摘要:

Seedling characters including anthocyanin pigmentation of eight species ofCicer,C.arietinum,C.pinnatifidum,C.judaicum,C.cuneatum,C.chorassanicum,C.anatolicum,C.montbretii, andC.pungens, representing all four sections of the genus were examined. The results support the concept of a separate monogeneric tribe, the Cicereae Alef.

ISSN:0008-4026    

DOI:10.1139/b85-001

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Trillium nivaleRiddell exists in restricted populations that often are composed of many individuals. The species is primarily calciphilic, and its range is mostly within the limits of previously glaciated territory. At the study sites in central Ohio reproductive maturity usually is attained by plants 3–4 years old. Individuals ofT.nivalelive to be at least 8 years old; maximum longevity has not been determined but is probably considerably longer than 8 years. Meiosis and tetrad formation occur in July and August; preformed pollen in buds with relatively mature floral organs overwinter, and flowering occurs in late February through March of the next spring. Seeds mature in ca. 3 months after fertilization; an elaiosome is produced on each seed and the diaspores are disseminated by ants. Germination apparently occurs in early spring at least one season after seed production. Clonal growth is of limited importance; rhizomes very rarely produce offsets by lateral budding. Individuals ofT.nivaleare self-compatible, weakly protogynous, and facultatively xenogamous. We reportn = 10 as the chromosome number in contrast to a previously published count ofn = 12.

ISSN:0008-4026    

DOI:10.1139/b85-002

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A forest site in southeastern Manitoba has been irradiated by a point source of gamma rays continuously since 1973, and measurements have been made yearly to study the change in boreal forest canopy cover along the radiation gradient. After 10 years of chronic irradiation, a zone of total tree death has resulted from mean dose rates between 25 and 62 mGy h−1. Tree canopy cover was reduced at mean dose rates exceeding ~ 4.5 mGy h−1and the largest reduction occurred in the first 2 years of irradiation. The temporal responses of seven woody species to gamma radiation are presented. Bebb's willow, trembling aspen, speckled alder, and paper birch were less sensitive to radiation than black spruce, balsam fir, and jack pine. The results confirm that gymnosperms are more sensitive to gamma rays than angiosperms.

ISSN:0008-4026    

DOI:10.1139/b85-003

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Half-tipped primary and lateral roots ofPhaseolus vulgarisbend toward the side of the root on which the intact half tip remains. Therefore, tips of lateral and primary roots produce growth effectors capable of inducing gravicurvature. The asymmetrical placement of a tip of a lateral root onto a detipped primary root results in the root bending toward the side of the root onto which the tip was placed. That is, the lesser graviresponsiveness of lateral roots as compared with primary roots is not due to the inability of their caps to produce growth inhibitors. The more pronounced graviresponsiveness of primary roots is positively correlated with the presence of columella tissues that are 3.8 times longer, 1.7 times wider, and 10.5 times more voluminous than the columellas of lateral roots. We propose that the lack of graviresponsiveness exhibited by lateral roots is due to the facts that they (i) produce smaller amounts of the inhibitor than primary (i.e., strongly graviresponsive) roots and (ii) are unable to redistribute the inhibitor so as to be able to create a concentration gradient sufficient to induce a pronounced gravitropic response.

ISSN:0008-4026    

DOI:10.1139/b85-004

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

TheRhizobium-induced root nodules ofParasponia rigida(Ulmaceae) outwardly resemble those formed on actinorhizal plants, being coralloid in shape and consisting of multiple, branched lobes. The details of nodule morphogenesis also resemble more closely those which occur in an actinorhizal association than a typicalRhizobium–legume association and include prenodule formation, initiation of modified lateral roots which are termed nodule lobe primordia, and rhizobial colonization of tissues derived from the nodule lobe primordia to form the primary nodule lobes. Mature nodule lobe structure is actinorhizallike. Each lobe has an apical meristem and a central vascular cylinder which is surrounded by an uninfected inner cortex and then a zone of infected tissue. Peripheral to the infected tissue is an uninfected outer cortex. Infection threads and intercellular rhizobia progress continuously toward the apical meristem but do not infect the meristem itself. The establishment of the symbiosis in the host cells involves continuous thread formation after the initial infection until the host cells are nearly filled with rhizobia enclosed in threads. The rhizobia remain in threads throughout the symbiotic relationship and are not released from the threads as occurs in bacteroid formation in legumes.

