Investigation on Allelopathic Effects of Khat Leaves Residues and Alleviative Effects of Salicylic Acid in Wheat Roots

Abstract

Allelopathic effects of khat leaves residues (25 and 50 g) and alleviative effects of salicylic acid (0.5 mM) in wheat roots were carefully investigated in this study. Khat leaves residues stimulated hydrogen peroxide (H 2 O 2), lipid peroxidation, ascorbate (ASA), glutathione (GHS) and non-proteinthiol (NPT) contents. Salicylic acid (SA) was found to inhibit the stimulatory role of khat leaves residues on the production of H 2 O 2 and lipid peroxidation in roots of wheat plants. On the other hand, SA increased ASA, GSH and NPT contents. Catalase (CAT) and ascrobate peroxide (APX) activities were increased significantly in plants growing in soil amended with khat leaves residues, while the activity of peroxidase (POD) was slightly decreased. SA additively inhibited the stimulatory effect of khat leaves residues on CAT and APX activities. In addition, the applied SA increased POD activity. Residues of khat leaves in the soil showed an inhibitory effect on pectin and cellulose fractions of roots. However, hemicellulose content of roots was stimulated. Soaking wheat caryopses in SA counteracted partially or completely the adverse effect of khat leaves residues on pectin and cellulose composition. Furthermore, the data clearly demonstrated the capability of SA treatment in retarding the stimulatory role of khat leaves residues on the production of hemicellulose in roots of wheat plants.