The reintroduction of Primulina tabacum Hance, a critically endangered endemic plant, in southern China

Summary

Primulina tabacum is a small perennial herb confined to the entrances of karst caves along the border of northern Guangdong and southern Hunan in southern China, growing only in alkaline, mineral-rich groundwater seepage. Fewer than 10,000 individuals remain, spread across just eight cave entrances, and the species carries national First Class protection status. Researchers at the South China Botanical Garden began studying the plant's distribution, genetics and pollination in 2002 and tried direct seed germination between 2003 and 2006, but no seeds sprouted. Tissue culture proved more successful: leaf explants taken in January 2007 yielded about 4,000 plantlets by July, of which roughly 7 percent died during acclimatization before 1,000 were transplanted into caves at Dixiahe, Lianzhou City in October 2007, unfenced, unfertilized and watered only in the first days after planting. Monthly monitoring for a year, then annual checks through 2012, tracked survival, height and cause of death, finding about 10 percent of transplants alive by 2012 and growing more slowly than wild plants, though those growing under a nurse moss, Gymnostomiella longinervis, fared notably better. The team also secured a small nature reserve at the site in 2007 and established an ex situ collection in 2010. The project is rated highly successful, and its authors credit the moss's sheltering effect as key to establishment.