scholarly journals Changes inSenna obstuifoliaGermination Requirements over 12 Months under Field Conditions

2009 ◽  
Vol 2009 ◽  
pp. 1-5
Author(s):  
Jason K. Norsworthy ◽  
Marcos J. Oliveira
Keyword(s):  
Thermal Conditions ◽  
Early Spring ◽  
Field Conditions ◽  
Specific Time ◽  
Physical Dormancy ◽  
Light Requirement ◽  
Thermal Requirements ◽  
Senna Obtusifolia ◽  
Temperature Requirements

Senna obtusifoliaseeds were collected in Fall 2003 and immediately field sown to assess dormancy alleviation and effect of after-ripening over a 12-month period on light and temperature requirements for germination. Seeds did not exhibit physical dormancy at maturation and readily germinated over a broad range of light and thermal conditions. Dormancy gradually increased during Winter months, resulting in only a small fraction of the population capable of germination by early Spring. Dormancy break did not occur at a specific time of the year nor did dormancy alleviation increase over the 12-month period following maturation. Conditions during Spring and Summer coincided with thermal requirements for germination of the nondormant fraction of the population.Senna obtusifoliaseeds were nonresponsive to red and far-red lights, and seeds did not acquire a light requirement following burial for 6 months.

scholarly journals Effects of Different Pretreatments and Seed Coat on Dormancy and Germination of Seeds of Senna obtusifolia (L.) H.S. Irwin & Barneby (Fabaceae)

2016 ◽  
Vol 8 (2) ◽  
pp. 77
Author(s):  
Stephen I. Mensah ◽  
Chimezie Ekeke
Keyword(s):  
Sulfuric Acid ◽  
Seed Dormancy ◽  
Water Uptake ◽  
Seed Coat ◽  
Critical Factor ◽  
Potassium Nitrate ◽  
Ex Situ ◽  
Mechanical Resistance ◽  
Physical Dormancy ◽  
Senna Obtusifolia

<p class="1Body">The seed dormancy of <em>Senna obtusifolia</em> was investigated through various methods, namely pretreatments in concentrated sulfuric acid, 2% potassium nitrate (KNO<sub>3</sub>), 99% ethanol, 99% methanol, and in hydrogen perioxide; examination of the seed coverings; and the determination of water uptake by the seeds in order to ascertain the most effective technique for breaking dormancy and also determine the dormancy type. The results showed that sulfuric acid treatment recorded the highest germination (100%); followed by 2% hydrogen peroxide treatment (24%) in 15minutes immersion. The methanol and ethanol pretreatments gave 18.33% and 16.5% germinations respectively. Pretreatment in 2% potassium nitrate gave the lowest germination (8.50%), while the intact seeds of <em>S. obtusifiolia</em> (control) gave 0% germination. The anatomy of the seed coat indicated the presence of hard, thickened and specialized cells of cuticle, macrosclereids, osteoscereids, and disintegrated parenchyma layers. The water uptake of intact seeds was low (13.5%) after 24 hr imbibitions. These findings revealed that the seed coat acts as barrier to germination by preventing water absorption, possibly gaseous diffusion in and out of the seed and conferring mechanical resistance to the protrusion of embryo. Pretreatments, such as immersion in H<sub>2</sub>SO<sub>4 </sub>will soften the seed coat and permit germination. Seed dormancy in <em>S. obtusifolia </em>can be considered of physical nature and classified as physical dormancy. The results obtained in this study may serve as useful information in the production and improvement of <em>S. obtusifolia </em>seedlings, as knowledge on seed dormancy and germination is a critical factor and requirements to the understanding of the propagation of this plant either in situ or ex-situ, in view of the economic potentials/attributes of this species.</p>

Phellinus igniarius. [Descriptions of Fungi and Bacteria].

