摘要:

Net photosynthetic rates, stomatal and mesophyll conductances to CO2uptake, water soluble and total nonstructural carbohydrates contents, specific leaf weights of fully expanded source leaves, and elongation rates of rapidly expanding leaves were measured on 2 days during a period of water stress in soybean and sunflower plants in a controlled environment. Compared with control plants, elongation rates of expanding leaves and translocation rates of dry weight from source leaves in the light were more reduced by stress than were net photosynthetic rates of source leaves. Over the 8-h light period, the dry weight increase of source leaves was up to 23 mg dm−2(1.5 × control) higher in stressed plants, but was not in all cases higher in stressed than control plants. In stressed plants a smaller fraction of the increase in dry weight in source leaves in the light was in nonstructural carbohydrates. At the end of the light period, water soluble and total nonstructural carbohydrates were up to 9 mg dm−2higher in stressed than control leaves in sunflower, but were not higher in soybean. No differences in carbohydrate contents at the end of the light period were found in sunflower between the 2 days of stress, although stress became more severe in terms of lower rates of photosynthesis, translocation, and leaf elongation. The approximately threefold reductions in net photosynthetic rates in stressed leaves were related to both lower stomatal and lower mesophyll conductances. Mesophyll conductances of stressed leaves were not significantly correlated with water soluble carbohydrate content, total nonstructural carbohydrate content, or specific leaf weight in either species.

ISSN:0008-4026    

DOI:10.1139/b82-026

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The pathogenisis ofVerticilliumvascular disease was evaluated in root-inoculated yellow-poplar trees grown under favorable, periodically saturated and chronically low soil moisture levels.Verticilliumwas significantly more aggressive in host trees stressed by periods of low moisture than in host trees subjected to periods of flooding. At no time did inoculated, flooded trees exhibit typicalVerticilliumsymptoms nor was pathogen reisolation obtained from the aboveground parts of these trees. In contrast, inoculated trees treated at favorable and low soil moisture levels incurred extensive pathogen colonization. Histological studies showed that the xylem vessels of petioles became occluded by fungus growth and a dark staining material at the time of first symptom expression. Additionally, macroscopic and microscopic observations of flooded trees indicated that acute injury occurred in the stem base and, under some conditions, the cortex in this region developed an aerenchyma induced by flooding.

ISSN:0008-4026    

DOI:10.1139/b82-027

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The cotyledonary axillary buds with most of their nuclei in the G1phase react to fusicoccin by showing a rapid elongation of their first two basal internodes. This elongation is achieved by the 15th h and is not accompanied by a passage of the nuclei to the S and G2phases. In response to decapitation or to 6-furfurylaminopurine (6-FAP) application, DNA synthesis starts again. The cell cycle is released immediately upon decapitation or before subapical elongation starts in 6-FAP treated plants. These results are discussed in relation to the current concepts on the action of fusicoccin and hormonal factors on H+/K+exchanges.

ISSN:0008-4026    

DOI:10.1139/b82-028

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Two watering systems used for growing minimally stressed plants are described. An aeroponics system, which relies on a mist of nutrient solution applied to roots without a root support medium, affords control over water availability and easy access to roots. A continuous circulation system, which constantly circulates nutrient medium, also provides control over water availability as well as control over pO2and stress duration in flooded plants. A comparison is made of the growth characteristics of plants grown in the two systems with those grown by traditional watering methods. The significance of watering prehistory to stress physiology experiments is discussed.

ISSN:0008-4026    

DOI:10.1139/b82-029

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Periphytic and planktonic algal populations were sampled over a yearly cycle in the Ogilvie and Swift rivers located in the northern and southern Yukon, respectively. Diatoms and green algae dominated periphytic assemblages during spring, summer, and fall, whereas the bulk of the overwintering cells was diatoms. The 96 species of periphytic diatoms were dominated byAchnanthes minutissimaKütz., an unidentified species ofAchnanthes, Cocconeis placentulaEhr.,Diatoma hiemalevar.mesodon(Ehr.) Grun.,Diatoma tenuevar.elongatumLyngb.,Anomoeoneis vitrea(Grun.) Ross, andFragilaria crotonensisKitton. Most diatoms encountered are also generally abundant in more temperate locations. Periphytic green algae were dominated byMougeotiasp.,Oedogoniumsp.,Ulothrixsp., andStigeocloniumsp. In high flow regions of the Ogilvie River the red algaLemanea fucinaBory was extremely abundant. Phytoplankton was sparse and generally represented by the same species as found in periphytic habitats. Results indicate that the phytoplankton cells were probably derived from sloughed periphytic cells.Achnanthes minutissima, Diatoma tenuevar.elongatum, Fragilaria construensvar.binodis(Ehr.) Grun.,Fragilaria vaucheriae(Kütz.) Peters, andSynedra ulna(Nitz.) Ehr. were the most abundant species in the plankton.

