摘要:

Hieracium florentinumAll. reproduces vegetatively by adventitious buds which have been shown by anatomical studies to arise from roots. Culture experiments indicate that undamaged roots and isolated root tips have the capacity for bud initiation. Vegetative propagation by means of root-borne buds is important in the expansion of existing populations ofH. florentinum.

ISSN:0008-4026    

DOI:10.1139/b71-011

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Pollen grains from the near-isogenic inbreds, Oh 43Rf1Rf1, Oh 43rf1rf1, 106Rf1Rf1, and 106rf1rf1were cultured on an artificial medium containing 15% sucrose and 0.6% bacto-agar supplemented with all possible combinations of two levels (0.00 and 0.03%) of calcium nitrate (Ca) and two levels (0.00 and 0.01%) of boric acid (B). At certain combinations of Ca and B, significant differences between theRf1Rf1andrf1rf1genotypes were obtained for germination percentage, rupturing percentage, and pollen tube length. However, the effect of theRf1andrf1alleles was not consistent in magnitude for both inbreds. Apparently, theRf1andrf1alleles can alter certain in vitro germination characteristics but genetic background is also involved.

ISSN:0008-4026    

DOI:10.1139/b71-012

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Application of benzyladenine (BA) to portions of a bean leaf either along or across the midvein or to one of the two primary leaves, on intact plants, retarded senescence of the treated part. When14carbon labeled CO2, IAA, leucine, or sucrose was fed to the untreated part on the same leaf, or to the untreated opposite leaf, there was less than 2%of the total radioactivity in the BA treated part after 24 h. It is concluded that retardation of leaf senescence by BA on intact bean plants is not dependent on mobilization of metabolites from other parts of the leaf.

ISSN:0008-4026    

DOI:10.1139/b71-013

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Penetration of the fine roots of Vernal alfalfa byPhytophthora megaspermawas investigated in solution culture. The zoospores encysted on the root tips around the zone of cell division and cell extension and directly penetrated the host by a small infection peg. No appressoria were observed, but the flattened base of the cyst adhered to the host and appeared to serve the same function. Inside the root the hyphae were inter- and intra-cellular. In naturally infested and artificially inoculated field soils most of the fine roots were destroyed and large lesions appeared on the tap root. The latter originated from infection of the spongy-phellem cells formed around the base of the fine lateral roots. Restricted lesion development on the tap root was associated with the formation of wound periderm around the infection court. No wound periderm was formed when the vascular system was infected and only minor damage occurred when invasion was restricted to the cortex. Root damage reduced growth rates in older plants and severe infection produced yellow foliage, premature defoliation, and wilting.

ISSN:0008-4026    

DOI:10.1139/b71-014

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Photosynthetic14CO2-fixation by excised leaves of Canada thistle (Cirsium arvense(L.) Scop.) and soybean (Glycine max(L.) Merr., cultivar Harosoy 63) was reduced significantly by prior exposure of the roots of source plants to 4-amino-3,5,6-trichloropicolinic acid (picloram) at 1, 10, or 20 ppm. At 10 ppm (0.036 mM) fixation was about half of that in corresponding controls. In corn (Zea maysL., cultivar Morden 77) no inhibition occurred at 10 ppm picloram but at 20 ppm the reduction in fixation (13%) was significant. The treatments had no marked effect on14CO2-fixation in the dark. Treatments which caused 50% or more inhibition of fixation resulted in nearly 50% reduction in labeled sucrose and alanine in the leaves. Relative amounts of labeled malic acid, aspartic acid, glutamic acid, asparagine, and serine, on the other hand, increased. Translocation of14C-assimilates from leaves to roots in intact Canada thistle and soybean plants was inhibited if roots were treated with 1 or 10 ppm picloram for 24 h before exposure to14CO2. Young leaves of plants so treated, especially soybeans, accumulated very little assimilated14C compared with similar leaves in control plants. Transport of14C-assimilates in corn plants was not significantly affected by picloram treatment. Our results suggest that the inhibitory effects of picloram on photosynthetic14CO2-fixation and on translocation of labeled assimilates in sensitive and resistant species are indirect and are a result of disturbances of other physiological processes.

