摘要:

The penetration and establishment ofPleiochaeta setosain lupin leaflets was studied with light microscope and scanning and transmission electron microscopes. Healthy lupin leaves were also studied at the ultrastructural level. Conidium germination, appressorium formation, and host penetration were found to take place non-synchronously, and the method of penetration of the pathogen through either the cuticle or stomata was determined by the method of inoculation. Disease symptoms were manifested 17 h after inoculation. The ultrastructure of stomatal penetration involved the formation of no specialized structures. Appressoria adhered to the host surface by means of adhesion blocks which penetrated the wax layer. Penetration through the cuticle was by a thin-walled infection peg that expanded below the cuticle to form a swollen infection hyphae from which hyphae ramified indiscriminately throughout the host. It is suggested that extracellular enzymes diffused in advance of the invading pathogen. The ultra-structure of the host reaction is described together with that of the invading fungus.

ISSN:0008-4026    

DOI:10.1139/b77-147

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Conidia ofAlternaria brassicaeare transformed into microsclerotia on some naturally infected, partially decayed rapeseed leaves stored at 3 °C in the dark. On V-8 juice agar medium, formation of microsclerotia occurs after 2-week-old cultures are exposed to 3 °C for at least 6–10 days. When rose bengal is added to the medium, growth is restricted and the transformation of conidia into microsclerotia is also initiated during gradual desiccation. Mature microsclerotia are darkly pigmented, many-celled, unevenly spheroidal, and about 60–150 μm in diameter. Microsclerotia are resistant to desiccation and freezing. On a 1% malt extract solution, germination of frozen–thawed microsclerotia results almost exclusively in the direct production of conidiophores and conidia, and germination of untreated microsclerotia results primarily in the production of germ tubes that extended into hyphae.Chlamydospores also form within conidium cells after cold temperature (3 °C) treatment or during gradual desiccation in cultures. Conidia placed on natural soil at room temperature become empty or form endocellular chlamydospores.

ISSN:0008-4026    

DOI:10.1139/b77-148

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The life history ofGracilariasp. was completed in culture demonstrating a typicalPolysiphonia-typelife history. Carpospores released by plants collected in nature developed into tetrasporophytes and subsequent release and germination of tetraspores gave rise to a gametophytic generation morphologically similar to the tetrasporophyte. Development of tetrasporophytes from carpospores released by the carposporophytic generation completed the life history. A male to female ratio of 1:1 was found for plants originating from tetraspores and only female plants grown in the presence of male plants formed fertile cystocarps. Detached plants showed the greatest reproductive potential; reproductive maturation of these plants occurred in 8–10 weeks after spore germination. Vegetative propagation through rapid regeneration of adventitious branches from wound tissue was observed.

ISSN:0008-4026    

DOI:10.1139/b77-149

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Levels of N, P, Ca, Mg, K, Al, Fe, Zn, Mn, and B were determined in foliage from tamarack (Larix laricina(DuRoi) K. Koch) in a bog, conifer swamp, and fen from budbreak to leaf abscission. Elongation of needles and lateral shoots as well as dry and ash weight of needles were determined. Expansion of needles and shoots ceased at similar dates for all sites, but trees in the fen had significantly longer needles and lateral shoots.On August 13, foliar concentrations of N, Ca,and Mg were higher in the fen than in the conifer swamp or bog, while concentrations of Al, Fe, Zn, Mn, and B were higher in the bog than the other two sites. Phosphorus concentrations in foliage were similar on this date in the fen and conifer swamp but were lower in the bog site. Despite significant between-site variation for certain foliar elements, two patterns of seasonal variation in nutrient concentrations were discerned. Significant between-site differences in the amounts and rates of needle and shoot elongation, foliar nutrient concentrations at a single sampling time, and patterns of certain foliar elements were associated with variations in nutrient status and moisture–aeration conditions of the study sites.

ISSN:0008-4026    

DOI:10.1139/b77-150

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Excess supply of the heavy metals Mn, Cu, Zn, Co, and Ni to barley caused their accumulation in shoots and specially in roots and induced symptoms characteristic of the particular heavy metal involved, the syndrome of which varied with the different treatments. The effectiveness of the heavy metals in inducing visual symptoms was in the order of Ni2+ > Co2+ > Cu2+ > Mn2+ > Zn2+. These treatments caused a decrease in dry matter yield of plants in the order Ni2+ > Co2+ > Zn2+ > Mn2+ > Cu2+.Studies using59Fe indicated that an excess supply of each of the heavy metals reduced iron absorption by plants and affected its distribution in roots and shoots. Excess of Co2+, Cu2+, Mn2+, and Zn2+reduced iron translocation to shoots, induced chlorosis, and decreased catalase activity of young leaves. Excess nickel, which was most active in producing toxic effects, did not inhibit translocation of iron to young leaves. Unlike iron deficiency, an excess of Ni2+did not decrease the activity of catalase and stimulated the activity of peroxidase. Excess supply of each of the heavy metals increased the concentration of non-reducing sugars. Observations suggest that toxicity to heavy metals does not necessarily involve induction of iron deficiency, their redox potentials, or the stability of their organometal complexes.

