Methods

Experimental design:

Figure 3. Winter wheat pots in the greenhouse.

    The experiments were arranged as a Completely Randomized Design with ten pots as one treatment group. The pot size was 7 inches in diameter by 10 inches in height, and each pot contained one winter wheat plant; they were placed in the greenhouse-controlled environment cabinets. All pots contain the same type and amount of soil, and any fertilizer applications or irrigation activities should be treated simultaneously and evenly on all the plants.


Before and after the 7-day heat and drought treatment (39 days after the seeding date), the greenhouse was set to maintain a constant temperature (21℃) and humidity (50%) all day to establish the optimum growing condition; supplemental lights turned on when the sunlight is below 300 W/m2 at daytime. During the 7-day stress period, for the heat treatment, the environmental temperature during the daytime was increased to 33℃, the humidity remained the same; the nighttime temperature was still maintained at 21℃ for eight hours. For the drought treatment, the watering amount was only 35% of regular watering. A timeline of activities is presented in Table 1. 

Table 1. Timeline of project activities for heat and drought stress on winter wheat grown under the controlled environment.

Table 2. Experimental treatments tested on winter wheat under the controlled environment.

There were four treatment groups in this experiment. All treatment groups had heat and drought stress tests, but only treatment group one got no PB application. Treatment group two had one PB application when winter wheat plants reached stage BBCH 21 when tiller initiation happened (19 days after the seeding date). Treatment group three also had one application, but this happened when plants reached stage BBCH 45-53 during early boot to early panicle emergence (37 days after the seeding date). Treatment group four had both two applications. The experimental treatments are presented in Table 2. All PB applications will be conducted in a spray chamber, each using 100L/ha of PB with a rate of 1.5L/ha. 

Figure 4. PBs is being applied to winter wheat in the spray chamber.

Data collection: 

Plants were hand harvested as they reach maturity (94 days after the seeding date). Measurements included plant height (cm), plant dry biomass (g), number of spikes per plant, and number of seeds per plant.