Fig. 3
Principal component analysis of various indices at different growth stages. PF, peak flowering stage; PB, peak boll stage; BO, boll opening stage; AGB, aboveground biomass; ROB, reproductive organ biomass; Fv/Fm, φPSII, qP, and NPQ represent the primary light energy conversion efficiency of PSII in the dark, quantum yield of PSII, coefficient of photochemical quenching and coefficient of nonphotochemical quenching, respectively. Pn, Gs, Ci, and Tr represent the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and transpiration rate, respectively. t, Tm, and Vm represent the duration of the fast growth period, occurrence time of maximum speed during the fast growth period and maximum speed of biomass accumulation during the fast growth period, respectively