TABLE 1.

A spectrum of compounds that accumulate in plant cells along with ABA during biotic/abiotic stress and can promote stomatal closure.

Hormone/compound	Type of stress	References	Reason of closure
ABA	Drought, cold, salinity and heat	Nakashima et al., 2014	Increased ABA levels
Allyl isothiocyanate (AITC)	Wounding, insect, herbivore (biotic)	Khokon M.A. et al., 2011	Production of ROS and NO. elevated Ca2+ levels
Ethylene (ET)	Drought, ozone	Wilkinson and Davies, 2010	Mediated H2O2 production in ABA signaling
Hydrogen sulfide (H2S)	Drought	Jin et al., 2013	H2S affected ABA responses and ABA increased H2S levels
Inositol 1,4,5-trisphosphate (IP3)	Drought and salt stress	Jia et al., 2019	Stimulated Ca2+ release in the cell and ABA responses
Methyl jasmonate (MJ)	Wounding (biotic)	Förster et al., 2019	Signaling events overlap with ABA action
	Pathogen, insects (biotic)	Verma et al., 2016	Marked interaction with ABA and SA
Phosphatidic acid (PA)	Heavy metal (Arsenic) stress	Armendariz et al., 2016	Induced accumulation of PLD and PA, are due to ABA
Polyamines (PAs)	Drought	Adamipour et al., 2020	ROS and NO production. ABA caused accumulation of PAs
	PEG-induced osmotic stress, chilling	Pál et al., 2018	Increased PAs stimulated ABA accumulation
Proline and G-substances	Drought	Raghavendra and Reddy, 1987	Decreased proton efflux and K+ content, as in case of ABA
Salicylic acid (SA)	Bacterial invasion (biotic)	Melotto et al., 2006	SA-action overlapped with ABA signaling
Sphingosine-1-phosphate (S1P)	Drought	Ng et al., 2001	Mobilized Ca2+ and mediated stomatal closure by ABA
Strigolactone (SL)	Drought and salt stress	Ha et al., 2014	ABA and SL cross-talk positively regulated stomatal closure
Sulfate (in xylem sap)	Drought	Malcheska et al., 2017	Promoted ABA synthesis in guard cell

The compounds are arranged in alphabetical order. The abbreviations are listed in the Appendix (last page).