"Amniotic Fluid" in Womb-Like Flower Bracts Protects Floral Development and Promotes Drought Resistance in Karst Habitats.

Water serves diverse functions in plant growth and reproduction. Here, we report a novel strategy in the terrestrial karst plant Hemiboea magnibracteata analogous to amniotic fluid in mammals. Developing flower buds enclosed in 'womb-like' bracts are completely immersed in fluids and protected against excessive temperature and desiccation. The reservoir of water also likely limits drought and calcium stress in the highly specialized abiotic conditions of karst habitats.