*4.2. Determination of Shoot Dry Weight (DW)*

The shoots were collected at 0 h, 0.5 h, 12 h, and 48 h after being exposed to light, washed with tap water and rinsed twice with distilled water, gently wiped with a paper towel, and then oven-dried to a constant weight at 80 ◦C for DW determination.

### *4.3. Determination of Chlorophyll, Carotenoids and Protein*

Chlorophyll and carotenoids were extracted from 0.1 g fresh rice seedlings with 80% acetone. The absorbance of the extract was recorded at 663, 646, and 470 nm according to Lichtenthaler and Wellburn using a spectrophotometer (UV-1750, Shimadzu, Japan) [63]. Protein content was determined by the Bradford method [64].

### *4.4. Determination of Chlorophyll Precursors*

δ-Aminolevulinic acid (ALA) was measured according to Dei [65]. Briefly, 0.5 g of fresh leaf was ground in 10 mL of 4% trichloracetic acid with an ice bath, then centrifuged at 18,000× *g* for 15 min. Next, 500 μL of the supernatant was mixed with 2.35 mL of 1 mol/L sodium acetate and 1.5 mL of acetyl-acetone. The mixture was then heated in boiling water for 10 min. After cooling to 25 ◦C, 2 mL of the mixture was added to 2 mL of Ehrlich-Hg and reacted in the dark for 15 min. The absorption was recorded at 553 nm. The content of ALA was evaluated from the calibration curve prepared from known concentration of ALA.

Porphobilinogen (PBG) was extracted as described by Bogorad [66] with some modifications. Briefly, 0.5 g of fresh leaf was homogenized with 5 mL of extraction solution (0.6 mol/L Tris, 0.1 mol/L EDTA, pH 8.2) in an ice bath and centrifuged for 10 min at 18,000× *g*. Next, 2 mL of the mixture was mixed with 2 mL of Ehrlich-Hg and reacted in the dark for 15 min, with absorbance measured at 553 nm.

Uroporphyrinogen III (urogen III) and coproporphyrinogen III (coprogen III) were assessed according to Bogorad [66] and Rebeiz et al. [67], with some modifications. To determine urogen III content, 1.0 g fresh sample was extracted in an ice bath with 10 mL 0.067 mol/L PBS pH 6.8, then centrifuged for 10 min at 18,000× *g*. Next, 5 mL of the supernatant was mixed 0.25 mL of 1% Na2S2O3. The mixture was illuminated by strong light for 20 min, after which the pH was adjusted to 3.5 with 1 mol/L formic acid. The mixture was extracted three times with 5 mL of ether. The water phase was used to measure the absorbance at 405.5 nm. For analysis of coprogen III, the ether phase was extracted with 0.1 mol/L HCl three times. The HCl phase was used to measure the absorbance at 399.5 nm.

Protoporphyrin IX (Proto IX) was measured based on the method of Rebeiz et al. [67]. Fresh leaves (1.0) were homogenized with extracted solution (acetone: 0.1 mol/L NH3·H2O, 9:1, *v*/*v*) in an ice bath, then centrifuged for 10 min at 18,000× *g*. Next, 5 mL of the supernatant was mixed with 2 mL n-hexane. The acetone phase was used to record the fluorescence emission spectra at 400, 622, 633, and 640 nm.

Similarly, Mg-protoporphyrin IX (Mg-proto IX), Mg-Proto monomethyl ester (Mpe), Mg-protoporphyrin IX diester (Mpde), protochlorophyllide (Pchlide), and chlorophyllide (Chlide) were determined based on their fluorescence emission spectrums [67]. Heme was extracted and quantified as described by Wilks [68].
