Utilization of protein hydrolysates to enhance growth and productivity of tomato under soilless cultivation systems

The objective of this study is to examine the potential of utilizing protein hydrolysate as a plant activator. This study investigated the use of protein hydrolysate (PH) obtained from rainbow trout ( Oncorhynchus mykiss ) fish waste as a bioactivator in soilless tomato cultivation. PH applications were applied to roots and leaves at different doses (0, 0.2, 0.4 and 0.8 g/L) in order to determine their effects on yield and fruit quality of tomatoes. In general, it was determined that hydrolysate applications increased plant growth, development, and physiological parameters compared to control plants. In the study, the highest SSC (3.98%) and anthocyanin (0.19 g cyn-3-gluc kg − 1 ) contents in tomato fruits were determined in the control treatment. The highest chlorophyll content (CCI), stomatal conductance (797.2 mmol m − 2 s − 1 ), photosynthesis rate (39.3µmol m − 2 s − 1 ) and plant nutrient content were determined at the 0.2 g/L dose. The highest APX, MDA and Proline values in leaves were determined at the 0.4 g/L dose application as 50.4 mmol, 0.010 nmol g − 1 and 0.21 mg/g, respectively. The highest average fruit weight (114.3 g), lycopene (34.4), and CAT (0.71 Ug −1 min − 1 ) enzyme activity in leaves were determined from the 0.8 g/L PH application dose. Protein hydrolyzate applications significantly contributed to tomato yield, quality, plant physiology, fruit nutrient content and enzyme activity. Yield and profitability increased with PH doses of 0.4 and 0.2 g/L, respectively. The findings suggest that the foliar application method plays a supportive role in maintaining the plants’ physiological homeostasis under standard greenhouse cultivation.