Biostimulant activity of two protein hydrolysate in peroxidase and esterase activity of maize seedlings.

Two protein-hydrolysate-based fertilizers (PHFs), one from legume (LH) and one from the mixture of Spirulina spp. and alfalfa (SA), were studied chemically and biologically. LH and SA showed a different chemical composition and different degree of hydrolysis. The biostimulant activity was investigated using two specific and sensitive bioassays of auxins (IAA) and gibberellins (GA). Extracts of LH and SA elicited an auxin and gibberellin-like activity. To improve our understanding on the biostimulant activity of PHFs, LH and SA were supplied to maize plants and their effect on growth, chlorophyll and sucrose content was studied. Besides, the effect of PHFs was tested on peroxidase and esterase activity, enzymes notoriously used as markers in growth, differentiation and organogenesis- related processes. The biostimulant products increased leaf growth and induced morphological changes in root architecture similarly to growth factors. Therefore, it may be supposed that PHFs and IAA and GA can share the same properties. LH and SA positively affected peroxidase and esterase activities, suggesting their important role in the induction of growth and cell differentiation. Moreover, the addition of PHFs to plants increased chlorophyll content and decreased the level of sugars, indicating a positive influence of the PHFs on the photosynthetic process.