THE BIOLOGY OF CANADIAN WEEDS.: 37 Poa annua L.

1979 ◽  
Vol 59 (4) ◽  
pp. 1053-1066 ◽  
Author(s):  
S. I. WARWICK
Keyword(s):  
Habitat Type ◽  
Seed Viability ◽  
Acid Soils ◽  
Poa Annua ◽  
Biological Information ◽  
Factors Affecting ◽  
Pollution Levels ◽  
Highly Correlated ◽  
Response To Temperature ◽  
Postemergence Herbicides

A summary of biological information is provided on Poa annua L. (annual blue grass), which is common throughout the temperate regions of the world as a weed of cultivated and wasteground habitats. The distribution of distinct erect-annual and prostrate-perennial variants of the species is highly correlated with habitat type, with the latter predominating in closely mowed turf and the former in open fields, wasteground, etc. Poa annua is a serious weed in turfgrass. It is found on most soil types and exhibits a high tolerance to trampling, mowing and poorly aerated soils. The species, however, lacks tolerance of strongly acid soils, high pollution levels and extremes of temperature and moisture. The species is fully self-compatible and is predominantly selfing. Seed production and seed viability are generally high. Factors affecting seed germination are summarized; these include response to: temperature, moisture, O2 partial pressure, light, cultivation practises, fertilizers, pH and the environmental conditions under which the parent plant was grown. Selective herbicide control of established annual blue grass is difficult. Present postemergence herbicides include endothal and linuron. Differential herbicide response in P. annua has been recorded for endothal, metoxuron and atrazine.

Factors Affecting Poa annua L. Control

Weeds ◽  
1967 ◽  
Vol 15 (2) ◽  
pp. 98 ◽  
Author(s):  
Felix V. Juska ◽  
A. A. Hanson
Keyword(s):  
Poa Annua ◽  
Factors Affecting

scholarly journals Viability of Neotyphodium endophytic fungus and endophyte-infected and noninfected Lolium multiflorum seeds

Botany ◽  
2009 ◽  
Vol 87 (1) ◽  
pp. 88-96 ◽  
Author(s):  
Pedro E. Gundel ◽  
M. Alejandra Martínez-Ghersa ◽  
Lucas A. Garibaldi ◽  
Claudio M. Ghersa
Keyword(s):  
High Temperature ◽  
Water Content ◽  
Lolium Multiflorum ◽  
Seed Viability ◽  
Cool Season ◽  
Differential Survival ◽  
Factors Affecting ◽  
Neotyphodium Endophyte ◽  
Endophyte Fungi ◽  
Seed Water Content

Neotyphodium endophyte fungi are vertically transmitted symbionts of cool-season grasses. The seed phase of the grass’ life cycle appears to be critical for the persistence of the fungus. Endophyte viability decreases faster than seed viability, but little is known of the effects of this endophyte on seed viability. The endophyte could affect seed viability through changes in water content. Here, we assessed the effects of the endophyte on seed viability, the differential survival of endophyte and seed, and the effects of infection on seed water content. Viability of endophyte-infected and noninfected seeds and endophyte were evaluated over a period of 729 d under 12 controlled environmental conditions. Seed viability was reduced by the infection at high temperature and high relative humidity, but not under other conditions. Moreover, endophyte viability decreased faster than seed viability only under high humidity or high temperature. Seed water content was not affected by endophyte presence. The proportion of viable infected seeds was mainly affected by the loss in endophyte viability and secondly by the differential survival of infected and noninfected seeds. Knowledge on the relative importance of these processes is critical to understand the factors affecting the efficiency of endophyte vertical transmission and the frequency of endophyte-infected plants.

