Seed Morphology and Germination of Native Tulipa Species

Abstract

Seeds are important for the preservation and reproduction of wild tulips in situ, but only a few studies have been carried out on their seed morphology and germination characteristics. In this study, the eight wild tulip species native to China were used. Their seed morphology and superficial ornamentation, the relationship between seed morphology and germination, and the effects of manipulating incubation temperature, seed coat, and gibberellin (GA3) application were studied. The seeds are diverse in shape, size, color, weight, and superficial ornamentation, as observed by stereomicroscopy and scanning electron microscopy. Tulipa edulis (Miq.) Baker had a half-moon-shaped seed with the embryo invisible and irregular striped ornamentation, which was different from the other seven species that had sector-shaped seeds with the embryo visible and irregular reticulate ornamentation. Especially, the muri feature and the decorative pattern in meshes were highly variable and decisive at both section and species levels of Tulipa L. We also classified the seed dormancy type of the eight wild tulip species as nondeep complex (MPD). Embryo length, embryo/seed length ratio, and seed coat color were correlated with germination (T50), while the T50 of eight wild tulip species was still mainly affected by optimized temperatures of 4 °C and/or 4/16 °C. Gibberellin (GA3) has a positive regulating effect on the T50 of tulip species, and 100 μM gibberellin was considered the most effective concentration. These results highlight the taxonomic significance of the genus Tulipa based on seed testa morphology, and we support the notion that T. edulis should be regarded as an independent genus—Amana. Meanwhile, our study provided a way that the seed germination of wild tulip species could be shortened within 2 months under the experimental conditions, which will help to rapidly multiply and utilize wild tulip resources.