Leaf Traits, Breeding Characteristics And Their Genetic Basis In Rehmannia Species

Biological characteristics of species (including phenotype, physiology, reproduction traits et al.) are the product of interaction between species and environments. In present study, distribution pattern, reproduction characteristics, leaf traits and genetic divergence in Rehmannia species were researched to investigate the interspecific differences and their adaptation to specific envirionments. The main results are as follows:(1) The Maxent ecological niche models was used to predict the potential distribution area of Rehmannia in china. The potential distribution of Rehmannia is close to the actual area except for R. henryi. Their suitable potential distribution areas in future are highly similar to the present. According to the prediction of the distribution area we could estimate the distribution and quantity of Rehmannia. R. chingii is still distributed in Jiangsu provinces and Zhejiang provinces, and R. piasezkii and R. solanifolia are located in central China. R. glutinosa is widely distributed in north China. R. henryi is distributed in eastern and central of China.(2) Rehmannia species flowers are hermaphroditic. The flowering duration of a single florescence was 5-7 days, and the whole population flowering duration was 40-60 days. There are distinct difference among the five Rehmannia species in inflorescence types, floral characteristics, flower colors, pollen amounts and P/O values. We found that R. solanifolia was pollen abortion. Out-crossing index, pollen-ovule ratio and the hybridization experiment supported that the breeding system of Rehmannia was belonged to cross pollination system, partially self-compatible, with no apomictic ability, and pollinators required. We also found there was vegetative reproduction in Rehmannia, especially in R. glutinosa and R. solanifolia. There are nectaries on the base of Rehmannia corolla and they can produce nectar with higher concentration of sugar, and this also supports the existence of pollinators. However, we did not observe any effective pollinators in Rehmannia species except in R. glutinosa with bees, which might be due to the scattered individual, isolated habitats and the bad weather conditions during pollination observation. Longer flowering duration could compensate for the insufficiency of pollinator visits. According to our results, we suppose that the different flower display of five Rehmannia species possibly attracting distinct pollinators, together with genetic, geographic and ecological isolation, results in the differentiation of the breeding system in Rehmannia species.(3) The main results of leaf traits show: R. henryi could grow in a hostile environment for its lower SLA and higher LMA. R. chingii could grow well in resourceful and suitable environment due to the highest SLA and lowest LMA. Owing to the lowest leaf nitrogen (N) and phosphorus (P) in R. solanifolia, we speculate that photosynthetic rate of R. solanifolia is low in nature, and we get the similar results in the studies on photosynthetic physiology in Rehmannia.With the increase of the light intensity, net light photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency have increased to different extent in Rehmannia, while the intercellular CO2 concentration decreased significantly. Among the five species, R. glutinosa is the highest in the net photosynthetic rate, the light saturation point, stomatal area and palisade tissue thickness, while the lowest in the intercellular CO2 concentration, and stomatal density. It indicates that R. glutinosa has good assimilative capacity and adaptive ability to the strong light, and could grow better in the condition of strong light and drought. And then R. henryi and R. piasezkii rank only second to R. glutinosa. R. solanifolia and R. chingii have the lowest light compensation point, and adapt to low light conditions and humid habitats with t with strong precipitation. They have the slow growth rate, which is also supported by the high N/P ratio. Correlation analyses showed that, the photosynthetic physiological index was non-significantly negatively correlated with leaf palisade tissue/leaf thickness (r=-0.538, P=0.092) and leaf structure traits (r=-0.267, P= 0.599), but significantly related to the ecological factors (the average temperature of the wet season) (r= 0.7191, P=0.025).(4) The transcriptome of Rehmannia leaf and flower were analyzed by high-throughputthe next generationsequencing technology to predict functional genes. PI gene, belonging to MADS-box gene family, is selected for its correlation to flower color and pollen abortion in plants. HEMA gene is also selected according to its function involving in the male sterility and the photosynthesis in plant. Phylogenetic trees of the two genes constructed by maximum likelihoodmethod are similar to the previous studies. The MFDM test showed that the PI gene and HEMA gene might not undergo natural selection.