Figure 5.

Time course of changes in the E_i of the xanthophyll cycle, expressed as (V + 0.5 × A)/(V + A + Z) in intact attached leaves of PqR E. canadensis (A) under LL (200 μmol m⁻² s⁻¹) in the absence (□, LL control) or In the presence (▵, Pq + LL) of 0.1 mm Pq. Effect of a short-term (5-min) HL (1,100 μmol m⁻² s⁻¹ PPFD) pre-illumination (B) on the time course of E_i in intact attached leaves of PqR E. canadensis under LL (200 μmol m⁻² s⁻¹) in the absence (□, 5 min HL + LL) or in the presence (▵, Pq + 5 min HL + LL) of 0.1 mm Pq. Pq was applied under dim-light (15 μmol m⁻² s⁻¹) and the treated leaves were then kept in the dark for 10 min to allow the surface of the leaves to become dry before any illumination. The short-term pre-illumination was followed by another 10-min dark period before the LL measurement to synchronize the fluorescence (Figs. 6 and 7) and xanthophyll cycle measurements. The data are means of six replicates and ses are shown when larger than the symbols.