Table 2.

Overview of small-molecule compounds that induce AR formation and development under stresses in plants.

Small-Molecule Compounds	Plant Species	Stress Condition	Small Signal Molecule Mediated Effects	References
NO	Cucumber	Osmotic stress	Fv/Fm, ɸPSII, qP, NPQ, SOD, CAT, and APX↑; H2O2 and O2−↓	[22]
	Marigold	Drought stress	chl (a+b) content, Fv/Fm, ɸPS II and qP, and soluble carbohydrate and protein content↑; starch content↓	[16]
	Rice	AsV stress	APX↑	[31]
H2	Cucumber	Drought stress	RWC, leaf chlorophyll content, Fv/Fm, ɸPSII and qP, SOD, POD, CAT, and APX↑	[18]
		Cd stress	DHA, GSSG, APX, DHAR, MDHAR, GR, POD, and PPO↑; MDA, H2O2, O2−, TBARS, AsA, GSH, REC, LOX, and IAAO↓	[34]
CO	Cucumber	Drought stress	leaf chlorophyll content, SOD, POD, CAT, and APX↑; RWC↓	[18]
H2O2	Marigold	Drought stress	chl (a + b) content, Fv/Fm, ɸPS II and qP, and soluble carbohydrate and protein content↑; starch content↓	[16]