How can biochar and polyamine treatments mitigate salt toxicity by changing the physiological traits in garlic plants?

An experiment was conducted in 2018 to investigate the effect of polyamine and biochar treatments on physiological traits of garlic under saline conditions. Salinity increased the activities of the enzymes (2.38-166.66%), 2,2-diphenyl-1-picrylhydrazyl (DPPH) (3.72–8.32%) and 2,2^′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) (7.88–9.85%) radical scavenging activity, malondialdehyde (MDA) (32-59.15%), proline (21.39–45.29%) and soluble sugars contents (35.58–71.67%), ion leakage (22.95–62.01%) and also leaf temperature (LT) (13.18–39.37), but decreased leaf water content (LWC) (2.17–14.90%), chlorophylls (Chl a (32–45%), Chl b (26–54%) and chlorophyll index (CCI)) contents (10.67–21.78%), chlorophyll fluorescence (Fv/Fm) (9.06–16.44%) and total phenolic concentration (33.19–64.24%). Application of biochar and polyamines decreased LT, MDA and proline contents, ion leakage, soluble sugars and enzymes activities, but increased the Chl a, Chl b and CCI contents, Fv/Fm and total phenolic concentration. Also, application of biochar enhanced the LWC (1.97–3.88%) and carotenoid (6.23–14.19%) contents. Climate change had caused many threats soil ecosystem, among them, soil salinity. Salinity is one of the widespread and main challenges in the recent era that hinders environmental sustainability and global food security. Thus several strategies are suggested to mitigate this issue. In this context, biochar and polyamines are known as potent amendments able to alleviate the salt stress on the crops. Application of biochar and polyamines alleviated the harmful effects of soil salinity on physiological performance of plants such as garlic and also application of putrescine and 20% of biochar were superior treatments compared to other treatments. Our findings suggest a valuable starting point for developing crop management strategies based on biochar and polyamine applications to enhance plant performance under saline conditions and reduce freshwater dependence in agriculture.