Dormancy and Germination of Seed of Eight Populations of Themeda australis

1982 ◽  
Vol 30 (4) ◽  
pp. 373 ◽  
Author(s):  
RH Groves ◽  
MW Hagon ◽  
PS Ramakrishnan
Keyword(s):  
Population Stratification ◽  
Physiological Adaptation ◽  
Dormant Seed ◽  
Seed Formation ◽  
Fresh Seed ◽  
Temperature Regimes ◽  
Germination Characteristics ◽  
Moisture Regimes ◽  
Different Populations ◽  
Climatic Characteristics

Seed of eight populations of Themeda australis (R.Br.) Stapf from sites nith the widest range of climates in Australia and Papua New Guinea (P.N.G.) was tested for its dormancy status and germination responses to different temperature and moisture regimes. The populations were from Lae. P.N.G.. Katherine. N.T.. Mundubbera. Qld. Alice Springs. N.T.. Tantangara. N.S.W.. Adelaide Hills. S.A.. Bunbury, W.A. and Hobart. Tas. Dormancy of fresh seed was negligible in Lae and Mundubbera populations. considerable in the Alice Springs population and intermediate in populations from Katherine and all temperate sites. Addition of gibberellic acid hastened the release from dormancy of seed from Katherine and Bunbury. Exposure of plants to three different temperature regimes during seed formation had an effect on dormancy of the Katherine population. Stratification at 4°C and high alternating daily temperatures (45 20°C) hastened the loss of dormancy of fresh seeds of some populations. Germination of non-dormant seed of the different populations was relatively unaffected b) temperatures between 20 and 40°C. Germination of the Alice Springs population was the most sensitive to increasing water stress and that from Lae the least sensitive. Radicle elongation of seedlings from Alice Springs was significantly greater than that of most other populations at a water potential of - I .0 MPa. The differences reported for seed dormancy and germination characteristics of T. australis populations do not reflect a strong physiological adaptation to the climatic characteristics of the sites from which they were collected.

Effects of light, temperature and population variability on the germination of seven Spanish pines

2002 ◽  
Vol 12 (4) ◽  
pp. 261-271 ◽  
Author(s):  
A. Escudero ◽  
F. Pérez-García ◽  
A. L. Luzuriaga
Keyword(s):  
Habitat Preferences ◽  
Population Variability ◽  
Nested Models ◽  
Germination Response ◽  
Germination Characteristics ◽  
Different Populations ◽  
Effects Of Temperature ◽  
Germination Traits ◽  
The Relationship ◽  
Pine Species

AbstractMost Pinus species are obligate seeders. Thus, knowledge of germination characteristics can help in the understanding, prediction and manipulation of the regeneration and dynamics of pine forests. Seven pine species with contrasting habitat preferences and different genetic pairwise distances are present in the Iberian Peninsula and the Canary Islands: P. halepensis, P. nigra, P. pinaster, P. pinea, P. sylvestris, P. uncinata and P. canariensis. These seven pine species comprise an exceptional experimental set to test some questions related to germination traits, such as: (1) What are the effects of light and temperature on germination, taking into account interpopulation variability? (2) Is there any association of germination traits with habitat (montane versus lowland) preferences? and (3) What is the relationship between germination traits and the genetic distance between pine species? P. nigra, P. sylvestris and P. uncinata seeds showed faster germination rates. Seeds of P. nigra and P. sylvestris reached high total germination percentages in every temperature and light treatment, suggesting an opportunistic germination strategy. Unlike montane pines, lowland pines did show significant effects of temperature on germination response: final germination was higher between 15°C and 20°C than at warmer and alternating temperatures. Relatively low temperatures associated with the winter rainy season would favour germination of most of these species. Nested models showed that population variability was the main source of variation in germination response. Thus, there is no phylogenetic control of the germination response and, surprisingly, germination traits were not related to habitat preferences. As a consequence, we believe that studies of the germination characteristics of a pine species should consider different populations.

