Opportunistic Germination Behaviour of Gypsophila (Caryophyllaceae) in Two Priority Habitats from Semi-arid Mediterranean Steppes

Gypsophila tomentosa and G. struthium are closely related species, characteristic of two European priority habitats, salt and gypsum inland steppes, respectively. Germination strategies of the two taxa were investigated in plants from two nearby populations, growing under the same climatic conditions but on different types of soil, and belonging to different plant communities. Their germination patterns were studied at five constant temperatures in darkness: 5oC, 10oC, 15oC, 20oC and 25oC, and the base temperature and the thermal time requirement were calculated. As the distribution area of both species is subjected to a Mediterranean continental climate with significant differences between day and night, the possible preferences for an alternating temperature regime (25/10oC) were contrasted, as well as the influence of cold stratification and freezing. The effects on seed germination of light at constant 20oC and a 12/12 h photoperiod were also compared in the two species. The main conclusions of the work are the similarity of behaviour of both species, with an absence of seed dormancy, their opportunistic germination strategy, and water availability as the principal limitation to seed germination and plant establishment. The base temperature and thermal time indicate higher competitiveness of G. struthium at low temperatures, but seed germination of G. tomentosa is the most efficient at temperatures higher than 13.3oC. Optimal temperature and illumination conditions for nursery propagation depend on the species. The high viability of seeds observed after freezing prove the orthodox character of these seeds, providing additional information for long term seed conservation procedures.

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Seed Germination Variation among Crop Years from a Pinus sylvestris Clonal Seed Orchard

Asian Journal of Research in Agriculture and Forestry ◽

10.9734/ajraf/2019/v3i130031 ◽

2019 ◽

pp. 1-14

Author(s):

Melusi Rampart

Keyword(s):

Seed Germination ◽

Seed Weight ◽

Seed Orchard ◽

Climatic Conditions ◽

Thermal Time ◽

Base Temperature ◽

Germination Capacity ◽

Seed Collection ◽

Clonal Seed Orchard ◽

The Mean

Maternal effects were assessed by germinating seeds sourced over multiple years from the same cloned mother trees, comparing germination capacity and rate between crop years. The relationships between climatic variables, seed characteristics and germination capacity were determined, and thermal time parameters were used to predict seed dormancy release and germination under the climatic conditions in the year after seed collection. There were significant differences in seed weight (P < 0.05), seed length and embryo occupancy (both P < 0.001) among crop years. Temperature during the seed development period explained 70% of the variation in seed weight and 63% of the variation in embryo occupancy. Germination capacity was significantly (P <0.001) different among crop years, among temperatures and among chilling durations, and thermal time requirements for germination increased from older (2007) to younger (2012) seeds. The mean base temperature without chilling was 7.1°C, while after chilling it was 4.6°C and 3.6°C for four and eight weeks chilling respectively. The mean thermal time to 50% germination without chilling was 135.1°Cd, while after chilling it was 118.3°Cd and 154.0°Cd for four and eight weeks chilling respectively. This experiment demonstrates that year-to-year differences in the environment experienced by mother trees during seed maturation can affect seed germination characteristics.

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Application of the thermal time model for different Typha domingensis populations

10.21203/rs.2.23547/v3 ◽

2020 ◽

Author(s):

Fanny Mabel Carhuancho León ◽

Pedro Luis Aguado Cortijo ◽

María del Carmen Morató Izquierdo ◽

María Teresa Castellanos Moncho

Keyword(s):

