open access

https://doi.org/10.11501/3071536

https://hdl.handle.net/2115/51180

低温ストレスに対する高等植物の情報発現

日本語

1993-03-25

Hokkaido University

72p.

Cold temperature affects metabolic response to the variety of organisms. In plants, some of them can survive under low temperature milieu, but the mechanisms that support the plant life under stressed conditions remained unclear and some researches have been done to solve this problems. A series of enzyme activities of which dispose of peroxide was increased during the winter season (11-13). These reports suggested that the level of peroxide in the plant cell increased in winter season or under cold treatment. In this report, I show the relationship between peroxide formation and cold temperature, and discussed the role of peroxide in cells under the cold temperature. At second section, the relationship between cold treatment and artificial oxidativetreatment on levels of enzymatic acitivities and substlate in leaves of winterwheat were discussed. Artificial oxidative treatment was attained by the treatment of paraquat or 3-amino-1,2,4-triazole, which affects the actiyities in the cell compartments of chloroprast and cytosol, respectively. Cold and these chemical treatments increased concurrently the activities of glucose-6-phosphate dehydrogenase and levels of sugar phosphates. The levels of ascorbate and glutathione showed different patterns of responses toward these treatments. This result suggests that the response to peroxide is different between cytosol or mitochondria and chloroplast. Third section showed the evidence of the formation of hydrogen peroxide caused by cold treatment in leaves of winter wheat. The levels of hydrogen peroxide in leaves increased three times (1.5μmol/g fresh weight) of the control by cold treatment in the dark with-in a few min, and then the level decreased to the normal level within 10-15 min. This increase in the level of hydrogen peroxide was also shown in cotyledon of cucumber, and these high concentrations of hydrogen peroxide might cause oxidation of cellar components. Fourth section showed the formation of hydrogen peroxide in stems of winter wheat caused by cold treatment. The stem is known to be a non-photosynthetic tissue and the formation of hydrogen peroxide by cold treatment occurred in samples which pre-treated in the dark. This result suggests that the formation of hydrogen peroxide caused by cold treatment may occur as a result of an abrupt retardation of electron flow at electron tratnsport system in mitochondria. The decreasing levels of ascorbate and reduced glutathione and the increasing level of dehydroascorbate occurred simultaneoysly at the formation of hydrogen peroxide, and these data indicate directly the oxidation of cells caused by cold treatment. Fifth section showed the formation of methanesulfinic acid (MSA) by cold treatment from dimethyl sulfoxide (DMSO) in stems of winter wheat. MSA is considered as one of reaction products of DMSO and hydroxyl radicals (82). Hydroxyl radical is known as a most reactive radical and may cause disruption of membrane or genetic materials (77-79). This radical is known to be formed from hydrogen peroxide (75.76). In this experiment, the formation of MSA was shown only when the samples were treated at the low temperatures, of critical point and the temperature was corresponded to the limiting temperature for plant survival. These results indicate that to ayoid hydroxyl radical formation is one of the important factor devoid of freezing damage.

1993-03-25

甲第3240号

博士(農学)

博士論文

Version of Record