Monitoring Agricultural Drought in the Near East

2005 ◽  
Author(s):  
Eddy De Pauw
Keyword(s):  
Near East ◽  
Potential Evapotranspiration ◽  
Groundwater Resources ◽  
Winter Season ◽  
Aridity Index ◽  
Agricultural Drought ◽  
Moisture Regime ◽  
Temperature Regimes ◽  
Moisture Regimes ◽  
Dry Climates

The countries of North Africa and West Asia, hereafter referred to as the “Near East,” cover a large part of the world (more than 7,200,000 km2). This region is characterized by diverse but generally dry climates, in which evaporation exceeds precipitation. The level of aridity is indicated by the aridity index, the ratio of annual precipitation to annual potential evapotranspiration, calculated by the Penman method (UNESCO, 1979). The degree of aridity is shown spatially in figure 16.1 and summarized per country in table 16.1. These data show that the region is characterized by humid, subhumid, semiarid, and arid to hyperarid moisture regimes. In addition, temperature regimes vary considerably, particularly due to the differences in altitudes and, to a lesser extent, due to the oceanic/continental influences. For most of the region, the precipitation generally occurs during the October–April period and thus is concentrated over the winter season. Table 16.1 shows that, with more than 90% of the land area in hyperarid, arid, or semiarid moisture regimes, aridity is very significant in the Near East. Turkey is better endowed with surface and groundwater resources due to the orographic capture of Atlantic cyclonal precipitation, but much of the interior is semiarid. If one excludes the hyperarid zones, which cover the driest deserts and have no potential for agricultural use, nearly 34% of the region, or about 2,460,000 km2, is dryland (i.e., the area with arid or semiarid moisture regime). These are the areas with some potential for either dryland farming (in semiarid zones) or for extensive rangeland (in arid zones). In the Near East countries, agriculture contributes about 10–20% to the gross domestic product and is therefore a major pillar of their economies. However, the indirect importance of agriculture is larger because it provides the primary goods that constitute the majority of merchandise exports and because of the relatively high number of people employed in agriculture. Because of the high degree of aridity in large parts of the region, agriculture in the Near East is particularly vulnerable to drought. Most of the agricultural systems depend on rainfall.

scholarly journals SEED GERMINATION PLASTICITY OF TWO ENDANGERED SPECIES OF FERULA IN THE CONTEXT OF CLIMATE CHANGE

2020 ◽  
Vol 80 ◽  
pp. 13-33
Author(s):  
Parvin Salehi Shanjani ◽  
Amir Mousavi ◽  
Faeze Rasoulzadeh Farsad
Keyword(s):  
Climate Change ◽  
Medicinal Plants ◽  
Low Temperatures ◽  
Seedling Emergence ◽  
Cold Stratification ◽  
Local Adaptations ◽  
Germination Characteristics ◽  
In The Wild ◽  
Different Populations ◽  
Germination Cues

Ferula assa-foetida and F. gummosa, Apiaceae, are important endemic and endangered medicinal plants. Survival of the species is threatened by climate change, overexploiting (as source of oleo-gum resin and for-age) and lack of organized cultivation. Cultivation of these valuable medicinal plants is restricted by insuffi-cient domestication knowledge. Germination characteristics of different populations of Ferula taxa were studied with the aim of describing and comparing their responses to continuous cold stratification condition. Germination cues for the species were complex, with dormancy mechanisms present to restrict germination until cold stratification are fulfilled. Results indicated that a period of 4 weeks of stratification is sufficient for germination of F. assa-foetida, but optimal germination of F. gummosa require stratification for periods of 8 weeks. Both species were able to germinate at very low temperatures (4°C). Within-taxon differences in dor-mancy breaking and seedling emergence may interpret as local adaptations. The continued regeneration and propagation of the species in the wild will depend on the temperature and moisture status of the soil during winter and the maintenance of conditions suitable for stratification for an appropriate length of time.

Seed quality and germination characteristics of tamarack in northwestern Ontario

1986 ◽  
Vol 16 (3) ◽  
pp. 680-683 ◽  
Author(s):  
Robert E. Farmer Jr. ◽  
Ronald W. Reinholt
Keyword(s):  
Seed Quality ◽  
Northwestern Ontario ◽  
Temperature Regimes ◽  
Germination Characteristics ◽  
Before And After ◽  
Alternating Temperature ◽  
Individual Trees ◽  
Incubation Temperatures

Tamarack seed from provenances in northwestern Ontario were incubated in light and dark under a range of alternating temperature regimes (5–15, 10–20, and 20–30 °C) before and after 33 days stratification. Unstratified sound seed germinated completely in light at all incubation temperatures. Partial germination of unstratified seed took place in the dark at 20–30 °C, but stratification was required for dark germination at lower temperatures. Wide variation in dark germination was noted among seed lots from individual trees, but stand and provenance differences were nonsignificant. Much of the variation in seed quality among tree lots was related to differences in the degree of embryo failure.

