Alone or Combined Effect of Seaweed and Humic Acid Applications on Rapeseed (Brassica napus L.) under Salinity Stress

Abstract

Organic fertilisers and biostimulants play a very important role in the germination, seedling stage, yield and quality of plants. Seaweed and humic acid are organic substances known for their positive effects. Therefore, the aim of this study was to investigate the effects of humic acid, seaweed extract and their combined applications against salt stress in oilseed rape at the seedling development stage. The effects of foliar application of seaweed extract (SW1, SW2, SW3) (0, 10, 20 mL), humic acid (HA1, HA2, HA3) (0, 10, 20 mL) and SW + HA (SW1 + HA1, SW2 + HA2, SW3 + HA3) (0, 10(5 + 5 mL L− 1 SW + HA), 20 mL L− 1 (10 + 10 mL L− 1 SW + HA)) on resistance to salt concentrations (S1, S2, S3) (0, 50, 100 mM) in oilseed rape cultivar (Elvis) under greenhouse conditions. In this study, seedling length (SL), root length (RL), total chlorophyll (Total Chl), carotenoids (Crt), electrolyte leakage (EL), malondialdehyde (MDA), superoxide dismutase (SOD), total phenolic compounds (TPC), relative water content (RWC) and proline (Pro) parameters were examined. Both applications played a significant role in reducing the negative effects of salt stress on all parameters studied. The combined application of SW + HA resulted in a remarkable increase in SL, RL TPC, SOD and RWC. In particular, the SW3 + HA3 dose played a more effective role in the antioxidant protective mechanism against stress. According to the PCA analysis, the studied parameters could be divided into 3 different groups. It was concluded that SW and HA can be evaluated as an effective natural, eco-friendly material that can be used to increase the resistance of plants to salt stress. In conclusion, in this study all applications are compared with each other, it has been determined that SW + HA is more effective application in reducing the effects of salt stress than others.