Seed Germination ◽

Mean Value ◽

Thermal Time ◽

Plant Responses ◽

Base Temperature ◽

Typha Domingensis ◽

Time Model ◽

Germination Response ◽

Thermal Regimes ◽

Thermal Time Model

Abstract Background: Cattail (Typha domingensis Pers.) is a perennial emergent plant which is used in Green Floating Filters (GFFs), one of the most innovative systems of wastewater treatment to bioremediate eutrophic waters and produce biomass as biofuel feedstocks. The establishment of cattails in GFFs depends on the seed germination and plant responses under conditions of a new habitat. This study analysed the germination responses of four different populations of cattails through a thermal time model to know their basic parameters of germination and which population would be more adapted to the conditions tested.Results: Seeds from the Badajoz (Ba), Cuenca (Cu), Madrid (Ma), Seville (Se) and Toledo (To) populations were exposed to different thermal regimes (constant, and alternating temperatures between 15 and 30°C) and different darkness treatments (between 0 and 20 days with 24h dark photoperiod, then exposed to light with 12h light/dark photoperiod) to determine the parameters of the thermal model from germination levels in each treatment. To population was used to validate the thermal time parameters of other populations. Regardless of the other parameters, no germination occurred in total darkness. The mean value of base temperature (Tb) was 16.4±0.2°C in all treatments. Optimum temperature (To) values in Ma and Ba were 25°C, and those in Cu and Se were 22.5°C. The germination response decreased when the temperature approached Tb and increased when it was close to To. In comparison to alternating temperatures, constant temperatures had the highest germination response and lowest thermal time (θT(50)). Darkness treatments had a direct relationship with θT(50). The population origin also affected seed germination; Cu had the highest values of To and germination response but had a lower θT(50), which coincides with the lowest mean ambient temperatures. Conclusion : According to these results, the germination response of cattails was high in all populations under optimal conditions but was affected to a greater or lesser extent depending on thermal regimes, darkness treatments, and populations. The thermal time model allowed us to determine that To was between 22.5-25ºC and that Cu is the best population regarding the germination response under the conditions tested.

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Temperature- and moisture-dependent models of seed germination and shoot elongation in green and redroot pigweed (Amaranthus powellii, A. retroflexus)

Weed Science ◽

10.1017/s0043174500088718 ◽

1997 ◽

Vol 45 (4) ◽

pp. 488-496 ◽

Cited By ~ 27

Author(s):

Joseph O. E. Oryokot ◽

Stephen D. Murphy ◽

A. Gordon Thomas ◽

Clarence J. Swanton

Keyword(s):

Seed Germination ◽

Water Potential ◽

Weed Management ◽

Germination Rate ◽

Shoot Elongation ◽

Thermal Time ◽

Base Temperature ◽

Mathematical Function ◽

Redroot Pigweed ◽

Mean Temperature

To predict weed emergence and help farmers make weed management decisions, we constructed a mathematical model of seed germination for green and redroot pigweed based on temperature and water potential (moisture) and expressing cumulative germination in terms of thermal time (degree days). Empirical observations indicated green pigweed germinated at a lower base temperature than redroot pigweed but the germination rate of redroot pigweed is much faster as mean temperature increases. Moisture limitation delayed seed germination until 23.8 C (green pigweed) or 27.9 (redroot pigweed); thereafter, germination was independent of water potential as mean temperatures approached germination optima. Our germination model, based on a cumulative normal distribution function, accounted for 80 to 95% of the variation in seed germination and accurately predicted that redroot pigweed would have a faster germination rate than green pigweed. However, the model predicted that redroot pigweed would germinate before green pigweed (in thermal time) and was generally less accurate during the early period of seed germination. The model also predicted that moisture limitation would increase, rather than delay, seed germination. These errors were related to the mathematical function chosen and analyses used, but an explicit interaction term for water potential and temperature is also needed to produce an accurate model. We also tested the effect of mean temperature on shoot elongation (emergence) and described the relationship by a linear model. Base temperatures for shoot elongation were higher than for seed germination. Shoot elongation began at 15.6 and 14.4 C for green and redroot pigweed, respectively; they increased linearly with temperature until the optimum of 27.9 C was reached. Elongation was dependent on completion of the rate-limiting step of radicle emergence and was sensitive to temperature but not moisture; hence, elongation was sensitive to a much smaller temperature range. Beyond mathematical changes, we are testing our model in the field and need to link it to ecophysiological, genetic, and spatially explicit population processes for it to be useful in decision support for weed management.

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Germination response of black nightshade (Solanum nigrum) to temperature and the establishment of a thermal time model

Weed Science ◽

10.1017/wsc.2021.60 ◽

2021 ◽

pp. 1-26

Author(s):

Ziqing Ma ◽

Hongjuan Huang ◽

Zhaofeng Huang ◽

Dongjing Guo ◽

Muhammad Saeed ◽

...

Keyword(s):