1968 ◽  
Author(s):  
D. N. Pegler
Keyword(s):  
Great Britain ◽  
North America ◽  
Central America ◽  
Geographical Distribution ◽  
Early Spring ◽  
Field Conditions ◽  
Airborne Spores ◽  
Phellinus Igniarius ◽  
Late Autumn

Abstract A description is provided for Phellinus igniarius. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Common on the trunks of Salix and Populus, also recorded on Acer, Arbutus, Arctostaphylos, Betula, Carpinus, Castanopsis, Cornus, Erythropheum, Fagus, Fraxinus, Juglans, Ostrya, Pericopsis, Prunus, Pyrus, Quercus, Rhamnus and Ulmus. DISEASE: White heart rot. Causing a destructive decay of the general delignifying type. The decayed area becomes soft and white, bounded by conspicuous dark zones or black lines with an irregularly concentric arrangement. GEOGRAPHICAL DISTRIBUTION: Africa (Eritrea, Madagascar, Zambia); Asia (Japan, U.S.S.R.); Europe (Bulgaria, Czechoslovakia, Germany, Great Britain, Hungary, Netherlands, Norway, Rumania, Sweden); North America (Canada, U.S.A.); Central America (Nicaragua, Venezuela). TRANSMISSION: By airborne spores, which are continuously produced from early spring until late autumn when the temperature drops below 5°C (Riley, 1952). Spores remain viable for several months under field conditions (Iverson, 1968). Infection occurs mainly through branch wounds.

scholarly journals Bioclimatic conditions and thermal seasons of the year in Szczecin

2021 ◽  
Vol 94 (2) ◽  
pp. 283-299
Author(s):  
Agnieszka Mąkosza
Keyword(s):  
Climate Change ◽  
Air Temperature ◽  
Meteorological Data ◽  
Thermal Conditions ◽  
Thermal Spring ◽  
Early Spring ◽  
Climate Index ◽  
Relative Air Humidity ◽  
Thermal Climate ◽  
Bioclimatic Conditions

Climate change is an empirical fact evidenced by subsequent IPCC reports. The observed climate change is also manifested in the altered date of occurrence and duration of the seasons in a year. Variability of thermal conditions due to climate warming will have its toll on the bioclimatic conditions. The assessment of bioclimatic conditions was conducted with the use of Universal Thermal Climate Index (UTCI). The present elaboration is based on hourly values of the following meteorological elements: air temperature, relative air humidity, wind speed and cloud cover. The meteorological data were obtained from the Institute of Meteorology and Water Management – National Research Institute (IMGW-PIB) in Szczecin and cover the period 2000-2019. Variability of bioclimatic conditions is considered per periods corresponding to thermal seasons of the year as identified by the Gumiński (1948) method on the basis of monthly air temperature values. The analysed UTCI values with respect to thermal seasons indicate that mean UTCI values in the period 2000-2019 representative for thermal summer amount to 22.6°C, thermal spring 9,9°C, thermal autumn 8.4°C, thermal winter -10.4°C, early spring -4.6°C, and early winter -7.9°C. For the periods with identified lack of thermal winter, mean UTCI value was -6.6°C. The aim of the present paper is an attempt to assess the variability of biothermal conditions as calculated using the UTCI index against the thermal seasons of the year in Szczecin.

Developmental and Environmental Effects on Assimilate Partitioning in Canada Thistle (Cirsium arvense)

Weed Science ◽  
1992 ◽  
Vol 40 (1) ◽  
pp. 79-85 ◽  
Author(s):  
Thomas Tworkoski
Keyword(s):  
Environmental Effects ◽  
Environmental Conditions ◽  
Growth Stage ◽  
Early Spring ◽  
Field Conditions ◽  
Cirsium Arvense ◽  
Growth Chamber ◽  
Assimilate Partitioning ◽  
Canada Thistle ◽  
Flower Bud

Under field conditions, more photoassimilate moved to roots of Canada thistle at the bolt than at the bud, flower, or postflower stages. Similarly, greater photoassimilate accumulated in roots of Canada thistle in the greenhouse at the rosette and bolt than at the flower bud stage. Growth chamber experiments indicated that environmental conditions typical of fall, and possibly early spring, favored photoassimilate movement to the root and superseded growth stage control of assimilate partitioning. Allocation of assimilate within the root was strongly influenced by growth stage, with most assimilate being utilized for growth at the rosette stage and for fructan reserves in bolt and flower bud stages.

