Elevation difference of Ca^(2+) levels in young leaf cells of bromegrass and induced cold-tolerant enhancement under different controlled chilling temperatures

The changes of Ca2＋ levels in young leaf cells of bromegrass under different controlled chilling temperatures were inves- tigated by an antimonite precipitation cytochemical method. The main results were as follows： under 25/20℃ （day/night） tempera- ture and 14 h photoperiod, electron-dense Ca2＋ antimonite precipitates, indicators of Ca2＋ localization, were mainly localized in the vacuoles, cell walls and intercellular spaces; few Ca2＋ deposits were observed in the cytosol and nuclei. After a 3℃ chilling treatment for 3 h, many Ca2＋ precipitates appeared in the cytosol and nuclei, indicating that Ca2＋ influx had occurred in the cytosol and nuclei. When the 3℃ treatment was prolonged to 8 h, more Ca2＋ deposits appeared in the nuclei and cytosol, but the amount of Ca2＋ deposits in both the cytosol and nuclei decreased markedly after a 24 h treatment and most Ca2＋ deposits were returned to the vacuoles and intercellular spaces after an 8 d treatment. When bromegrass was exposed to 7℃ for 3 h, the Ca2＋ distribution in the cells had no visible changes, compared with that of the 25/20℃ grown control plants. However, when the chilling treatment of 7℃ was prolonged to 8 h, a Ca2＋ influx occurred, where many Ca2＋ deposits were observed in the nuclei and cytosol. More Ca2＋ deposits appeared in the nuclei and cytosol after a 24 h treatment, but the amount of Ca2＋ deposits in the cytosol and nuclei was reduced markedly after an 8 d treatment. After a 14 d treatment, the remaining low level of Ca2＋ was recovered in both the cytosol and nuclei and the Ca2＋ deposits were again located in the vacuoles and the intercellular spaces. The dynamics of subcellular Ca2＋ localization in young leaf cells of bromegrass during a 12℃ chilling treatment were similar to those of the 7℃ treatment. Besides, the results showed that the frost tolerance ofbromegrass exposed to 3℃ for 8 d increased by 6℃, for 7℃ and 8 d by 4℃ and for 12℃ and 14 d by 3℃, compared with the controls. Finally, the relationship between different Ca2＋ dynamics and induced frost tolerance was also explored.

中国东北地区低温冷害研究进展与展望(英文)

Focused on the major agro-meteorological disaster in northeast China area-low temperature chilling injury,the research progresses of low temperature chilling injury in northeast China were reviewed systematically.The basic concepts which included the connotation and extension of chilling damage,the circulation characteristics and effect factors which formed summer low temperature in northeast China,the prediction,forecast and defense of low temperature chilling injury were summarized and done the outlook.

Sensory Evaluation of Different Packaged Roast Beef Treatments Designed for the Extension of Its Shelf Life

This study was carried out to investigate the effect of different nitrite concentrations on the sensory parameters of roast beef including color, flavor, juiciness, texture and overall acceptability. Four roast beef batches were formulated;the first three treatments were with nitrite concentrations of 0.006%, 0.012% and 0.018% and stored at abused chilling temperature (12°C), while the fourth one was a control treatment with 0.026% nitrite and storage at 4°C. Results showed that increasing nitrite concentration from 0.006% to 0.026% enhanced the shelf life of roast beef stored for 7 days without affecting the sensory characteristics whether at 12°C or 4°C since there were no significant differences (P > 0.05) between all treatments regarding color, flavor, juiciness, texture and overall acceptability. These results could direct us to use high nitrite concentration to protect this product and elongate its shelf life without affecting its preference parameters.

Evaluation of the Shelf Life of Packaged Roast Beef and Some Treatments for Its Extension

This study was carried out to investigate the effect of nitrite concentration, and abused chilling temperature against proper chilling temperature on the chemical, microbiological and shelf life of roast beef stored at 4°C and 12°C. Three roast beef treatments were formulated to investigate the effect of nitrite concentration (0.006%, 0.012% and 0.018%) and abused chilling temperature (12°C) against control treatment (0.026% nitrite and storage at 4°C) on the chemical, microbiological and shelf life. Results showed that roast beef containing 0.026% nitrite and stored at 4°C for 25 days had the lowest thiobarbituric acid (TBA) value while the highest TBA values were in the treatment containing 0.006% added nitrite, stored at 12°C. The aerobic plate count, Enterobacteriaceae, lactic acid bacteria (LAB), and spore former count were increased throughout the storage period which was lower in 0.026% and 0.018% containing nitrite treatments while higher in other two treatments. The lowest percentage of nitrite losses during storage was in the samples having 0.026% added nitrite to roast beef. The results emphasized the risk of abused temperature and the importance of keeping this product under efficient and consistent refrigeration during storage and the use of high nitrite concentration to protect it and elongate its shelf life.