Seed Germination ◽

Seedling Emergence ◽

Northern China ◽

Solanum Nigrum ◽

Thermal Time ◽

Base Temperature ◽

Time Model ◽

Black Nightshade ◽

Germination Response ◽

Thermal Time Model

Abstract Black nightshade (Solanum nigrum L.) is one of the worst weeds in crop fields, and it spreads mainly by the dispersal of seeds. Temperature is one of the key environmental factors affecting seed germination. We investigated the seed germination response to temperature in six populations of S. nigrum from mid to northern China and derived mathematical models from germination data. The results showed that S. nigrum seeds exhibit distinct germination responses to temperature within the range of 15 to 35 °C. The optimum temperatures for the populations XJ1600, JL1697 and HLJ2134 were 30 °C, and those for the populations NMG1704, HN2160 and LN2209 were 25 °C, 20 °C and 15 °C, respectively. Based on the nonlinear fitting and thermal time models, the predicted base temperatures of the six populations ranged from 2.3 to 6.4 °C, and the required accumulated growing degree days (GDD) ranged from 50.3 to 106.0 °C·d. The base temperatures and the accumulated GDD for germination differed among populations, and there was a significant negative correlation. HLJ2134 population required a high base temperature and accumulated GDD for germination, indicating that it might highly adapted to a warmer and moister environment. Based on the different germination responses of S. nigrum populations to temperature, the thermal time model reflects an innate relationship between base temperature and accumulated GDD required for initiation of seed germination, which provides a better basis for predicting seedling emergence and the timing for optimal control of S. nigrum under field conditions.

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Effects of grazing on crop crown temperature: implications for phenology

Crop and Pasture Science ◽

10.1071/cp13380 ◽

2015 ◽

Vol 66 (4) ◽

pp. 235 ◽

Cited By ~ 2

Author(s):

Matthew T. Harrison ◽

Walter M. Kelman ◽

Jim M. Virgona

Keyword(s):

Stem Elongation ◽

Grazing Intensity ◽

Smoothing Splines ◽

Thermal Time ◽

Base Temperature ◽

Contrast Effects ◽

Vegetative Development ◽

Physiological Feedback ◽

Long Term Trends

In many regions, livestock are allowed to graze grain crops during their vegetative development, before grain is harvested at crop maturity. Little is known of the effects of grazing on crop microclimate, particularly the effects of defoliation on crown temperatures. Knowledge of such effects is important because temperature is the main factor underpinning crop ontogeny, and ontogeny drives dry matter allocation, leaf appearance rates and the timing of anthesis, which are key determinants of grain yield. The primary aim of this study was to examine the influence of grazing intensity and duration on the crown temperatures of winter wheat crops grown at Canberra, Australia. A secondary aim was to examine the association between crown temperature and phenology. In 2007, wheat cv. Mackellar was grazed at intensity–duration combinations of low–short (LS, 33 sheep/ha for 31 days), heavy–short (HS, 67 sheep/ha for 31 days) or low–long (LL, 33 sheep/ha for 62 days). In 2008, cvv. Mackellar and Naparoo were grazed at the HS intensity-duration. Cubic smoothing splines were fitted to crown temperature data measured between the end of grazing and anthesis to facilitate identification of long-term trends and statistical differences caused by the effects of defoliation on crown temperature. Grazing treatments with greater intensity or longer duration significantly elevated maximum daily crown temperature; differences of 6–7°C were common in the month following grazing. Cubic-spline analysis showed that long-term trends in maximum crown temperature of the HS and LL treatments were significantly greater than corresponding temperatures of controls for the entire post-grazing duration. By contrast, effects of grazing on minimum diurnal crown temperature were small. Increasing biomass removal significantly delayed stem elongation and anthesis. We demonstrate that although initial phenological delays caused by defoliation are large, greater diurnal crown temperature fluctuation in grazed crops leads to greater growing degree-day accumulation between the end of grazing and anthesis. This increases the rate of thermal time accumulation during the post-grazing–anthesis period and is likely prominent in driving greater development rates of grazed crops. We further demonstrate that delays in phenology associated with grazing can be largely accounted for by a thermal time constant, with the LS, HS and LL treatments delaying stem elongation by ~52, 141 and 214 degree-days, respectively, above a base temperature of 0°C. Results from these experiments and interpretations herein will be of use in designing crop-grazing regimes, and in studies examining implications of defoliation on vegetative microclimate and on physiological feedback effects caused by elevated temperature.

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Cardinal Temperatures and Thermal Time for Seed Germination of Brunonia australis (Goodeniaceae) and Calandrinia sp. (Portulacaceae)

HortScience ◽

10.21273/hortsci.46.5.753 ◽

2011 ◽

Vol 46 (5) ◽

pp. 753-758 ◽

Cited By ~ 5

Author(s):

Robyn L. Cave ◽

Colin J. Birch ◽

Graeme L. Hammer ◽

John E. Erwin ◽

Margaret E. Johnston

Keyword(s):

