Petunia Performance Under Application of Animal-Based Protein Hydrolysates: Effects on Visual Quality, Biomass, Nutrient Content, Root Morphology, and Gas Exchange

Abstract

Sustainable plant production practices have been implemented to reduce the use of synthetic fertilizers and other agrochemicals. One way to reduce fertilizer use without negatively impacting plant nutrition is to enhance crop uptake of nutrients with biostimulants. As the effectiveness of a biostimulant can depend on the origin, species, dose, and application method, the aim of this research was to evaluate the effect of a commercial animal-based protein hydrolysate (PH) biostimulant on the visual quality, biomass, macronutrient content, root morphology, and leaf gas exchange of a petunia (Petunia × hybrida Hort. “red”) under preharvest conditions. Two treatments were compared: (a) three doses of an animal-based PH biostimulant: 0 (D0 = control), 0.1 (D0.1 = normal), and 0.2 g L–1 (D0.2 = high); (b) two biostimulant application methods: foliar spray and root drenching. The dose × method interaction effect of PH biostimulant on the plants was significant in terms of quality grade and fresh and dry biomass. The high dose applied as foliar spray produced petunias with extra-grade visual quality (number of flowers per plant 161, number of leaves per plant 450, and leaf area per plant 1,487 cm2) and a total aboveground dry weight of 35 g, shoots (+91%), flowers (+230%), and leaf fresh weight (+71%). P and K contents were higher than in untreated petunias, when plants were grown with D0.2 and foliar spray. With foliar spray at the two doses, SPAD showed a linear increase (+21.6 and +41.0%) with respect to untreated plants. The dose × method interaction effect of biostimulant application was significant for root length, projected and total root surface area, and number of root tips, forks, and crossings. Concerning leaf gas exchange parameters, applying the biostimulant at both doses as foliar spray resulted in a significant improvement in net photosynthesis (D0.1: 22.9 μmol CO2 m–2 s–1 and D0.2: 22.4 μmol CO2 m–2 s–1) and stomatal conductance (D0.1: 0.42 mmol H2O m–2 s–1 and D0.2: 0.39 mmol H2O m–2 s–1) compared to control. These results indicate that application of PH biostimulant at 0.2 g L–1 as foliar spray helped to achieve extra-grade plants and that this practice can be exploited in sustainable greenhouse conditions for commercial production of petunia.

Growth of Tea Nursery Plants as Influenced by Different Rates of Protein Hydrolysate Derived from Chicken Feathers

“…In agreement with our findings, the soil application of animal-derived protein hydrolysates significantly enhanced the leaf N content by 17% in potted snapdragon [44]. In a most recent study, root drenching of animal-origin protein hydrolysates improved the leaf N and P contents of Petunia plant by 38 and 47%, respectively [55]. The root length and surface area are the key criteria determining the uptake of nutrients and water [56].…”

Effects of Protein Hydrolysate Derived from Anchovy By-Product on Plant Growth of Primrose and Root System Architecture Analysis with Machine Learning

“…These results support the potential use of PH comprising short-chain peptides and certain amino acids, such as phenylalanine, that have been reported to increase the production of endogenous auxin by functioning as signaling molecules, showing favorable effects on roots and improved vegetative growth [46,57,58]. In addition, enhancement of chlorophyll content by applying animal-derived PH has been found in corn, soybean, tomato [59], petunia [60], and chrysanthemum [54]. The mechanisms responsible for increased chlorophyll content due to protein hydrolysates remain largely unexplored [59].…”

Biostimulants induce positive changes in the radish morpho-physiology and yield

“…The use of amino acid-based biostimulants positively impacts the plants' metabolic processes and favors sustainable agriculture (Alfosea-Simón et al, 2020 ). In addition, animal-based protein hydrolysates significantly increase the gaseous exchange and chlorophyll fluorescence (Cristiano and De Lucia, 2021 ). Without chemical fertilizers, the foliar application of biostimulants, vitamins, and coenzyme Q10 significantly improves the radish root-shoot biomass under green-house conditions (Rehim et al, 2021 ).…”