Quality and morphological characteristics of alfalfa as affected by soil moisture, pH and phosphorus fertilization

1992 ◽  
Vol 72 (1) ◽  
pp. 147-162 ◽  
Author(s):  
Hélène V. Petit ◽  
A. R. Pesant ◽  
G. M. Barnett ◽  
W. N. Mason ◽  
J. L. Dionne
Keyword(s):  
Soil Moisture ◽  
Soil Ph ◽  
Plant Morphology ◽  
Field Capacity ◽  
Phosphorus Fertilization ◽  
Moisture Regime ◽  
Available Water ◽  
Soil Moisture Regime ◽  
Temperature Regimes ◽  
Moisture Regimes

Alfalfa (Medicago sativa L. ’Saranac’) was grown in a greenhouse on Ste-Rosalie clay and Danby gravelly sandy loam to determine the effects of phosphorus fertilization, air temperature, soil moisture regime and soil pH on chemical composition and plant morphology. The following treatments were applied in factorial combination: three moisture regimes (1, semi-dry, with soil moisture between field capacity or 100% of available water and wilting point or 0% of available water; 2, optimal, between field capacity and 70% of available water; 3, wet, between saturation point and field capacity), three rates of phosphorus in the form of disodium phosphate (0, 12.5 and 25.0 P kg−1 of dry soil) and three soil pH levels (natural, near 5.4, 6.5 and 7.5). Half the alfalfa was grown in a warm greenhouse section with a minimum daytime temperature of 25 °C and 19 °C at night and the other half was grown in a cool section with a daytime minimum of 15 °C and 9 °C at night. Quality of alfalfa was generally improved by water deficit as shown by decreased concentrations of acid detergent fiber (ADF) and acid detergent lignin (ADL) and increased concentrations of crude protein (CP). Cold temperatures decreased ADF content which indicates that quality of alfalfa grown under cold compared to warm temperature regimes is better. Phosphorus fertilization seemed to have more effects on plant morphology and quality under cold than warm temperature regimes. In general, concentrations of CP, ADF and ADL, stem length, leaf area and the number of stems increased in parallel with soil pH. The data indicate that low temperature and low soil moisture regimes were generally associated with higher quality alfalfa than were high temperature and wet soil moisture regimes.Key words: Alfalfa, soil moisture regime, air temperature, phosphorus fertilization, soil pH

scholarly journals The Germination of Perennial Wall Rocket (Diplotaxis Tenuifolia (L.) DC.) and Annual Garden Rocket (Eruca Sativa Mill.) Under Controlled Temperatures

2014 ◽  
Vol 65 (1) ◽  
pp. 15-28 ◽  
Author(s):  
Matthew Hall ◽  
Jenny Jobling ◽  
Gordon Rogers
Keyword(s):  
Germination Percentage ◽  
Perennial Species ◽  
Eruca Sativa ◽  
Ambient Temperatures ◽  
Temperature Regimes ◽  
High Germination ◽  
Germination Characteristics ◽  
Diurnal Temperatures ◽  
Germination Value ◽  
Respective Species

AbstractThe germination characteristics of three cultivars of perennial wall rocket and annual garden rocket were assessed at constant and diurnal temperatures for ten days. The seeds were exposed to constant temperatures of 5, 10, 15, 20, 25, 30 and 35°C or diurnal temperatures of 24/10, 28/16 and 18/5°C, with a 12/12 h exposure of each regime. The diurnal temperatures were chosen to reflect the minimum and maximum ambient temperatures experienced in Ellis Lane, Australia; during the spring, summer and winter. The total germination percentage (TGP) of perennial wall rocket was the highest at 20 to 30°C, whereas the highest TGP occurred at 10 to 30°C for annual garden rocket. The daily germination speed (DGS) and germination value (GV) are two useful formulas used to express the germination characteristics of seeds that under certain conditions do not achieve ≥50% germination. For both species, there was a significant interaction between the cultivar and temperature for the DGS and GV at both constant and diurnal temperatures; illustrating that the commercial cultivars of these species germinate at different rates in response to different ambient temperatures. This has important implications for the commercial production of these species, as cultivars with high germination rates need to be chosen for different seasonal conditions. At diurnal temperatures, there was an interaction between the cultivar and temperature for perennial wall rocket, with the cvs. DT1 and DT2 having similar TGPs across all of the temperature regimes, whereas the cv. DT3 had lower TGPs across all of the regimes. There was no interaction between the cultivar and diurnal temperature for annual garden rocket; however, temperature did influence the TGP, with higher values at 24/10 and 18/5°C. The germination of the smaller seeds from the perennial species was found to be more dependent on temperature than the larger seeds from the annual species. This is likely due to differences in stored reserves and the influence of secondary dormancy in the respective species.

