where T = treatment temperature, \(b\) = steepness of the
curve, \(c\) = lower asymptote, \(d\) = upper asymptote orQYmax and \(e\) is the inflection point. We
extracted three measures from the fittedFv/Fm temperature response
curves: 1) a breakpoint temperature referred to asT5 calculated as the temperature at whichFv/Fm starts to decline below
95% of the QYmax level, 2)T50 , the temperature whereFv/Fm is half ofQYmax level and finally (not same as parametere from Equation 1) 3) T95 the temperature
at which Fv/Fm is at 5% of theQYmax level. The difference betweenT5 and T95 is referred to
as decline width (DW= T95 –T5 ), the window whereFv/Fm declines from 95% to 5%
of the QYmax level (Figure 2). Response curves
were fitted using the ‘drc’ function of the ‘drm’ package (Xia, Ritz,
Baty, Streibig, & Gerhard, 2015) in R, version 3.5.0 (R Core Team,
2018).