*4.11. Determination of Malondialdehyde (MDA) and Electrolyte Leakage (EL)*

The level of membrane lipid peroxidation was estimated by MDA content, which was determined by thiobarbituric acid (TBA) assay [78]. Fresh leaves (0.5 g) were homogenized in 5 mL of 5% (*m*/*v*) trichloroacetic acid (TCA) and centrifuged at 4 ◦C for 10 min at 8000× *g*. Next, 2 mL of 0.5% TCA containing 0.67% TBA was added to 2 mL of the supernatant. The mixture was incubated at 95 ◦C for 30 min and then instantly cooled on ice and centrifuged at 4 ◦C for 10 min at 5000× *g*. The absorbance of the supernatant was recorded at 450, 532 nm, and 600 nm.

EL of rice leaves was determined using an electrical conductivity meter (DDS-309+, Chengdu, China) following Ning et al. [79]. Relative EL was expressed as the ratio of initial conductivity to the conductivity after the samples were boiled for 15 min to achieve 100% electrolyte leakage.

#### *4.12. Trypan-Blue Staining*

Dead cells were visually detected using a Trypan-blue staining method as described by Liang et al. [80] with some modifications. Leaves were stained with lactophenol–Trypan blue solution for 20 min under vacuum conditions. The stained leaves were then decolorized in boiling ethanol (90%, *v*/*v*) for 2 h. Samples were equilibrated with 70% glycerol for scanning.

#### *4.13. Characteristics of Epidermis Cell and Stomata*

The upper and lower epidermis layers of rice leaves after 48 h of greening were observed using light microscopy by transparent nail polish imprint method [81]. The epidermis cells' characteristics and stomatal characteristics, including stomatal length, width, size, and density, were observed via Olympus fluorescence microscopy (DP71) (40 × 10) and measured and counted by an image analysis system (Image-Pro Plus 6.3). Five microscope fields were randomly selected in each slide. Each treatment group was repeated 50 times to measure all the characteristic parameters under the microscope.