LDH-B enzyme expression: the mechanisms of altered gene expression in acclimation and evolutionary adaptation

1994 ◽  
Vol 267 (4) ◽  
pp. R1150-R1153 ◽  
Author(s):  
J. A. Segal ◽  
D. L. Crawford
Keyword(s):  
Fundulus Heteroclitus ◽  
Temperature Acclimation ◽  
Acclimation Temperature ◽  
Enzyme Expression ◽  
Temperature Dependent ◽  
Northern Population ◽  
Protein Levels ◽  
Altered Gene ◽  
Highly Correlated ◽  
Response To Temperature

The temperature-dependent expression of lactate dehydrogenase-B (LDH-B) was compared between two environmentally distinct populations of Fundulus heteroclitus acclimated to 10 degrees C and 20 degrees C. The variability in LDH-B protein expression both within and between populations is consistent with a model of thermal compensation. The northern population from the colder environment expresses a twofold greater amount of LDH-B protein than the warmer southern population at both acclimation temperatures. Correspondingly, both populations have 1.3-fold greater levels of the enzyme at an acclimation temperature of 10 degrees C in comparison to 20 degrees C. In 20 degrees C-acclimated individuals there is a similar twofold difference between populations for LDH-B mRNA concentrations, and LDH-B protein and mRNA are highly correlated (r = 0.81). After acclimation to 10 degrees C, this difference between populations is not seen and in the northern population there is no relationship between LDH-B mRNA and protein levels. Thus the molecular mechanism regulating LDH-B enzyme expression changes in response to temperature acclimation and is different between populations.

Factors Affecting Alkalinity Concentrations of Streamwater during Snowmelt in Central Ontario

1989 ◽  
Vol 46 (10) ◽  
pp. 1658-1666 ◽  
Author(s):  
Lewis A. Molot ◽  
P. J. Dillon ◽  
B. D. LaZerte
Keyword(s):  
Organic Acid ◽  
Headwater Streams ◽  
Base Cations ◽  
Base Cation ◽  
Major Contributor ◽  
Factors Affecting ◽  
Concentration Changes ◽  
Highly Correlated ◽  
Spring Snowmelt

Relative contributions of changes in base cations and acid anions to alkalinity decreases during spring snowmelt in 1984–86 were analyzed for 15 headwater streams and lake outflows in three central Ontario catchments. During episodes, concentration changes in ions which contributed to alkalinity decreases were partially offset by smaller changes in other ions which contributed to alkalinity increases. The major contributor to alkalinity depressions was base cation dilution by snowmelt water. Akalinity depressions were more likely to be dominated by SO42− increases in streams that were more acidic. Neither nitrate nor organic acid anions were significant contributors to alkalinity depressions. Discharge was highly correlated with alkalinity in a circumneutral stream but not in an acidic stream and is consistent with dilution being less important as a cause of alkalinity depressions as streams become more acidic.

A COMPARISON OF LIME REQUIREMENT METHODS FOR ACID CANADIAN SOILS

1977 ◽  
Vol 57 (3) ◽  
pp. 361-370 ◽  
Author(s):  
M. D. WEBBER ◽  
DIANE CORNEAU ◽  
P. B. HOYT ◽  
M. NYBORG
Keyword(s):  
British Columbia ◽  
Organic Matter ◽  
Soil Ph ◽  
Acid Soils ◽  
Toxic Level ◽  
Laboratory Methods ◽  
Exchangeable Al ◽  
Canadian Soils ◽  
Highly Correlated ◽  
Diagnostic Index

Several laboratory methods for estimating lime requirements of acid soils were compared using 24 soils from Alberta and northeastern British Columbia and 15 from elsewhere in Canada. The Peech, Schofield, Woodruff and SMP (Shoemaker et al. 1971) buffer methods were equally well correlated with lime requirements for raising soil pH to 5.5 or 6, which in turn were highly correlated with the amounts of soluble and exchangeable Al and organic matter in the soils. The SMP buffer method is recommended for use as the diagnostic index of lime requirement to achieve pH 5.5 or 6 because of its speed and simplicity. A refinement is suggested for Alberta and northeastern B.C. soils on the basis that lime need not be added to achieve pH 5.5 but should be added to reduce Al below the toxic level for sensitive crops. The lime requirements to reduce Al in those soils were highly correlated with the amounts of 0.02 M CaCl2-soluble Al they contained and it is recommended that the 0.02 M CaCl2-soluble AI be used as the diagnostic index of lime requirement. Lime requirements related to SMP (pH) and 0.02 M CaCl2-soluble Al are presented.