ISSN:0008-4026    

DOI:10.1139/b77-151

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Long-shoot terminal bud (LSTB) development in western white pine (Pinus monticolaDougl.) was studied throughout the annual growth cycle to determine the phenology of LSTB development and the time of cone-bud differentiation. Development of LSTB began in early April and cataphylls were initiated from mid-August until early November. Cataphyll initiation was slow during May and June when shoots were elongating and then rapid just after shoot elongation was completed. Proximal cataphylls were sterile, whereas more distal cataphylls began to initiate axillary buds by late June or early July. Axillary buds were initiated first in the proximal portions of the LSTB and then acropetally in rapid succession. The last cataphylls to be initiated in the fall remained as sterile bud scales enclosing the LSTB apex. Axillary buds initiated sterile cataphylls which functioned as bud scales. The number varied with the type of axillary bud. Proximal axillary buds initiated few cataphylls and began to differentiate into dwarf shoots or pollen cones in August. The more distal axillary buds differentiated into dwarf shoots during September and October, The most distal axillary buds initiated many cataphylls during September and October but did not differentiate into seed-cone buds or lateral branch buds until after winter dormancy. Consequently, attempts to induce or enhance seed-cone production inP. monticolawould probably be most successful in the spring when seed-cone buds differentiate. LSTB bearing seed cones were larger, had broader apices, and produced more cataphylls during the growing season than did LSTB bearing pollen cones. The phenology of LSTB development in soft pines and hard pines is discussed in relation to reports available on the association of cone crops and climatic conditions in several species ofPinus.

ISSN:0008-4026    

DOI:10.1139/b77-152

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Three isolates ofPhytophthorathat are pathogens of legumes and three that are nonpathogens were tested for sensitivity toL-canavanine. Growth of only one pathogen was affected by this amino acid.Phytophthora megaspermavar.sojaerace 1 was inhibited by canavanine when cultured in the basal medium. When starved mycelium of this isolate was treated with canavanine, total uptake of [H3] uridine andL-[H3] leucine and incorporation of these labeled compounds into insoluble fractions of trichloroacetic acid were enhanced. This demonstrated that under these conditions, canavanine supported some synthetic processes in the fungus.Of thePhytophthorasp. tested that are nonpathogens of legumes, one was affected by canavanine. Growth ofP. cactorumwas enhanced to a low degree. When asparagine (1.5 × 102 M) was replaced by canavanine (1.8 × 10−4 M) in the basal medium, growth was significantly higher than that in the asparagine-deficient basal medium. Labeling experiments withP. cactorumdemonstrated that canavanine enhanced incorporation of [H3]uridine andL-[H3]leucine into insoluble fractions of trichloroacetic acid.Phytophthora cactorumapparently detoxifies canavanine and utilizes it in growth-supporting activities.

ISSN:0008-4026    

DOI:10.1139/b77-153

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Serial-section analysis of synchronous spore populations of a species ofSaprolegniashow that the organelles of primary and secondary zoospores undergo a sequence of changes in both arrangement and morphology during the change from motile spores to cysts and vice versa. The morphological changes include elongation and shortening of mitochondria, reversible stacking of endoplasmic reticulum cistemae, and formation and use of bars and newly described K bodies. These observations show that considerable synthetic and assembly activity occurs in the various spore stages. All organelles remain in characteristic locations in the motile spores but most become randomly arranged in the cysts, thus demonstrating the existence of some unsuspected and as yet undefined morphogenic cytoplasmic components. The functional implications of the described changes are discussed.

ISSN:0008-4026    

DOI:10.1139/b77-154

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The activity of 5-aminolevulinic acid synthetase (δ-aminolaevulinate synthase, EC 2.3.1.37) in achlorophyllous peanut cells in suspension culture was determined in the presence of 1 mMlevulinic acid. It never exceeded 10% of the activity in green tissue. A feedback inhibition by protoheme may be the cause of low enzyme activity. The concentration of protoheme was 10- to 20-fold greater in these cultured cells than in leaves. The pool of protoheme was shown to act as a reservoir for peroxidase synthesis. This synthesis continued for 48 h in the presence of levulinic acid. The heme prosthetic group of peroxidase was only slowly labelled during the feeding with [14C]5-aminolevulinic acid.

ISSN:0008-4026    

DOI:10.1139/b77-155

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Nine different types of mycorrhizae were observed on naturally occurring white fir seedlings in the north central Sierra Nevada, including one formed by the ubiquitousCenococcum graniforme. The macro- and micro-scopic characteristics and reactions to different chemical reagents are described for five types. Possible mycorrhizal fungi of white fir are listed. Nursery-grown seedlings examined were ectomycorrhizal; intracellular penetration was not observed. None of the naturally occurring mycorrhizal types were found on nursery seedlings.

ISSN:0008-4026    

DOI:10.1139/b77-156

出版商:NRC Research Press    

年代:1977

数据来源: NRC