cell cytoplasm and in mitotic division occurred in advance of the penetrating infection thread. A nodule meristem developed in the outer cortex next to the infected root hair by 4 days and was accompanied by cell division across the cortex.

ISSN:0008-4026    

DOI:10.1139/b82-018

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The effect of different sulphate concentrations (2 × 10−5to 10−2 M) in the labelling medium on [35S]sulphate uptake and incorporation into National Research Council of Canada gametophytic strain T4Chondrus crispushas been investigated. Sulphate uptake appears to be multiphasic as in higher plants. An apparentKmfor sulphate uptake has been determined over the range of concentrations 10−4to 10−2 M. Sulphate incorporation is also altered at different sulphate concentrations.

ISSN:0008-4026    

DOI:10.1139/b82-019

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The asclepiad pollinium germinates through a specific region of the pollinial wall designated as the germ furrow. In untreated and ungerminated pollinia ofAsclepiasandCalotropis, the germ furrow is indistinguishable, by light microscopy, from the rest of the pollinial wall. Under the scanning electron microscope, however, the furrow appears as a discontinuous region marked by apertures of various sizes and shapes. On acetolysis, the wall materials that separate or surround the various openings on the germ furrow region dissolve and a characteristic narrow continuous opening (referred to as the slit) becomes visible.The position of the germ furrow, as revealed by the slit on acetolysis, is genus specific in all the 14 genera screened in this study. This specificity is maintained even in the relatively large pollinia of colchicine-induced tetraploids ofAsclepias curassavica.By culturing sealed and cut pollinia and by standard bioassay methods it was shown that the polarity of pollen tubes within the pollinium is governed by the permeability of the germ-furrow region and not by the previously attributed factors such as innate orientation of pollen grains or chemotropic factors.

ISSN:0008-4026    

DOI:10.1139/b82-020

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

A membranous film (MF) covers the hymenium of the ascocarp ofSclerotinia sclerotiorum(Lib.) de Bary. The MF is reported for the first time using a scanning electron microscope. Development of the MF is described in relation to the morphogenesis of apothecia. At the early stage the MF develops centripetally from the edge of the hymenium adjoining the rim of the ascocarp. At the beginning of the intermediate stage, the surface of the hymenium is fully covered by the MF which has many small holes and a few fenestrations. The MF is thin and smooth at the center but thick and wavy near the margin of the ascocarpic disc. Since the MF ruptures at or just before the massive ascospore discharge which occurs at the intermediate stage, it may protect the developing asci from loss of moisture before the initial spore discharge.

ISSN:0008-4026    

DOI:10.1139/b82-021

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

A procedure employing serologically specific electron microscopy (SSEM) which consistently detected barley yellow dwarf virus (BYDV) in single aphids was developed. Using an antiserum against theSitobion avenae(SA)-specific variant of BYDV, the virus was detected in aphids after 1 day of acquisition feeding and up to 9 days after removal from the virus source plant. The method was equally effective with alate or apterous aphids. SSEM scores of single aphids for presence of virus showed good agreement with virus transmission by aphids. In addition to the SA-specific variant, the nonspecific andSchizaphis graminumspecific variants of the virus were also detected in their vectorsRhopalosiphum padiandS. graminum, respectively, using the antiserum to SA-specific variant. The SA-specific variant was also detected in aphids considered "nonvectors" (R. padi, R. maidis, and S.graminum) when fed on this variant. Application of the procedure for determining the proportion of viruliferous aphids in a population are discussed.

ISSN:0008-4026    

DOI:10.1139/b82-022

出版商:NRC Research Press    

年代:1982

数据来源: NRC