Effects of polyploidization on petal characteristics and optical properties of Impatiens walleriana (Hook.)

Abstract

Impatiens walleriana (Hook.) (2n = 2x = 16) is a popular flowering species in the Balsaminaceae family. In order to investigate the effects of polyploidy induction in this species, shoot tip explants measuring 1.5 cm in length were treated with 0, 15, 30, and 60 μM oryzalin for 6, 12, 24, and 48 h in vitro. After conducting the flow cytometric analysis of the plantlets, it was revealed that 68.75% of the explants treated with 60 μM oryzalin for 24 h became tetraploid (2n = 4x = 32), indicating that this treatment is the most effective for tetraploidy induction. The tetraploid plants exhibited increased leaf area, leaf thickness, ovary width, pollen cell length, and stomatal size, as well as a greater number of chloroplasts within stomatal guard cells. Furthermore, tetraploid plants showed decreases in plant height, stomatal guard cell density, and number of flowers. Epidermal conical cells were enlarged by about 1.7 times in tetraploid flowers. Optical examination of petals revealed that reflection of light from the tetraploid petals was reduced among almost all spectra. Reflection was reduced in the spectral region between 350 and 400 nm, which may have occurred as a result of changes in size of the epidermal conical cells. Furthermore, the petals in the tetraploid flowers had more total anthocyanin content. The latter two observations may explain the deepening of color in tetraploid petals. The new features observed in tetraploid flowers may be useful for generating new traits in classical breeding programs. It is also possible that these changes may be caused by alterations in gene expression and protein activity and can thus be examined to identify the genetic factors associated with flowering time and flower morphology in tetraploid I. walleriana. Further investigations are needed to study the interactions between tetraploid I. walleriana and pollinators. The latter can be important for understanding the evolutionary relationship between pollinators and the polyploidy process in this plants. Treating I. walleriana with oryzalin can produce tetraploid plants. Compared to their diploid counterparts, the tetraploid plants have significant differences in their vegetative and reproductive characteristics. Changes in the form and color of the flowers can be attributed to the changes in the size of the conical cells on the surface of the epidermis, along with the increase in the total anthocyanin content in petals.