Biostimulant action of a plant-derived protein hydrolysate produced through enzymatic hydrolysis

Abstract

The aim of this study was to evaluate the biostimulant action (hormone like activity, nitrogen uptake, and growth stimulation) of a plant-derived protein hydrolysate by means of two laboratory bioassays: a corn (Zea mays L.) coleoptile elongation rate test (Experiment 1), a rooting test on tomato cuttings (Experiment 2); and two greenhouse experiments: a dwarf pea (Pisum sativum L.) growth test (Experiment 3), and a tomato (Solanum lycopersicum L.) nitrogen uptake trial (Experiment 4). Protein hydrolysate treatments of corn caused an increase in coleoptile elongation rate when compared to the control, in a dose-dependent fashion, with no significant differences between the concentrations 0.75, 1.5, and 3.0 ml/L, and inodole-3-acetic acid treatment. The auxin-like effect of the protein hydrolysate on corn has been also observed in the rooting experiment of tomato cuttings. The shoot, root dry weight, root length, and root area were significantly higher by 21, 35, 24, and 26%, respectively, in tomato treated plants with the protein hydrolysate at 6 ml/L than untreated plants. In Experiment 3, the application of the protein hydrolysate at all doses (0.375, 0.75, 1.5, and 3.0 ml/L) significantly increased the shoot length of the gibberellin-deficient dwarf pea plants by an average value of 33% in comparison with the control treatment. Increasing the concentration of the protein hydrolysate from 0 to 10 ml/L increased the total dry biomass, SPAD index, and leaf nitrogen content by 20.5, 15, and 21.5%, respectively. Thus the application of plant-derived protein hydrolysate containing amino acids and small peptides elicited a hormone-like activity, enhanced nitrogen uptake and consequently crop performances.

Keywords: SPAD index; bioassay; biostimulant; gibberellin-like activity; indole-3-acetic acid; nitrogen uptake.

FIGURE 1

Corn coleoptile elongation rate in six different solutions: four increasing concentrations (0.375, 0.75, 1.5, and 3.0 ml/L) of plant-derived protein hydrolysate “Trainer” (PH), 1.75 mg/L of inodole-3-acetic acid (IAA), and deionized water (control). Different letters indicate significant differences according to Duncan’s test (P = 0.05). Values are the means of three replicate samples.

FIGURE 2

Tomato cuttings treated with 0 (A) and 6 ml/L (B) of plant-derived protein hydrolysate “Trainer” at end of the Experiment 2.

FIGURE 3

Shoot length of normal and dwarf pea plants treated with six different solutions: four increasing concentrations (0.375, 0.75, 1.5, and 3.0 ml/L) of plant-derived protein hydrolysate “Trainer” (PH), 100 mg/L of gibberellic acid (GA₃), and deionized water (control). Dashed lines indicate shoot length of normal and dwarf pea plants in control treatment. Different letters indicate significant differences according to Duncan’s test (P = 0.05). Values are the means of four replicate samples.