PHYSIOLOGICAL AND BIOCHEMICAL DEFENSE REACTIONS OF ARABIDOPSIS THALIANA TO PHELIPANCHE RAMOSA INFECTION AND SALT STRESS.

The effects of salinity stress on growth parameters and the activities of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), glutathione reductase (GR), and ascorbate peroxidase (APX)) were investigated in Arabidopsis thaliana during Phelipanche ramosa mediated biotic stress. The experiment was conducted using 100 mM NaCl on infected 18-dayold A. thaliana plants in Gamborg B5 medium. P. ramosa infection reduced root length and shoot dry weight (DW) in A. thaliana. After salt stress treatment shoot fresh weight (FW) decreased in A. thaliana plants infected with P. ramosa. Salt stress treatment produced a significant reduction in carotenoid and total chlorophyll content while it did not change the chl a/b ratio of infected plants. POX and APX activities increased during P. ramosa infection in A. thaliana. Additional NaCl treatment decreased the level of lipid peroxidation accompanied by an increment in SOD, POX, GR, CAT and APX activities, while chl a/b ratio and total chl content decreased. These results, presented for the first time, demonstrated induction of the antioxidant defense system against P. ramosa infection by NaCl treatment in A. thaliana. [ABSTRACT FROM AUTHOR]