Associated growth of wheat and annual ryegrass. 2. Effect of varying the time of ryegrass germination in stands of wheat

1980 ◽  
Vol 31 (4) ◽  
pp. 659 ◽  
Author(s):  
K Rerkasem ◽  
WR Stern ◽  
NA Goodchild
Keyword(s):  
Pure Culture ◽  
Fertilizer Application ◽  
Total Density ◽  
Annual Ryegrass ◽  
Competitive Effects ◽  
Pure Cultures ◽  
Reproductive Rates ◽  
Rate Of Decline ◽  
High Level ◽  
Positive Intervention

In a field experiment, wheat cv. Gamenya and annual ryegrass cv. Wimmera were sown in four proportions, 80W : 20R, 60W : 40R, 40W : 60R, 20W : 80R, at a total density of 300 plants m-2 and in which a high level of nitrogen fertilizer application was maintained. Ryegrass was sown 17 days before, simultaneously with, and 17 days after wheat. At the simultaneous sowing there were also pure cultures of wheat and ryegrass; pure culture data for ryegrass corresponding to all the germination treatments were obtained in a supplementary experiment. All treatments were harvested on five occasions. Observations were made on tiller numbers, yield of dry matter, seed numbers and the yield components of wheat. There were marked effects of early and simultaneous sowing of ryegrass and of proportions; the results also showed interactions between the later sowings and proportions. In all treatments wheat tiller numbers rose to a maximum and declined to about half after about 100 days. A similar rise and fall was observed in the early and simultaneous germination of ryegrass, but not in the late one. In ryegrass, tiller numbers were much greater than in wheat, and the rate of decline was not as marked. In the late germination treatment ryegrass development and growth were seriously depressed. With respect to wheat, seed yield and ear numbers per unit area in the early and simultaneous sowings were less, while ears and grains per plant were greater in the presence of ryegrass than in pure culture. In ryegrass, seed production was highest in the early and least in the late treatments and was depressed as the proportion of wheat was increased; even in the treatment with the lowest proportion of ryegrass, seed numbers of ryegrass remained high. Relative reproductive rates showed a consistent pattern with time of sowing and with proportion, and the results suggest that control of ryegrass seed numbers cannot be achieved by manipulating planting treatments but requires positive intervention. Relative crowding coefficients (k) calculated from the data suggest that wheat was the stronger competitor. The results are discussed in terms of the competitive effects between species and the likelihood that wheat has the greater competitive ability. As in the previous study, it was noted that effects of competition were discernible at 28 days.

SOME FACTORS INFLUENCING THE GROWTH AND SURVIVAL OF RHIZOBIA IN HUMUS AND SOIL CULTURES

1948 ◽  
Vol 26c (2) ◽  
pp. 174-187 ◽  
Author(s):  
R. A. Hedlin ◽  
J. D. Newton
Keyword(s):  
Sodium Chloride ◽  
Calcium Carbonate ◽  
Magnesium Sulphate ◽  
Pure Culture ◽  
Mineral Soil ◽  
Growth And Survival ◽  
Factors Influencing ◽  
Pure Cultures ◽  
Dipotassium Phosphate ◽  
High Level

A study was made of the growth of rhizobia outside the host plant in three high humus mixtures and a mineral soil. Rhizobia grew better in pure cultures than in an unsterile base. Incubation in Erlenmeyer flasks gave, as a rule, higher counts than in paper cartons. Addition of a mixture of sucrose, calcium carbonate, sodium chloride, dipotassium phosphate, and magnesium sulphate led to increased numbers of rhizobia in pure culture in all bases used, and produced increased numbers in the unsterilized mineral soil also. Addition of this mixture to the unsterile high humus bases increased the total numbers of bacteria, but not the number of rhizobia. When the bases were sterilized, the highest counts of rhizobia were obtained in the high humus bases. When sterilization was not carried out, the greatest numbers of rhizobia occurred in the mineral soil. In tightly stoppered flasks that did not permit aeration, the rhizobia appeared to die out completely when stored for more than a few days, whereas in loosely stoppered flasks the counts remained at a high level until the base became desiccated.

