Table 1.

Published scientific reports of seed priming with proline to enhance stress tolerance.

Plant	Stress	Observed Effects	Reference
Chenopodium quinoa Willd.	Low-temperature (Seeds kept at 4 °C for 20 h before sowing)	Plant growth improved by increasing the content of chlorophyll, carotenoids, proline, ascorbic acid, total free amino acids, phenols, total soluble sugars, the activity of SOD, POD and CAT and reducing MDA	Yaqoob et al., 2019 [90]
Hordeum vulgare	Salinity (0, 100 and 200 mM NaCl)	Proline treatment decreased the salinity impacts by increasing the activity of antioxidant enzymes (SOD, CAT and POX) and affecting leaf anatomy	Agami, 2014 [83]
Oryza sativa L.	Salinity (0 and 100 mM NaCl)	Rice germination, relative germination rate and, the amylase activities under stress heve been increased	Hua-long et al., 2014 [88]
Oryza sativa L.	Salinity (0, 50, 100, 150 and 200 mM NaCl)	The percentage of germination, seed vitality index, and alpha-amylase activity significantly increased	Singh et al., 2018 [85]
Triticum aestivum L.	Salinity (0 and 150 mM NaCl)	The growth and activity of the antioxidant enzyme improved, which depends in part on the plant’s ability to absorb sodium and distribute it to the roots	Shafiq et al., 2018 [86]
Vigna unguiculata L.	Cadmium (0 and 100 $\mathsf{\mu }$M cadmium chloride)	The uptake and displacement of cadmium and MDA reduced, the amount of chlorophyll, stomatal conductance, and RWC, the activity of SOD, CAT and APX increased	Sadeghipour, 2020 [12]
Zea mays L.	Drought (0 and −0.5 MPa by polyethylene glycol (PEG 6000))	Root treatment by 1 mM PRO were more effective than foliar spraying on water potential, chlorophyll content, proline level, net photosynthetic rate, transpiration rate, stomatal conductance, and sub-aperture $C{O}_2$ concentration	Demiralay et al., 2017 [87]
Zea mays L.	Salinity (0 and 100 mM NaCl)	IAA, GA3, zeatin, SOD, GPOX Activities, protein concentrations, RWC, membrane stability index increased and ABA and CAT decreased under salt stress	Rady and Hemida, 2016 [89]
Zea mays L.	Cadmium (0, 5 and 50 $\mathsf{\mu }$M Cd${}^{2+}$ ions obtained from CdCl${}_2·$2.5H${}_2$O)	Improving defensive mechanisms, like proline and sugar synthesis and increasing Cd accumulation induced by proline priming	Karalija and Selović, 2018 [84]