Seed Germination ◽

Cumulative Distribution Function ◽

Thermal Time ◽

Cumulative Distribution ◽

Maximum Temperature ◽

Base Temperature ◽

Percentage Germination ◽

Maximum Temperatures ◽

Seed Propagation ◽

Cardinal Temperatures

Seed germination of Brunonia australis Sm. ex R.Br. and Calandrinia sp. (Mt. Clere: not yet fully classified) was investigated using a thermogradient plate set at different constant temperatures to determine seed propagation requirements of these potential floriculture species. Germination responses were tested at 3, 7, 11, 15, 18, 22, 25, 29, 34, and 38 °C. Germination data were modeled using the cumulative distribution function of the inverse normal, which provides information on lag, rate, and maximum seed germination for each temperature regime. To determine cardinal temperatures, the reciprocal time to median germination (1/t50) and percentage germination per day were calculated and regressed against temperature. Base temperature estimates for B. australis were 4.9 and 5.5 °C and optimum temperatures were 21.4 and 21.9 °C, whereas maximum temperatures were 35.9 and 103.5 °C, with the latter being clearly overestimated using the 1/t50 index. Base temperatures for Calandrinia sp. were 5.8 and 7.9 °C, whereas optimum and maximum temperature estimates of 22.5 and 42.7 °C, respectively, were reported using the percentage germination per day index. Maximum seed germination of 0.8 to 0.9, expressed as the probability of a seed germinating, occurred at 11 to 25 °C for B. australis, whereas maximum germination for Calandrinia sp. was 0.5 to 0.7 at 18 to 25 °C. Thermal time, the accumulation of daily mean temperate above a base temperature, was calculated for different germination percentages. Estimates of thermal time (°Cd) for 50% seed germination were 54 and 90 °Cd for B. australis and Calandrinia sp., respectively.

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Assessing Effects of Temperature Change on Four Limonium Species from Threatened Mediterranean Salt-Affected Habitats

Notulae Botanicae Horti Agrobotanici Cluj-Napoca ◽

10.15835/nbha46111010 ◽

2018 ◽

Vol 46 (1) ◽

pp. 286-291 ◽

Cited By ~ 5

Author(s):

Mariola MONLLOR ◽

Pilar SORIANO ◽

Josep V. LLINARES ◽

Monica BOSCAIU ◽

Elena ESTRELLES

Keyword(s):

Seed Germination ◽

Principal Component ◽

Fast Response ◽

Germination Percentage ◽

Thermal Time ◽

Eastern Coast ◽

Soil Parameters ◽

Base Temperature ◽

Temperature Regimes ◽

Saline Habitats

Evaluation of tolerance to temperatures in the germination stage is an important tool to foresee the possible effect of global warming. Moreover, establishing germination protocols for endemic and threatened species is most interesting for restoration and management plans that focus on habitat conservation. Seed germination was analysed in four species of the genus Limonium (L. virgatum, L. narbonense, L. girardianum and L. santapolense) growing in two saline habitats on the eastern coast of the Iberian Peninsula. The study aim was to compare responses of seed germination to different temperature regimes. Seeds were collected in two protected areas, ‘L´ Albufera de Valencia’ (province of Valencia) and ‘Clot de Galvany’ (province of Alicante). Responses to temperature were checked within a constant range, 10-30 °C at 5 °C intervals, by considering the environmental conditions at both sampling sites. The final germination percentage and mean germination time (MGT) were calculated after 30 days. In order to compare thermal responses, base temperature (Tb) and thermal time (S) were determined for each species. The possible correlations of soil parameters with the species´ germination pattern were also analysed. To identify distinct behavioural groups, a non-linear principal component analysis was performed. Significant differences between species were found in the velocity of germination. A fast response as opportunistic germination was observed in all the species. The base temperature and thermal time showed significant differences in competitiveness between species.

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Thermal requirements and germination niche breadth of Polygonum ferrugineum Wedd. from southeastern Brazil

Seed Science Research ◽

10.1017/s0960258521000106 ◽

2021 ◽

pp. 1-7

Author(s):

Andréa R. Marques ◽

Ana Letícia B. R. Gonçalves ◽

Fábio S. Santos ◽

Diego Batlla ◽

Roberto Benech-Arnold ◽

...

