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.
Highlights
The growing demand for food, feed, fuel, fiber, and raw materials and the increasing resource depletion and ecosystem degradation impose the use of more sustainable methods in the agriculture production systems
The auxin-like activity was checked by evaluating the effect of the protein hydrolysate on the corn coleoptile elongation rate which is a typical bioassay for auxins (Audus, 1972)
The application of 1.75 mg/L of inodole-3-acetic acid (IAA) led to an increase of 272% in coleoptile elongation rate when compared to the control
Summary
The growing demand for food, feed, fuel, fiber, and raw materials and the increasing resource depletion and ecosystem degradation impose the use of more sustainable methods in the agriculture production systems. Many studies (MoralesPayan and Stall, 2003; Parrado et al, 2007; Kowalczyk et al, 2008; Ertani et al, 2009; Gurav and Jadhav, 2013) reported beneficial effects of soil and foliar protein hydrolysates applications on growth, yield and fruit quality of agricultural crops (e.g., corn, banana, papaya, strawberry, red grape). Cerdán et al (2009) and Ertani et al (2009) observed that applications of plantderived protein hydrolysates on corn and tomato plants increased nutrient uptake in particular nitrogen and iron as a result of increased nitrate reductase and glutamine synthetase activities, and Fe(III)-chelate reductase activity, respectively. Protein hydrolysates can improve crop tolerance to abiotic stresses as reported by Ertani et al (2013) who observed that root applications of a plant derived-protein hydrolysate improved salinity tolerance of corn due to a better nitrogen metabolism, and an higher K/Na ratio and proline accumulation in leaves
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