A theoretical morphological model for quantitative description of the three-dimensional floral morphology in water lily (Nymphaea)

Abstract

Water lilies (Nymphaea spp.) have diverse floral morphologies. Water lilies are not only commonly used as ornamental plants, but they are also important for understanding the diversification of basal angiosperms. Although the diversity in floral morphology of water lily provides useful information for evolutionary biology, horticulture, and horticultural science, it is difficult to describe and analyze the three-dimensional morphology of flowers. In this study, we propose a method to describe the floral morphology of water lily using a threedimensional theoretical morphological model. The theoretical model was constructed based on three components, i.e., (1) the gradual change in size of floral organs, (2) spiral phyllotaxis, and (3) the interpolation of elevation angles, which were integrated into the model. We generated three-dimensional representation of water lily flowers and visualized theoretical morphospaces by varying each morphological parameter. The theoretical morphospace is a mathematical space of morphological spectrum generated by a theoretical morphological model. These morphospaces seems to display the large part of morphological variations of water lily. We measured morphological parameters of real flowers based on our theoretical model and display the occupation pattern of morphological parameters. We also surveyed the relation between morphological parameters and flower shape descriptions found in a catalog. In some parameters, we found breeders' description can link to our morphological model. In addition, the relationship between the global features of floral morphology and the parameters of the theoretical model was calculated with flower silhouettes simulated with a range of parameter values and the global features of the silhouette. We used two simple indices to assess the global morphological features, which were calculated with the convex hull. The results indicated that our method can effectively provide an objective and quantitative overview of the diversity in the floral morphology of water lily.

Model-based plant phenomics on morphological traits using morphometric descriptors

“…Thus, it is difficult to interpret the meaning and actual appearance quantitatively. Kirie et al (2020) proposed a theoretical morphological model for Nymphaea (water lilies) flowers to describe the morphological diversity of horticultural cultivars; the floral morphology was reduced to three hierarchical rules, namely (1) morphologies of tepals, (2) the spiral phyllotaxis, and (3) the blooming state.…”

“…Thus, it is difficult to interpret the meaning and actual appearance quantitatively. Kirie et al (2020) proposed a theoretical morphological model for Nymphaea (water lilies) flowers to describe the morphological diversity of horticultural cultivars; the floral morphology was reduced to three hierarchical rules, namely (1) morphologies of tepals, (2) the spiral phyllotaxis, and (3) the blooming state. To demonstrate the versatility of this model, a theoretical morphospace was generated by varying several parameters, especially those related to the gradual change in size and shape through a series of tepals.…”

“…This figure was created based on partially modified Figs. 3 and 5 in Kirie et al (2020) (Licensed under CC-BY 4.0).…”