Physiological studies in birch

1984 ◽  
Vol 85 (1-2) ◽  
pp. 97-113
Author(s):  
K. A. Longman
Keyword(s):  
Shoot Growth ◽  
Seed Viability ◽  
Cambial Activity ◽  
Seasonal Cycles ◽  
Leaf Production ◽  
Factors Affecting ◽  
Whole Plant ◽  
Branching Patterns ◽  
Activity Onset ◽  
Unpublished Research

SynopsisAspects of whole-plant physiology of birch are reviewed, and previously unpublished research is presented. Seasonal cycles of shoot growth and bud dormancy are discussed, with environmental and hormonal factors affecting the rate and duration of shoot extension and leaf production. Also covered are variability in branching patterns, aspects of cambial activity, onset of the reproductive phase, factors affecting flowering and sex ratio, and seed viability and dormancy. Finally, the regenerative capacity of birch is described, and its future roles are mentioned.

Mycofloral Succession and Viability Losses in Pigeon pea Seed in Puerto Rico

1969 ◽  
Vol 68 (1) ◽  
pp. 19-31
Author(s):  
P. R. Hepperly ◽  
R. Rodríguez
Keyword(s):  
Puerto Rico ◽  
Soil Moisture ◽  
Seed Germination ◽  
Seed Viability ◽  
Pigeon Pea ◽  
Fungal Colonization ◽  
Fusarium Spp ◽  
Storage Losses ◽  
Highly Correlated ◽  
Total Fungi

Using the cellulose pad and potato dextrose agar (PDA) assays, twenty three fungi were found on pigeonpea seed in Puerto Rico. In the PDA assay, Botryodiplodia theobromae was the most common (29%). On cellulose pads, the same fungus was not very common (7%). PDA assay favored increased detection of Alternaria tenuissima, Phomopsis sp., and total fungi compared with cellulose pads. Cellulose pads favored detection of Cladosporium sp. In both assays, incidences of B. theobromae, Fusarium spp., and total fungi were negatively correlated with seed germination. Measurements for seedlot germination were highly correlated (r = 0.77**) between the two assays. The influences of seed type and delayed harvest on pigeonpea seed viability were studied. Pigeonpeas "28-Bushy," with large tan seeds, showed reduced seed viability and higher incidence of B. theobromae and Fusarium spp. compared with segregants of the same cultivar with small flattened hard red seed. A 3-week delayed harvest drastically increased incidence of B. theobromae, Fusarium spp., and total fungi, and reduced germination in "Kaki" pigeonpeas from Santa Isabel. Pigeonpea seed viability and mycoflora were followed before and after farm storage. Incidences of Fusarium spp., Phomopsis sp., Cladosporium sp., and B. theobromae after storage were 15, 26, 30, and 38% of their respective prestorage values. Incidence of species of Penicillium, Rhizopus, and Aspergillus increased during storage. Although less than 3% Aspergillus spp. was detected in the cellulose pad assay at 27° C, 28 to 92% was detected when seed were incubated at 35° C using pigeonpea seed extract in 2% agar. With the Aspergillus selective assay, seed viability losses during storage were highly correlated with incidence of Aspergillus spp. (r = 0.96**). Aspergillus incidence in the cellulose pad assay was not associated with storage losses in seed germination (r = 0.18 NS). Emergence and fungal colonization of pigeonpea seed were dependent on soil moisture. Pigeonpea seed did not emerge at either 25 or 100% soil moisture holding capacity (SMHC). Optimum emergence was found at 50% SMHC. Pythiaceous fungi were predominent on seed at and above 75% SMHC, whereas Aspergillus spp. predominated at 50% SMHC or less. Mixed populations of the two were visible at 50 and 75% SMHC.

