Figure 1.

Variations of (A–C) leaf net CO₂ assimilation rate (A; μmol m⁻² s⁻¹), (D–F) respiration rate (R; μmol m⁻² s⁻¹), (G–I) stomatal conductance (g_s; mol m⁻² s⁻¹), (J–L) C_i/C_a ratio (unitless) and (M–O) leaf-to-air vapor pressure deficit (D_l; kPa) on the day 1 (circle), day 3 (triangle), day 5 (square) and day 7 (diamond) of the drought treatment in Chloris virgata (annual C₄), Hemarthria altissima (perennial C₄) and Leymus chinensis (perennial C₃). Diurnal average values are presented as an inset figure. Different lowercase letters in the inset figures indicate significant differences (P < 0.05) between the sampling dates (Tukey's test). Data are reported as the arithmetic mean ± 1 standard error (n = 5). The shaded area denotes the dark period.