Associated growth of wheat and annual ryegrass. 1. Effect of varying total density and proportion in mixtures of wheat and annual ryegrass

1980 ◽  
Vol 31 (4) ◽  
pp. 649 ◽  
Author(s):  
K Rerkasem ◽  
WR Stern ◽  
NA Goodchild
Keyword(s):  
Seed Production ◽  
Intraspecific Competition ◽  
Dry Matter ◽  
Relative Yield ◽  
Point Of View ◽  
Total Density ◽  
Annual Ryegrass ◽  
Main Effect ◽  
Pure Cultures ◽  
Similar Growth

A field study was undertaken in which wheat (T. aestivum L.) cv. Gamenya and annual ryegrass (Lolium rigidum Gaud.) cv. Wimmera were grown at total densities of 33, 100,300 and 900 plants m-2 in pure cultures and in mixtures in the proportions 33W : 67R, 50W : 50R, 67W : 33R. In densities of 100 and 900 plants m-2, five sequential harvests were made for total dry matter of each species in each pure culture and proportion. Interactions between proportion and density at the first and some subsequent harvests were noted, while at others these treatments behaved independently. At maturity, all plots were sampled for dry matter of each species, grain yield in wheat and seed production in ryegrass. With respect to dry matter and seed numbers, there was no interaction between density and proportion, but a main effect of density was noted. Seed numbers in ryegrass were between 31,000 and 45,000 m-2, and increasing the proportion of wheat had little effect on ryegrass seed production. An examination of the yield components of wheat (ears per plant, spikelets per ear and grains per spikelet) showed that intraspecific competition replaced interspecific competition as density rose. Although in pure cultures the two species had a similar growth pattern, the results showed that the effects of the species on one another were not identical and at final harvest, relative yield totals (RYT) > 1.0 were recorded in some treatments. The results are discussed in terms of inter- and intraspecific competition. From the practical point of view, this study shows that increasing either the density or proportion of wheat does not reduce the seed production of ryegrass to any great extent, and therefore its potential as a weed in wheat crops.

scholarly journals STAKEHOLDERS’ PERCEPTION AND WILLINGNESS TO COLLABORATE FOR EFFECTIVE WATERSHED MANAGEMENT IN TRINIDAD

2018 ◽  
Vol 9 (3) ◽  
pp. 3
Author(s):  
Jeanelle D D Joseph ◽  
Wayne Ganpat
Keyword(s):  
Watershed Management ◽  
Community Education ◽  
Climate Change Impacts ◽  
Community Activities ◽  
Constructive Dialogue ◽  
Mitigate Climate Change ◽  
High Level ◽  
Institutional Stakeholders ◽  
Positive Intervention ◽  
Purposive Sample

Proper watershed management is important for several reasons; the latest, and maybe most important, being to help mitigate climate change impacts. For countries with small landmasses and burgeoning populations, watersheds are increasingly at risk of being negatively impacted. The environment and water supply are particularly vulnerable if no actions are taken to manage them properly. This study sought to understand the perceptions of the various stakeholders who interact with the largest and most important watershed in Trinidad; their perceptions of the problems, the causes of the problems and possible solutions. It also investigated their willingness to collaborate on action plans to manage the watershed. A purposive sample of 266 respondents from four stakeholder groups was selected and interviewed using a structured questionnaire; comprising in the main of three perception scales and a modified Wilder Collaboration Factor Inventory. The latter is used to assess stakeholders willingness to collaborate. ANOVA results showed that there were similarities in perceptions to 5 of the 10 identified problems, 7 of the 18 possible causes and 6 of the 10 solutions presented. Such results suggested that there were opportunities for positive intervention and 21.3% of the stakeholders expressed a high level of willingness and a further 69.5% a moderate level of willingness to collaborate on community activities geared toward addressing water management issues. Recommendations included; increased community education on watershed importance, more constructive dialogue among stakeholders to achieve better agreements on the watershed issues and increased engagement with institutional stakeholders who are key to fashioning developmental plans for the watershed.

Effect of Enrichment Media and Sampling Protocol on Recovery of Listeria monocytogenes

1990 ◽  
Vol 53 (6) ◽  
pp. 505-507 ◽  
Author(s):  
J. S. BAILEY ◽  
D. L. FLETCHER ◽  
N. A. COX
Keyword(s):  
Listeria Monocytogenes ◽  
Pure Culture ◽  
Sampling Protocol ◽  
Enrichment Broth ◽  
Secondary Enrichment ◽  
Pure Cultures ◽  
University Of Vermont

These studies examined the differences in recovery of Listeria monocytogenes from pure culture and in the populations of mixed aerobic microflora from chicken and Brie cheese incubated in University of Vermont (UVM) and Listeria enrichment broth (LEB) enrichment broths for different times and conditions. No significant differences were observed in levels of L. monocytogenes from pure cultures in UVM or LEB on any sampling day. No differences were observed in the levels of mixed microflora from Brie cheese in either UVM or LEB, but from chicken rinse the level of mixed flora competitors was significantly higher on all sampling days in LEB as compared to UVM. No differences were observed between a single enrichment in UVM or LEB for 2 d and a transfer to a secondary enrichment tube after 1 d. Overall, the level of mixed microflora capable of growing in enrichment broths was greater from chicken rinse than from Brie cheese. The ratio of L. monocytogenes to mixed microflora which survived the selective enrichments was most favorable for recovery of L. monocytogenes after 2 d of enrichment.

