中国科学院南京地质古生物研究所机构知识库

Sacred lotus (Nelumbo nucifera) has been cultivated as a crop in Asia for thousands of years An similar to1300-yr-old lotus fruit. recovered from an originally cultivated but now dry lakebed in northeastern China, is the oldest germinated and directly C-14-dated fruit known In 1996, we travelled to the dry lake at Xipaozi Village, China. the source of the old viable fruits. We identified all of the landmarks recorded by botanist Ichiro Ohga some 80 yr ago when he first studied the deposit, but found that the fruits are now rare. We (1) cataloged a total of 60 lotus fruits. (2) germinated four fruits having physical ages of 200-500 yr by C-14 dating: (3) measured the rapid germination of the old fruits and the initially fast growth and short dormancy of their seedlings: (4) recorded abnormal phenotypes in their leaves, stalks, roots. and rhizomes; (5) determined gamma-radiation of similar to2.0 mGy/yr in the lotus-bearing beds: and (6) measured stratigraphic sequences of the lakebed strata. The total gamma-irradiation of the old fruits of 0 1-3 Gy (gray. the unit of absorbed dosage defined as 1 joule/kg, 1 Gy = 100 rad). evidently resulting in certain of the abnormal phenotypes noted in their seedlings, represents the longest natural radiobiology experiment yet recorded Most of the lotus abnormalities resemble those of chronically irradiated plants exposed to much higher irradiances. Though the chronic exposure of the old fruits to low-dose gamma-radiation may be responsible in part for the notably weak growth and mutant phenotypes of the seedlings it has not affected seed viability. All seeds presumably repair cellular damage before germination. Understanding of repair mechanisms in the old lotus seeds may provide insight to the aging process applicable also to other organisms.