Table III. Summary of evidence for and against the declines in leaf water potential (Ψ_leaf), turgor potential (Ψ_P), solute potential (Ψ_S), or RWC or cell volume as drivers of ABA accumulation in previous studies, and whether the putative driver is supported as important for ABA accumulation in studies using externally applied pressure, as analyzed in Table II.

Cell Behavior during Dehydration Potentially Driving ABA Accumulation	Correlative Evidence for a Role in Driving ABA Accumulation	Evidence against a Role in Driving ABA Accumulation	Supported by Observed Effect of External Pressure on ABA Accumulation?
1. Leaf water potential decline	Correlation with ABA production in dehydrating leavesa	Weak relation with ABA production in dehydrating leavesa	No: Ψleaf is 0 for the treated leaves
2. Turgor pressure decline	Correlation with ABA production in dehydrating leavesa	–	No: ΨP increased in the treatmentb,c; this itself should not cause ABA accumulationc
3. Solute potential decline	–	Weak relation with ABA production in dehydrating leavesa	Potentially: ΨS declined in the treatmentb
		No relation to ABA production in leaf samples floated on solute solutionsd
4. Relative water content or cell volume decline	Correlation with ABA production in dehydrating leavesa	–	Yes: Increase of ABA coincided with RWC decline in four studiesb,c

^aPierce and Raschke (1980) and references therein.

^bOur analysis of data of McAdam and Brodribb (2016); Sussmilch et al. (2017; Table I).

^cAckerson and Radin (1983); Jia et al. (2001).

^dCreelman and Zeevaart (1985); Jia et al. (2001).