Plant growth and exudates sampling
Samples collected for this experiment were part of our previous study (Vescio et al., 2021) conducted using maize plants (Zea mays L., genotype KXB7554 provided by KWS Italia) as a model. Plants were grown in pots filled with a mix of collected field soil and quartz sand (1:2, v:v). Quartz sand (Ø1-2 mm, Croci Trading Company s.r.l., Italy) was previously autoclaved for 3 hours at 121°C, allowed to cool overnight, and then autoclaved further 3 hours at 121 °C. The soil physicochemical parameters are reported in Gelsomino et al. (2010). Plants were initially grown for 2 weeks at 25°C, 70% relative humidity and at 14h:10h light:dark photoperiod. Then, plants were exposed to two levels of water availability (30% and 80% of soil field capacity, corresponding to a severe drought and no drought) and air temperature (25°C and 32°C) for one week. Finally, the following abiotic stress treatments were obtained: 25°C and 80% soil field capacity (T1 or control); 25°C and 30% soil field capacity (T2 or drought stress); 32°C and 80% soil field capacity (T3 or heat stress); 32°C and 30% soil field capacity (T4 or combined stress).