Compute the median germination time (\(t_{50}\)). Median germination time is the time to reach 50% of final/maximum germination.
t50(germ.counts, intervals, partial = TRUE, method = c("coolbear", "farooq"))Germination counts at each time interval. Can be partial
or cumulative as specified in the argument partial.
The time intervals.
logical. If TRUE, germ.counts is considered as
partial and if FALSE, it is considered as cumulative. Default is
TRUE.
The method for computing median germination time. Either
"coolbear" or "farooq".
The median germination time (\(t_{50}\)) value in the same unit
of time as specified in the argument intervals.
With argument method specified as "coolbear", median
germination time is computed according to the formula by
Coolbear et al. (1984)
as follows.
\[t_{50}=T_{i}+ \frac{(\frac{N+1}{2}-N_{i})(T_{j}-T_{i})}{N_{j}-N_{i}}\]
Where, \(t_{50}\) is the median germination time, \(N\) is the final number of germinated seeds, and \(N_{i}\) and \(N_{j}\) are the total number of seeds germinated in adjacent counts at time \(T_{i}\) and \(T_{j}\) respectively, when \(N_{i} < \frac{N + 1}{2} < N_{j}\).
Similarly with argument method specified as "farooq", median
germination time is computed according to the formula by by
Farooq et al. (2005)
as follows.
\[t_{50}=T_{i}+ \frac{(\frac{N}{2}-N_{i})(T_{j}-T_{i})}{N_{j}-N_{i}}\]
Where, \(t_{50}\) is the median germination time, \(N\) is the final number of germinated seeds, and \(N_{i}\) and \(N_{j}\) are the total number of seeds germinated in adjacent counts at time \(T_{i}\) and \(T_{j}\) respectively, when \(N_{i} < \frac{N}{2} < N_{j}\).
Coolbear P, Francis A, Grierson D (1984).
“The effect of low temperature pre-sowing treatment on the germination performance and membrane integrity of artificially aged tomato seeds.”
Journal of Experimental Botany, 35(11), 1609--1617.
Farooq M, Basra SMA, Ahmad N, Hafeez K (2005).
“Thermal hardening: A new seed vigor enhancement tool in rice.”
Journal of Integrative Plant Biology, 47(2), 187--193.
x <- c(0, 0, 0, 0, 4, 17, 10, 7, 1, 0, 1, 0, 0, 0)
y <- c(0, 0, 0, 0, 4, 21, 31, 38, 39, 39, 40, 40, 40, 40)
int <- 1:length(x)
# From partial germination counts
#----------------------------------------------------------------------------
t50(germ.counts = x, intervals = int, method = "coolbear")
#> [1] 5.970588
t50(germ.counts = x, intervals = int, method = "farooq")
#> [1] 5.941176
# From cumulative germination counts
#----------------------------------------------------------------------------
t50(germ.counts = y, intervals = int, partial = FALSE, method = "coolbear")
#> [1] 5.970588
t50(germ.counts = y, intervals = int, partial = FALSE, method = "farooq")
#> [1] 5.941176