A description of the demonstration version
Analysis of germination tests
SeedCalculator is a dedicated software program for the seed industry developed by Plant Research International. Cumulative germination data and seedling scores are presented in the form of a spreadsheet. Germination parameters and seedling scores, including standard error, can be quickly calculated, then viewed either graphically or in table format.
The complete test can be stored and printed, including details on which germination protocol was used. Different tests can be compared using student’s t-Test.
The basis of SeedCalculator
SeedCalculator uses a mathematical equation with three variables to fit the cumulative germination data. The equation starts at zero value at time T=0, and ends at the maximum germination for T approaching infinity. The shape of the curve is very flexible. Depending on the values of the three variables, the shape can be symmetric to anti-symmetric. Having calculated the best fit, SeedCalculator calculates ten germination parameters of the replicates and the mean germination data (including standard errors, s.e.). The standard errors of the parameters of the mean germination are calculated from values of the replicates. There is an option to calculate the parameters based on the maximum germination (Gmax) or the number of seeds (N) used. Gmax is given by the maximum germination of each replicate, or by the averaged maximum germination of the mean germination. For the calculation towards N, the number of each replicate is used to calculate the parameters, or the averaged total seeds used for the mean germination.
Definitions of the parameters
- T1:time to 1% of Gmax or N; define the onset of germination.
- T10:time to 10% of Gmax or N.
- T25:time to 25% of Gmax or N.
- T50:time to 50% of Gmax or N.
- T75:time to 75% of Gmax or N.
- T90:time to 90% of Gmax or N.
- Uniformity I (T75-T25):time between 25 and 75% of Gmax or N.
- Uniformity II (T90-T10):time between 10 and 90% of Gmax or N.
- MGT (Mean Germination Time):calculated by integration of the fitted curve and proper normalisation.
- Skewness (T50/MGT):a measure for the anti-symmetry of the curve. Normally the value of MGT is between 0 and 1. A value of 1 means that the curve is symmetric and a value between 0 and 1 means that the curve is anti-symmetric. The closer the curve is to 0, the more anti-symmetric it is. A value of 0.9 means that the rate of germination before T50 is larger than the rate of germination after T50 (normally the case). A smaller value of MGT, i.e. 0.8, means that the relative difference between the rate of germination before T50 and the rate of germination after T50 is larger, as in the case of MGT=0.9. In some cases MGT>1 can occur, when the rate of germination before T50 is smaller than the rate of germination after T50.