| Research Abstract |
This research has been performed to clarify the basic conditions adequate for storing plant seeds for a long term over 50 years at -3.5ﾟC in permafrost. In general, the longevity of plant seeds has been known to depend on their moisture contents and storage temperature, being longer at low relative humidity (RH) and temperature. During this research, we succeeded to demonstrate the mechanisms of seed deterioration which takes place depending upon moisture and temperature. Tha rapid deterioration at higher moistures seems to be due to the loss of co-enzymes, such as CoA・SH and acetyle CoA,and of ability of development of mitochondria. The low temperature can perhaps prolongs the longevity ofseeds by retarding the loss of co- enzymes and/or mitochondrial development. On the other hand, the slow deterioration under lower moistures seems to be due to the participation of carbonyl compounds, such as acetaldehyde and propanal so on, which were produced by seeds themselves. We identified 59 k
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inds ofvolatile componds evolved by seeds temselves using GC-MS,15 of which were carbonyl compounds. Acetaldehyde and 3-methylbutanal out of them were the most toxic ones, accelerat- ing the deterioration. Intertestingly, the levels of these carbonyl compounds within the seeds were higher when they were stored at 33-53% RH than when stored at 75% RH,which suggests that the natural aging of dry seeds during a storage perioday be involved in the accumulation of these volatiles within the seeds. This possibility was demonstrated by the facts that the contents of buffer soluble proteins are decreased by exposure to acetaldehyde, the part of them being denatured, and the denaturation of soluble proteins is accompanied by the products of acetaldehyde-protein adducts, which occurring during natural aging of seeds. Based on these facts, it was suggested that a periodical evacuation treatment of seed containers is recommended to remove both moisture and produced carbonyl compounds in order to the long term storage of seeds under permafrost conditions. Less
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