Sacred lotus, the long-living fruits of China Antique
In the West, lotus (Nelumbo nucifera Gaertn.) is relatively little known. However, for more than 3000 years, lotus plants have been cultivated as a crop in Far-East Asia, where they are used for food, medicine and play a significant role in religious and cultural activities. Holder of the world’s record for long-term seed viability (1300 years) is a lotus fruit (China Antique) from Xipaozi, Liaoning Province, China. Five offspring of this variety, from 200–500-year-old fruits (14C dates) collected at Xipaozi, have recently been germinated, and are the first such seedlings to be raised from directly dated fruits. The fruits at Xipaozi, preserved in a dry ancient lakebed, have been exposed to low-dose γ-radiation for hundreds of years (having an accumulated soil irradiation of 0.1–1.0 Gy). Offspring from these old fruits show abnormalities that resemble those in various modern seedlings irradiated at much higher doses. Although these lotus offspring are phenotypically abnormal, the viability of old seeds was evidently not affected by accumulated doses of up to 3 Gy. Growth characteristics of first- and second-year lotus offspring of these fruits, products of the longest-term radiobiological experiment on record, are summarized here (rapid early growth, phenotypic abnormalities, lack of vigour, poor rhizome development and low photosynthetic activity during second-year growth). Aspects of their chromosomal organization, phenotype and physiology (rapid recovery from stress, heat-stable proteins, protein-repair enzyme) are discussed. Important unsolved problems are suggested to elicit interest among members of the seed science community to the study of old fruits recently collected at Xipaozi, with particular emphasis on aspects of ageing and repair.