Figure 1.

Influence of systemic light signaling on the induction phase of net CO₂ assimilation (A and C–F) and T50 or T90 (B). A and B, Preillumination was provided to the shoot apex, upper leaves (UL; fifth and sixth leaves), and lower leaves (LL; first to third leaves) with WL at an intensity of 300 μmol m⁻² s⁻¹ for 30 min before CO₂ assimilation was analyzed in the fourth leaves. C, The apex was preilluminated with R or FR light for 30 min before CO₂ assimilation was analyzed in the fourth leaves. D, The apex was preilluminated with different R/FR light ratios for 30 min, in which R light was kept at 300 μmol m⁻² s⁻¹, before CO₂ assimilation was measured in the fourth leaves. E, A reciprocal R/FR light pulse at 5-min intervals with six cycles was applied on the apex before CO₂ assimilation was measured in the fourth leaves. F, Preillumination was provided by WL at an intensity of 300 μmol m⁻² s⁻¹ for 30 min before CO₂ assimilation was analyzed in the fourth leaves of the grafted plants. During the illumination treatments, the other parts of the plant were kept in darkness. Net photosynthetic rates are expressed as percentage of the maximum net CO₂ assimilation. Plants without preillumination (dark [D]) were used as controls. L, WL. Values are means of four plants ± sd. Different letters indicate significant differences at P < 0.05 according to Tukey’s test.