ABSCISIC ACID AND WATER RELATIONS MODELS OF SEED GERMINATION.

Cell growth models were applied to characterize the response of seed germination, based upon the timing of radicle emergence, to y and ABA. Using probit analysis, three basic parameters can be derived to describe the population characteristics of seed lots. In the response of seed germination to osmotic stress, these three parameters are the “hydrotime constant” (q H), the mean base water potential (y b), and the standard deviation (s b) population. In the response to ABA, they are the “ABA-time constant” (q ABA), the mean base ABA concentration (ABAb), and the standard deviation (s ABAb) of the seed population. Using only these three parameters, germination time courses can be predicted at any corresponding medium y or ABA concentration. In the presence of both ABA and osmotic stress, the same parameters can be used to predict seed germination time courses with any combination of y and ABA concentration. The water relations model and the ABA model were additive and it appeared that the two factors slowed down germination independently. Effects of osmotic stress and ABA on the parameters in Lockhart equation are also discussed.

Download Full-text

Hydrothermal time analysis of tomato seed germination at suboptimal temperature and reduced water potential

Seed Science Research ◽

10.1017/s096025850000204x ◽

1994 ◽

Vol 4 (2) ◽

pp. 71-80 ◽

Cited By ~ 84

Author(s):

Peetambar Dahal ◽

Kent J. Bradford

Keyword(s):

Seed Germination ◽

Water Potential ◽

Time Course ◽

Hydrothermal Time ◽

Tomato Seed ◽

Time Model ◽

Germination Time ◽

Radicle Emergence ◽

Time Courses ◽

Hydrotime Model

AbstractBoth temperature (T) and water potential (ψ) have consistent and quantifiable effects on the rate and extent of seed germination (radicle emergence). Germination at suboptimal T can be characterized on the basis of thermal time, or the T in excess of a base (Tb) multiplied by the time to a given percentage germination (tg). Similarly, germination at reduced ψ can be characterized on a hydrotime basis, or the ψ in excess of a base (ψb) multiplied by tg. Within a seed population, the variation in thermal times to germination for a specific percentage (g) is based upon the normal distribution of ψb values among seeds (ψb(g)). Germination responses across a range of suboptimal T and ψ might be accounted for by a general hydrothermal time model incorporating both T and ψ components. We tested this hypothesis for tomato (Lycopersicon esculentum Mill.) seeds of two genotypes differing in germination rates and tolerance of suboptimal T and ψ. For combinations of T (10−25°C) and ψ (0 to −0.9 MPa), a general hydrothermal time model accounted for approximately 75% of the variation in times to germination within the seed populations of both genotypes, and over 96% of the variation in median germination rates. However, ψb(g) distributions were sensitive to both the T and ψ of imbibition, resulting in a poor fit of the model to specific time course data. Analysis of germination timing separately for low and high ψ ranges within a given T resulted in specific models accounting for 88−99% of the variation in individual germination times and >99% of the variation in madian germination rates. Thus, for a given T and ψ range, the hydrotime model closely matched tomato seed germination time courses. Accumulated hydrothermal time accounted well for germination rates at ψ> −0.5 MPa across suboptimal T if ψb(g) was allowed to vary with T. Germination did not show a consistent response to T at ψ < −0.5 MPa, and estimated Tb values varied over different T ranges. Generalization of the hydrothermal time model across the entire range of suboptimal T and ψ was limited by physiological adjustments of the seeds to their current environment. The hydrothermal time model detected and quantified these adjustment processes that would otherwise not be evident from inspection of germination time courses. Temperature and water potential influence the time to germination via physiological mechanisms that reciprocally interact.

Download Full-text

Comparing independent climate-sensitive models of aboveground biomass and diameter growth with their compatible simultaneous model system for three larch species in China

International Journal of Biomathematics ◽

10.1142/s1793524519500530 ◽

2019 ◽

Vol 12 (07) ◽

pp. 1950053

Author(s):

Zhigang Gao ◽

Qiuyan Wang ◽

Zongda Hu ◽

Peng Luo ◽

Guangshuang Duan ◽

...

