Daphne giraldii Nitsche. (Thymelaeaceae) is a slow-growing shrub which has been used in Chinese folk medicine and commonly called 'Zu Shima'. In this study, we assembled the complete chloroplast (cp) genome of D. giraldii using data from high-throughput Illumina sequencing. The D. giraldii cp genome is 171,643 bp in size and includes two inverted repeat regions of 41,798 bp each, which is separated by a large single copy region of 85,171 bp and a small single copy region of 2876 bp. A total of 137 genes were predicted, including 38 tRNA, 8 rRNA, and 90 protein-coding genes. In addition, 10 PCG genes possess a single intron, 92 PCG genes no intron, 1 gene harbor two introns. Six tRNA genes harbor a single intron. Phylogenetic analysis indicated that D. giraldii is closer to Daphne kiusiana and Daphne tangutica than other taxa.

The complete chloroplast genome sequence of Daphne tangutica Maxim. (Thymelaeaceae), a medicinal plant distributed in northwest alpine region of China, was characterized the complete nucleotide sequence of chloroplast (cp) genome. The total length of cp genome is 169,944 bp, including a large single copy (LSC) region of 84,884 bp, a small single copy (SSC) region of 2248 bp, and a pair of inverted repeats (IRs) of 41,406 bp. The cp genome of D. tangutica contains 137 genes, including 90 protein-coding genes (75 PCG species), 39 transfer RNA genes (31 tRNA species), and eight rRNA genes (four RNA species). A total of 12 genes (tRNA-Lys (UUU), tRNA-Leu (UAA), tRNA-Val (UAC), tRNA-Ile (GAU), tRNA-Ala (UGC), rpl16, rpoC1, petD, rps16, rpl2, ndhB, and ndhA) contains a single intron, and two genes (ycf3 and rps12) contains two introns. The GC content in whole cp genome, LSC region, SSC region, and IR region were 36.8%, 34.8%, 28.6%, and 38.9%, respectively, which are similar to other Thymelaeaceae plants. Phylogenetic analysis suggested that D. tangutica has the closely reltionship with congeneric D. kiusiana.

Daphne retusa Hemsl. (Thymelaeaceae) is an evergreen shrub plant. First, we characterized the complete nucleotide sequence of chloroplast (cp) genome of D. retusa. The total length of cp genome was found to be 170,553 bp, including a large single copy (LSC) region of 84,886 bp, a small single copy (SSC) region of 2,437 bp, and a pair of inverted repeats (IRs) of 41,617 bp. The cp genome of Daphne retusa Hemsl. contains 134 genes, including 90 protein-coding genes (75 PCG species), 37 transfer RNA genes (29 tRNA species), and 6 rRNA genes (3 RNA species). A total of 13 genes (trnK-UUU, trnS-CGA, atpF, rpoC1, trnL-UAA, trnC-ACA, petD, rpl16, rpl2, ndhB, trnE-UUC, ndhA, and trnA-UGC) contain a single intron, and one gene (ycf3) contains two introns. The GC content in whole cp genome, LSC region, SSC region, and IR region was 36.75%, 34.83%, 28.19%, and 38.96% respectively, like other Thymelaeaceae plants. Phylogenetic analysis suggested that D. retusa has a close relationship with congeneric Daphne tangutica.

Daphne giraldii Nitsche (Thymelaeaceae) is a perennial evergreen shrub that is widely used in the ornamental plant and pharmaceutical industries in China. It exhibits dormancy, which delays and reduces germination. This study determined the effects of chemical treatment, stratification and burial treatment for overcoming the seed dormancy of D. giraldii. Results showed that chemical pre-treatment was less effective in breaking dormancy. The best germination percentage (G P ) was 52.33 %, a germination rate (G R ) of 1.19 only observed after 70 d of seed stratification at 5 °C treatment, indicating that the germination behavior of D. giraldii was not significantly affected by stratification. The physiological dormancy of D. giraldii seeds was alleviated during burial. Seeds buried at 100 cm depth for 170 days showed the highest germination success with G P of 86.5 % and G R of 10.11, which was the most effective treatment to alleviate seed dormancy. This information may be useful to restore and conserve other shrubs grown in Northwestern China and elucidate their survival under similar extreme environments. Resumen Daphne giraldii Nitsche (Thymelaeaceae) es un arbusto de hoja perenne utilizado ampliamente como planta ornamental y en la industria farmacéutica de China. La planta exhibe latencia que retrasa y reduce la germinación. Este estudio determinó los efectos del tratamiento químico, la estratificación y el tratamiento de siembra de semillas para interrumpir la latencia de D. giraldii. Los resultados mostraron que el pretratamiento químico fue el menos eficaz. El mejor porcentaje de germinación (G P ) fue 52.33 % y solamente se observó una tasa de germinación (G R ) de 1.19 después de 70 días de la estratificación de semillas a una temperatura de 5 °C. Esto indica que el comportamiento de la germinación de D. giraldii no se vio afectado significativamente por la estratificación. La latencia fisiológica de semillas de D. giraldii se mitigó durante la siembra de semillas. Las semillas enterradas a 100 cm de profundidad por 170 días germinaron exitosamente con 86.5 % e índice de germinación de 10.11, por lo que fue el tratamiento más eficaz para mitigar la latencia de las semillas. Esta información puede ser útil para restaurar y conservar otros arbustos que crecen en el noroeste de China y dilucidar su supervivencia en condiciones extremas similares.Received: April 14, 2015 / Accepted: November 25, 2015. Palabras clave:Estratificación, ácido giberélico, 6-benciladenina, siembra de semilla, capacidad de germinación