Coating seeds with purified-hydrocolloids extracted from conventional activated sludge affects the growth physiology of wheat under gradient salt stress

With continuous innovations in wastewater treatment technology, the use of excess sludge has become a research focus. Purified-hydrocolloids obtained from aerobic granular sludge (AGS) and conventional activated sludge (CAS) have many practical applications, including waterproofing, adsorption, flame retardance, slow-release properties, and seed coating. In this study, purified-hydrocolloids extracted from CAS was used as a new seed coating, which was uniformly sprayed onto the surface of wheat seeds. Purified-hydrocolloids was most effective in resisting salt stress in wheat seedlings at a NaCl concentration of 125 mmol/L (soil salinity 2.74 g/Kg). The germination percentage, plant height, K+/Na+ ratio, soluble sugar and soluble protein contents of purified-hydrocolloids-coated seeds increased by 13.33 %, 46.32 %, 37.25 %, 8.89 %, and 36.22 %, respectively, compared with wheat seeds without purified-hydrocolloids coating. Inhibition of O2− production activity and malondialdehyde content was reduced by 38.62 % and 48.00 %, respectively. Therefore, the purified-hydrocolloids coating had a mitigating effect on wheat seed germination and seedling growth in salt-stressed environments, and this application would be beneficial to the use of saline soil resources and the improvement of ecosystems in coastal areas.