摘要:

X-ray microanalysis and backscattered electron imaging were used to investigate silica deposition in the lower glume, lemma, and palea of wheat (Triticum aestivumL. cv. Highbury). In the lemma and glume awns, all of the outer epidermal walls were silicified, with the greatest concentration in prickles and papillae. The glume and lemma had similar structures, exhibiting silicified short cells, prickles, and papillae on both inner and outer surfaces and having macrohairs confined to areas on the inner surfaces beneath the awns. Silicified macrohairs were abundant at the apex and margins of the palea. The results are discussed with respect to previous investigations of grass inflorescence bracts. The applicability of X-ray microanalysis and backscattered electron imaging to the analysis of silica deposits in inflorescence bracts is assessed.

ISSN:0008-4026    

DOI:10.1139/b89-041

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Steroids have been detected in a range of plant species. To investigate the prevalence of four steroids in plants, radioimmunoassay was used to detect the presence of androstenone (boar taint), androgen, estrogen, and progesterone. Androstenone is known only from pigs and humans, but the others are widespread in mammals. A total of 128 species from over 50 families was sampled. All four steroids were widespread, with androstenone and progesterone being found in more than 80% of species, androgen in 70%, and estrogen in 50%. All seed samples contained androgen but none contained androstenone. In three species, androgen was more abundant in male flowers than female flowers, but progesterone and estrogen, when present, were at higher level in female flowers. The function of these steroids in plants is not known.

ISSN:0008-4026    

DOI:10.1139/b89-042

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The synthesis of barley (Hordeum vulgareL. cv. Himalaya) aleurone xylanase was found to be dependent on both gibberellic acid (GA3) and Ca2+, but inhibited by cycloheximide and cordycepin. Studies using density labeling of barley aleurone layers showed that xylanase was synthetizedde novoin response to GA3and Ca2+. Neither GA3nor Ca2+alone induced a large increase in xylanase activity. The concentration of Ca2+required for maximum xylanase induction was 5 – 40 mM. Xylanase activity was found to develop simultaneously with that of α-amylase in the incubation medium during the first 24 h of incubation with GA3. A critical point with respect to the role of xylanase is the extent of its activity by the time of the initial release of α-amylase. The release of α-amylase into the medium was detectable at 6 h. From 2 to 6% of the cell wall was hydrolysed by xylanase after incubation for 6 h, which was probably sufficient to permit the release of α-amylase. Scanning electron microscopy showed that the purified barley aleurone xylanase hydrolysed the cell walls of barley aleurone layers in the absence of GA3. It is likely that xylanase plays an important role in the release of enzymes from aleurone cells.

ISSN:0008-4026    

DOI:10.1139/b89-043

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Experiments were conducted on leaf laminae to determine the effects of intact, excised, and abraded epidermal layers on the success of graft unions inCatharanthus roseusandSedum telephoides. Lamina surfaces grafted together within 2 – 4 weeks when the epidermis was removed from both graft partners. In contrast, the presence of epidermis on one or both graft partners prevented grafting. Intact epidermal cells adjacent to wounds did not divide or undergo other visible changes except for plasmolysis and death in a few grafting situations. Epidermal cells are developmentally distinctive from underlying parenchymatous cells in that they fail to respond to stimuli that elicit redifferentiation and dedifferentiation in subepidermal tissues. Abrasion with carborundum effectively stripped the cuticular layer from parts of the leaf surfaces put into contact for grafting and increased the permeability of the surfaces to large, water-soluble, calcofluor-white molecules. Similar to grafting attempts with intact surfaces, abraded surfaces failed to graft, produce callus, or undergo any other of the observable changes that occur in exposed subepidermal cells. These results indicate that the cuticle is not responsible for the failure of intact surfaces to graft. Rather, the epidermal cell appears to be uniquely restricted in its capacity to dedifferentiate and redifferentiate. Grafting failure between freely permeable surfaces (after cuticle abrasion) refutes the notion that the cuticle obstructs passage of diffusible agents necessary to induce epidermal dedifferentiation and grafting.

ISSN:0008-4026    

DOI:10.1139/b89-044

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Sporidesmium sclerotivorum, a mycoparasite of sclerotia ofSclerotiniaspp., produces two types of asexual spore, macroconidia and microconidia of theSelenosporellatype. Macroconidia developed by dilation of the conidiophore apex, which then divided to form up to eight cells. The outer layers of the thick spore walls were heavily pigmented and contained phenolic compounds. The cytoplasm of mature spores contained polysaccharides and proteins but there were no specialized storage bodies. Germ tubes emerged through a pore in the wall of the distal cell of the macroconidia. They grew over the surface of host sclerotia and entered between rind cells without formation of specialized infection structures. Microconidia of theSelenosporellastate ofS.sclerotivorumformed on simple or branched conidiophores. Sympodial conidiogenous cells bearing the microconidia were arranged in a verticil at the tips of these conidiophores.

