A transgenic barley line(LSY-11-1-1) with overexpressed Phalaris coerulescens thioredoxin gene(PTrx) was employed to measure the growth,protein oxidation,cell viability,and antioxidase activity in barley roots during germination on the presence of 2 mmol/L AlCl3 on filter paper.The results show that(1) compared with the non-transgenic barley,LSY-11-1-1 had enhanced root growth,although both were seriously inhibited after AlCl3 treatment;(2) the degree of protein oxidation and loss of cell viability in roots of LSY-11-1-1 were much less than those in roots of non-transgenic barley,as reflected by lower contents of protein carbonyl and Evans blue uptakes in LSY-11-1-1;(3) activities of catalase(CAT) ,glutathione peroxidase(GPX) ,ascorbate peroxidase(APX) ,and glu-tathione reductase(GR) in LSY-11-1-1 root tips were generally higher than those in non-transgenic barley root tips,although these antioxidase activities gave a rise to different degrees in both LSY-11-1-1 and non-transgenic barley under aluminum stress.These results indicate that overexpressing PTrx could efficiently protect barley roots from oxidative injury by increasing antioxidase activity,thereby quenching ROS caused by AlCl3 during germination.These properties raise the possibility that transgenic barley with overexpressed PTrx may be used to reduce the aluminum toxicity in acid soils. A transgenic barley line (LSY-11-1-1) with overexpressed Phalaris coerulescens thioredoxin gene (PTrx) was employed to measure the growth, protein oxidation, cell viability, and antioxidant activity in barley roots during germination on the presence of 2 mmol / L AlCl3 on filter paper. The results show that (1) compared with the non-transgenic barley, LSY-11-1-1 had enhanced root growth, although both were severely inhibited after AlCl3 treatment; (2) the degree of protein oxidation and loss of cell viability in roots of LSY-11-1-1 were much less than those in roots of non-transgenic barley, as reflected by lower contents of protein carbonyl and Evans blue uptakes in LSY-11-1-1; ( 3) activities of catalase (CAT), glutathione peroxidase (GPX), ascorbate peroxidase (APX), and glu-tathione reductase (GR) in LSY-11-1-1 root tips were generally higher than those in non-transgenic barley root tips, although these antioxidase activities gave a rise to different degrees in both LSY-11-1-1 and non-transgenic barl ey under aluminum stress. this results in that overexpressing PTrx could efficiently protect barley roots from oxidative injury by increasing antioxidant activity, thereby quenching ROS caused by AlCl3 during germination. These properties raise the possibility that transgenic barley with overexpressed PTrx may be used to reduce the aluminum toxicity in acid soils.