*4.1. Plant Materials and Treatments*

The *G. hirsutum* L. accession TM-1 was used in this study. The seeds were provided by the National Mid-term Genebank of the Institute of Cotton Research in China. Cotton seeds were sterilized, and germinated in vermiculite under greenhouse conditions: 30/22 ◦C day/night temperature, 55–70% relative humidity, and a 14/10 h light/dark cycle under 450 µmol m−<sup>2</sup> ·s −1 light intensity. At the two-leaf stage, healthy seedlings were placed in pots containing aerated nutrient solution. Plants were cultured under normal conditions for 10 d to ensure full establishment before starting the drought and salt stress treatments. The pH was maintained close to 6.9 by adding H2SO<sup>4</sup> or KOH as required. The roots of cotton seedlings were irrigated with 20% PEG to test the response to drought. The seedlings were treated with 150 Mm NaCl solution to test the response to salt. After exposing the seedlings to drought and salt stress for 24 h, leaves were harvested directly into liquid nitrogen and stored at −80 ◦C for subsequent use.
