Simulation analysis of morphological characteristics of motor cell silica bodies on mixed samples from Indica and Japonica rice (Oryza sativa L.) of China

To understand morphological characteristics of plant opals from motor cells in rice detected from soil samples of archaeological site, computer simulation was conducted by sampling from silica bodies of 50 native varieties (25 Indica and 25 Japonica) from Taihu valley, China (population 1) and those of 10 varieties (5 Indica and 5 Japonica) randomly selected from population 1 (population 2). Every sample was composed of 50 silica bodies of Indica and Japonica, in which the number of Indica ranged 50 to 0 decreased progressively by a number of five and that of Japonica ranged 0 to 50 increased progressively by the same number. Thus, there were 11 combinations all for the composition of silica bodies. Sampling for each combination was carried out by three repetitions and without repetition. Morphological characteristics-vertical length (VL), horizontal length (HL), lateral length (LL), and shape coefficient (b/a)-of silica bodies sampled and their variations were examined. The result showed that the four characters of Indica changed gradually to that of Japonica and discriminating score for classifying Indica and Japonica based on the four characters shifted, too, gradually from the negative value of Indica to the positive value of Japonica when mixing silica bodies of Japonica to those of Indica. Oppositely, when mixing silica bodies of Indica to those of Japonica, reversal change was observed. When the number of silica bodies of Indica or Japonica became a half, the characteristics, too, became a medium type between Indidca and Japonica and the discriminating score approached to zero. Also, the coefficient of variation for each shape character became bigger than that of original varieties. This variation tendency is always obvious regardless of the number of varieties to be mixed. Therefore, the shape characteristics can be known by comparing the shape and its coefficient of variation of plant opals detected from soil samples with those of native varieties. If the shape of plant opals shows a medium type between Indica and Japonica, the discriminating score is near zero, and the coefficient of variation is great, there exists a high possibility that the plant opals are mixed with those from both Indica and Japonica. The characteristics could be understood more clearly if the data of plant opals detected from soil layers with a clear relationship of upper and lower are involved in such comparison. It was proved from the shape analysis result of the plant opals in Caoxieshan site