Germination of common bean under constant and alternating cool temperatures

2005 ◽  
Vol 85 (3) ◽  
pp. 577-585 ◽  
Author(s):  
T. Nleya ◽  
R. A. Ball ◽  
A. Vandenberg
Keyword(s):  
Common Bean ◽  
Germination Rate ◽  
Base Temperature ◽  
Moisture Availability ◽  
Temperature Regimes ◽  
Moisture Regimes ◽  
Cold Tolerant ◽  
Parental Material ◽  
Petri Dishes ◽  
Cool Conditions

In western Canada, common bean is often sown in cool soils, which causes poor germination and uneven stand establishment. A major goal in bean breeding is to find and assess cold-tolerant parental material. Seed germination and emergence of 12 diverse common bean genotypes, which included adapted Prairie cultivars, were evaluated in petri dishes under 15 alternating and five constant temperature regimes. Cumulative heat hours to maximum germination were calculated for all 12 genotypes using a base temperature of 9°C. Six genotypes were tested for emergence in soil in growth chambers at two temperature and three soil moisture regimes. In petri tests, optimal temperatures for bean germination were 16/16°C (day/night temperature) or higher. G8823, G9345 and AC Polaris germinated below 10°C, and all genotypes germinated at 12°C or higher. Rapid germinating genotypes with >0.09 cumulative heat hours per percentage germination were G8823, G9345 and AC Polaris, which took the least number of cumulative heat hours to germinate (<1100 heat hours). CDC Pinnacle was the highest representative of the medium germination rate group, having 1170 heat hours to germination. Emergence and plant development in soil were decreased by low moisture availability or cooler temperatures. Genotypes with >80% emergence in soil were CDC Crocus, CDC Nighthawk, CDC Pinnacle and CDC Polar Bear. Differing genotype rankings in soil versus petri dishes demonstrated that germination in controlled cool conditions may still be complicated by dormancy, moisture availability, seed coat thickness, imbibition rate and differing viabilities of seed lots. G8823, G9345 and AC Polaris are promising genotypes for developing cultivars that can germinate under cool temperatures (<10°C) at the highest rate. Key words: Phaseolus vulgaris, common bean, germination, temperature

Population, Temperature, and Substrate Influences on Common Milkweed (Asclepias syriaca) Seed Germination

Weed Science ◽  
1986 ◽  
Vol 34 (4) ◽  
pp. 525-528 ◽  
Author(s):  
Janis M. Farmer ◽  
Steven C. Price ◽  
C. Ritchie Bell
Keyword(s):  
Geographical Origin ◽  
Source Population ◽  
Strongly Correlated ◽  
Substrate Type ◽  
Asclepias Syriaca ◽  
Experimental Conditions ◽  
Germination Response ◽  
Temperature Regimes ◽  
Percent Germination ◽  
Different Populations

Seed from 21 common milkweed (Asclepias syriacaL. # ASCSY) populations from six states were germinated on six substrates (filter paper, sand, peat, clay, and mixtures) under three temperature regimes. The variation in germination response between populations and experimental conditions was analyzed. The greatest percent germination (59% average over all substrates) was obtained with an alternating 20 C (16 h), 30 C (8 h) temperature regime. At a constant temperature of 30 C, germination was lower (32% average) and much more variable among seeds from different populations. At 25 C, average percent germination dropped to 1.2% over all substrates. Germination appeared to be strongly correlated with seed source (population), temperature, and substrate type, and poorly correlated with seed size. No association was found between geographical origin and germination response.

Seasonal synchronization of emergence in Dolania americana (Ephemeroptera: Behningiidae)

1987 ◽  
Vol 65 (12) ◽  
pp. 3177-3185 ◽  
Author(s):  
Janice G. Peters ◽  
William L. Peters ◽  
Thomas J. Fink
Keyword(s):  
Water Temperature ◽  
Temperature Dependent ◽  
Blackwater River ◽  
Temperature Regimes ◽  
Different Populations ◽  
Seasonal Synchronization

This paper summarizes factors regulating seasonal emergence of Dolania americana in the Blackwater River, Florida, U.S.A. Emergence is temperature-dependent, and emergence on a given day can be predicted from the period of nymphal maturation and the pattern of temperatures on previous mornings. Development of the last two nymphal instars follows a pattern that can be interpreted linearly or by day-degree summations. Increases in water temperature at time of emergence (dawn) on the previous day provide the best correlation with emergence. Different responses to temperature events that cue emergence probably result from the effects of different temperature regimes in which the different populations develop. In experiments, males emerged equally 1 and 2 days after increases in the daily low water temperature, while females emerged more frequently after 2 days of increasing temperatures.

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