University of Isfahan Journal of Plant Biological Sciences 3041-9603 17 4 2026 02 20 Impact of salicylic acid priming on physiological, biochemical, and photochemical responses of Zygophyllum fabago under drought and high light stress Impact of salicylic acid priming on physiological, biochemical, and photochemical responses of Zygophyllum fabago under drought and high light stress 27 46 30678 10.22108/ijpb.2026.149146.1454 FA Mahtab Alizade Department of Biology, Payame Noor University, Tehran, Iran Ghader Habibi Department of Biology, Payame Noor University, Tehran, Iran Hamid Sobhanian Department of Biology, Payame Noor University, Tehran, Iran Soheila Samadi Department of Biology, Payame Noor University, Tehran, Iran Journal Article 2026 06 02 Although salicylic acid (SA) is known to increase plant tolerance to either drought or high light (HL), its effectiveness under their simultaneous occurrence remains unclear. Here, we examined the impact of SA seed priming (50 ppm) on growth, oxidative status, and chlorophyll a fluorescence in Zygophyllum fabago L. subjected to drought (withholding water for 20 days), HL (800 μmol m⁻² s⁻¹) or their combination. All stress treatments, particularly the combined one, markedly reduced growth, whereas SA priming significantly increased shoot fresh and dry weight only under drought. Fast chlorophyll a fluorescence OJIP transients showed that drought, HL, and their combination enhanced the O–J phase, whereas SA-primed plants exhibited a slight attenuation of this rise. All stress treatments reduced phenomenological energy flux parameters and altered quantum yield for electron transport, but SA partially restored these parameters, bringing them closer to control values. The biplot of principal component analysis (PCA) indicated that under SA+Drought, higher antioxidant enzyme and phenylalanine ammonia-lyase (PAL) activities, along with increased phenolic and flavonoid contents, were key drivers of protection and growth maintenance under water stress. In contrast, under HL and combined Drought+HL, SA provided little protection, as shown by higher malondialdehyde (MDA), lower catalase (CAT) activity and maximum quantum yield of PSII (Fv/Fm ), and no recovery of shoot dry weight. Overall, our findings highlighted the stress-specific nature of SA-induced tolerance and emphasized the need to assess exogenous protectants under multifactorial stress to predict their agronomic relevance. Although salicylic acid (SA) is known to increase plant tolerance to either drought or high light (HL), its effectiveness under their simultaneous occurrence remains unclear. Here, we examined the impact of SA seed priming (50 ppm) on growth, oxidative status, and chlorophyll a fluorescence in Zygophyllum fabago L. subjected to drought (withholding water for 20 days), HL (800 μmol m⁻² s⁻¹) or their combination. All stress treatments, particularly the combined one, markedly reduced growth, whereas SA priming significantly increased shoot fresh and dry weight only under drought. Fast chlorophyll a fluorescence OJIP transients showed that drought, HL, and their combination enhanced the O–J phase, whereas SA-primed plants exhibited a slight attenuation of this rise. All stress treatments reduced phenomenological energy flux parameters and altered quantum yield for electron transport, but SA partially restored these parameters, bringing them closer to control values. The biplot of principal component analysis (PCA) indicated that under SA+Drought, higher antioxidant enzyme and phenylalanine ammonia-lyase (PAL) activities, along with increased phenolic and flavonoid contents, were key drivers of protection and growth maintenance under water stress. In contrast, under HL and combined Drought+HL, SA provided little protection, as shown by higher malondialdehyde (MDA), lower catalase (CAT) activity and maximum quantum yield of PSII (Fv/Fm ), and no recovery of shoot dry weight. Overall, our findings highlighted the stress-specific nature of SA-induced tolerance and emphasized the need to assess exogenous protectants under multifactorial stress to predict their agronomic relevance.

https://ijpb.ui.ac.ir/article_30678_1d36c819861d1ab6f0666496e5137cba.pdf