摘要:

A15N dilution technique is proposed to determine the role of nitrogen reserves in the plant on the estimation of dinitrogen fixation, during regrowth of perennial legumes. It is based on labelling of nitrogen compartments of the plant. Since the kinetics of utilization of nitrogen reserves of ryegrass (Lolium italicumL.) and red clover (Trifolium pratenseL.) appear similar, ryegrass would be a good control plant. Despite this observation, the comparison of two methods (based on two or three sources of nitrogen) to estimate dinitrogen fixation shows the difficulty in applying the technique using15N-labelled substrate over earlier periods of regrowth. In this case, the15N method described for determining symbiotic dinitrogen fixation could be applied in controlled conditions.

ISSN:0008-4026    

DOI:10.1139/b85-134

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Diverse anatomical patterns observed in 18 narrow-leavedFestucataxa are illustrated by composite block diagrams formed from a synthesis of at least 10 leaf cross sections from five plants chosen across the geographical range of each taxon; the terms used are described; and cross sections are illustrated using semithin leaf sections and block diagrams. Measurements on seven variables and notes on sclerenchyma patterns from the cross sections are presented in anatomical descriptions for 18 taxa (16 species and 2 infraspecies). Results of analyses of variance and deviance show that five of the seven variables have significant differences in mean values that coincide with the taxonomy. However, the range of values observed for each taxon was found to overlap with that of others so much that measuring these variables for an unknown plant would not always give a reliable identification to species, although it would reduce the possibilities.

ISSN:0008-4026    

DOI:10.1139/b85-135

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Decomposition of Scots pine needle litter was studied in a Scots pine forest in central Sweden. A 6-year series with annual incubations of needle litter was used to analyse the climatic influence on the process. The original litter was of similar chemical properties between years and each year new litter was incubated, in the same way, in the autumn. Sampling took place at time intervals ranging from 1 month to 1 year. Soil climate variables such as temperature and water contents and tensions were calculated with a soil water and heat model from standard meteorological data. Decomposition rates from periods longer than 145 days were correlated with different soil climatic factors. The responses for the 1st and 2nd incubation years were not significantly different, but higher coefficients of determination (r2) were found for the 2nd year. Estimated actual evapotranspiration or soil temperature explained temporal variation of decomposition to about 70%; soil water content only or soil water tension only explained 90%. When moisture and temperature were combined, 95 and 99% of the variation could be explained for the 1st and 2nd year, respectively. When time periods down to 1 month were included, very poor fits were found with the same climate response functions. However, the relationships were improved by an inertia function which indicated a time lag of 2–3 months between soil climate and the response in decomposition rate.

ISSN:0008-4026    

DOI:10.1139/b85-136

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Besides adventitious buddingin vitro, rejuvenation of meristems could possibly be achieved by micrografting. We report here successful auto- and homo-graftingin vitroinPinus pinaster. Apices 5–7 mm in length either (i) collected from 2- to 3-month-old seedlings or (ii) producedin vitrofrom an 11 -year-old tree by means of successive axillary budding cycles over a 5-year period were successfully grafted onto the epicotyl of 2- to 3-month-old seedlings. Grafted plants have been successfully transfered to field conditions. If grafted onto the hypocotyl, plants did not survive.

ISSN:0008-4026    

DOI:10.1139/b85-137

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Glyphosate (N-(phosphonomethyl)glycine) inhibited the growth of myxotrophically culturedEuglena gracilis. This inhibition was reversed by a combination of end products of the aromatic amino acid biosynthetic pathway, including the quantitatively minor vitamin precursors. This suggested a stringent inhibition of the early-pathway reactions, five consecutive reactions of which are catalyzed by thearomprotein. Glyphosate was shown to affect the catalytic properties of thearomprotein, thus providing a new means for studying the relationships of intrapathway catalytic sites to one another in this unique protein.

ISSN:0008-4026    

DOI:10.1139/b85-138

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A chemostat culture system is described in which measurements of rates associated with carbon and nitrogen assimilation may be made inin situsteady-state cultures of N2-fixing cyanobacteria. Net C and N assimilations were determined from the steady-state cellular carbon and nitrogen contents and the steady-state growth rate of the cultures. O2evolution in the light and short-term14C assimilation were measured simultaneously in unperturbed culture cuvettes.14C assimilation was linear with time through the origin over the 20-min sampling period, thereby providing a measure of gross photosynthesis. C2H2reduction was measured within the culture cuvette using an open gas analysis system. Steady-state rates of C2H2reduction were obtained within 10 min and remained constant for up to 1 h. Preliminary results showed that at similar growth rates (0.018–0.019 h−1) cultures grown onand N2contained heterocysts, were smaller, and had higher chlorophyll contents than cells grown on NH3. Corresponding gross photosynthesis was 1.6 to 1.8 times higher than net photosynthesis inand N2-grown cells; however, for NH3-grown cells the ratio of gross photosynthesis:net photosynthesis was close to unity. These results are discussed with reference to the energetic costs associated with N assimilation in cyanobacteria.

