Change in catalase activity was examined in leaves of rice plant exposed to salinity. Depending on the method of preparation of crude protein extract from leaf and the constituents of the assay medium, a significant d...Change in catalase activity was examined in leaves of rice plant exposed to salinity. Depending on the method of preparation of crude protein extract from leaf and the constituents of the assay medium, a significant difference in enzyme activity was recorded. Inclusion of sorbitol or mannitol or sucrose in the extraction and enzyme assay medium enhanced the enzyme activity in salt-stressed samples by nearly 1.5-1.8 fold, compared to the activity found in un- stressed plants, which otherwise showed a 50% declined activity in leaf extract prepared in buffer solution and assayed in a medium depleted of these sugars. In view of the accumulation of osmolytes under saline condition, these observations suggest that the catalase activity is modulated by the osmolytes and maintains a high rate of hydrogen peroxide scavenging property in vivo and serves as the major antioxidant enzyme to scavenge the salt-induced formation of peroxide. Therefore, the salt-stress induced appearance of low activity of the enzyme under normal buffer extraction and assay conditions, as reported in literature may represent an apparent than for its real in vivo activity.展开更多
Two contrasting barley (Hordeum vulgare L.) cultivars: Kepin No.7 (salt sensitive), and Jian 4 (salt tolerant) were grown hydroponically to investigate the microdistribution of mineral ions in roots as affected by sil...Two contrasting barley (Hordeum vulgare L.) cultivars: Kepin No.7 (salt sensitive), and Jian 4 (salt tolerant) were grown hydroponically to investigate the microdistribution of mineral ions in roots as affected by silicon (Si) with respect to salt tolerance. The experiment was undertaken consisting of two treatments with 3 replicates: (i) 120 mmol·L-1 NaCI alone (referred to as Si-NaCI+), (ii) 120 mmol·L-1 NaCI + 1.0 mmol·L-1 Si (as potassium silicate) (referred to as Si+NaCI+). Plant root tips were harvested for microanalysis using an energy dispersive X-ray microanalyzer (EDX) 30 d after transplanting. Higher Cl and Na X-ray peaks were recorded in the root epidermal, cortical and stelar cells of roots for the treatment Si-NaCI+ with the majorities of Na and Cl being accumulated in epidermal and cortical cells, while relatively low K peaks were observed regardless of the barley cultivars used. By contrast, considerably higher K peaks were detected in the epidermal, cortical and stelar cells of the roots for the treatment Si+NaCI+, but lower Cl and Na peaks were also observed for this treatment with both Na and Cl ions being evenly distributed in the epidermal, cortical and stelar cells. These findings directly support our previous finding, which showed that Si depressed the uptake of sodium but enhanced the uptake of potassium by salt-stressed barley. We believe that one of the possible mechanisms involved in Si-enhancement of salt tolerance in barley is attributed to the Si-induced changes in the uptake and microdistribution of mineral ions in plants.展开更多
To identify salt stress-responsive genes, we constructed a cDNA library with the salt-tolerant rice cultivar, Lansheng. About 15000 plasmids were extracted and dotted on filters with Biomeck 2000 HDRT system or by han...To identify salt stress-responsive genes, we constructed a cDNA library with the salt-tolerant rice cultivar, Lansheng. About 15000 plasmids were extracted and dotted on filters with Biomeck 2000 HDRT system or by hand. Thirty genes were identified to display altered expression levels responding to 150 mmol/L NaCI. Among them eighteen genes were up-regulated and the remainders down-regulated. Twenty-seven genes have their homologous genes in Gen-Bank Databases. The expression of twelve genes was studied by Northern analysis. Based on the functions, these genes can be classified into five categories, including photosynthesis-related gene, transport-related gene, metabolism-related gene, stress- or resistance-related gene and the others with various functions. The results showed that salt stress influenced many aspects of rice growth. Some of these genes may play important roles in plant salt tolerance.展开更多
文摘Change in catalase activity was examined in leaves of rice plant exposed to salinity. Depending on the method of preparation of crude protein extract from leaf and the constituents of the assay medium, a significant difference in enzyme activity was recorded. Inclusion of sorbitol or mannitol or sucrose in the extraction and enzyme assay medium enhanced the enzyme activity in salt-stressed samples by nearly 1.5-1.8 fold, compared to the activity found in un- stressed plants, which otherwise showed a 50% declined activity in leaf extract prepared in buffer solution and assayed in a medium depleted of these sugars. In view of the accumulation of osmolytes under saline condition, these observations suggest that the catalase activity is modulated by the osmolytes and maintains a high rate of hydrogen peroxide scavenging property in vivo and serves as the major antioxidant enzyme to scavenge the salt-induced formation of peroxide. Therefore, the salt-stress induced appearance of low activity of the enzyme under normal buffer extraction and assay conditions, as reported in literature may represent an apparent than for its real in vivo activity.
基金This work was jointly supported by the National Natural Science Foundation of China (Grant Nos.39470424 & 39770441) and the International Foundation for Science. The authors are grateful to Dr. B. Forster of the Scottish Crop Research Institute, Dundee
文摘Two contrasting barley (Hordeum vulgare L.) cultivars: Kepin No.7 (salt sensitive), and Jian 4 (salt tolerant) were grown hydroponically to investigate the microdistribution of mineral ions in roots as affected by silicon (Si) with respect to salt tolerance. The experiment was undertaken consisting of two treatments with 3 replicates: (i) 120 mmol·L-1 NaCI alone (referred to as Si-NaCI+), (ii) 120 mmol·L-1 NaCI + 1.0 mmol·L-1 Si (as potassium silicate) (referred to as Si+NaCI+). Plant root tips were harvested for microanalysis using an energy dispersive X-ray microanalyzer (EDX) 30 d after transplanting. Higher Cl and Na X-ray peaks were recorded in the root epidermal, cortical and stelar cells of roots for the treatment Si-NaCI+ with the majorities of Na and Cl being accumulated in epidermal and cortical cells, while relatively low K peaks were observed regardless of the barley cultivars used. By contrast, considerably higher K peaks were detected in the epidermal, cortical and stelar cells of the roots for the treatment Si+NaCI+, but lower Cl and Na peaks were also observed for this treatment with both Na and Cl ions being evenly distributed in the epidermal, cortical and stelar cells. These findings directly support our previous finding, which showed that Si depressed the uptake of sodium but enhanced the uptake of potassium by salt-stressed barley. We believe that one of the possible mechanisms involved in Si-enhancement of salt tolerance in barley is attributed to the Si-induced changes in the uptake and microdistribution of mineral ions in plants.
基金This work was supported by the Major Basic Research Program of China (G 1999011703) the National Transgenic Plants Program of China (JOO-A-008-02), the National Natural Science Foundation of China (Grant No. 39900009) the National High-Tech Program
文摘To identify salt stress-responsive genes, we constructed a cDNA library with the salt-tolerant rice cultivar, Lansheng. About 15000 plasmids were extracted and dotted on filters with Biomeck 2000 HDRT system or by hand. Thirty genes were identified to display altered expression levels responding to 150 mmol/L NaCI. Among them eighteen genes were up-regulated and the remainders down-regulated. Twenty-seven genes have their homologous genes in Gen-Bank Databases. The expression of twelve genes was studied by Northern analysis. Based on the functions, these genes can be classified into five categories, including photosynthesis-related gene, transport-related gene, metabolism-related gene, stress- or resistance-related gene and the others with various functions. The results showed that salt stress influenced many aspects of rice growth. Some of these genes may play important roles in plant salt tolerance.
