Excerpt from Methods section:

Data Collection

Using the Web of Science (Thompson-ISI, Philadelphia, PA, USA) and the China Knowledge Resource Integrated Databases, a survey on the wheat and rice response to drought from 1980 to 2017 was completed. The database was built based on keywords such as wheat or rice, water stress, water deficit, drought, growth, yield, and productivity. Only studies that met the following selected criteria were included in the database: (1) involved plants that experienced drought under field conditions and pot studies, (2) the reported effect data of a water deficit was taken from the experiments including two datasets of a well-watered control group and a drought condition treatment group without other treatments (e.g., addition of fertilizer, modification of temperature, CO2 or O3), (3) contained any of the plant growth parameters of rice and wheat listed in Table 2, and (4) included replication in the experimental design. Data from the figures were digitized using data extraction software (Plot Digitizer-Windows). In total, 120 cultivars from 60 published wheat studies and more than 70 cultivars from 55 published rice studies were used in the global meta-analysis, which excluded all additional treatments (see Table S1).