Keyword(s):

Seed Germination ◽

Niche Breadth ◽

Thermal Time ◽

Southeastern Brazil ◽

Base Temperature ◽

Light Conditions ◽

Thermal Requirements ◽

Thermal Range ◽

Thermal Limits ◽

Ceiling Temperature

Abstract Temperature may regulate seed dormancy and germination and determine the geographical distribution of species. The present study investigated the thermal limits for seed germination of Polygonum ferrugineum (Polygonaceae), an aquatic emergent herb distributed throughout tropical and subtropical America. Seed germination responses to light and temperature were evaluated both before (control) and after stratification at 10, 15 and 20°C for 7, 14 and 28 d. Germination of control seeds was ~50% at 10 and 15°C, and they did not germinate from 20 to 30°C. The best stratification treatment was 7 d at 10°C, where seed germination was >76% in the dark for all temperatures, except at 30°C, and < 60% in light conditions. A thermal time approach was applied to the seed germination results. Base temperature (Tb) was 6.3°C for non-dormant seeds and optimal temperature (To) was 20.6°C, ceiling temperature (Tc (<50)) was 32.8°C, and thermal time requirement for 50% germination was 44.4°Cd. We concluded that a fraction of P. ferrugineum seeds is dormant, has a narrow thermal niche to germinate (10 and 15°C) and that cold stratification (10°C) alleviated dormancy and amplified the thermal range permissive for germination of the species. Consequently, P. ferrugineum is expected to occur in colder environments, for example, at high altitudes. Higher temperatures decrease the probabilities of alleviate dormancy and the ability of their seeds to germinate.

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Effects of thermal model and base temperature on estimates of thermal time to bud break in white spruce seedlings

Canadian Journal of Forest Research ◽

10.1139/x10-129 ◽

2010 ◽

Vol 40 (9) ◽

pp. 1815-1820 ◽

Cited By ~ 18

Author(s):

Rongzhou Man ◽

Pengxin Lu

Keyword(s):

White Spruce ◽

Climatic Conditions ◽

Thermal Time ◽

Growing Degree Days ◽

Base Temperature ◽

Bud Break ◽

Bud Burst ◽

Degree Days ◽

Growing Degree Hours ◽

Time Requirements

To improve the predictability of bud burst and growth of boreal trees under varying climate, the thermal time for bud break in white spruce ( Picea glauca (Moench) Voss) seedlings was evaluated under a range of temperature conditions in controlled environment chambers. Thermal time requirements were calculated as the sum of growing degree days or growing degree hours above base temperatures ranging from –1 to 5 °C. The results indicated that the common modeling approach, which uses a high base temperature of 5 °C and growing degree days, may not be appropriate for future climatic conditions. Estimates of thermal time requirements using a base temperature of 5 °C varied considerably among temperature treatments and thus would reduce the predictability of bud burst under changing climate. In contrast, estimates of thermal time requirements with lower temperatures closer to 1 °C were relatively consistent among treatments. Growing degree hour models were less sensitive to base temperature than degree day models. These results should help in the selection of appropriate base temperatures and thermal time models in quantification of thermal time for bud burst modeling in other boreal trees.

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Thermal Niche for Seed Germination and Species Distribution Modelling of Swietenia macrophylla King (Mahogany) under Climate Change Scenarios

Plants ◽

10.3390/plants10112377 ◽

2021 ◽

Vol 10 (11) ◽

pp. 2377

Author(s):

Salvador Sampayo-Maldonado ◽

Cesar A. Ordoñez-Salanueva ◽

Efisio Mattana ◽

Michael Way ◽

Elena Castillo-Lorenzo ◽

...

Keyword(s):

Climate Change ◽

Seed Germination ◽

Potential Distribution ◽

Germination Rate ◽

Thermal Time ◽

Base Temperature ◽

Climate Change Scenarios ◽

Swietenia Macrophylla ◽

Climate System Model ◽

Current Scenario

Swietenia macrophylla is an economically important tree species propagated by seeds that lose their viability in a short time, making seed germination a key stage for the species recruitment. The objective of this study was to determine the cardinal temperatures and thermal time for seed germination of S. macrophylla; and its potential distribution under different climate change scenarios. Seeds were placed in germination chambers at constant temperatures from 5 to 45 °C and their thermal responses modelled using a thermal time approach. In addition, the potential biogeographic distribution was projected according to the Community Climate System Model version 4 (CCSM4). Germination rate reached its maximum at 37.3 ± 1.3 °C (To); seed germination decreased to near zero at 52.7 ± 2.2 °C (ceiling temperature, Tc) and at 12.8 ± 2.4 °C (base temperature, Tb). The suboptimal thermal time θ150 needed for 50% germination was ca. 190 °Cd, which in the current scenario is accumulated in 20 days. The CCSM4 model estimates an increase of the potential distribution of the species of 12.3 to 18.3% compared to the current scenario. The temperature had an important effect on the physiological processes of the seeds. With the increase in temperature, the thermal needs for germination are completed in less time, so the species will not be affected in its distribution. Although the distribution of the species may not be affected, it is crucial to generate sustainable management strategies to ensure its long-term conservation.

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