Compute the Germination index according to Melville et al. (1980) and its modification by de Santana and Ranal (2004) (Ranal and de Santana 2006) .
Usage
GermIndex(
germ.counts,
intervals,
partial = TRUE,
total.seeds,
modification = c("none", "santanaranal")
)Arguments
- germ.counts
Germination counts at each time interval. Can be partial or cumulative as specified in the argument
partial.- intervals
The time intervals.
- partial
logical. If
TRUE,germ.countsis considered as partial and ifFALSE, it is considered as cumulative. Default isTRUE.- total.seeds
Total number of seeds.
- modification
The modification to be applied. Either
"none"or"santanaranal". Default is"none"(see Details).
Value
The value of the Germination index in the same unit of time as
specified in the argument intervals.
Details
Germination index (\(GI\)) is computed as follows (Melville et al. 1980) .
\[GI = \sum_{i=1}^{k}\frac{\left | \left ( T_{k} - T_{i} \right ) N_{i}\right |}{N_{t}}\]
Where, \(T_{i}\) is the time from the start of the experiment to the \(i\)th interval (day for the example), \(N_{i}\) is the number of seeds germinated in the \(i\)th time interval (not the accumulated number, but the number corresponding to the \(i\)th interval), \(N_{t}\) is the total number of seeds used in the test, and \(k\) is the total number of time intervals.
A modified germination index (\(GI_{mod}\)) was proposed by
(de Santana and Ranal 2004)
where total number of
seeds tested (\(N_{t}\)) is replaced by the total number of germinated
seeds (\(N_{g}\)) in the expression of
Melville et al. (1980)
to
remove the effect of sample size
(Ranal and de Santana 2006)
. It is computed as follows
(Specified by the argument modification = "santanaranal").
\[GI_{mod} = \sum_{i=1}^{k}\frac{\left | \left ( T_{k} - T_{i} \right ) N_{i}\right |}{N_{g}}\]
The term Germination index (\(GI\)) has also been used to describe the
mathematical expression for Speed of germination
(GermSpeed) by
AOSA (1983)
.
References
AOSA (1983).
Seed Vigor Testing Handbook.
Association of Official Seed Analysts, Ithaca, NY, USA.
de Santana DG, Ranal MA (2004).
Analise Da Germinacao: Um Enfoque Estatistico.
Universidade de Brasilia, Brasilia.
Melville AH, Galletta GJ, Draper AD, Ng TJ (1980).
“Seed germination and early seedling vigor in progenies of inbred strawberry selections.”
HortScience, 15(6, I), 749–750.
Ranal MA, de Santana DG (2006).
“How and why to measure the germination process?”
Brazilian Journal of Botany, 29(1), 1–11.
Examples
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
#----------------------------------------------------------------------------
GermIndex(germ.counts = x, intervals = int, total.seeds = 50)
#> [1] 5.84
GermIndex(germ.counts = x, intervals = int, total.seeds = 50,
modification = "none")
#> [1] 5.84
GermIndex(germ.counts = x, intervals = int, total.seeds = 50,
modification = "santanaranal")
#> [1] 7.3
# From cumulative germination counts
#----------------------------------------------------------------------------
GermIndex(germ.counts = y, intervals = int, partial = FALSE,
total.seeds = 50)
#> [1] 5.84
GermIndex(germ.counts = y, intervals = int, partial = FALSE,
total.seeds = 50,
modification = "none")
#> [1] 5.84
GermIndex(germ.counts = y, intervals = int, partial = FALSE,
total.seeds = 50,
modification = "santanaranal")
#> [1] 7.3