Keyword(s):

Standard Deviation ◽

Growth Models ◽

Model System ◽

Maximum Temperature ◽

Tree Biomass ◽

Climate Zones ◽

Temperature And Precipitation ◽

Larch Species ◽

The Mean ◽

Simultaneous Model

Accurate estimate of tree biomass is essential for forest management. In recent years, several climate-sensitive allometric biomass models with diameter at breast height [Formula: see text] as a predictor have been proposed for various tree species and climate zones to estimate tree aboveground biomass (AGB). But the allometric models only account for the potential effects of climate on tree biomass and do not simultaneously explain the influence of climate on [Formula: see text] growth. In this study, based on the AGB data from 256 destructively sampled trees of three larch species randomly distributed across the five secondary climate zones in northeastern and northern China, we first developed a climate-sensitive AGB base model and a climate-sensitive [Formula: see text] growth base model using a nonlinear least square regression separately. A compatible simultaneous model system was then developed with the climate-sensitive AGB and [Formula: see text] growth models using a nonlinear seemingly unrelated regression. The potential effects of several temperature and precipitation variables on AGB and [Formula: see text] growth were evaluated. The fitting results of climatic sensitive base models were compared against those of their compatible simultaneous model system. It was found that a decreased isothermality ([mean of monthly (maximum temperature-minimum temperature)]/(Maximum temperature of the warmest month-Minimum temperature of the coldest month)) and total growing season precipitation, and increased annual precipitation significantly increased the values of AGB; an increase of temperature seasonality (a standard deviation of the mean monthly temperature) and precipitation seasonality (a standard deviation of the mean monthly precipitation) could lead to the increase of [Formula: see text]. The differences of the model fitting results between the compatible simultaneous system with the consideration of climate effects on both AGB and [Formula: see text] growth and its corresponding climate-sensitive AGB and [Formula: see text] growth base models were very small and insignificant [Formula: see text]. Compared to the base models, the inherent correlation of AGB with [Formula: see text] was taken into account effectively by the proposed compatible model system developed with the climate-sensitive AGB and [Formula: see text] growth models. In addition, the compatible properties of the estimated AGB and [Formula: see text] were also addressed substantially in the proposed model system.

Download Full-text

Reduction of Phytotoxicity in Polyurethane Foam-containing Potting Media

HortScience ◽

10.21273/hortsci.27.3.225 ◽

1992 ◽

Vol 27 (3) ◽

pp. 225-227 ◽

Cited By ~ 1

Author(s):

David Wees ◽

Danielle Donnelly

Keyword(s):

Seed Germination ◽

Polyurethane Foam ◽

Raphanus Sativus ◽

Tap Water ◽

Plant Performance ◽

Germination Time ◽

Medium Component ◽

Potting Medium ◽

Potting Media ◽

The Mean

Leachates were produced by washing Hydra-fill, a polyurethane ester foam, with water. These leachates decreased radish (Raphanus sativus L.) and tomato (Lycopersicon esculenturn Mill.) seed germination and were phytotoxic to seedlings. Washing the foam for as little as 5 minutes (compared to not washing) before collecting the leachate significantly decreased the mean seed germination time by 0.6 to 1 day. Rinsing the foam with ethanol before collecting the leachate was detrimental to germination. When used as a potting medium component, the foam reduced radish shoot and root dry weights compared to potting media without foam. Washing the foam with tap water before use resulted in increased radish shoot and root dry weights. Hydra-fill generally reduced plant performance when included in potting media. However, radish grew well in fresh 25% Hydra-fill (raw or washed) mixed with loam.

Download Full-text

Influence of seed size and ecological factors on the germination and emergence of field bindweed (Convolvulus arvensis)

Planta Daninha ◽

10.1590/s0100-83582013000100005 ◽

2013 ◽

Vol 31 (1) ◽

pp. 39-51 ◽

Cited By ~ 20

Author(s):

A Tanveer ◽

M Tasneem ◽

A Khaliq ◽

M.M Javaid ◽

M.N Chaudhry

Keyword(s):