ISSN:0008-4026    

DOI:10.1139/b71-015

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Consideration of the population curves ofOocystis crassaandO. lacustrisin Lake Manitoba during the summers of 1966 and 1967, and July 1968, indicated that the aquatic fungusChytridium deltanumwas able in two instances to attack growing populations of these algae. This strongly suggested that the fungus was a parasite. However, in July 1965, in Cadham Bay, the fungus bloomed as the host population stopped growing and began to decline. Probably the host cells were slightly senescent at that time and thus more susceptible to fungus attack. Consideration of the composition of the fungus population showed that during one epidemic at least, large numbers of zoospores were released every 7 to 9 days. This suggested a nearly synchronous development of the fungus population. It was also observed that zoospores, able to encyst and successfully infect one host, were sometimes unable to attack another potential host present at the same time. In 1966 and 1967 the fungus appeared a few days after the water had reached 25C. Comparison of culture data for the algae and field studies indicated thatChytridium deltanummost commonly grew on the algae at temperatures above the optimum for the algae.

ISSN:0008-4026    

DOI:10.1139/b71-016

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The cytotaxonomy of three closely related species ofDrabais discussed and a key is given:D. canaRydberg (2n = 32),D. cinereaAdams (2n = 48 and 64), andD. groenlandicaE. Ekman (2n = 64). Evidence is presented to show that the nameD. lanceolataRoyle has been misapplied to plants that should be calledD. cana.Scanning electron microscope examinations were made of hairs on leaves and silicles and the value of the different types of hairs as morphological characters in the taxonomy ofDrabaspecies is stressed.

ISSN:0008-4026    

DOI:10.1139/b71-017

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The effects of soil pH, ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), and clay content on the formation ofCenococcum graniformemycorrhizae on basswood (Tilia americanaL.) were evaluated by assessing the degree of mycorrhizal infection of seedlings from natural forests in southern Ontario.Six hundred and thirty-nine basswood seedlings were collected, with adhering soil, from 22 woodlots between 43°30′ N. and 44°36′ N. The soils were mainly sandy and clay loams and the pH ranged from 6.2 to 8.4.The development ofCenococcummycorrhiza was found to decrease as the pH, clay content, or NO3-N of the soil increased. Concentration of NH4-N was not found to be correlated with mycorrhizal infection. For a subsample of alkaline soils ranging in pH from 7.1 to 8.4, no correlation was evident between NO3-N and mycorrhizal infection.

ISSN:0008-4026    

DOI:10.1139/b71-018

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A study of apical dominance in isolated rhizomes ofAgropyron repensL. Beauv. showed that increasing the length of the rhizome significantly reduced the degree of dominance only in rhizomes from plants grown at a high nitrogen level (210 ppm). Exposing the rhizomes to light also reduced dominance more effectively in high-nitrogen rhizomes but the response of rhizomes from low-nitrogen plants was greatly increased by supplying water through the end of the rhizome. Further experiments with low-nitrogen rhizomes showed that buds could be released from apical dominance by treatment with kinetin. When isolated from the plant the buds showed a significant increase in length after 24 h and an associated increase in moisture and insoluble nitrogen content. Soluble nitrogen and carbohydrate increased concurrently during the next 24 h. Rhizomes kept in darkness showed a small reduction of bud inhibition when water was supplied through the cut end; NH4NO3solution had a greater effect, while solutions in which both nitrogen and carbohydrate (as sucrose) were supplied resulted in the almost complete elimination of apical dominance.The results suggest that apical dominance in isolated, low-nitrogen rhizomes was due mainly to competition between the apex and the lateral buds for water, nitrogen, and carbohydrate.

ISSN:0008-4026    

DOI:10.1139/b71-019

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

It is possible to distinguish two stages in the influence of light on the germination ofLactuca sativavar. Grand Rapids (lettuce) seeds. The first stage, which is represented by the photoactivation or transformation of phytochrome, requires only a relatively low seed water content. Slightly higher seed water content is required for maximum far-red light repression, than for red light stimulation of germination. The second stage is indicated by the well-known situation in which previous red irradiations of the seeds can enhance germination but this takes place only with relatively high seed water content. Phototransformed phytochrome appears to persist and to be susceptible to photoreversal for at least 24 h after irradiation in the seeds with relatively low water content.

ISSN:0008-4026    

DOI:10.1139/b71-020

出版商:NRC Research Press    

年代:1971

数据来源: NRC