Anatomy of Different Ages of Streblus asper Leaves and Their Drought Resistance

The leaf thickness, stratum corneum thickness, epidermis thickness, palisade tissue thickness and sponge tissue thickness of Streblus asper leaves at different ages were observed by using paraffin section technology and optical microscopic observation to explore the anatomic adaptive response mechanism to drought stress, also to provide a theoretical basis for S. asper introduction. The results showed that under drought stress, various parts of S. asper leaf anatomy showed some characteristics adapted to water environment. Leaf palisade tissue cells became shorter, increasing from 1-2 layers to 2-3 layers; sponge cells were arranged in neat and compact long column shape, and the upper and down epidermis were thickened. The upper and down epidermis produced more trichomes to resist stress. After rehydration, leaf porosity increased and trichomes had a corresponding reduction. The principal component analysis showed that the stratum corneum thickness, leaf thickness and palisade were available to describe the impact of stress and rehydration on different ages of S. asper leaf anatomy. Under drought stress, S. asper leaf stratum corneum thickness and leaf thickness increased and leaves returned to normal after rehydration. Middle and top leaves were better than basal leaves in response to drought stress sensitivity.

The Biomass Dosage Influences the Effects of Diethyl Aminoethyl Hexanoate on Micropropagation of Echinacea purpurea (L.) Moench

The plant growth regulator diethyl aminoethyl hexanoate (DA-6) has proved highly effective on micropropagation of the medicinal plant purple coneflower (Echinacea purpurea (L.) Moench), however, sharp variation of the effects existed among explants in the same treatment, making the application of DA-6 in micropropagation difficult. In order to clarify factors that influencing the treating results of DA-6, explants with different biomass dosage were prepared and inoculated onto medium supplemented with different concentrations of DA-6. It was found that among the three kinds of biomass dosage explants, the lowest biomass explants required the lowest concentration of DA-6, and the highest biomass explants required the highest concentration of DA-6 for the best results on adventitious buds regeneration. Similar results were obtained when regenerated buds of three different biomass dosages were cultured. It could be concluded from the above experimental results that for achieving better DA-6 application results, the concentration of DA-6 should be determined not only by the types but also by the biomass dosage of the explants. The present finding might help to improve the micropropagation efficiency in E. purpurea, and might be applicable for other species

Mannitol and Sorbitol Improve Uniformity of Adventitious Shoots Regeneration in Echinacea purpurea L. Moench

Mannitol or sorbitol was added into the Murashige and Skoog (MS) medium contain-ing certain concentrations of 6-Benzyladenine (BA) which was used to induce adventi-tious buds of Echinacea purpurea L. Results showed that the induced adventitious buds growing from medium added with 15 g·L-1 mannitol or sorbitol of the same con-centration were more consistent in height. The regeneration rates in MS medium containing 0.2 mg·L-1 BA and 15 g·L-1 mannitol were increased, while in MS medium containing 0.2 and 0.5 mg·L-1 BA, and 15 g·L-1 sorbitol, the regeneration rates were suppressed. On the other hand, genotype of explants and the concentration of BA in-fluenced the incidence of hyperhydricity, and the hyperhydricity of regenerated buds was more severe when the petiole explants were inoculated on medium with 15 g·L-1 mannitol or 15 g·L-1 sorbitol. The present study offers new possibility to the production of uniform plantlets for commercial cultivation in this important medicinal plant.

A high-quality Bougainvillea genome provides new insights into evolutionary history and pigment biosynthetic pathways in the Caryophyllales

Bougainvillea is a perennial ornamental shrub that is highly regarded in ornamental horticulture around the world.However,the absence of genome data limits our understanding of the pathways involved in bract coloration and breeding.Here,we report a chromosome-level assembly of the giga-genome of Bougainvillea×buttiana‘Mrs Butt’,a cultivar thought to be the origin of many other Bougainvillea cultivars.The assembled genome is∼5 Gb with a scaffold N50 of 151756278 bp and contains 86572 genes which have undergone recent whole-genome duplication.We confirmed that multiple rounds of whole-genome multiplication have occurred in the evolutionary history of the Caryophyllales,reconstructed the relationship in the Caryophyllales at whole genome level,and found discordance between species and gene trees as the result of complex introgression events.We investigated betalain and anthocyanin biosynthetic pathways and found instances of independent evolutionary innovations in the nine different Caryophyllales species.To explore the potential formation mechanism of diverse bract colors in Bougainvillea,we analyzed the genes involved in betalain and anthocyanin biosynthesis and found extremely low expression of ANS and DFR genes in all cultivars,which may limit anthocyanin biosynthesis.Our findings indicate that the expression pattern of the betalain biosynthetic pathway did not directly correlate with bract color,and a higher expression level in the betalain biosynthetic pathway is required for colored bracts.This improved understanding of the correlation between gene expression and bract color allows plant breeding outcomes to be predicted with greater certainty.