Comparison of the morphological and physiological characteristics of diploid and tetraploid Luculia pinceana Hook.

Abstract Background To explore the physiological and biochemical differences between different ploidy Luculia pinceana Hook. varieties and to obtain germplasm resources with excellent horticultural characteristics and strong resistance, we analysed and compared the morphological characteristics, photosynthetic properties, and physiological indices of diploid and tetraploid L. pinceana. Results (1) Tetraploid L. pinceana exhibited distinct polyploid characteristics, including a smaller plant, rounder, thicker, and darker green leaves, as well as coarser and longer leaf and stem hairs. Moreover, the flowers of tetraploids are relatively large, and the diameters of the flowers, the lengths of the corolla tubes and the lengths of the pistils are all extremely significantly greater than those of diploids. Compared with those of tetraploids, the leaf width and thickness of the diploid plants increased by 16.38% and 14.71%, respectively, whereas the leaf length, leaf area, and plant height decreased by 21.20%, 3.46%, and 54.86%, respectively. (2) The diurnal variation curve of photosynthesis in L. pinceana was unimodal, reaching a maximum value at approximately 10:00. Compared with diploid plants, tetraploid plants presented a significantly greater maximum net photosynthetic rate (Pmax), light saturation point (LSP), and light compensation point (LCP). (3) Compared with diploids, tetraploid leaves presented significantly greater activities of antioxidant enzymes, including superoxide dismutase (SOD, + 51.61%), peroxidase (POD, + 6226%), and catalase (CAT, + 211.66%). Additionally, the concentrations of osmolytes [soluble sugar (SS, + 80.11%), soluble protein (SP, + 63.49%), and proline (Pro, + 57.40%)] were markedly elevated. Conversely, the malondialdehyde (MDA) content was substantially decreased (-46.16%). Conclusion These results demonstrate that the tetraploid L. pinceana has greater ornamental value, fertility and resistance. It is an excellent breeding material for the germplasm resources of L. pinceana and provides a material basis for the cultivation of new varieties of L. pinceana.