Sepal morphology affects flower and fruit development in Luffa cylindrica.

Sepal is a part of the flower of angiosperms. It is the outmost whorl of a flower and usually functions as protection and support for the petals. Some plants can even retain their sepals even after fruits become matured. Sepals can also affect the flower development by coordinating cell division, cell differentiation and cell expansion with other parts of the flower whorl. The morphology of the sepals varies among species and it has been associated to the yield and quaity of the fruit. Thus, many researchers utilized sepal morphology as an important character for new species identification. However, the correlation between sepal morphology and flower/fruit development has only been characterized in qualitative description. To establish a quantitative relationship between sepal morphology and flower/fruit development, we collected 15 different subspecies of Luffa cylindrica Roem and performed measurements of multiple traits associated with sepal morphology and flower/fruit development. Using Pearson partial correlation analysis, we built trait factor loadings matrix and the factor model. Our results suggest that larger sepal size and small projections on backside of sepals tightly associate with the protection of flower whorl and better fruit quality. Through analysis using mathematical model of X-pxl = A(pxm) . F-mxl + e(pxl), we found that sepal morphology of Luffa cylindrical is mainly determined by sepal length and width, rather than by sepal area and sepal shape coefficient. Our study for the first time presented quantitative analysis and mathematic model of correlation between sepal morphology and flower/fruit development, which provides tools and basis for further genetic studies in the future.