Effects of ploidy level on the cellular, photochemical and photosynthetic characteristics in Lilium FO hybrids.

Polyploidy plays an important role in plant breeding, inducing a wide range of effects on photosynthetic performance, cellular and photochemical aspects of photosynthesis. Although the impacts of polyploidization on photosynthesis have been examined in several genera, comparatively little is known about the photosynthetic responses to polyploidy in Lilium. In this study, diploid and colchicine-induced tetraploid Lilium FO hybrids were used to study the effects of polyploidization on cellular, photochemical and photosynthetic characteristics in Lilium. Polyploidization caused a significant change in leaf anatomical structure, chloroplast ultrastructure and photosynthetic pigment contents. Thicker epidermal and spongy tissue, more and thicker thylakoid lamellae and higher chlorophyll and carotenoid contents were observed in the tetraploid than in the diploid. More regularly and tightly arranged thylakoids were closely associated with more efficient light-harvesting machinery. And the tetraploid plants showed a higher net photosynthetic rate (Pn) and maximum net photosynthetic rate (P) than the diploid plants, under both natural conditions and gradients of light intensity/CO concentration. In addition, the tetraploid had a significantly higher light saturation point (LSP), but a lower light compensation point (LCP) than the diploid, indicating that tetraploid plants acquired light energy more efficiently. These results suggested that cellular and photochemical alterations caused by polyploidization improve the capacity for light absorption and conversion and further enhanced the photosynthetic performance in Lilium FO hybrids.