摘要:

Bog ericads, such as Labrador tea (Ledum groenlandicum), bog laurel (Kalmia polifolia), and leatherleaf (Chamaedaphne calyculata), retain individual leaves for two growing seasons in southern Ontario, presumably to facilitate nutrient movement between overlapping leaf cohorts. The objective of this study was to evaluate the effects of nutrient availability, shade, and the removal of new growth on the longevity of leaves during their second growing season. Longevity was extended significantly (p < 0.05) by removing new growth, but not by shading leaves (p > 0.05). The addition of nitrogen fertilizer increased onlyC. calyculatalongevity. Interspecific variation in treatment effects appeared to be related to the positions occupied by the three species on environmental gradients. None of the experimentally treated leaves survived past the end of their second growing season, with the magnitude of treatment effects ranging from a reduction in longevity of 10 days to an increase of 25 days.

ISSN:0008-4026    

DOI:10.1139/b80-201

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The relative effectiveness of diurnal and nocturnal pollinators of two milkweed species,Asclepias syriacaandA. vcerticillata, was assessed experimentally and related to patterns of nectar production. Nocturnal pollinators inserted and removed fewer pollinia than diurnal vectors but caused equal pod set, and inA. syriaca, caused greater seed set. We suggest that observed peak nectar production patterns are adaptive in attracting nocturnal pollinators that may be of higher quality than diurnal species. This is one of the first attempts to compare the relative effectiveness of diurnal and nocturnal pollinators of any plant species. The excess of vector visits over that needed to obtain maximum pod set may allow selective abortion and (or) be adaptive in increasing reproductive success through pollinia donation.

ISSN:0008-4026    

DOI:10.1139/b80-202

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Purified preparations of peach rosette mosaic virus (PRMV), were shown by rate-zonal centrifugation in sucrose and equilibrium centrifugation in CsCl to be composed of two nucleoprotein components with buoyant densities of 1.47 (middle) and 1.51 (bottom) g/cm3. The virus contains two RNA species with molecular weights of 2.5 × 106(RNA 1) and 2.2 × I06(RNA 2), and a single protein subunit with a molecular weight of 57 000. RNA 1 and RNA 2 reside separately in components B and M, respectively. Both RNAs are required for infection thus indicating that the virus has a divided genome. The nucleotide composition of both RNAs is similar except for cytidilic acid. The hyperchromic profile for the M component is broader than that of B and theTmvalue is higher (for MTm = 55 °C; for BTm = 48 °C). Particle disruption and release of RNA progresses slowly over the absorbance–temperature transition. Only half of the particles were dissociated at theTmvalue. Freezing dissociates most of M component into RNA 2 and protein but had no effect on the B component. Sodium chloride protected the M particles from low temperature disruption. The data support the conclusion that PRMV is a nepovirus with particular properties of the tomato ring-spot virus (TomRSV) subgroup.

ISSN:0008-4026    

DOI:10.1139/b80-203

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Four species ofCicuta(family Umbelliferae) are recognized for North America:C. maculataL. (2n = 22),C. douglasii(DC.) Coult. & Rose (2n = 44),C. virosaL. (2n = 22), andC. bulbiferaL. (2n = 22).Cicuta maculatahas 22 large somatic chromosomes,C. virosahas 22 small somatic chromosomes,C. bulbiferahas 22 medium sized chromosomes, andC. douglasiihas 22 large chromosomes and 22 small chromosomes. Four varieties ofC. maculataare recognized: var.maculata, var.angustifoliaHook., var.victorinii(Fernald) Boivin, and var.bolanderi(S. Wats.) G. A. Mulligan, stat. nov.Cicuta mackenzieanaRaup is considered conspecific withC. virosu. The nomenclature, distribution, and relationships of the North American species are given together with an identification key to species and varieties.

ISSN:0008-4026    

DOI:10.1139/b80-204

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

All taxa ofSuksdorfia, Hieronymusia, andBoykinia(including the segregatesNeoboykinia, Peltoboykinia, andTelesonix), and one species each ofBolandraandSullivantiawere examined for their flavonoids. A diverse array of flavone and flavonol mono-, di-, and tri-glycosides was found. 3-O-Methylation and 6-oxygenation were common, as was 3, 7-O-triglycosylation. Groups of flavonol monoglycosides with either charged or acetylating functions were also observed. Taxonomically, the flavonoid relationships are many, various, and somewhat reticulate, indicating a close relationship among all taxa. The data provide only limited help in defining generic limits. They do, however, support the placement ofBoykinia jamesiiinBoykinia, or near it (asTelesonix), rather than inSaxifraga. The data also favour the retention ofNeoboykiniawithinBoykinia. The exceptionally simple flavonoid profile ofBoykinia tellimoidescould support its elevation to generic rank (Peltoboykinia) were it made on other grounds. The evolutionary trends of flavonoid reduction and diversification are seen operating in the genera. Parallelism involving several different flavonoid structures is common in the Saxifraginae and supports the inclusion ofChrysospleniumin the subtribe.

