The effect of seed priming with chitosan on germination characteristics and activity of antioxidant enzymes in rice seedlings (Oryza Sativa L.) under salinity stress

In order to investigate the effect of seed priming with chitosan on germination characteristics and activity of antioxidant enzymes in rice seedlings under salinity stress, a factorial experiment was conducted in a completely randomized design with four replications at the Mohaghegh Ardabil University in 2022. Treatments included four salinity levels (0, 50, 100 and 150 mM) and four chitosan levels (0, 0.25, 0.50 and 0.75% by weight-volume, all of which were dissolved in 1% acetic acid). The results showed that salinity stress reduced germination rate (GR), germination percentage (GP), radicle, pedicel and seedling length (RL, PL and SL), radicle and pedicel fresh and dry weight (RFW, PFW, RDW and PDW), seedling length and weight vigor index (SLVI and SWVI). But, seed pretreatment with chitosan reduced the effect of salinity and improved these traits. However, the comparison of the means showed that there was a significant difference between the levels of chitosan, so that the highest number of traits obtained from the use of chitosan was 0.75%, and the lowest was obtained without chitosan. Salinity increased the Mean Germination Time (MGT), so that the highest was observed at (0.366 day) salinity of 150 mM and the lowest at 0.75% chitosan (0.101 day) and the highest allometry coefficient (AC) (0.452) was observed in priming with chitosan 25% and salinity of 150 mM. The activity of Catalase (CAT), Peroxidase (POX) and superoxide dismiotase (SOD) in priming with chitosan 0.75% and salinity of 150 mM were the application 40, 35 and 31% higher than the control (distilled water) and without salinity, respectively. Salinity also reduces the activity of the enzyme amylase. Thus, the lowest amylase (6.400 mg g-1 FW min-1) was obtained in the control (distilled water) and salinity of 150 mM. The results showed that chitosan by stimulating antioxidant enzymes and neutralizing free radicals can reduce the harmful effects of salinity stress on some traits in rice seedlings and improve seedling growth.