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Fig. 5. The effect of photosynthetic photon flux (PPF) on yield. Both grain yield (open circles, r2 = 0.986) and vegetative biomass (including roots, closed circles, r2 = 0.990) increased with higher PPF, so harvest index remained relatively constant (r2 = 0.07) at slightly below 50%. Increase in yield was likely due to higher number of fertile heads at higher PPF (r2 = 0.969). No fertile heads were observed at PPF of 200 µmol m–2 s–1 or less. Error bars indicate standard error of means (n = 4 for each point).
