Table 2.

Examples of protein hydrolysates from different fish and animal sources and their application as plant biostimulants.

Source	Plant	Growth Media	Method of Application	Bioactive Compounds	Biostimulant Activity	Reference
Fish-derived protein hydrolysate	Lettuce	Field soil	Exogenous (during watering)	Peptides, amino acids	Increased leaf number and root biomass Enhanced chlorophyll content, photosynthetic rate	[42]
Commercial amino acids preparation	Lettuce	Field soil	Foliar	Glycine and glutamine	Increased yield, leaf chlorophyll and vitamin C content	[54]
Meat flour protein hydrolysate	Maize	Hoagland solution	Seedlings immersed in solution	Small peptides and amino acids	Stimulation of root and leaf biomass Induced nitrate conversion to organic nitrogen Stimulate efficient nutrient utilization by plants	[47]
Commercial preparation of chicken feather hydrolysate	Wheat	Field soil	Foliar	Short peptides and amino acids	Increased yield and nutrient content of grains	[45]
Chicken feather hydrolysates	Maize	Field soil	Foliar	Peptides and amino acids	Increased micro- and macronutrient concentration of leaves Increased yield and grain protein content	[55]
Commercial amino acid preparation	Coriander	Hoagland nutrient solution	Dissolved into growth media	Glycine	Increased growth of roots and shoots Increased micronutrient content of leaves	[56]
Fe-amino acid chelates preparation	Tomato	Nutrient solution	Dissolved into nutrient solution	Arginine, glycine and histidine	Increased uptake of Fe and improved root and shoot growth	[57]
Commercial animal-derived calcium protein hydrolysate	Rojo Brillante	Field soil	Irrigation	Peptides, amino acids and metal elements	Lower chloride uptake and reduction in leaf necrosis	[58]
Commercial animal-derived amino acids product	Tomato	Nutrient solution	Foliar and root application	Amino acids	No effects on Iron nutrition Caused severe plant depression	[59] [60]
Commercial preparation of amino acids and peptides	Passion fruit	Commercial growing medium	Foliar	Amino acids and peptides	Promotes the photosynthetic process in plants Improved transplanting successes	[61]
Animal derived gelatin	Cucumber, pepper, broccoli, tomato, arugula, and field corn	Field soil	Exogenous (adjacent to seeds)	Amino acids and peptides	Increased shoot dry weight Increased root N assimilation	[23]