Abscisic acid (ABA) application to Populus × canescens in hydroponics

4 weeks old rooted plantlets of P. × canescens (Clone INRA717 1-B4) were cultivated in hydroponics in 2 l pots in Long Ashton nutrient solution in a culture room for 8 weeks before treatments started. Three treatments were applied to the plants: control treatment (-ABA), continuous 100 µM ABA treatment (+ABA) and discontinuous 100 µM ABA treatment (±ABA). ABA was fed to +ABA plants during the whole treatment period of 30 days. ABA was fed to ±ABA plants for three days in two weeks. Developing xylem and mature xylem were collected separately during the harvest and shortly frozen in liquid nitrogen. RNA was extracted from these samples and followed by RNA-sequencing.