Taxonomic Studies on Australian Isolates of Stemphylium spp. And Associated Teleomorphs

1986 ◽  
Vol 34 (3) ◽  
pp. 281 ◽  
Author(s):  
JAG Irwin ◽  
R Dill-Macky ◽  
M Stirling
Keyword(s):  
Medicago Sativa ◽  
Pure Culture ◽  
Herbarium Specimens ◽  
Simmondsia Chinensis ◽  
Pure Cultures ◽  
Taxonomic Studies ◽  
Ascospore Morphology

Taxonomic studies on monosporic pure cultures of Australian isolates of Stemphylium revealed the presence of three species, namely S. botryosum, S. globuliferum and S. vesicarium. A group intermedi- ate between S. botryosum and S. vesicarium but more closely resembling S. vesicarium was recognised. The circumscription of S. vesicarium was broadened to accommodate this taxon which was found on Medicago sativa, M. rugosa and Simmondsia chinensis. Studies on herbarium specimens deposited as S. botryosum on M. sativa from a number of overseas locations indicated that in all cases the pathogen fitted our concept of S. vesicarium. Teleomorphs were induced in pure culture for each of the above-mentioned anamorphs, and in all instances the teleomorph was identified as Pleospora herbarum. The ascospore morphology was similar for all isolates, and the shape of the ends of the spore and the number of longitudinal septa were variable characters even within an isolate. However, the teleomorphs could be separated into two distinct groups on the basis of ascal length.

The ecology and genetics of fitness in Chlamydomonas . II. The properties of mixtures of strains

1990 ◽  
Vol 240 (1298) ◽  
pp. 323-350 ◽  
Keyword(s):  
Pure Culture ◽  
General Tendency ◽  
Average Effect ◽  
Physical Environments ◽  
Unicellular Green Alga ◽  
Excess Production ◽  
Pure Cultures ◽  
Predictor Of Success ◽  
Genotype Interaction ◽  
Series Of Experiments

Whether or not mixtures of strains possess special properties depends on whether or not their component genotypes interact with one another. This paper describes a series of experiments designed to investigate genotype-by-genotype interaction among species of the unicellular green alga Chlamydomonas when grown axenically as liquid cultures in chemically defined media. It was shown that strains varied substantially in their average effect on the overall production of mixed cultures, and that specific interactions between pairs of genotypes were also significant, though small. This conclusion was confirmed by experiments in which strains were cultured separately in growth medium that had been con­ditioned by the prior culture of another strain. However, there was no consistent general tendency for mixtures to be more productive than the average of their components in pure culture; some mixtures in some physical environments were markedly more productive than their com­ponent means, but other mixtures in other environments were markedly less productive. The average effect of a strain on the production of mixtures was uncorrelated with its performance in pure culture, showing that fitness measured in pure culture may be a poor predictor of success in mixed populations. However, the average effect of a strain in simple mixtures was correlated with its effect in more complex mixtures. Com­plex mixtures themselves displayed properties similar to, but more extreme than, those of simple mixtures; thus, in an environment where pairwise mixtures tended to outyield pure cultures, excess production tended to increase with mixture complexity. The results of these experiments seem to be consistent with those of comparable agronomic trials.

Biological nitrification inhibition by weeds: wild radish, brome grass, wild oats and annual ryegrass decrease nitrification rates in their rhizospheres

2017 ◽  
Vol 68 (8) ◽  
pp. 798 ◽  
Author(s):  
Cathryn A. O'Sullivan ◽  
Kelley Whisson ◽  
Karen Treble ◽  
Margaret M. Roper ◽  
Shayne F. Micin ◽  
...  
Keyword(s):  
Root Exudates ◽  
Pure Culture ◽  
Nitrification Inhibition ◽  
Annual Ryegrass ◽  
Wild Radish ◽  
Weed Species ◽  
Wild Oats ◽  
Biological Nitrification ◽  
Brome Grass ◽  
The Impact

