摘要:

Growth pouches were used to establish ectomycorrhizae ofPinus strobususingPisolithus tinctoriusas inoculum. An epi-illumination technique was used to follow changes in external morphology of short roots as they became colonized by hyphae and dichotomized. Apices became broader and flatter before an obvious dichotomy was apparent. Secondary dichotomies often formed after the primary dichotomy of the original short roots. Sectioned material showed that a central group of cells in the meristem stopped dividing and became vacuolated as dichotomy was initiated. Two lateral growth centres were established which led to the formation of two apical meristems.

ISSN:0008-4026    

DOI:10.1139/b82-194

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The radial walls of the hypodermis in onion and corn roots were impermeable to the apoplastic fluorescent dye Tinopal CBS. All walls of the hypodermis as well as the walls of the epidermis were autofluorescent when viewed under violet light. After clearing with hot NaOH, however, autofluorescence was observed only in the radial walls of the onion and corn hypodermis and in the walls of the onion epidermis. The fluorescence could be intensified by staining with an extract ofChelidonium majusroot. The Casparian band of the onion and corn endodermis likewise acted as a barrier to Tinopal CBS diffusion and continued to autofluoresce after treatment with hot NaOH. It is concluded that a Casparian band exists in the hypodermis of onion and corn roots. In the hypodermis the entire radial wall is occupied by the Casparian band. In longitudinal view, the hypodermal Casparian band appears in all the radial and transverse walls of the cells and is continuous from one cell to the neighbouring cells.

ISSN:0008-4026    

DOI:10.1139/b82-195

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The flower ofSymplocarpus foetidusis characterized by an inferior unilocular ovary containing a suborthotropous ovule in apical position. Several authors consider the gynoecium ofSymplocarpusto be pseudomonomerous. Our study of the organization of the vascular bundles does not confirm this hypothesis. Furthermore, pseudomonomery has yet to be demonstrated for any of the members of the Calloideae. The flower ofSymplocarpusshows many similarities with that ofGymnostachys(Pothoideae) and ofAglaonema(Philodendroideae). InSymplocarpus, we also observe four vascular bundles in the style but they are not homologous to those ofAglaonemaand cannot be interpreted as belonging to two different carpels.

ISSN:0008-4026    

DOI:10.1139/b82-196

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Artificial dehydration of 3-day-old seedlings ofAllium cepaproduces physiological and ultrastructural changes. Osmium fixation caused various alterations in dictyosomes, the endoplasmic reticulum, and the nuclear envelope. Seedling dehydration was accompanied by a lowering of the reduction capacity of various cell components. This lower reduction capacity also affected the same organelles in seed tissues. When seedlings were dehydrated, their tissues returned to a resting state, and became cold resistant. When artificially dehydrated seedlings were treated with liquid nitrogen (−196 °C), cells only underwent slight changes. These alterations were reversible both after dehydration and after freezing to −195 °C. During rehydration, the changes in cell structures and their reactivity following the osmic fixation technique were observed. [Journal translation]

ISSN:0008-4026    

DOI:10.1139/b82-197

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The hypothesis that a bicolored fruit display increases fruit consumption by birds was supported by results of experimental displays ofPrunus serotinafruits in solitary infructescences. However, at the level of a whole-tree fruiting display, the hypothesis was not supported: there was no significant difference in removal rates from bicolored and all-black displays on isolated trees; an all-black display was more attractive to avian dispersers on trees in a clumped distribution. ForRubus occidentalis, there was no significant difference in removal rates in different colored displays. There may be more reward per unit searching time in all-black trees because of more ripe fruits and perhaps more available insects; these possibilities are testable but leave unattended the problem of the evolution of bicolored displays.

ISSN:0008-4026    

DOI:10.1139/b82-198

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Plant nutrient dynamics in decomposing needle litter were measured during a 5-year period in a Scots pine forest in central Sweden. As seen over the whole 5-year period, the nutrients were retained (to a litter weight loss of about 75%) in the order Mn < Ca < K < Mg < S < N < P. During the first 1.5 years there was a net increase of N and P whereafter a net release took place. A similar but less pronounced development could be seen for S, whereas Ca, K, Mn, and Mg were released from the start of the incubation. It is suggested that P was the most limiting element for microbial activity during this first phase. There appeared to be only little initial leaching from the litter and the different behaviours of the elements could largely be explained by their concentration in litter in relation to the needs of microorganisms and to their solubility. K and Mg were the elements that were released at rates most similar to organic matter weight loss.

ISSN:0008-4026    

DOI:10.1139/b82-199

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Three types of resistant or resting structures were found to occur in the entomogenous hyphomyceteNomuraea rileyiwhen unfavorable conditions (e.g., low humidity) inhibited conidiogenesis. Intrahyphal hyphae, which are regenerative hyphae within deteriorating parent hyphae, were observed in both the disintegrating larval tissue ofAnticarsia gemmatalisand the extracuticular fungal mat. Thick-walled hyphae and chlamydospores were found in the external mat, and lipid-filled, thin-walled hyphae were prevalent in the larval tissue. Chlamydospores formed as apical swellings of thick-walled hyphae. Resistant structures remained viable for at least 12 weeks. Upon rehydration, cells resumed metabolic activity and after several days, conidiophores and conidia were produced. Verification of the existence of such structures provides an explanation as to how the fungus survives in the field under adverse environmental conditions.

ISSN:0008-4026    

DOI:10.1139/b82-200

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Clathroconium arachnicolagen. and sp. nov. is described from a spider, collected on a cocoa leaf in Ghana. The fungus is characterized by yellow–brown, solitary, clathroid conidia.

ISSN:0008-4026    

DOI:10.1139/b82-201

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The authors agree with the choice of lectotype forOxytropis monticolaGray made by Barneby in 1952 and present reasons for its retention.

ISSN:0008-4026    

DOI:10.1139/b82-202

出版商:NRC Research Press    

年代:1982

数据来源: NRC