The samples were homogenized by shaking for 24 h at 4 ◦C and then
centrifuged at 10,000 × g for 5 min at 4 ◦C. The clear supernatant
was taken into an Eppendorf-vial, stored on ice and used to determine
abscisic acid (ABA) concentration through an enzyme linked
immunosorbent assay (ELISA) using a monoclonal antibody for ABA
(AFRC MAC252) (Asch, 2000).