Benzoic acid regulates the physio-biochemical responses of chia (Salvia hispanica L.) seedlings under salinity stress
ENGLISH Plant immobility renders plants constantly susceptible to various abiotic and biotic stresses. These stresses generate reactive oxygen species (ROS), which cause cellular damage through osmotic or oxidative stress, ultimately constraining agricultural productivity worldwide. To mitigate the challenges caused by these stresses, plants have evolved a variety of adaptive strategies, including the secretion of phenolic acids in response to environmental stresses. Phenolic acids can be categorised into different subclasses based on their chemical structures, such as hydroxybenzoic acids and hydroxycinnamic acids. Among them, benzoic acid (B.A) serves as a signaling molecule that mediates physiological responses to various environmental stresses and enhances stress tolerance. This study investigated the effects of exogenously applied B.A on chia during germination and plant growth under salinity stress. Chia seeds were exposed to varying concentrations of sodium chloride (10–400 mM NaCI) and benzoic acid (10–400 μM) to determine the optimal conditions for plant growth promotion and salinity stress mitigation. Plant growth parameters such as shoot and root lengths, fresh and dry weights, relative water content, and leaf area were measured. Essential macronutrients were analyzed using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Significant differences (p < 0.05) were observed with increasing NaCl concentration. Supplementing B.A to 100 mM NaCl improved plant performance (p < 0.05) compared to salinity stress (100 mM NaCl) alone. Exogenous application of B.A alleviated osmotic stress-induced damage by reducing superoxide anion (O₂˙⁻) levels, altering total phenolic content (TPC) and total flavonoid content (TFC), and preventing the increase in cell death, observed under 100 mM NaCl. These results suggest that exogenously applied benzoic acid enhances chia tolerance to osmotic stress by scavenging O₂˙⁻, preventing lipid peroxidation, and protecting against cell death. Furthermore, B.A application increased total phenolic and flavonoid content (p < 0.05), enhancing antioxidant defence and maintaining higher levels of essential ions such as potassium (K), magnesium (Mg), and calcium (Ca), which are crucial for salinity (NaCI) tolerance. ISIZULU ISIFINYEZO Ukunganyakazi kwezitshalo kubenza bahlale bebhekene nezinsongo ezihlukahlukene ezibangelwa yisimo sezulu noma izinto eziphilayo. Lezi zinsongo zaziwa ngokuthi zikhiqiza ama-reactive oxygen species (ROS), okuyizakhi ezidala ukusabela okwesibili kwamangqamuzana (ukucindezeleka kwe-osmotic noma i-oxidative), okudala izinselelo ezinkulu ekukhiqizeni ezolimo emhlabeni jikelele. Ukuze zilwe nalezi zinkinga ezibangelwa izinsongo, izitshalo zithuthukise amasu ahlukahlukene okuvikelwa. Ama-phenolic acids ayingxenye ebalulekile yala masu, njengoba aziwa kakhulu ngokuthi akhishwa izitshalo uma zibhekene nezinsongo ezibangelwa yisimo sezulu noma izinto eziphilayo. Ama-phenolic acids angahlukaniswa abe izigaba ezahlukene ngokuya ngesakhiwo samakhemikhali awo, njenge-hydroxybenzoic acids kanye ne-hydroxycinnamic acids. I-Benzoic acid (B.A) iyisikhuthazi sokuxhumana kwezitshalo esithinta ukusabela ngokomzimba kwezitshalo ezimeni ezahlukene zezinsongo zemvelo futhi ithuthukise ukumelana nezinsongo. Lolu cwaningo luhlolisise umphumela we-B.A esetshenziswa ngaphandle ezitshalweni ze-chia ngesikhathi sokuhluma kanye nokukhula kwezitshalo ngaphansi kwezimo zokucindezeleka kwesawoti. Imbewu ye-chia yahlolisiswa ngokuthi ibekwe ezingeni elihlukahlukene le-sodium chloride (10–400 mM NaCl) kanye ne-Benzoic acid (10–400 μM) ukuze kutholakale izimo ezinhle kakhulu zokukhula kwezitshalo nokumelana nokucindezeleka kwesawoti. Izinkomba zokukhula kwezitshalo ezifana nobude besiqu nempande, izisindo ezimanzi nezomile, okuqukethwe kwamanzi okuhlobene, kanye nendawo yamahlamvu kwalinganiswa. Ama-macronutrients abalulekile ahlaziywa kusetshenziswa i-Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Kutholakale umehluko obalulekile (p<0.05) lapho kuqina amazinga e-NaCl. Ukwenezelwa kwe-B.A ku-100 mM NaCl kuthuthukise ukusebenza kwezitshalo (p<0.05) uma kuqhathaniswa nokucindezeleka kwesawoti kuphela (100 mM NaCl). Ukwenezelwa kwe-B.A kwangaphandle kwehlise umonakalo odalwa ukucindezeleka kwe-osmotic ngokunciphisa amazinga e-superoxide anion (O₂˙⁻), ukushintsha okuqukethwe kwe-total phenolic (TPC), okuqukethwe kwe-total flavonoid (TFC), nokufa kwamangqamuzana, okwakhuphuka ngaphansi kwe-100 mM NaCl. Le mibiko ibonisa ukuthi i-Benzoic acid esetshenziswa ngaphandle ithuthukisa ukumelana kwe-chia nokucindezeleka kwe-osmotic ngokukhipha i-O₂˙⁻, ukuvimbela i-lipid peroxidation, kanye nokuvikela ekuqothulweni kwamangqamuzana. Ngaphezu kwalokho, lolu cwaningo lwabonisa ukuthi ukusetshenziswa kwe-B.A kwandisa okuqukethwe kwe-total phenolic kanye ne-flavonoid (p<0.05), kuthuthukise ukuzivikela kwe-antioxidant futhi kwagcina amazinga aphezulu wezinsimbi ezibalulekile ezifana ne-potassium (K), magnesium (Mg), kanye ne-calcium (Ca), ezibalulekile ekumelaneni nesawoti (NaCl).
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