*3.2. Chloroplast Isolation and Chlorophyll Quantitative Determination*

Intact chloroplasts were isolated from spinach leaves (*Spinacea oleracea* L.), as previously described [12,22,25]. Chlorophyll concentration was measured spectrophotometrically through a chloroplast suspension in a solution of 400 mM sucrose, 5 mM MgCl, 10 mM KCl, 30 mM tricine-KOH, and pH 8.0 [12].

#### *3.3. Measurement of Noncyclic Electron Transport Rate*

The light-induced noncyclic electron-transport activity from water to MV was determined polarographically employing a Clark-type electrode in the presence of 50 μM of MV [19]. Basal electron transport was quantified by illuminating a solution of chloroplasts (20 μg Chl/mL) in 3 mL of 100 mM sorbitol, 10 mM KCl, 5 mM MgCl2, 0.5 mM KCN, 15 mM tricine-KOH, and 50 μM MV at pH 8.0 for 1 min. The phosphorylating electron-transport rate was estimated for the basal electron transport from water to MV, adding 1 mM of ADP and 3 mM KH2PO4. In turn, uncoupled electron transport was evaluated in the same solution used for basal step, with 6 mM NH4Cl added as an uncoupler [12].