scholarly journals Different strategies for breaking physical seed dormancy in field conditions in two fruit morphs of Vachellia caven (Fabaceae)

2018 ◽  
Vol 28 (1) ◽  
pp. 8-15 ◽  
Author(s):  
Ana E. Ferreras ◽  
Paula I. Marcora ◽  
M. Paula Venier ◽  
Guillermo Funes
Keyword(s):  
Seed Dormancy ◽  
Environmental Conditions ◽  
Environmental Variables ◽  
Environmental Heterogeneity ◽  
Environmental Changes ◽  
Gradual Increase ◽  
Field Conditions ◽  
Fruit Morphology ◽  
Physical Dormancy ◽  
And Coping

AbstractDifferences in fruit morphology among or within species might indicate differences in other regenerative traits, such as seed dormancy and germination. In species with physical dormancy (PY), environmental conditions are suggested to be responsible for dormancy break in field. Seeds of Vachellia caven have PY. This species exhibits two fruit morphs highly represented in Córdoba forests, Argentina: one is dehiscent and the other is indehiscent. In this study we performed a burial experiment with the aim to determine if the differences in V. caven fruit morphology were related to different patterns of PY break of their seeds in field conditions. We related these patterns to (1) environmental conditions that could influence the loss of PY, and (2) histological features of the lens zone. Seeds of both morphs exhibited dormancy break within 14 months of the start of the experiment, but with different patterns. The dehiscent morph showed an abrupt percentage of seeds that broke dormancy 14 months after the beginning of the experiment, probably after undergoing environmental changes similar to those suggested by the two-stage softening model. The indehiscent morph showed a gradual increase in seeds that broke dormancy, not clearly related to any of the environmental variables studied. No differences in seed coat structure of the lens zone were observed between morphs. The existence of both morphs could confer the species with higher possibilities of establishing and coping with environmental heterogeneity. Those characteristics contribute to the understanding of the success of this species in open and disturbed environments.

scholarly journals Thermal requirements of secondary schoolchildren in winter

1969 ◽  
Vol 67 (1) ◽  
pp. 59-65 ◽  
Author(s):  
A. Auliciems
Keyword(s):  
Regression Analysis ◽  
Thermal Conditions ◽  
Optimum Conditions ◽  
Comfort Zone ◽  
Thermal Requirements

SUMMARYSecondary schoolchildren in England were asked to assess thermal conditions in winter according to subjective sensations of warmth. Conditions of normal occupancy and activity were maintained and optimum conditions established in terms of four thermal measures by regression analysis of over 2500 assessments by boys and girls. The comfort zone was delineated as that within which 60% of the children were comfortable and in terms of the commonly used dry-bulb temperature this zone lay between 59 and 70° F. in still air. The optimum conditions for children were also compared with those recommended for adults.

scholarly journals Effect of water availability and seed source on physical dormancy break of Vicia villosa ssp. villosa

2016 ◽  
Vol 26 (3) ◽  
pp. 254-263 ◽  
Author(s):  
Juan P. Renzi ◽  
Guillermo R. Chantre ◽  
Miguel A. Cantamutto
Keyword(s):  
Release Rate ◽  
Water Availability ◽  
Soil Seed Bank ◽  
Gompertz Model ◽  
Field Conditions ◽  
Seed Source ◽  
Considerable Proportion ◽  
Physical Dormancy ◽  
Vicia Villosa ◽  
Environmental Selection

