Figure 4.
In M. glyptostroboides, foliar ABA level is augmented by the combination of both time and Ψl. A, Foliar ABA levels increased linearly with time (black line) after 6 h in branches that were maintained at prescribed Ψl below −1.1 MPa (gray triangles, −1.12 MPa; white circles, −1.55 MPa; black squares, −2.33 MPa). Foliar ABA levels did not increase in branches that were excised and dehydrated on the bench for times less than 6 h (black circles) or maintained at −0.12 MPa for 48 h (black circles; gray line). B, Foliar ABA levels in plants experiencing drought stress increase when the plant reaches Ψl more negative than turgor loss point (Ψtlp). C, The percentage contribution to stomatal closure that was caused by foliar ABA level increases in a drought-stressed plant beyond 6 d of water withholding and remains high until death beyond 21 d.