摘要:

The vegetative development of natural populations ofVitis ripariais reported in detail for the first time, using a combination of three-dimensional and histological techniques. The initiation of both uncommitted primordia (which can develop into either inflorescences or tendrils) and leaf primordia is documented and correlated with their position in the primordium initiation cycle. There are four possible states: (i) a leaf at a lower tendril node, which arises on the flank of a dome-shaped apex directly above a leaf; (ii) a leaf at either an upper tendril node or a tendrilless node, which arises on the flank of a broad apex directly above a tendril; (iii) a lower uncommitted primordium, which arises very high on the apical flank, separated from the subjacent leaf by the initiation of one primordium on the opposite side of the apex; and (iv) an upper uncommitted primordium, which arises on the apical flank, separated from the subjacent leaf by the initiation of two primordia on the opposite side of the apex. This study shows that there is evidence to support the view that the uncommitted primordium is both terminal and lateral. We have extended the reports of the presence of tendril hydathodes inVitisto this species. Axillary bud initiation and development are the same as has been reported for other species ofVitis, with each winter bud being initiated in the axil of the basal prophyll of the previous one.

ISSN:0008-4026    

DOI:10.1139/b88-037

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Cadmium reduced the growth rate ofPaxillus involutusin pure cultures either on agar or liquid medium. On Cd-containing agar most of the mycelium grew submerged rather than on the surface as occurs on Cd-free agar. Cadmium increased hyphal density by both increasing the number of laterals at a branch point and decreasing the distance between branch points. These variables were included in a new model to determine the specific growth rate on the basis of mycelial length for the fungus growing on agar. The degree to which Cd reduced the specific growth rate was the same whether based on mycelial length from agar plates according to the new model or on mycelial mass from a liquid medium. The new model for specific growth rate (length) derived from agar cultures is particularly suited to those situations where a growth-modifying agent alters the branching frequency and the distance between branch points.

ISSN:0008-4026    

DOI:10.1139/b88-038

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Research plots in a wheat–wheat–fallow rotation at Indian Head, Sask., were sprayed annually with 2,4-dichlorophenoxy-acetic acid (2,4-D) for 36 consecutive years. Two species susceptible to 2,4-D,Chenopodium albumL. andThlaspi arvenseL., were dominant in these plots. From 1981 to 1983,C.albumandT.arvenseseedlings that emerged during four periods of the growing season were marked and their mortality, seed production, and size recorded. From these data and other studies, 10 ways in whichC.albumandT.arvensemanaged to survive herbicide application were identified. These are intermittent germination, herbicide tolerance, small size of late-emerging seedlings, short life cycle, hardiness, failure of control practices, long-term dormancy, seed dispersal, viability of immature seeds, and winter annual life cycle ofT.arvense.

ISSN:0008-4026    

DOI:10.1139/b88-039

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A marked decline in wild rice production was observed 5 years after a northwestern Ontario lake was seeded. A paired-comparisont-test detrmined that sediment manganese, zinc, copper, magnesium, and potassium had all declined in concentration, but nitrogen showed the greatest decrease. Discriminant analysis indicated that sediment nitrogen contributed most to a function distinguishing between years. A controlled experiment using several fertilizer formulations also found that addition of nitrogen to sediment from the lake promoted the greatest increase in wild rice growth. Changes in distribution of wild rice and in values of water depth, organic matter, dry weight of other macrophytes, and wild rice density and dry weight indicated that the decrease in sediment nitrogen was probably associated with movement of wild rice straw within the lake.

ISSN:0008-4026    

DOI:10.1139/b88-040

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Aggressiveness of conidia ofBipolaris sorokiniana(Sacc.) Shoemaker on wheat seedlings was reduced after 30 days of incubation on sterilized soil inoculated with microorganisms. The effect was greater with bacteria than with fungi or actinomycetes. Recovery of aggressiveness occurred when stressed conidia were incubated with nutrients. With increasing stress a longer period of incubation was needed for recovery. The14C exudation from conidia was greater in unsterilized soil than in soil containing specific microorganisms. Exudation from conidia was inversely related to aggressiveness and germination.

ISSN:0008-4026    

DOI:10.1139/b88-041

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Relationships between the distribution and numbers of apothecia ofSclerotinia sclerotiorum(Lib.) de Bary and the distribution and incidence of white mold of white bean (Phaseolus vulgarisL.) were investigated in a field plot at Arkell, Ont., in 1981 and 1982. The spatial distributions of both apothecia and disease were aggregated and were most consistently described by the negative binomial distribution, although the Poisson, Poisson binomial and logarithmic with zeros distributions were also significant for some sampling dates. Numbers of apothecia were correlated with disease incidence within areas 1.4 (r = 0.07–0.67), 36 (r = 0.11–0.72), and 108 m2(r = 0.21–0.95). The quantitative relationships between apothecia within a field of beans and the incidence of white mold may be useful in predicting the disease.

