Brandisia hancei (Paulowniaceae) is a widely distributed shrub in karst regions in southwestern China. Its seeds have a membranous wing, and they mature just before the rainy season begins. To assess the effect of the wing on seed dispersal and germination of B. hancei, we measured the dispersal distance at varying wind speeds and release heights, falling duration from different release heights, floating duration on still water, rates of imbibition of water, and drying and soil adherence to seeds. Germination experiments were conducted on intact and de-winged seeds immediately after harvest. The wing increased the falling duration in still air and the floating ability on water. Dispersal distance of winged and de-winged seeds did not differ at a wind speed of 2.8 m s−1, but at 3.6 and 4.0 m s−1 dispersal distances were greater for de-winged than for winged seeds. Seed wing had little effect of absorption and retention of water, but significantly increased soil adherence to the seeds. Mature seeds were non-dormant and germinated to over 90% with a mean germination time of about 10 days. By combining the environmental conditions in karst habitat with the seed traits of B. hancei, we conclude that dispersal and germination of winged seeds are adapted to the precipitation seasonality in heterogeneous habitats absence of soil.

Background: Secondary pollen presentation (SPP) is a phenomenon where pollen is relocated from within the anthers to other floral structures for presentation. Aims: We report a new mechanism of androecial SPP on anther hairs, which is involved in increasing reproductive fitness in Brandisia hancei. Methods: The morphological change of anther hairs during floral ageing was recorded, and pollen grains were quantified after anther hair removal to clarify the roles played by hairs in pollen retention. Additionally, fruit set and seed set were assessed to investigate the efficiency of anther hairs to reproductive success. Results: Young flowers of B. hancei showed approach herkogamy, while autonomous selfing was achieved by changes in relative positions of the stigma and anthers during floral ageing. In B. hancei, anthers developed characteristic hairs of epidermal origin, and hairs originated along the furrow between the paired pollen sacs and were used for SPP after anther dehiscence. Anther hairs increased pollen retention by over 70% in later floral-age stages, and seed set decreased by about 30% after anther hairs had been removed. Conclusions: In the process of autonomous selfing, SPP on anther hairs enhances both the male and female functions of the flowers of B. hancei.

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.

The thermoregulation of plants through the heliocaminiform effect of hollow structures is widespread but overlooked. Winter‐flowering plants in subtropical regions often suffer from low temperatures; however, the reproductive adaptations of these plants are not well understood. The functional advantages of persistent calyx and labiate corolla in Brandisia hancei were studied to clarify the mechanism of flower thermoregulation via heliocaminiform structures, and to understand the reproductive adaptation of floral temperature increases in winter. The daily dynamics of floral temperature were recorded under two weather conditions. Floral temperatures were also measured (1) under shaded conditions, (2) after calyx or corolla removal, and (3) after a hole was made or after the hole in the corolla was sealed. Seed production was then evaluated after perianth manipulation. The heliocaminiform effect of persistent calyx and labiate corolla was obvious under sunny conditions, and a maximum temperature excess up to 10°C was recorded. However, the temperature excess disappeared under overcast to rainy conditions or after shading. The removal of either the calyx or corolla generally reduced floral temperatures compared to intact flowers. Making a hole in the corolla also led to a slight decrease in floral temperature, which was partially restored after sealing the hole. Consistent with these thermal effects, the removal of the calyx and corolla even at later stages caused a reduction in seed production. Notably, making only a small hole in the corolla reduced seed production, whereas the number of seeds also rebounded after the hole was sealed. By effectively increasing floral temperature, the heliocaminiform effect of the calyx and corolla enhances the reproductive fitness of B. hancei. Our study presents empirical evidence for floral thermoregulation via heliocaminiform structures and for reproductive adaptation through floral temperature increases in winter conditions in subtropical regions.