ISSN:0008-4026    

DOI:10.1139/b82-030

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Germination of sclerotia, growth, production bySclerotium rolfsiiwere inhibited by the bacterium,Pseudomonas aeruginosain culture and in soil. Inhibition of growth in soil was demonstrated by a new soil–agar plate technique. Preliminary evidence is presented which suggests that inhibition ofS. rolfsiibyP. aeruginosais associated with the production of the antibiotic, pyocyanin.

ISSN:0008-4026    

DOI:10.1139/b82-031

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Guard cells ofPaphiopedilumleaves lack chlorophyll, a unique condition. Whether potassium fluxes are involved in stomatal movements is controversial. In attempting to resolve this controversy, we have dissected individual guard cell pairs from frozen-dried epidermal peels of three species. These samples were assayed for potassium using quantitative histochemical methodology. We were unable to detect a correlation between guard cell potassium content and stomatal aperture size. With certain reservations, these results indicate potassium is not the major osmoticum causing stomata of these species to open.

ISSN:0008-4026    

DOI:10.1139/b82-032

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Cultures and anamorphs of six species ofDiatrypeandDiatrypellaare described.Diatrypella favaceaproduces conidia from sympodially proliferating conidiogenous cells, whereasDiatrype stigmaproduces conidia from percurrently proliferating (annellated) conidiogenous cells. Both of these types of conidiogenous cell proliferation were found inDiatrypella verrucaeformis, Diatrypella pulvinata, Diatrype virescens, andDiatrype albopruinosa. Both the sympodial and percurrent modes of conidiogenous cell proliferation appear to be associated with holoblastic conidiogenesis.

ISSN:0008-4026    

DOI:10.1139/b82-033

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Lignin degradation by the white-rot fungiPhanerochaete chrysosporium, Coriolus versicolor, Pycnoporus cinnabarinus, Lentinus edodes, Grifola frondosa, Polyporus brumalis, andMerulius tremellosuswas faster in an atmosphere of oxygen than in air.Gloeoporus dichrous, Pleurotus ostreatus, andBondarzewia berkeleyidegraded lignin at equal rates in oxygen and in air. Increased oxygen partial pressure also stimulated carbohydrate consumption by most of the fungi. In liquid shake culture, the fungi grew as well under an atmosphere of oxygen as air. However, respiration was faster under oxygen, suggesting that the fungi required more energy for growth and maintenance in oxygen. On delignified wood, most of the fungi grew equally rapidly in air and oxygen. Apparently, the growth of these fungi in wood in air is limited by the rate of lignin degradation.

ISSN:0008-4026    

DOI:10.1139/b82-034

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The ability of the first internode ofPisum sativumepicotylary axis to produce adventitious roots was examined with respect to dark and light growing conditions and depth position of the soaked seeds in vermiculite. Root initiation began on the 7th day and moved acropetally until the 16th day, with no formation of new roots between older ones. DNA synthesis in the diploid interfascicular cells followed the first mitoses of root initiation. The cell layer that would normally have differentiated into an endodermis reacted more slowly and built a primordial root cap, protecting the root as it grew through the cortex. When the new root emerged a new root cap – protoderm complex was rebuilt from the subapical cells of the root meristem. The increase in cell number was highest during the first 24 h following root initiation, and the cell cycle was extremely short with a very reduced G1phase. Only the elongation zone of the mature adventitious root showed polyploidy.

ISSN:0008-4026    

DOI:10.1139/b82-035

出版商:NRC Research Press    

年代:1982

数据来源: NRC