how to get a ALT0183 point on my x and y axis labels

Question

I want to get a point (the one you get by typing ALT0183) between my metrics in the x and y axis labels.

This is what I want to get on my x-axis: Time averaged photon flux (µmoles·m^-2·s^-1)

This is what I want to get on my y-axis: O2 (µmoles·min^-1·mg[ChlA]^-1)

Thusfar, I have only managed to get the labels without the points. My second question is if you know how I can keep the ChlA between brackets [] without it being made a subscript, as [ChlA] stands for concentration of chlorophyl A.

This is my code:

I <- c(30,40,50,60,70,80,100,120,140,160,200)

P <- c(-0.593219548,0.213028562,0.559175617,-0.011447228,0.792755457,0.753335175,1.606054041,1.505984062,2.121712423,2.097202009,1.810391275)

fit = nls(P ~ pm*tanh(a*I/pm), start=list(pm=pm, a=a))

pm=2
a=0.03

par(mgp = c(2.5,1,0))

plot(I,P,
xlab=expression(Time ~ averaged ~ photon ~ flux ~(µmoles ~ m^{-2} ~ s^{-1})),
ylab=expression(O[2] ~ (µmoles ~ min^{-1} ~ mg ~ ChlA^{-1})), cex.lab=1, main="PI-curve Synechocystis batch 1 from 29/05")

Hopefully it is a bit clear what I aim to get in my plot.

Answer 1

I fortunately found the '·' answer myself!

By putting '%.%' instead of the '~' sign, a cdot is created in the axis label.

So the code for plotting my graph became:

plot(I,P,
xlab=expression(Time ~ averaged ~ photon ~ flux ~(µmoles %.% m^{-2} %.% s^{-1})),
ylab=expression(O[2] ~ (µmoles %.% min^{-1} %.% mg ~ ChlA^{-1})), cex.lab=1, main="PI-curve Synechocystis batch 1 from 29/05")

However, I'm still looking for the answer for the notation of [ChlA] without it becoming a subscript.