ABA catabolism to phaseic acid requires rehydration for
activation
The rewatering of drought stressed plants activated the catabolism of
ABA to PA (Figure 3). In the angiosperm species U. californicarewatering whole plants from a Ψl of -6 MPa, when
foliage ABA levels were the lowest of the entire drought period,
resulted in a reduction in foliage ABA levels over four days from 1.62
±0.35 µg g-1 FW to 0.297 ±0.025 µg
g-1 FW (Figure 3). This reduction in foliage ABA
levels in U. californica corresponded to an increase in foliage
PA levels from 0.42 ±0.08 µg g-1 FW to 1.08 ±0.076 µg
g-1 FW in the 24 h after rewatering (Figure 3). In the
conifer species C. rhomboidea rewatering whole plants from a
similar initial Ψl at the angiosperm U.
californica restored water status and also drove a decline in foliage
ABA levels from 0.54 ±0.15 µg g-1 FW to 0.16 ±0.03 µg
g-1 FW in 48 h (Figure 3). Like in the angiosperm
species, PA levels in C. rhomboidea increased from 0.057 ±0.03 µg
g-1 FW to 0.4 ±0.13 µg g-1 FW
(Figure 3).