ModElasticity {pvldcurve}

Modulus of elasticity

Description

Determines pressure potential and the modulus of elasticity

Usage

ModElasticity(data, sample = "sample",
  water.potential = "water.potential", RWD = "RWD", graph = TRUE,
  show.legend = TRUE)

Arguments

data

data frame containing columns of equal lengths giving the numerical coordinates of the curve: water potential (bar) and RWD (%), ordered by sample by descending water potential. A column containing the sample IDs is optionally required if several samples were measured

sample

optional column name in data containing the sample ID, default: "sample"

water.potential

optional column name in data containing the water potential values of the leaf (bar), default: "water.potential"

RWD

optional column name in data containing the relative water deficit values (%), default: "RWD"

graph

set FALSE if no plots are to be returned

show.legend

set FALSE if no legend is to be shown in the plots

Details

Relative water deficit at turgor loss point is determined via the function TurgorLossPoint() and osmotic potential is calculated via the function OsmoticPot().

Pressure potential is derived by subtracting osmotic potential from water potential. The part of the pressure potential prior the turgor loss point is then fitted linearly and the modulus of elasticity (M.Elasticity) equals the slope of the fitted line.

Before using this function, check the raw data for an initial plateau. If the exponential decline does not onset directly, fitting might not succeed.

Value

List splitted by sample consisting of

modulus.elasticity

modulus of elasticity (bar)

formula

formula of the transformed linear osmotic potential fit (1/-bar) and the pressure potential (bar) fit

coef

coefficients of the osmotic (1/-bar) and pressure potential (bar) fit

conf_int

upper (97.5 %) and lower (2.5 %) border of 95 % confidence interval of model parameters

If graph = TRUE, the original data is displayed with the x- and y-axis intercepts of the turgor loss point, the osmotic potential fit and the linear regression line of the pressure potential.

Examples

#get example data, calculate Relative Water Deficit
data <- RelativeWaterDeficit(pressure_volume_data)[pressure_volume_data$sample == 1, ]

# determine modulus of elasticity and the fitting parameters. Do not plot results.
m_elasticity <- ModElasticity(data, graph = FALSE)