Gmin {pvldcurve}

Minimum leaf conductance

Description

Determines mean minimum leaf conductance and minimum leaf conducance at full turgidity and stomatal closure in experimentally obtained water loss curves.

Usage

Gmin(data, sample = "sample", time.since.start = "time.since.start",
  conductance = "conductance", RWD = "RWD.interval",
  stom.clos.threshold = FALSE, graph = TRUE, show.legend = TRUE)

Arguments

data

data frame containing columns of equal lengths giving the coordinates of the curve: time since start (minutes), conductance (mmol m^-2 s^-1) and RWD (%), ordered by sample by ascending time since start. 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

time.since.start

optional column name in data containing the numerical values for time since start of the experiment (min), default: time.since.start

conductance

optional column name in data containing the numerical conductance values (mmol m^-2 s^-1), default: "conductance"

RWD

optional column name in data containing the numerical relative water deficit values (%), default: "RWD.interval" (RWD average of an interval, as outputted by RWDInterval)

stom.clos.threshold

threshold value for stomatal closure. Automatic determination by default.

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

The coordinates of stomatal closure are determined via the function StomatalClosure().
Conductance data including and following stomatal closure are then extracted and the average is taken (mean.gmin). A linear regression is applied to the data and the y axis intercept (gmin.full.sat) and the coordinate at the RWD point of stomatal closure (lin.gmin) are calculated from the function.

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

gmin

mean minimum conductance (mean.gmin) (mmol m^-2 s^-1) after stomatal closure of the measurement interval, minimum conductance at full saturation (gmin.full.sat) (mmol m^-2 s^-1) and minimum conductance at stomatal closure based on the linear fit (lin.gmin) (mmol m^-2 s^-1)

formula

formula of the linear regression of gmin vs. RWD

coef

coefficients of linear fit

conf_int

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

If graph = TRUE, the plotted original data is displayed with the x-axis intercept of the point of stomatal closure and the linear regression line of gmin showing the point of y-intercept (gminfullsat).

Examples

# get example data
df <- WeatherAllocation(leaf_drying_data, weather_data)   # allocate weather to weight loss data
df <- TimeSinceStart(df) # calculate time since start
df <- df[df$fw.plateau != "yes",] # remove plateauing data
df <- FittedFW(df, graph = FALSE) # correct noises in fresh weight
df <- RWDInterval(df, fresh.weight = "fitted.fw") # calculate RWD based in the intervals
df <- Conductance(df, fresh.weight = "fitted.fw") # calculate conductance

# calculate gmin and plot graphs
gmin <- Gmin(df)