Cd significantly inhibited the growth of both rice cultivars. The Tainung 67 cultivar is more tolerant to Cd than Taichung 1 cultivar after 48 h incubation in CdCl2 solution. The Cd tolerant cultivar¡XTainung 67¡¦s PODs in roots might synthesize more lignin in Cd-treatments. Meanwhile, the decrease of H2O2 levels is accompanied with the enhancement of POD activity in Cd-treated tissues. PODs here might also remove excess H2O2, thus serving detoxifying role and synthesizing more lignin for protection. In Taichung 1 cultivar, the accumulation of H2O2 in Cd-treated tissues could be due to the less amount of POD enhancement induced by Cd. In response to Cd treatment, the Taichung 1 cultivar also synthesizes little lignin, and therefore is Cd-sensitive.

In our investigation, fully expanded tobacco leaves were used to study the hypersensitive response caused by the inoculation of INF1 purified from E. coli strains DH5£\

The adverse effect of Cu on growth is apparent from the reduction in root length of the Cu-treated Arabidopsis roots. Arabidopsis seems to be more resistant to Cu in comparison with that of soybean in terms of root growth. The increase of the levels of H2O2 was observed in Cu-treated Arabidopsis roots. The lignin biosynthesis related enzymes, PODs and laccases were enhanced during the Cu treatments. The lignin contents slightly increased in Cu-treated Arabidopsis roots. To our surprise, the Arabidopsis can be tolerant to high concentration of Cu (200 µM), because only part of high levels of H2O2 accumulated in Cu-treated tissues are used by PODs to synthesize the lignin.

Copper-treated rice seeding (Oryza sativa cv. Tainung 67 and Taichung native 1) showed significant inhibition in rice root growth, and an enhancement in POD activity. POD within Tainung 67 rice roots might synthesize more lignin in Cu-treated tissue. Meanwhile, the decrease of H2O2 levels is accompanied with the enhancement of POD activity in Cu-treated tissues. The increase in POD activity induced by Cu might remove excess hydrogen peroxide serving a detoxifying role and synthesizing more lignin for protection. In Taichung native 1 rice cultivar, high amounts of H2O2 accumulated in Cu-treated tissues could be due to the less amounts of POD induced by Cu. In response to Cu treatment, the Taichung native 1 cultivar also synthesizes a little lignin, and is more Cu-sensitive. Therefore, The Tainung 67 cultivar is more tolerant to Cu than Taichung native 1.

Cadmium-treated rice seeding (Oryza sativa L. cv. Taichung Native 1 and O. sativa L. cv. Tainung 67) showed inhibition in the growth of rice roots or leaves, and an enhancement in POX activity. In Tainung 67 cultivar, Cd treatment may have influence over cis-regulatory elements in POX promoter region and enhanced transcription of POX or enhance glycosylation of POX. The increase in POX activity induced by Cd might remove excess hydrogen peroxide serving a detoxifying role and synthesizing more lignin for protection. In Taichung Native 1 cultivar, high amounts of H2O2 accumulated in Cd-treated tissues could be due to the less amounts of POX induced by Cd. In response to Cd treatment, the Taichung Native 1 cultivar also synthesizes a little lignin, and is more Cd-sensitive. Therefore, the Tainung 67 cultivar is more tolerant to Cd than Taichung Native 1.

The adverse effect of Cd on growth is apparent from the reduction in root length of the Cd-treated Arabidopsis thaliana roots. The increase of the levels of H2O2 was observed in Cd-treated A. thaliana roots. The lignin biosynthesis related enzymes, POXs and laccases were enhanced during the Cd treatments. The lignin contents slightly increased in Cd-treated A. thaliana roots¡]48 h¡^. The A. thaliana can be tolerant to high concentration of Cd (500 µM), and only part of high levels of H2O2 accumulated in Cd-treated tissues are used by POXs to synthesize the lignin.

The adverse effect of Zn on growth is apparent from the reduction in root length of the Zn-treated Arabidopsis roots. The levels of H2O2 were increased rapidly in Zn-treated Arabidopsis roots. The lignin biosynthesis realated enzymes, peroxidases and laccases were enhanced during the Zn treatments. The lignin contents increased in Zn-treated Arabidopsis roots. Arabidopsis can be tolerant to high concentration of Zn (4 mM), because part of high levels of H2O2 accumulated in Zn-treated tissues are utilized by peroxidases to synthesize the lignin.

Abstract The significant root growth inhibition in zinc-treated soybean (Glycine max) seedling correlated with the increase of PODs and laccases activity. The increase of the activities of PODs (pI 8.3, pI 7.7, pI 4.8, pI 4.4 and pI 3.7) and laccases (pI 9.4, pI 8.3, pI 7.4, and pI 3.7) are accompanied by a rise of lignin contents in Zn-treated tissues. Our results suggested that laccases work during the early stage of Zn treatment. Laccases and peroxidases work cooperatively in lignin synthesis when the time of Zn treatment was prolonged.

Aluminum-treated rice seeding (Oryza sativa L. cv. Taichung Native 1 and O. sativa L. cv. Tainung 67) showed significant inhibition in rice root growth, and an enhancement of POX activity. In Tainung 67 cultivar rice synthesizes more lignin in Al-treated tissue. Meanwhile, the decrease of H2O2 levels is accompanied with the enhancement of POX activity in Al-treated tissue. The increase in POX activity induced by Al might remove excess hydrogen peroxide serving a detoxifying role and synthesizing more lignin for protection. In Taichung native 1 cultivar, high amounts of H2O2 accumulated in Al-treated tissues could be due to the less amounts of POX induced by Al. In response to Al treatment, the Taichung native 1 cultivar synthesizes less lignin in comparison with that of Tainung 67, and is more Al-less tolerant. Therefore, the Tainung 67 cultivar is more tolerant to Al than Taichung native 1.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 156-165). Also available on the World Wide Web.