That's because the increase in plant growth and leaf size caused by additional CO2 diluted nitrogen levels.
(That; 's; the increase in plant growth and leaf size) (plant growth and leaf size; caused; by additional CO2 diluted nitrogen levels) (CO2; diluted; nitrogen levels)
That plant growth and leaf size CO2
's caused diluted
the increase in plant growth and leaf size
by additional CO2 diluted nitrogen levels
nitrogen levels