Seaweed-Derived Bio-Stimulant (Kelpak®) Enhanced the Morphophysiological, Biochemical, and Nutritional Quality of Salt-Stressed Spinach (Spinacia oleracea L.)

Biostimulants such as seaweed extracts are emerging as crop management products that can enhance crop productivity and nutritional quality under abiotic stress conditions. Therefore, this study aimed to assess the effectiveness of a seaweed-derived biostimulant (Kelpak®) in alleviating salinity stress in spinach. A greenhouse experiment which consisted of five treatments (T1 = Control plants (no NaCl or seaweed extract (SWE), T2 = plants subjected to 300 mM NaCl without SWE, T3 = 300 mM NaCl + 1% dilution of SWE, T4 = 300 mM NaCl + 2.5% dilution of SWE, and T5 = 300 mM NaCl + 5% dilution of SWE) was conducted. The results showed that salinity without the addition of SWE reduced crop growth, relative water content, chlorophyll, and nutritional quality. Similarly, salinity induced severe oxidative stress, indicated by excessive amounts of superoxide radicals, malondialdehyde and the upregulation of catalase, peroxidase, polyphenols, and flavonoids. Interestingly, plants treated with 5% SWE displayed a substantial enhancement in crop performance, reduction in oxidative stress, and improved nutritional quality, characterised by considerable amounts of minerals, proximate constituents, and vitamins. These results support the use of seaweed extract (Kelpak®) as a biostimulant in enhancing growth and nutritional quality of spinach under saline cultivation.