Potential of natural stimulants and spirulina algae extracts on Cape gooseberry plant: A study on functional properties and enzymatic activity

The need to discover new strategy to enhance agricultural productivity while minimizing negative effects on cultivation system is the driving force behind much novel research. Little is known about the use of natural growth promoters, in combination with Spirulina algae extract (Sae), on plants' quality and quantity characteristics. This can be an effective strategy to reduce the impact of environmental stress on plants. The aim of this study was to investigate the effects of natural growth promoters in combination with Sae on the functional properties and enzymatic activity of Cape gooseberry plants. For this purpose, natural growth stimulants, Kitoplus® and Azotobacter, were foliar applied to plants in a completely randomized factorial design under greenhouse conditions, with varying concentrations of Sae. Results indicated that the use of Sae in conjunction with natural growth promoters had a significant impact on increasing the yield of Cape gooseberry plants. The study found that using Kitoplus® and Spirulina extract at a concentration of 0.5% increased the yield of Cape gooseberry plants by 35.82% compared to control plants, with a yield of 310.43 g per plant. The leaves of Physalis plants treated with 0.5% Kitoplus®, Azotobacter biofertilizer, and Sae had the highest amount of chlorophyll, which was observed to be 46.2%, 40.1%, and 32.3% higher than that of control, respectively. Exposure to Kitoplus® (0.5%) and Azotobacter biofertilizer (0.5%) resulted in the highest percentage (25.49%) of dry to fresh weight ratio (DF) per fruit in the plant. Additionally, plants treated with Kitoplus® at 0.5% in combination with Azotobacter (0.5%) and Sae (0.5%) showed a 14.83% increase in vitamin C (VITC) levels compared to control plants. The highest levels of total antioxidant content (73.8%) and total carbohydrate content were obtained from plants treated with Spirulina algae extract spray at a concentration of 0.5% in the presence of Kitoplus® and Azotobacter. Results also showed that the highest activity of peroxidase (POD) (by 43.5% and 38.8%) and ascorbate peroxidase (APX) (by 29.1% and 28.4%) enzymes was observed in plants sprayed with natural growth promoters in the presence of Spirulina algae extract at concentrations of 0.25% and 0.5%, respectively. Overall, this research opens the possibility of utilizing foliar spray of effective biostimulants in combination with Sae to improve the quantity and quality of Cape gooseberry plants. Implementing this simple, safe, eco-friendly, and low-cost management tool can result in nutritionally rich fruit that benefits the consumer at little or no additional cost.