ISSN:0008-4026    

DOI:10.1139/b88-042

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Root and leaf growth of the arctic sedgeEriophorum vaginatumL. were studied from early spring (June 7) to early fall (August 7) in the foothills of the Brooks Range in northern Alaska. The observations were designed to test the hypothesis that root and leaf growth occur at similar rates. The results confirmed this hypothesis. The root/leaf biomass ratio remained constant over the growing season. Thus, root biomass can be estimated based on harvested leaf biomass. It was also shown that root and leaf surface areas can be calculated from the respective biomass values. However, changes in the specific weights of leaves and roots over the growing season would affect the accuracy of root biomass or root surface area predictions.

ISSN:0008-4026    

DOI:10.1139/b88-043

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Guard cells of species representing 27 genera from the Orchidaceae were surveyed under fluorescence microscopy. With the exception of the genusPaphiopedilum, chlorophyllafluorescence was observed in all species, indicating that, as in other families, chloroplasts are strongly conserved in the stomata of the Orchidaceae. The achlorophyllous stomata ofPaphiopedilumtherefore constitute a unique variation in that pattern, with its expression at the generic level pointing to an early, stable evolutionary event. Five of the orchid species,Vanilla aromaticum,Phragmipedium longifolium,Haemaria discolor,Paphiopedilum harrisianum, andPaphiopedilum insigne, were also studied ultrastructurally. There was a close correlation between plastid fluorescence intensity in guard cells and the presence of grana thylakoids in the organelles, withVanillashowing an intense fluorescence and extensive grana stacking, while thePaphiopedilumstomata were completely devoid of both features.Phragmipediumstomata had an intermediate level of fluorescence and a reduced number of thylakoids, whereasHaemariaguard cells, which had no chlorophyll fluorescence in intact tissue but a weak fluorescence in cryostat sections, showed an unusual array of pleomorphic plastids with only a few exhibiting some thylakoids. Other ultrastructural features of orchid guard cells were also documented. These observations and a marked variation in fluorescence intensity and plastid number and size seen in the guard cells of the surveyed genera point to a broad structural diversity in the guard cell plastids of the Orchidaceae. This diversity could underlie specialized functional properties associated with stomatal adaptations to different growing habitats.

ISSN:0008-4026    

DOI:10.1139/b88-044

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Salix uva-ursiPursh is a prostrate shrub typical of windy arctic–alpine tundra sites of eastern North America. According to Grime's thesis, plants living in growth-limiting conditions should satisfy the following criteria: (1) limited growth rate, (2) extended individual longevity, (3) reduced allocation to reproduction, (4) infrequent reproduction, (5) regeneration by vegetative multiplication or seedling bank rather man seed bank, (6) reduced plasticity, and (7) persistent leaves.Salix uva-ursidisplays a few of these criteria (1, 2, 4) and is capable of layering (5). However, contrary to Grime's conditions (3, 6, and 5, respectively), allocation of annual biomass to reproduction is considerable, structure is variable, depending on wind exposure, and a seedling bank is absent and regeneration depends in part on a large number of small, wind-dispersed seeds. ThusS.uva-ursitakes advantage of wind, which is usually a limiting factor, to reach the few favorable microhabitats of an otherwise inhospitable environment. Finally, the leaves ofS.uva-ursidie each fall (contrary to 7) but remain attached to the plant for several years. This may increase the boundary layer in winter and allow for protection against snow erosion.Salix uva-ursidominates sites with very high levels of stress but its biology is not always consistent with Grime's predictions of the stress tolerance strategy.

ISSN:0008-4026    

DOI:10.1139/b88-045

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Rooted cuttings ofChrysanthemum morifolium'Paragon' grown in nutrient solution were given a 24-h pulse exposure to salinity by amending the solution with 200 mequiv. NaCl/L. The cuttings were then returned to nonsalinized solution; one half were inoculated with motile zoospores ofPhytophthora cryptogeaPethybr. & Laff, and the other half were maintained as non-inoculated controls. Nonstressed cuttings also were inoculated withP.cryptogea, and roots from all treatments were sampled at various intervals thereafter for light and electron microscopy. Penetration of nonstressed roots byP.cryptogeawas frequently limited to three or four cell layers 6–12 h after inoculation. Formation of appositions adjacent to hyphae, increased wall staining density, and accumulation of osmiophilic material in cell vacuoles were associated with sites of limited penetration. In contrast, hyphae ofP.cryptogearapidly colonized salinity-stressed roots, causing extensive necrosis within 12–24 h after inoculation. The cytological responses to infection seen in nonstressed roots were rarely observed in stressed roots, indicating that salinity stress inhibits active root defense mechanisms.

ISSN:0008-4026    

DOI:10.1139/b88-046

出版商:NRC Research Press    

年代:1988

数据来源: NRC