2.2.1. Rice Growth Condition

KDML105 rice, DH103, and CSSL seeds were incubated at 60 ◦C for 48 h before planting. The seeds were then germinated by soaking in distilled water for seven days in plastic cups. Rice seedlings were transferred to a plastic tray and continuously grown in WP nutrient solution [13]. Twenty-eight days after germination, rice plants were drought-stressed for three days by the addition of 10% polyethylene glycol 6000 (PEG6000). This condition was previously shown to cause drought stress in rice [14,15]. In order to induce the stronger drought-stress condition, after treatment with WP nutrient solution with 10% PEG6000 for three days, the solution was then changed to WP nutrient solution with 15% PEG. Plants grown in WP nutrient solution without PEG6000 were used as controls. A complete randomized design (CRD) with four replicates was used for physiological evaluation in each parameter.

### 2.2.2. Net Photosynthesis Rate and Leaf Water Status Detection

The net photosynthesis rate (Pn) of twenty-eight-day-old rice plants was determined with a LI-6400 XT portable photosynthesis system (LI-COR, Lincoln, NE, USA). The measurement was taken at the middle part of the younges<sup>t</sup> fully expanded leaves between 9 am and 2 pm, with the following conditions: the molar flow of air per unit leaf area was 500 mmol l−<sup>1</sup> m<sup>−</sup><sup>2</sup> s<sup>−</sup>1, the photosynthetically active radiation (PAR) at the leaf surface was 1200 μmol m<sup>−</sup><sup>2</sup> s<sup>−</sup>1, the leaf temperature ranged from 30.0 to 37.0 ◦C, with a CO2 concentration of 380.0 mol mol−1. The leaf water potential (LWP) was measured in the younges<sup>t</sup> fully expanded leaves using plant water status console model 3005 (Soilmoisture, Goleta, CA, USA).