A COMPARISON OF FOUR SYSTEMS OF MANAGING YEARLING BEEF STEERS ON ROTATIONALLY GRAZED, BROMEGRASS-ALFALFA PASTURE

1979 ◽  
Vol 59 (3) ◽  
pp. 519-529
Author(s):  
J. A. ROBERTSON ◽  
D. A. COOKE ◽  
S. E. BEACOM
Keyword(s):  
Dry Matter ◽  
Average Daily Gain ◽  
Dry Matter Production ◽  
Beef Steers ◽  
Factors Affecting ◽  
Animal Management ◽  
Matter Production ◽  
Highly Correlated ◽  
Daily Gain ◽  
Selection Of

Four systems of animal management were applied to a rotationally grazed mixed sward of bromegrass (Bromus inermis Leyss.) and alfalfa (Medicago media Pers.) for a period of 7 yr using yearling beef steers. The systems included (i) put and take stocking; (ii) set stocking at 2.5 steers/ha with surplus herbage conserved as silage and fed later in the season; (iii) set stocking at 3.7 steers/ha, pasture herbage supplemented with oat soilage and (iv) set stocking as in (iii), pasture herbage supplemented with dry-rolled barley. Nitrogen, at the rate of 90 kg N/ha, was applied each spring during the last 4 yr of the experiment. Forage dry matter production varied from 1760 to 5750 kg/ha between years and was highly correlated with precipitation during the growing season. Average daily gains were similar for treatments i–iii at 1.03 kg/head. Feeding supplementary barley increased rate of gain to 1.19 kg (P < 0.01), produced an additional 20 kg liveweight per steer per season and was utilized with an average efficiency of 6.6 kg dry matter per kilogram gain. Average daily gain varied significantly (P < 0.01) between years and was inversely related to dry matter production. The feeding of oat soilage or barley and the harvesting and feeding of silage reduced the variation in gain both within and between seasons compared to the put and take stocking system. Factors affecting the selection of the most appropriate management system by a producer are discussed.

scholarly journals Factors affecting the distribution and abundance of the Endangered volcano rabbit Romerolagus diazi on the Iztaccihuatl volcano, Mexico

Oryx ◽  
2014 ◽  
Vol 49 (2) ◽  
pp. 366-375 ◽  
Author(s):  
Michael Hunter ◽  
Will Cresswell
Keyword(s):  
Habitat Type ◽  
Grazing Intensity ◽  
Cattle Grazing ◽  
Faecal Pellet ◽  
Conservation Priorities ◽  
Lower Altitude ◽  
Factors Affecting ◽  
Closed Forest ◽  
Pellet Counts ◽  
Strict Enforcement

AbstractThe volcano rabbit Romerolagus diazi is an Endangered species endemic to Mexico, with a range of < 400 km2. We investigated threats from destruction, fragmentation and degradation of habitat, hunting, and cattle grazing intensity in relation to the distribution and abundance of the volcano rabbit on the Iztaccihuatl volcano. Faecal pellet counts were taken as a proxy for rabbit abundance in 1,718 random 0.2 m2 quadrats at 859 sampling points along 25 transects, covering an area of c. 100 km2 at altitudes of 3,400–4,000 m. Presence of the species was significantly associated with absence of closed forest, absence of long grass types (not bunchgrass), shallow inclines, absence of cattle grazing, lower altitude, low hunting pressure (measured by proximity to ranger station), absence of bare ground and, contrary to previous findings, increased frequency of fire. The species was significantly more abundant in habitats with a greater percentage cover of zacaton (bunchgrass) and short grass types. It was significantly less abundant in areas with more hunting (measured by proximity to ranger station) and cattle grazing. Key conservation priorities are therefore the protection of the subalpine zacaton bunchgrass-dominated habitat type, strict enforcement of hunting laws and the removal of livestock from relevant national park boundary areas. However, the results suggest that frequent fires have a significant positive effect on the occurrence of the volcano rabbit as a result of habitat improvement and this is often a consequence of anthropogenic management of land for cattle grazing.

Sign in / Sign up

Export Citation Format

Share Document