Foliar spraying of pig blood-derived protein hydrolysates increases growth and quality of cherry tomato

  Objectives  We studied the effects of pig blood-derived protein hydrolysate (PP) on the growth and quality of cherry tomato.

  Methods  Pot culture method was used in the research, and cherry tomato cultivar “Potted Red” was the test material. PP concentrations of 1 and 2 g/L were used as treatments and distilled water was used as control (CK). During flowering period, PP was foliar sprayed six times with intervals of 7 days. The growth, photosynthesis, and nutritional and antioxidant quality of cherry tomato were analyzed after the third spike of fruit was harvested at full maturity.

  Results  PP applications increased N, P, and K content in tomato shoot, roots, and fruits; significantly increased chlorophyll content, net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) of tomato leaves; PP1 and PP2 increased shoot fresh weight by 18.2% and 40.6%, and shoot dry weight by 42.3% and 57.4%, respectively, compared with CK. Compared with CK treatment, PP2 exhibited better effect than PP1. Compared with CK, PP2 treatment significantly increased yield per plant, individual fruit weight, the transverse and longitudinal diameter, and fruit firmness by 37.4%, 26.6%, 16.3%, 10.3%, and 30.8%, respectively, thus effectively improved appearance quality of cherry tomatoes. PP treatments improved the content of soluble sugar, soluble protein, ascorbic acid and glutathione in fruits by 24.2%, 25.5%, 96.6%, and 30.9%, respectively, compared with CK. PP2 treatment also significantly promoted the accumulation of total phenol, flavonoid, and anthocyanin content by 18.7%, 33.3% and 56.2%, respectively, and enhanced the DPPH free radical scavenging capacity and ferric reducing antioxidant power by 27.7% and 29.4%, respectively, which significantly improved the antioxidant activity of tomato fruits.

  Conclusions  Foliar application of PP can effectively improve photosynthesis and nutrient content of tomato plants, which in turn promotes plant growth and quality, fruit yield, and nutritional quality of cherry tomatoes.