Water-mediated fertilization has been considered a unique feature of early land plants. Currently, the prevailing view is that water-mediated fertilization has been lost during the evolutionary history of terrestrial flowering plants because it is non-adaptive.
The potentially positive effects of water on plant reproduction in terrestrial angiosperms have been largely ignored, aside from the obvious requirements of water for plant growth.
In a recent issue of New Phytologist, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) report a previously unknown water-mediated fertilization mechanism in Cautleya gracilis, a perennial herb in the ginger family (Zingiberaceae) in subtropical SW China.
The researchers began by documenting the floral biology of C. gracilis, including pollinator observations, compatibility status and the facility for autonomous self-pollination and the timing of this process.
The researchers discovered two pollen conditions: granular and a filiform mass depending on external weather conditions, which motivated them to evaluate the hypothesis that pollen transformation was induced by water (rain) and played a key role in reproduction.
They found that rainwater caused pollen germination in C. gracilis and that pollen tubes transported sperm to ovules resulting in fertilization and seed production.
“To our knowledge, this is the first demonstration of water-mediated fertilization under natural conditions in a terrestrial flowering plant”, said Dr. FAN Yongli, the first author of the study.
“We propose that the occurrence of water-mediated fertilization in C. gracilis is probably an adaptive reproductive mechanism, given the particular climatic context (i.e. in moist valleys above 1800 m above sea level in subtropical SW China ) in which this subtropical ginger occurs”, said Dr. FAN.
FAN Yongli Ph.D
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
Water-mediated fertilization in Cautleya gracilis, a subtropical terristrial flowering ginger plant.
(Images by FAN Yongli)