Colchicine-induced chromosome doubling in Cinnamomum camphora and its effect on morphological and terpenoid storage structures

Cinnamomum camphora (family Lauraceae) is an economically significant tree valued for its aromatic, medicinal and forest-bathing properties. Polyploid induction offers a potential strategy for enhancing tree genetics, but success in this woody species has been limited. In this study, pre-soaked seeds of C. camphora were treated with colchicine solutions ranging from 0 % to 1 % for varying durations. Flow cytometry and chromosome counting were used to confirm the induction of tetraploids. The optimal treatment for tetraploid induction was found to be a 0.8 % colchicine solution for 24 h, achieving a 33.33 % induction. Chromosome doubling impacted various plant traits, such as morphology, physiology, and reproductive development. The average guard cell length and width in tetraploids show an approximate 40 % increase compared with those in diploid stomata. Conversely, the stomatal density in tetraploids was reduced by about 41.5 %. The average oil cell and oil drop (terpenoid storage structures) diameter in tetraploids increased by 26.71 % and 79.39 %, respectively, compared with diploids. Moreover, tetraploid plants exhibited extensive variation in characteristics, including faster or slower growth, larger leaf area, and higher specific leaf weight. Although there was no significant difference in the essential oil yield per unit mass of leaves between field-grown tetraploid and diploid plants, the significantly increased leaf biomass of tetraploid plants suggests their potential to enhance total essential oil production. Some tetraploid leaves displayed atypical vein structures, featuring 5 basal veins as opposed to the typical 3 basal veins found in diploid leaves. Intriguingly, a tetraploid genotype was observed to bloom early, flowering at just three years of age. These findings suggest that the induced polyploid plants may be valuable for breeding programs aimed at enhancing productivity in tetraploid C. camphora while promoting the low fertility of triploid variants. • Tetraploid Cinnamomum camphora can be successfully induced from seeds through colchicine treatment. • Tetraploid camphor trees have larger leaves and oil cells than diploid camphor trees. • Induced autotetraploid camphor tree has the potential to increase the biomass and essential oil yield. • Induced autotetraploid camphor tree exhibit early flowering trait.