Effect of different nitrogen to potassium ratios on physicochemical traits and antioxidant potential of physalis fruits (Physalis peruviana) under greenhouse conditions

Due to the high nutritional and medicinal importance of physalis fruits, this research was carried out to optimize the cultivation of this valuable plant in greenhouse conditions. In the present study, effects of different nitrogen to potassium ratios (including 1/1.25 as control, 1/1.5, 1/1.75 and 1/2) on physical parameters including fruit length, diameter, weight, and color parameters of a*, b*, L*, Chroma and hue, phytochemicals including total phenols and total flavonoid contents, as well as antioxidant activity were studied. According to the results, different ratios of nitrogen to potassium had a significant effect on studied traits. The highest fruit length (18.64 mm), fruit diameter (19.1 mm) and fruit fresh weight (4.31 g) were recorded in 1/1.75 and the lowest values for the mentioned parameters ​​were observed in treatment 1/2 of nitrogen to potassium ratio. The treatments had a positive and significant effects on a*, hue and chroma indices. The highest total phenols (253.58 mg gallic acid per 100 g fresh weight) and total flavonoids (29.5 mg quercetin in 100 g fresh weight) were recorded in the ratio of 1/2, and the highest antioxidant activity (55.58%) was observed in the ratio of 1 to 1.75 of nitrogen to potassium. The results showed that by modulating the mineral nutrient concentrations such as levels of potassium, which is a key element in plants, we can increase the productivity of greenhouse products, such as physalis.