This study investigated the ability of several plant species commonly occurring as weeds in Australian cropping systems to produce root exudates that inhibit nitrification via biological nitrification inhibition (BNI). Seedlings of wild radish (Raphanus raphanistrum), great brome grass (Bromus diandrus), wild oats (Avena fatua), annual ryegrass (Lolium rigidum) and Brachiaria humidicola (BNI-positive control) were grown in hydroponics, and the impact of their root exudates on NO3– production by Nitrosomonas europaea was measured in a pure-culture assay. A pot study (soil-based assay) was then conducted to confirm the ability of the weeds to inhibit nitrification in whole soils. All of the tested weeds slowed NO3– production by N. europaea in the pure-culture assay and significantly inhibited potential nitrification rates in soil-based assays. Root exudates produced by wild radish were the most inhibitory, slowing NO3– production by the pure culture of N. europaea by 53 ± 6.1% and completely inhibiting nitrification in the soil-based assay. The other weed species all had BNI capacities comparable to that of B. humidicola and significantly higher than that previously reported for wheat cv. Janz. This study demonstrates that several commonly occurring weed species have BNI capacity. By altering the N cycle, and retaining NH4+ in the soils in which they grow, these weeds may gain a competitive advantage over species (including crops) that prefer NO3–. Increasing our understanding of how weeds compete with crops for N may open avenues for novel weed-management strategies.

STUDIES IN THE GENUS CALICIOPSIS

1963 ◽  
Vol 41 (4) ◽  
pp. 503-543 ◽  
Author(s):  
A. Funk
Keyword(s):  
Pure Culture ◽  
Nitrogen Sources ◽  
Developmental Studies ◽  
Extensive Field ◽  
Carbon Compounds ◽  
Effects Of Ph ◽  
Pure Cultures ◽  
Dark Staining ◽  
Host Parasite ◽  
A New Species

Three species of the genus Caliciopsis, all of which produce cankers on conifers, were investigated with respect to development, morphology, general biology, and pathogenicity. Caliciopsis orientalis is described as a new species. Developmental studies have shown that the ascocarps originate from the surface of an erumpent stroma. The female sexual structures are formed from dark-staining hyphae which arise in the core of the young ascocarp. Certain of these hyphae send out trichogynes which penetrate to the outside of the ascocarp. The hyphae enlarge greatly and produce clusters of ascogonia by a budding process or through meristogenous division of the hyphal cells. The ascogonia may further divide by septum formation and thus become multicellular. Septate, branching ascogenous hyphae grow out from the ascogonia and give rise to tufts of asci from the terminal cells. The stalks of the asci elongate enormously as they are carried up into the hymenium. Homologous development and structure were shown in several members of the Caliceaceae. Differences in the final appearance of the hymenium were attributed to the absence of extensive ascogenous hyphae in the Caliceaceae, but the fundamental similarities were interpreted as evidence of a phylogenetic relationship with Caliciopsis. Comparison of the asci, hymenium, and general habit of two genera of the Coryneliaceae with Caliciopsis confirmed the opinion of previous workers that the two groups are related. Observations on fruiting cycles revealed developmental correlations which indicated the possibility of functional spermatia, but experimental spermatization failed to prove this. Data on spore dissemination, germination, and penetration were also gathered. Canker anatomy and host–parasite relationships were elucidated. Pure cultures were obtained from both spermatia and ascospores. The latter were used to determine nutritional requirements of the fungus by measuring growth response to 14 carbon compounds, 5 nitrogen sources, and 7 vitamins. The effects of pH, temperature, and aeration on vegetative growth in pure culture were also studied. Extensive field observations revealed that one species (C. pseudotsugae) is widespread in British Columbia on three native conifers, and that in addition to primary pathogenicity it offers opportunities for associative effects to other forest pathogens which may result in serious damage. Behavior in pure culture confirmed the evidence of association between the pathogens involved. Pathogenicity was proved by extensive field inoculations.

The isolation of blue-green bacteria in pure culture

1974 ◽  
Vol 20 (2) ◽  
pp. 272-273 ◽  
Author(s):  
Howard D. McCurdy Jr. ◽  
Walter Hodgson
Keyword(s):  
Pure Culture ◽  
Green Bacteria ◽  
Membrane Filters ◽  
Convenient Means ◽  
Pure Cultures

Omnimixer treatment followed by surface plating of colonies from membrane filters provides a convenient means for the isolation of pure cultures of blue-green bacteria.

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