Genetic Diversity of Frankia in Nodules of Hippophae rhamnoides ssp. Sinensis Effects of soil moisture levels on photosynthesis, transpiration, and moisture use efficiency of female and male plants of Hippophae rhamnoides ssp. Sinensis Molecular Evidence for Bidirectional Hybrid Origin and Hippophae rhamnoides ssp. sinensis as the Mainly Maternal Plant of the Diploid Hybrid H.goniocarpa(Elaeagnaceae)