ISSN:0008-4026    

DOI:10.1139/b89-045

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

To determine howVaccinium alaskaense,Cornus canadensis,Coptis asplenifolia,Tiarella trifoliata, andRubus pedatusinvade and maintain themselves in conifer forests, we conducted experiments on seed germination and seedling survival and examined clonal development in old-growth, young-growth, and 4- to 6-year-old stands. Seed of all species germinated well in laboratory and field tests (average 23 – 90%), but low germination rates ofC.canadensisandT.trifoliataunder actual field conditions may retard their invasion of young stands. Survival of all species at 3 and 4 years was lower in the young stand (40 years) than in the old stand (250 + years) and may be related to incident solar radiation. Regressions of the percentage of survival on percentage of transmitted solar radiation were significant (P≤ 0.05) for all species exceptC.canadensis. Seed predation and type of seedbed (moss, logs, duff) had little effect on germination and survival rates. Average annual rhizome or stolon growth was slower in the young stand (1 – 3 cm) than in the old stand (1 – 34 cm). In the clearcut, clones had dense foliage because of shorter internodes and more leaves per node and annual rhizome and stolon growth averaged 77 – 160 cm. Both seedling establishment among clones and continual clonal expansion maintain species in old stands, while invasion in young stands is primarily by seedling establishment.

ISSN:0008-4026    

DOI:10.1139/b89-046

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

In a series of experiments to determine the physiological effects of a triazanone antidehiscence chemical, 3-(p-chlorophenyl)-6-methoxy-s-triazine-2,4 (1H, 3H) dione triethanolamine (DPX-3778), sex determination of the tassels of corn (Zea mayssubsp.mays) was altered depending on the concentration and timing of application. Multiple applications of 0.005% (w/v) DPX-3778 to the leaf sheath of maize plants, or the addition of 1 ppm DPX-3778 to hydroponic growth medium, approximately 4 weeks before anthesis, caused reversion of staminate inflorescences to pistillate inflorescences. In addition to the normally developed gynoecium of the upper floret, DPX-3778 treatment resulted in the full development of the lower floret gynoecium in ear spikelets. These results could be duplicated in Northern Teosinte (Zea mayssubsp.mexicana, race Nobogame). DPX-3778 could thus be useful for investigating the cellular and developmental physiology of stamens and gynoecia in corn and other monoecious grass species.

ISSN:0008-4026    

DOI:10.1139/b89-047

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Spores ofLimbella tricostataand fragments of living gametophytes ofL.tricostataandL.fryeigerminated readily and grew prolificallyin vitro. Viability of fragments of live plants was directly proportional to the size of the fragment. Growth rates were similar to those observed for other aquatic mosses. Plants dried above 20 °C for longer than 24 h did not regenerate. Fungi appeared in cultures as decomposers, not pathogens.

ISSN:0008-4026    

DOI:10.1139/b89-048

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Two experiments were done to test how the removal of foliage from small branches in mountain birch,Betula pubescensspp.tortuosa, may influence the biomass increase of female inflorescences that emerge from reproductive buds on short shoots. First, all the leaves on small twigs were removed shortly after leaf flush in June. Defoliated twigs included on average of five leaves and two reproductive short shoots. Effects of the treatment on the final length and mass of female catkins were studied in August by comparing defoliated twigs to undefoliated ones of the same trees. Second, a similar experiment was carried out by defoliating larger branches with an average of 150 leaves and 56 short shoots and by comparing defoliated branches to adjacent undefoliated branches. The first treatment reduced final weight of inflorescences by about 17% and the second treatment by about 18%. Localized defoliations can thus have limited effects on the biomass increase of female inflorescences. Short shoots are therefore partially autonomous reproductive units that are integrated subunits of higher-level interactive units, e.g., branches, root – shoot subsystems, or entire plants.

ISSN:0008-4026    

DOI:10.1139/b89-049

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

An evaluation of electrophoretic analysis as a potential tool for elucidating systematic relationships ofQuercusutilized 478 trees representing 10 species from subgenusErythrobalanusand 8 from subgenusQuercus. Leaf tissue was used to resolve 18 putative genetic loci representing 12 enzyme systems in each taxon. Subgeneric differentiation was apparent with intrasubgeneric genetic differentiation (mean modified Rogers' distance (D):Erythrobalanus0.27;Quercus0.44) being less than between subgenera (D = 0.68). Relationships among species within subgenera derived from electrophoretic data often compared well with published affinities. However, several discrepancies existed that might reflect disparities in rates of morphological, ecological, and allozymic divergence, or hybridization within subgenera, or both. Electrophoretic analysis of oak leaf tissue has the potential to yield valuable data for elucidating relationships amongQuercus.

ISSN:0008-4026    

DOI:10.1139/b89-050

出版商:NRC Research Press    

年代:1989

数据来源: NRC