Evaluation of the Potential Use of a Collagen-Based Protein Hydrolysate as a Plant Multi-Stress Protectant

Protein hydrolysates (PHs) are a class of plant biostimulants used in the agricultural practice to improve crop performance. In this study, we have assessed the capacity of a commercial PH derived from bovine collagen to mitigate drought, hypoxic, and Fe deficiency stress in Zea mays. As for the drought and hypoxic stresses, hydroponically grown plants treated with the PH exhibited an increased growth and absorption area of the roots compared with those treated with inorganic nitrogen. In the case of Fe deficiency, plants supplied with the PH mixed with FeCl₃ showed a faster recovery from deficiency compared to plants supplied with FeCl₃ alone or with FeEDTA, resulting in higher SPAD values, a greater concentration of Fe in the leaves and modulation in the expression of genes related to Fe. Moreover, through the analysis of circular dichroism spectra, we assessed that the PH interacts with Fe in a dose-dependent manner. Various hypothesis about the mechanisms of action of the collagen-based PH as stress protectant particularly in Fe-deficiency, are discussed.

Dynamic role of iron supply in amelioration of cadmium stress by modulating antioxidative pathways and peroxidase enzymes in mungbean

Iron deficiency and cadmium (Cd) stress causes a rapid change in plant physiology. The aim of this work was to characterize the effects of Fe supplementation on redox reactions in leguminous plants under Cd toxicity. The experiments were performed in hydroponic nutrient media, using mungbean grown under 300 µM cadmium chloride with or without Fe for 10 days. The Fe concentration in plants grown under Fe deficiency was reduced by the presence of Cd; however, it recovered to control levels after Fe was supplied. Similarly, a very high Cd concentration was observed in plants grown under Fe deficiency in the presence of Cd toxicity but when Fe was supplied the Cd concentration decreased. After 5 days of Fe deficiency, the activities of antioxidant enzymes (superoxide dismutase, catalase, and glutathione reductase and ascorbate peroxidase) were significantly higher than in plants supplied with Fe in the absence or presence of Cd. However, after 10 days of Fe deficiency, these enzyme activities were severely decreased in the presence of Cd toxicity but increased when Fe was present. The activities of other peroxidase enzymes such as guaiacol peroxidase, syringaldazine peroxidase, polyphenol oxidase and benzidine peroxidase decreased after 10 days under Cd toxicity and were further reduced in the absence of Fe. Furthermore, the level of reduced glutathione and oxidized glutathione increased for the first 5 days under Cd toxicity under Fe deficiency but was reduced after Fe was supplied to Cd-treated plants. The data indicate that supply of Fe contributes to the alleviation of Cd toxicity in redox reaction pathways in mungbean plants.