AbstractPhysical dormancy (PY) plays a crucial role in the control of the reseeding process of Vicia villosa Roth, a winter annual species cultivated for pasture and hay, naturalized in several semi-arid temperate agroecosystems. As PY is considered a seed trait modulated by natural selection, populations from different origins are expected to show different responses to environmental regulatory factors. The present study aimed to determine the effect of: (1) water availability on PY-break dynamics of a naturalized population from Argentina (ASC) under both laboratory and field conditions; (2) the seed source on initial PY and dormancy release rate (wet storage at 20°C) of ASC compared to 45 other populations of V. villosa, including wild, naturalized, landraces and cultivars. Water availability increased PY loss rate under both storage and field conditions. ASC PY-break dynamics was adequately described by a Gompertz model with a lower thermal-time requirement estimated for dormancy break under fluctuating soil water conditions compared to seeds buried inside impermeable bags. During the field burial experiment, a considerable proportion of seeds (~70%) became water permeable during the summer season after dispersal, and retained low levels of residual PY for soil seed bank replenishment. Improved populations (i.e. breeding cultivars) showed the lowest percentages of initial PY compared to landraces, naturalized and wild populations. Naturalized populations of Argentina showed similar initial PY compared to landraces, although PY release rate was lower in the former and might be attributed to local environmental selection. Wild types showed the lowest PY release rates.

Primordia and leaf production in winter wheat, triticale, and rye under field conditions

1986 ◽  
Vol 64 (9) ◽  
pp. 1972-1976 ◽  
Author(s):  
L. A. Hunt ◽  
Anne-Marie Chapleau
Keyword(s):  
Winter Wheat ◽  
Triticum Aestivum L ◽  
Early Spring ◽  
Field Conditions ◽  
Late Winter ◽  
Winter Rye ◽  
Degree Days ◽  
Leaf Production ◽  
Winter Triticale ◽  
Leaf Emergence

Primordia production and leaf emergence were investigated in winter wheat (Triticum aestivum L. em Thell.) and two related species, winter rye (Secale cereale L.) and winter triticale (× Triticosecale Wittmack), under field conditions in Southern Ontario, a region with a humid continental climate. Primordia initiation could be adequately described by a linear regression of primordia number on accumulated degree-days in the 1st year of study, 1981 – 1982. In the 2nd year, however, a linear relationship was noticed only in the late winter and early spring, with the rate of primordia production being distinctly lower earlier in the season. The rate of primordia initiation was faster in the ryes than in the wheats, a superiority which was associated with greater spikelet production. Triticale had an intermediate rate of primordia initiation but was closer to wheat in the timing of double ridge and terminal spikelet formation. Leaves emerged at a constant rate (degree-days base) which was similar in most of the cultivars.

scholarly journals Variability in stream discharge and temperatures during ecologically sensitive time periods: a preliminary assessment of the implications for Atlantic salmon

2005 ◽  
Vol 2 (3) ◽  
pp. 691-729 ◽  
Author(s):  
D. Tetzlaff ◽  
C. Soulsby ◽  
A. F. Youngson ◽  
C. Gibbins ◽  
P. J. Bacon ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Juvenile Fish ◽  
Management Strategies ◽  
Thermal Conditions ◽  
Early Spring ◽  
Regulated River ◽  
High Temporal Resolution ◽  
Hydrological Variability ◽  
Discharge Temperature ◽  
Time Periods

Abstract. This study focused on improving the understanding of the temporal variability in hydrological and thermal conditions and their potential influences on two life stages of Atlantic salmon (Salmo salar) – stream resident juveniles and returning adult spawners. Stream discharges and temperatures in the Girnock Burn, NE Scotland, a small nursery stream, were characterised over a time period of ten hydrological years (1994/95–2003/04). Frequency, magnitude, duration and timing of thermal, hydraulic and hydrological conditions were examined using data with a high temporal resolution (hourly and subhourly). Particular attention was focussed on assessing variations during ecologically sensitive time periods when salmon behaviour is most susceptible to environmental perturbations. The Girnock Burn was characterised by a strong inter- and intra-annual variability in the hydrological and thermal regime. This has clear implications for the likely feeding opportunities for juvenile fish in winter and early spring and the emergence of fry in the late spring. The movement of adult spawners towards breeding areas showed a complex dependence on hydrological variability. If discharges were low, fish movement was increasingly triggered by suboptimal flow increases as spawning time approached. Elucidating links between discharge/temperature variability and salmon habitat availability and utilization at appropriately fine temporal scales is a prerequisite to the development of better conservation management strategies and more biologically meaningful flow regimes in regulated river systems.

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