ISSN:0008-4026    

DOI:10.1139/b85-005

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The symptomless relationship of tall fescue grass (Festuca arundinaceaSchreber) and its endophytic parasitic fungus,Sphacelia typhina(Fr.) Tul. (=Acremonium coenophialumfide Morgan-Jones et Gams), was studied with light and electron microscopy. The fungus was intercellular and was distributed throughout the plant with the exception of roots and leaf blades. The highest concentration of the fungus occurred in the base of the leaf sheath. In the seed the fungus was sequestered between the epithelial cells of the scutellum and the starchy endosperm. The seed embryo was not infected; infection was also not evident during the early stages of seed germination. At the ultrastructural level, the parasitic relationship was established in tissues where there were intercellular spaces. Micrographs indicated that the fungus did not separate the middle lamella of host cells, nor did it produce any obvious alteration in host cell morphology. Ultrastructural characteristics of the fungus depended on the age and type of fescue tissue. Hyphal cells possessed numerous vesicular and multivesicular structures, and in some sections, the hyphal walls were inordinately thickened and with or without an extracellular matrix. The fungus appeared to colonize the innermost areas of tissues in all infected organs and no signs of egress were ever detected.

ISSN:0008-4026    

DOI:10.1139/b85-006

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Effective root nodules formed onLotus pedunculatusbyRhizobium lotiNZP2037 andBradyrhizobiumsp. (Lotus) CC814s were examined by light and electron microscopy. NZP2037 nodules were larger than CC814s nodules as a result of a much thicker nodule cortex. The smaller CC814s nodules had a much larger infected zone and, consequently, larger volumes of infected cells, peribacteroid space, and host cytosol per nodule. As well, CC814s nodules demonstrated a significantly higher number of bacteria which typically contained prominent polar bodies and beta-polyhydroxybutyrate (PHB) granules. The bacteria of NZP2037 nodules lacked the polar bodies, but PHB deposits were occasionally observed. A correlated physiological study in which acetylene reduction was used to estimate nitrogen fixation showed CC814s nodules to be more active than NZP2037 nodules (Pankhurst, C. E., and D. B. Layzell. 1984. Physiol. Plant. 62(3) : 404–409.). This measured difference in nitrogen-fixing activity was considered due to the degree of infection and bacterial proliferation as well as differences in the carbon and nitrogen metabolism of the two nodule types. The significance of the structural observations and morphometric analyses and their relationship to differences in nitrogen fixation are discussed.

ISSN:0008-4026    

DOI:10.1139/b85-007

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Three different agents for cytoplasmic hypovirulence (CH) were transferred individually to a virulent (V) isolate (EP 155) ofEndothia parasitica. The CH agent HI2obtained from an Italian isolate ofE.parasiticahad little effect on the ability of EP 155 to sporulate asexually or to cause cankers on American chestnut. CH agent HM2from a Michigan isolate reduced these parameters by 60 and 80%, respectively, whereas CH agent HT2from a Tennessee isolate reduced both parameters almost totally. Agent HT2was markedly less efficient than HI2or HM2at conversion of mycelium and stromata in cankers incited by EP 155. Agent HT2also was transmitted through a much lower percentage of conidia than were HI2or HM2. This did not appear to be a barrier to the spread of cytoplasmic hypovirulence, however, as very few CH conidia in droplets of condial suspensions were required for conversion of resultant colonies to CH. Frequency of transmission of CH agents through conidia producedin vivoand invitrowas similar and did not change over time. Longevity of conidia containing agent HI2was similar to that for V conidia on all substrates tested.

ISSN:0008-4026    

DOI:10.1139/b85-008

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Clones ofAgrostis gigantea,Deschampsia caespitosa,Hordeum jubatuin, andPoa compressawere evaluated for their tolerance with respect to copper, nickel, and zinc. Most of the plants originated from acidic, copper- and nickel-contaminated soils near Sudbury, Ont. Metal tolerance was assayed by measuring all of the adventitious roots growing from tillers but excluding lateral roots. Tolerance of copper, nickel, and zinc was evident in the four clones ofD.caespitosaoriginating from Sudbury. One clone ofA.giganteaoriginating from a roast bed showed tolerance of copper, while none showed tolerance of cither nickel or zinc. One clone ofP.compressafrom Sudbury indicated increased tolerance of copper and nickel, yet its root growth was inhibited at lower zinc concentrations than that of a companion clone from Sudbury and a control. TheH.jubatumplants showed no tolerance of any of the metals. Copper was most toxic to all of the species, followed by nickel and then zinc.

ISSN:0008-4026    

DOI:10.1139/b85-009

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Several published allometric biomass equations may be available for a particular species. For some applications a method is needed to produce a single equation for the species. Several investigators have produced such an equation by refitting the combined original data used to develop the separate equations. We evaluated a method, previously examined for several hardwood tree species, for producing an equation fit to data generated from the published equations when the original data are not available. For the three tall shrub species groups (Acer spicatumLam.,Amelanchierspp., andSalixspp.) examined, the generated weighted data equation fit the combined weighted data as well as or better than the published equations.

ISSN:0008-4026    

DOI:10.1139/b85-010

出版商:NRC Research Press    

年代:1985

数据来源: NRC