A Comparative Study of Biseriate Glandular Trichomes of Allopolyploid Species <i>Drosera tokaiensis</i> and Its Parental Species

To discriminate allopolyploid species from their parental species in Drosera, a comparative analysis of biseriate glandular trichomes (BGTs) of D. tokaiensis and its parental species was carried out. Because accurate identification of allopolyploid species D. tokaiensis is difficult due to showing intermediate morphologies between the parental species D. rotundifolia and D. spatulata, the species confirmation of 11 strains of four Drosera species including D. anglica were performed by determining the somatic chromosome numbers first, and then, cytomorphological details of the BGTs were characterized. Except for D. anglica, the typical form of the BGT was a biseriate structure made up of three cell pairs (consisted of six cells): head part (two apical cells), stalk part (two stalk cells), and foot part (two basal cells). In D. tokaiensis and its parental species, the BGTs stained with DAPI exhibited a single nucleus in each cell. Among 16 cytomorphological BGT characters of the three species, the maximum value of the BGT width of D. spatulata was shorter than those of the minimum values of D. rotundifolia and D. tokaiensis. A canonical discriminant analysis showed that the BGTs gave a clear separation to distinguish D. tokaiensis from its parental species. In cross-validated discriminant analysis, the individual variation of BGTs robustly predicted the species of each BGT, demonstrating species specificity for simple and accurate species identification by the cytomorphological characters.