Studies on in vitro regeneration competence of pseudobulb cultures in Changnienia amoena Chien

An efficient procedure is outlined for rapid and mass propagation through in vitro culture of pseudobulbs collected in different seasons of an endangered orchid, Changnienia amoena Chien. Axillary buds formed on intact pseudobulbs (collected in April) after a 12-week incubation on half-strength Murashige and Skoog (1/2 MS) medium supplemented with 1 mg L-1 N6-benzyl- adenine (6-BA), 0.5 mg L-1 α-naphthaleneacetic acid (NAA), 100 ml L-1 coconut water and 0.8 g L-1 polyvinylpyrrolidone; no buds were observed on segmentalized pseudobulbs incubated on the same medium. The axillary buds obtained from pseudobulbs growing in the natural habitat in June were detached and incubated for 7 weeks on the same medium leading to 1.4 shoot buds per explant. With repeated subculturing of the shoots on 1/2 MS medium supplemented with 2 mg L-1 6-BA and 0.5 mg L-1 NAA, a mean of 3.3 shoot buds per explant were observed on successive shoot cultures. A mean of 4.5 roots per shoot were induced on the optimal root induction medium with 1/2 MS medium plus 1.0 mg L-1 NAA and 0.1 mg L-1 6-BA and the highest rooting per centage was 88.9%. Plantlets 4-5 cm in height were transplanted into pots containing a 1:1 humus and sand mixture and grown for 7 weeks in a greenhouse before being transferred to the field. The survival rate of these transplants was about 75% after two months of growth in the wild.

A taxonomic and phylogenetic perspective on plant community assembly along an elevational gradient in subtropical forests

Aims Biodiversity patterns along elevational gradients have been well documented.Yet,the variations of biodiversity patterns along elevations and their underlying mechanisms are still unclear.Integrating multiple facets of biodiversity provides novel insights into the mechanisms for driving community assembly.In this study,species abundance information was incorporated into taxonomic and phylogenetic diversity to reveal the ecological and evolutionary forces of plant community assembly along an elevational gradient in subtropical forests.Methods We selected 17 woody plant plots along an elevational gradient from 270 to 1470 m in eastern China’s subtropical forests.Both presence-based and abundance-based measures of angiosperm species were used to quantify taxonomic alpha diversity,phylogenetic alpha diversity,phylogenetic relatedness,as well as taxonomic and phylogenetic dissimilarity among these plots.And the relations between these measures and climatic and topographic variables were analyzed.Important Findings For both abundance-weighted and unweighted measures,we observed an overall increasing pattern for taxonomic alpha diversity along elevation,and distance-decay trends of taxonomic and phylogenetic similarity with increased elevational distances.However,there were disparity patterns of phylogenetic alpha diversity between abundance-weighted and unweighted measures.For phylogenetic structure,there was no significant trend along elevation.Both topographical and microclimatic variables were main drivers of diversity patterns and phylogenetic structure.Compared with unweighted measures,abundance-weighted measures were strongly related with the slope and stand basal area.Overall,our results prove that deterministic processes mediated by local species abundance imprint on plant community composition along the elevational gradient.