**2. Materials and Methods**

The experiment was conducted in a growth chamber under controlled conditions in a phytotron. Twenty-eight-day-old lettuce (*Lactuca sativa* L.) plants were transplanted to pots with 0.5 kg of agricultural soil (pH (CaCl2 0.01 mol L−1) 5.9; 43.9 mg dm-3 of P (Mehlich-1), 2.7 mmol dm-3 of K, 25.3 mmol dm-3 of Ca, 5.3 mmol dm-3 of Mg, 14.3 mmol dm-3 of H + Al). The experimental design was randomized with three treatments (n = 36). One treatment was carried out with B. subtilis inoculation, strain AP-3 [31]. The inoculation was performed with bacteria obtained by scraping cells multiplied in a solid medium, diluted in sterile water to a concentration of 1.0.109 cels. mL−1, and 0.1 mL per inoculum. The plants were cultivated for 14 days under the same irrigation conditions, maintaining the soil at field capacity. From the 14th day on, water restriction was applied.

The treatments were conducted as follows: (i) control group, with maintenance of the field capacity and without inoculation of the plants; (ii) stress group, with maintenance of 50% of the field capacity and without inoculation of the plants, and; (iii) bacteria group, with maintenance of 50% of field capacity and inoculation of the plants. The water replacement for field capacity maintenance of only 50% was conducted by the gravimetric method. The phytotron chamber maintained the same temperature (25 ◦C) and lighting conditions during the experiment. Water-deficit treatment was performed for 15 days and was completed on the 30th day after the transplantation of the plants to vessels. The experimental design and analysis are summarized below (Figure 1).

**Figure 1.** The workflow of the experimental analysis conducted in this study.
