The Effect of Plant Metabolism on Some Physiological Immune Responses Under Biotic Stress

Abstract

Abstract This work is part of a larger research project studying the immune responses of a variety of plants. Once image-based (unpublished data) and another time, as in this study, biochemical parameters based. Plant models included three metabolically different plants, Vica faba L. (C3), Zea mays L. (C4), Mesembryanthemum L. (CAM). Pathogen models had Alternaria alternate and Pseudomonas syringe. All of which, along with the control treatment, represent nine plant-pathogen systems applied with three replicates of each studied species. To investigate the extent to which the immune response is transferred from infected leaves to uninfected leaves on the same plant, several physiological and biochemical immune responses were examined, including: two plant hormones, abscisic acid and Salicylic acid, and two active enzymes, Catalase enzyme and Peroxidase enzyme, two free radicals, ROS and H2O2. Results show that The studied hormones were significantly affected by the type of plant metabolism and the type of pathogen, sometimes by an increase and sometimes by a decrease in which ABA and SA increased in C3 and CAM plants when infected by Alternaria and varied when infected by pseudomonas syringe. At the same time, both ABA and SA decrease in C4 plants. The studied enzymes did not follow a specific pattern of increasing and decreasing response to a bacterial or fungal infection. Still, they differed significantly between plants of different metabolism according to the type of pathogen causing the infection. Infection of all three studied plants by Alternaria alternate and Pseudomonas syringae did not cause any significant changes at p≤ 0.05 in the free radical production of the leaves for both ROS and H2O2.