Search Results (5)

In the traditional classification system of the Lauraceae family based on morphology and anatomy, the phylogenetic position of the genus Sassafras has long been controversial. Chloroplast (cp) evolution of Sassafras has not yet been illuminated. In this study, we first sequenced and assembled the complete cp genomes of Sassafras, and conducted the comparative cp genomics, phylogenomics, and divergence time estimation of this ecological and economic important genus. The whole length of cp genomes of the 10 Sassafras ranged from 151,970 bp to 154,011 bp with typical quadripartite structure, conserved gene arrangements and contents. Variations in length of cp were observed in the inverted repeat regions (IRs) and a relatively high usage frequency of codons ending with T/A was detected. Four hypervariable intergenic regions (ccsA-ndhD, trnH-psbA, rps15-ycf1, and petA-psbJ) and 672 cp microsatellites were identified for Sassafras. Phylogenetic analysis based on 106 cp genomes from 30 genera within the Lauraceae family demonstrated that Sassafras constituted a monophyletic clade and grouped a sister branch with the Cinnamomum sect. Camphora within the tribe Cinnamomeae. Divergence time between S. albidum and its East Asian siblings was estimated at the Middle Miocene (16.98 Mya), S. tzumu diverged from S. randaiense at the Pleistocene epoch (3.63 Mya). Combined with fossil evidence, our results further revealed the crucial role of the Bering Land Bridge and glacial refugia in the speciation and differentiation of Sassafras. Overall, our study clarified the evolution pattern of Sassafras cp genomes and elucidated the phylogenetic position and divergence time framework of Sassafras. Full article

Bamboo and wood-mixed forests are management models that remarkably enhance the balance and productivity of bamboo ecosystems. However, the effects of this model on soil nutrients and enzyme activities remain largely unknown. This study compared the soil organic carbon, nitrogen, phosphorus, and enzyme activity, along with the characteristics of fine roots in pure Moso bamboo plantations (CK) and those mixed with Liriodendron chinense (ML), Sassafras tzumu (MS), Cunninghamia lanceolata (MC), and Pseudolarix amabilis (MP). The results showed that mixed forests improve carbon pools in 0–40 cm soil layers, increasing the total organic C(TOC), free particulate organic C (fPOC), occluded particulate organic C (oPOC), hot-water-extractable organic C (DOC), and mineral-associated organic C (MOC). They also increase soil total N, total P, available N, available P, NH4+-N, NO3−-N, inorganic P, organic P, and microbial biomass N. Bacterial and fungal abundances, along with enzyme activities (urease, acid phosphatase, polyphenol oxidase, peroxidase, and β-glucosidase), also improved. MP and MS were the most effective. Moreover, MS and MP supported a higher biomass and length of fine root and increased the nitrogen and phosphorus uptake of Moso bamboo. In conclusion, Sassafras tzumu and Pseudolarix amabilis are optimal for mixed planting, offering substantial benefits to soil nutrient dynamics and preventing soil quality decline in Moso bamboo forests, thereby supporting better nutrient cycling and carbon sequestration. This research offers insights into enhancing soil quality through diversified Moso bamboo forestry. Full article

The deciduous tree species Sassafras tzumu (Hemsl.) Hemsl., unique to China, holds significant economic and ecological value. However, its seeds exhibit poor storage tolerance and rapid decline in seed vigor. This study primarily investigates the desiccation tolerance of S. tzumu seeds. The results show that S. tzumu seeds have recalcitrant seed characteristics, with a semi-inactivation water content (at which point half of the seeds lose viability) of 20.7%. As desiccation progresses, seed viability decreases significantly; at a reduced water content of 11.93%, only 18.3% of the seeds remain viable, while most lose their viability completely. Relative electrolytic leakage (REC) and H₂O₂ content gradually increase during this process, while MDA content initially decreases before increasing again, exhibiting distinct trends compared to antioxidant enzyme activities such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). SOD and POD activities exhibit an initial increase followed by a rapid decrease, whereas CAT activity shows a decline followed by a rapid increase. Dehydration to 15% water content in seeds is a key turning point in the process of seed desiccation in S. tzumu, and CAT is an enzyme key to maintaining seed viability. Both the accumulation of toxins and the decline in the activity of the antioxidant system contribute to the susceptibility of S. tzumu seeds to drought stress, a characteristic common to all recalcitrant seeds. To maintain high seed viability above 70% during storage, it is crucial to ensure water content above 23.58%. Full article

Sassafras tzumu (Hemsl.) Hemsl., as an Arctic Tertiary relict woody species, is an ecologically and economically important deciduous tree endemic to southern China. Nonetheless, the genetic resources and backgrounds of S. tzumu are still lacking and remain largely unclear. Here, we predicted 16,215 candidate polymorphic nuclear microsatellite (nSSR) loci from the assembled nucleus databases of six geographic-distant individuals of S. tzumu via CandiSSR. Among these nSSRs, the di- (75.53%) and tri-nucleotide (19.75%) repeats were the most abundant, and 27 new polymorphic SSRs were developed and characterized in 136 individuals from six natural populations of S. tzumu. The majority of the above 27 SSRs (24 loci, 88.89%) presented moderate polymorphism (mean PIC = 0.356), and the transferability of these markers in other Sassafras species was high (85.19%). A moderately low level of genetic diversity and a high variation (F_ST = 0.286) of six wild populations of S. tzumu were illuminated by 16 selected polymorphic nSSRs, with the average expected heterozygosity (H_E) of 0.430 at the species level and H_E ranging from 0.195 to 0.387 at the population level. Meanwhile, a bottleneck effect was shown in two populations. Consistent with the results of the principal coordinate analysis (PCoA) and phylogenetic trees, structure analysis optimally divided these six S. tzumu populations into two clusters, and the further strong population subdivision appeared from K = 2 to K = 5, which corresponded to two evolutionarily significant units (ESUs). Moreover, the significant correlation between genetic and geographic distance was tested by the Mantel test (r = 0.742, p = 0.006), clarifying the effect about isolation by distance (IBD), which could be possibly explained by the low gene flow (N_m = 0.625), a relatively high degree of inbreeding (F_IS = 0.166), a relatively large distribution, and mountainous barriers. Above all, our research not only enlarged the useful genetic resources for future studies of population genetics, molecular breeding, and germplasm management of S. tzumu and its siblings but also contributed to proposing scientific conservation strategies and schemes for the better preservation of S. tzumu and other Sassafras (Lauraceae) species. Full article

Sassafras tzumu (Chinese sassafras) is an economically and ecologically important deciduous tree species. Over the past few decades, increasing market demands and unprecedented human activity in its natural habitat have created new threats to this species. Nonetheless, the distribution of its habitat and the crucial environmental parameters that determine the habitat suitability remain largely unclear. The present study modeled the current and future geographical distribution of S. tzumu by maximum entropy (MAXENT) and genetic algorithm for rule set prediction (GARP). The value of area under the receiver operating characteristic curve (AUC), Kappa, and true skill statistic (TSS) of MAXENT was significantly higher than that of GARP, indicating that MAXENT performed better. Temperate and subtropical regions of eastern China where the species had been recorded was suitable for growth of S. tzumu. Relative humidity (26.2% of permutation importance), average temperature during the driest quarter (16.6%), annual precipitation (12.6%), and mean diurnal temperature range (10.3%) were identified as the primary factors that accounted for the present distribution of S. tzumu in China. Under the climate change scenario, both algorithms predicted that range of suitable habitat will expand geographically to northwest. Our results may be adopted for guiding the preservation of S. tzumu through identifying the habitats susceptible to climate change. Full article