ISSN:0008-4026    

DOI:10.1139/b85-139

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Tomato (Lycopersicon esculentumMill.) plants grown under low (LTR), intermediate (ITR), and high (HTR) temperature regimes produced fruits which were significantly different in certain characteristics. Under LTR, fruits were larger, both in fresh weight and size, and contained a greater number of locules than the fruits produced under ITR, which were larger than those developed under HTR. Fruits from plants maintained in temperature-controlled growth chambers before and after pollination were generally larger than those transferred to a greenhouse after pollination. Some abnormalities were observed in fruits grown under LTR but not in those produced under ITR and HTR.

ISSN:0008-4026    

DOI:10.1139/b85-140

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Pea seeds var. Kriter were stored aseptically at 92% relative humidity and 30 °C. After 0, 4, 6, 8, or 10 weeks of storage, viability, vigor, and volatile exudates were determined on sublots of seeds. As storage time increased, vigor, as measured by dehydrogenase activity, growth of embryonic axes, and conductivity decreased. Later, viability also decreased. Imbibing and germinating pea seeds produced ethanol, acetaldehyde, and lesser amounts of methanol. No qualitative differences in volatile exudates were observed from germinating seeds regardless of age or storage condition. Nonaged seeds with highest vigor produced the smallest amounts of volatiles, but with increased aging the quantities of ethanol and acetaldehyde gradually increased. Dry seed produced small quantities of both volatiles. The amount of these compounds produced reached a maximum between 12 and 48 h of germination. Infestation of seed samples withEnterobacter cloacaeorTrichoderma harzianumreduced the quantities of these compounds measured. These results indicate that determinations of acetaldehyde and ethanol in the space over germinating seeds by means of gas chromatography may be a useful seed vigor test.

ISSN:0008-4026    

DOI:10.1139/b85-141

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Responses of soil microorganisms to volatile exudates from germinating pea seeds of differing quality were determined. Germination of sclerotia ofRhizoctonia solaniandSclerotium rolfsiiand subsequent hyphal growth were stimulated by exposure to volatiles from aged but not nonaged pea seeds. Hyphae grew preferentially toward aged seeds. In natural soil, bacterial and fungal populations showed significant increases after exposure to volatiles from aged seed. For example,Fusariumspp. andPseudomonasspp. showed increases of 79 and 2200%, respectively, over their original population levels after a 48-h exposure to volatiles. Conversely,Pythiumpopulations and associated seed-rotting potential of soil decreased in natural soils exposed to volatiles. In autoclaved soils infested withP.ultimum(PHP4),Pythiumpopulations increased dramatically after exposure to volatiles from aged pea seeds. In soils infested with either soil fungi or bacteria in addition toP.ultimum,Pythiumlevels remained constant or decreased, respectively, with time of exposure. Exposure to the volatiles from aged pea seeds stimulated soil microbial activity. These results suggest thatPythiumgermlings, when unable to reach a host, are subjected to microbial antagonism in the presence of the native soil microflora. A decrease in cucumber seed rot coincided with decreases inPythiumnumbers.

ISSN:0008-4026    

DOI:10.1139/b85-142

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Changes in weight and nutrient concentrations (N, P, K, Ca, Mg) of foliage and twig litter fall were measured over an 18-month period at three positions along a topographic sequence of ecosystem types. Conifer foliage confined in litter bags was found to lose weight at the same rate on all three sites: about 35% after 12 and 40% after 18 months. Confined broadleaf foliage decomposed at about the same rates on all sites, but unconfined samples decomposed significantly faster on the lower, hygric sites, probably as a result of greater fragmentation losses. Twig weight loss of conifers was extremely variable, ranging from 10 to 28% after 12 months. The total mass of K, Mg, and Ca decreased over the study period in all foliage litter, while N increased and P was variable. K tended to be more mobile on the hygric sites. Ca was found to be the most rapidly lost element in almost all cases. It was concluded that the observed similarity in weight loss of conifer foliage on all sites is partially due to a confinement effect and partially to a substrate chemistry effect. The nutrient data suggest that there may be some differences in decomposition processes on the lower, hygric sites compared with other ecosystem types. This agrees with the observation that the humus form in the hygric site is different (duff mull) from that on the other two sites (felty mor).

ISSN:0008-4026    

DOI:10.1139/b85-143

出版商:NRC Research Press    

年代:1985

数据来源: NRC