Seed Germination ◽

Environmental Factors ◽

Osmotic Stress ◽

Germination Percentage ◽

Germination Index ◽

Convolvulus Arvensis ◽

Germination Time ◽

Wide Range ◽

Field Bindweed ◽

Mean Germination Time

An understanding of seed germination ecology of weeds can assist in predicting their potential distribution and developing effective management strategies. Influence of environmental factors and seed size on germination and seedling emergence of Convolvulus arvensis (field bindweed) was studied in laboratory and greenhouse conditions. Germination occurred over a wide range of constant temperatures, between 15 and 40 ºC, with optimum germination between 20 and 25 ºC. Time to start germination, time to 50% germination and mean germination time increased while germination percentage and germination index decreased with an increase in temperature from 20 ºC, salinity and osmotic stress. However, germination was tolerant to low salt (25 mM) or osmotic stress (0.2 MPa), but as salinity and osmotic stress increased, germination percentage and germination index decreased. Seeds of C. arvensis placed at soil surface showed maximum emergence and decreased as seeding depth increased. Seeds of C. arvensis germinated over a wide range of pH (4 to 9) but optimum germination occurred at pH 6 to 8. Under highly alkaline and acidic pH, time to start germination, time to 50% germination and mean germination time increased while germination percentage and germination index decreased. Increase in field capacity caused decreased time to start germination, time to 50% germination and mean germination time but increased germination percentage and germination index. Bigger seeds had low time to start germination, time to 50% germination and mean germination time but high germination percentage and germination index. Smaller seeds were more sensitive to environmental factors as compared to larger or medium seeds. It can be concluded that except for pH, all environmental factors and seed sizes adversely affect C. arvensis as regards seed germination or emergence and germination or emergence traits, and larger seeds result in improved stand establishment and faster germination than small seeds, regardless of moisture stress or deeper seeding depth.

Download Full-text

Quantifying the oxygen sensitivity of seed germination using a population-based threshold model

Seed Science Research ◽

10.1017/s0960258507657389 ◽

2007 ◽

Vol 17 (1) ◽

pp. 33-43 ◽

Cited By ~ 23

Author(s):

Kent J. Bradford ◽

Daniel Côme ◽

Françoise Corbineau

Keyword(s):

Standard Deviation ◽

Seed Germination ◽

Time Constant ◽

Threshold Model ◽

Seed Priming ◽

Population Based ◽

Physiological Status ◽

Wide Range ◽

Time Courses ◽

Germination Timing

AbstractSeeds vary widely in the sensitivity of germination to oxygen (O2) partial pressure, depending upon the species, temperature, dormancy state and physiological status of the seeds. Most analyses of the O2 sensitivity of germination have focused on final germination percentages and estimated the O2 percentage in air that is required to reduce germination to a given percentage (usually 50%). In contrast, we have applied a population-based threshold model utilizing time courses of germination to quantify three parameters related to seed germination sensitivity to O2 availability: the median base (or threshold) O2 percentage, the standard deviation of O2 thresholds among seeds in the population, and an oxygen–time constant that relates O2 percentage to germination timing. The model fits germination responses accurately across a wide range of O2 concentrations. The response to O2 was logarithmic in all cases, with the O2 percentage required for 50% germination ranging from 21% to as low as 0.005%, depending upon the species, the temperature and the seed dormancy level. Modelling indicated that some seeds can adapt to low O2 percentages and shift their thresholds to lower values over time. Lower temperatures decreased the minimum O2 threshold, as did after-ripening. Seed priming generally reduced the oxygen–time constant and increased the standard deviation of germination responses, but had relatively little effect on the O2 sensitivity per se. The population-based threshold model can be used to quantify the O2 sensitivity of seed germination and to predict germination rates and percentages when O2 availability is limiting.

Download Full-text

Effects of drought stress on germination and seedling growth of different field pea varieties

Zbornik Matice srpske za prirodne nauke ◽

10.2298/zmspn2140059p ◽

2021 ◽

pp. 59-70

Author(s):

Gordana Petrovic ◽

Tomislav Zivanovic ◽

Radmila Stikic ◽

Zorica Nikolic ◽

Dusica Jovicic ◽

...

Keyword(s):

Seed Germination ◽

Osmotic Stress ◽

Seedling Growth ◽

Germination Percentage ◽

Field Pea ◽

Tolerance Index ◽

Germination Time ◽

Mean Germination Time ◽

Effects Of Drought ◽

Osmotic Potentials

Germination and seedling growth of seven genotypes of field pea (Pisum sativum L.) were studied in PEG-6000 solution having osmotic potentials -0.1 and -0.2 MPa. A study was undertaken to evaluate the influence of different osmotic potentials (MPa) on seed germination percentage (GP) and mean germination time (MGT). Results show that the percentage of germination decreased with a decrease in osmotic potential, while mean germination time increased. Variety Javor is much more sensitive than the other varieties at all levels of osmotic stress. By contrast, the lowest sensitivity of germination and MGT was found in varieties Mraz and Trezor. Seed germination tests at -0.1 to -0.2 MPa have the potential to be used as tests in field pea. Osmotic stress exposure and its duration significantly affected the growth of seedlings (shoot and root) and the accumulation of biomass, while its effect was more prominent on the growth of the shoot than on root growth, which was also confirmed by the root tolerance index.