ISSN:0008-4026    

DOI:10.1139/b80-205

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The primary phycotoxic effects of various concentrations (5–50 μM) of cadmium sulfate (CdSO4) on synchronous cultures ofChlorella ellipsoideawere determined during a 14-h light and a 10-h dark incubation cycle. At a concentration of 5 μMCdSO4there was a slight stimulation in cell number, chlorophyll level, and dry weight whereas at higher concentrations (10–40 μM) a linear decrease in these parameters was evident. At even higher concentrations, 50 μMand above, cytolysis occurred. Inhibition of chlorophyll concentration and dry weight was greater the longer the cultures were exposed to cadmium. Cell division was completely arrested when toxic levels of cadmium were administered any time throughout the duration of the light phase. However, the severity of toxicity of cadmium, when applied during the dark phase, increased with the length of time of exposure. Cadmium toxicity also resulted in disturbances in cell division. Treated cells became larger than control cells. Unequal sporulation, microcolony and incipient microcolony formation, swelling, increased photolucence, and disruption of mitochondria occurred following treatment of cultures with toxic levels of cadmium. A further toxic effect of cadmium might relate to an increase in membrane permeability. Treatment of cultures with increasing concentrations of cadmium resulted in intracellular cadmium exceeding extracellular cadmium levels. The primary toxic effect of cadmium on synchronous cultures ofC. ellipsoideawas attributed to a lack of cell division probably related to insufficient synthesis of chlorophyll and dry weight components as well as to a disruption of membrane integrity.

ISSN:0008-4026    

DOI:10.1139/b80-206

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Several drought-deciduous species occur in the mediterranean type vegetation of central Chile, some of them extending to the slopes of the Coastal and Andean Ranges, up to 2300 m. The growth habits and phenology at different altitudes are compared in two drought-deciduous, malacophyllous shrubs:Talguenea quinquinervia, a species of restricted distribution, andProustia cuneifolia, of widespread distribution. The morphology and timing of seasonal events ofT. quinquinerviado not substantially change along its altitudinal range of distribution. In contrast, gradual displacement of phenology occurs inP. cuneifolia, with increasing altitude. Its growth habit varies from the presumably original chamaephyte to a phanerophyte, when under optimal conditions, or to a hemicryptophyte in the highest altitudes. Low temperatures and a prolonged snow cover constitute severe limiting factors for the survival of this drought-deciduous life form.

ISSN:0008-4026    

DOI:10.1139/b80-207

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Application of 10−4 Mbenzyladenine toPhaseolus vulgarisgerminated under etiolating conditions markedly delayed the onset of cotyledon senescence. Weight loss was curtailed, hydrolysis of starch and protein reserves was delayed, and the rate at which hydrolysis products were translocated out of the cotyledons was reduced in treated plants. Microsomal membranes of cotyledons from control seedlings acquired increasing proportions of gel phase lipid as senescence of the tissue intensified. The resulting mixture of liquid-crystalline and gel phase lipid within the membrane matrix renders the membranes leaky and may partially contribute to metabolite translocation out of the cotyledon storage cells during seedling development. This prospect is supported by the observation that in benzyladenine-treated plants the onset of gel phase lipid, and hence of membrane leakiness, was delayed in a manner that corresponded temporally with the decreased rate of metabolite translocation out of the cotyledons.

ISSN:0008-4026    

DOI:10.1139/b80-208

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Shoot apices from quiescent axillary buds of the European linden tree were collected at three periods during the winter and prepared for electron microscopy by freeze-fracturing without pretreatment (i.e., no chemical fixation or glycerol infiltration). Cell structures were well preserved and not damaged by ice crystal formation. Tissue fine structure was comparable with other winter-quiescent tissues (particularly cambia) and showed the following characteristics: plentiful oil droplets, smaller quantities of other storage materials (protein, starch), inactive dictyosomes, and unusual arrangements of endoplasmic reticula (particularly a peripheral reticulum). Oil droplets were not bounded by a membrane. The quantity of oil (by cytoplasmic volume) declined steadily through the winter, presumably fuelling metabolic activity. The relatively flaccid condition of plasma membranes indicated that osmotic pressure was similar inside and outside the cells. Membrane-particle partition coefficients (Kp) between plasma membrane fracture moieties was unusual (< 1), and the significance of this observation in relation to cold acclimatisation is discussed. The appearance of the mouths (neck constrictions) of plasmodesmata changed between midwinter (closed) and early spring (open) and the observations are interpreted to indicate dynamic changes in a sphincter controlling intercellular exchange.

ISSN:0008-4026    

DOI:10.1139/b80-209

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Quiescent shoot apical tissue from buds of the linden tree (Tilia europaeaL.), collected during winter months, was frozen without pretreatment and freeze-fractured for electron microscopy. A proportion of the nuclear envelopes bore unusually large nuclear pores, having diameters up to 175 nm. Results from cross-fractured nuclear envelopes were consistent with results from envelopes fractured in the membrane plane, indicating that the larger pores are unlikely to be artefacts of fracturing. In these large pores, it was not possible to determine the relationship between the annulus (the material contained within the membranous pore) and the membranous periphery of the pore. Particularly, it could not be determined whether the annulus expanded concomitantly with the pore. It is proposed that variations in nuclear pore diameter may arise as a result of pulsatory activity occurring in all pores, rather than representing static differences between individual pores.

ISSN:0008-4026    

DOI:10.1139/b80-210

出版商:NRC Research Press    

年代:1980

数据来源: NRC