Download Full-text

Establishment of a New Equation for Ultrasonographic Estimated Foetal Weight in Chongqing: a Prospective Study

10.21203/rs.3.rs-973686/v1 ◽

2022 ◽

Author(s):

Chenhuizi Wu ◽

Jianfeng Sun ◽

Xiaojing Dong ◽

Liuyun Cai ◽

Xinru Deng ◽

...

Keyword(s):

Standard Deviation ◽

Prospective Study ◽

Mean Absolute Error ◽

Local Population ◽

Absolute Error ◽

Population Characteristics ◽

Abdominal Circumference ◽

The Mean ◽

New Equation ◽

Weight Compensation

Abstract Background: Variations in foetal growth between populations should not be ignored, and a single universal standard is not appropriate for everyone. Therefore, it is necessary to develop a new ultrasound estimation equation that adapts better to regional population characteristics. The purpose of this study was to create a new equation for ultrasound estimation of foetal weight according to the local population in Chongqing and compare it with representative equations. Methods: This prospective study included data on pregnant women who gave birth to a child at full term in our hospital from December 2016 to November 2019. Foetal ultrasound parameters included biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur diaphysis length (FDL). The foetal weight compensation model was established by using the second-order linear regression model, and then, the foetal weight equation was established by utilizing the multiple reverse elimination regression technique. Last, the absolute error and relative error were used to compare the accuracy of the equations established in this study with representative equations. Results: Through the foetal weight compensation equation, the new equation suitable for Chongqing foetuses was successfully established with the variables of BPD, HC, AC, and FDL. The following foetal weight prediction equation was established in this study: Log 10 (EFW)=3.002741+0.00005944*(BPD^2)+0.00000222*(HC^2)-0.000002078*(AC^2)+0.00004262*(FDL^2)-0.008753*BPD-0.000884*HC+0.003206*AC-0.002894*FDL (BPD: mm; HC: mm; AC: mm; FDL: mm). In the sets established by the 1925 data, the mean absolute error and standard deviation of the estimation error of the new equation were 178.9 g and 140.3 g respectively. In the validation sets established with 300 data points, the mean absolute error and standard deviation of the new equation were 173.08 g and 128.59 g respectively. Compared with representative equations, the mean absolute error and the standard deviation of the new equation were the lowest. The equation established in this study better predicted foetal weight(P<.001). Conclusions: According to the local population characteristics of Chongqing, this study created a foetal weight estimation equation that is more accurate and suitable. This equation is clinically valuable for the monitoring and management of foetal weight.

Download Full-text

Establish a new equation for ultrasonographic estimated fetal weight in Chongqing: a prospective study

10.21203/rs.3.rs-86466/v1 ◽

2020 ◽

Author(s):

Chenhuizi Wu ◽

Jianfeng Sun ◽

Liuyun Cai ◽

Xinru Deng ◽

Fenglan Zhang ◽

...

Keyword(s):

Standard Deviation ◽

Mean Absolute Error ◽

Estimation Error ◽

Local Population ◽

Absolute Error ◽

Population Characteristics ◽

Fetal Weight ◽

The Mean ◽

New Equation ◽

Weight Compensation

Abstract Background: Variation in fetal growth between populations should not be ignored, and a single universal standard is not appropriate for everyone. Therefore, according to regional population characteristics, it is necessary to find a more accurate equation for ultrasound estimation of fetal weight. The purpose of this study was to create a new equation for ultrasound estimation of fetal weight according to the local population in Chongqing and compare it with representative equations. Methods: This prospective study included data on pregnant women who gave birth to a single child at full term in our hospital from December 2016 to November 2019. The fetal weight compensation model was established by using the second-order linear regression model, then the equation of fetal weight was established by utilizing the multiple reverse elimination regression technique. The accuracy of the equation established in this study was respectively compared with the Hadlock equation, Combs equation and Stirnemann equation by estimation error.Results: Through the fetal weight compensation equation, the predicted fetal weight equation suitable for Chongqing fetuses was successfully established with the variables of biparietal diameter, head circumference, abdominal circumference and femur length. In the sets established by 1925 data, the mean absolute error and standard deviation of the estimation error of the equation established in this study were 178.9g and 140.3g respectively. In the 300 validation sets, the mean absolute error and Standard deviation of Chongqing equation were 173.08g and 128.59g respectively. Compared with representative equations, the mean absolute error and the standard deviation of the new equation were the lowest.Conclusions: According to the local population characteristics of Chongqing, this study created the equation for estimated fetal weight, which is more accurate and suitable. This equation has high clinical guidance and reference value for monitoring and management of fetal weight and maternal delivery process.

Download Full-text