Moss Spores Can Tolerate Ultra-high Pressure

It was shown by the present authors' group that tardigrade can survive under very high hydrostatic pressure range of 7.5 GPa. In the case of small land plants, the tolerance to high pressure seems stronger than such a small animal, tardigrade. We have extended our experiments to two popular mosses, Ptychomitrium and Venturiella searching for lives under very high pressure range. Spore placentas of moss Ptychomitrium and Venturiella were sealed in a small Teflon capsule together with a liquid pressure medium. The capsule was put in the center of a pyrophillite cube, and the maximum pressure of 7.5 GPa was applied using a 250-t cubic anvil press. The pressure was kept constant at the maximum pressure for various duration of time between 6 and 144 h. After the pressure was released, the spores were seeded on agar medium, and incubated for one week and longer at 25 °C with white light of 2,000-2,500 Lx. It was proven that 80-90% of the spores of moss Ptychomitrium were alive and germinated after being exposed to the very high pressure of 7.5 GPa for up to 48 h. Furthermore, a relatively high germination rate of about 35% was retained even after exposure to 7.5 GPa for 144 h. It was also proven that 70-90% of the spores of moss Venturiella were alive and germinated after exposure to 7.5 GPa for up to 72 h. However, after exposed to 7.5 GPa for 144 h, only four individuals in a hundred were germinated. The pressure tolerances of the mosses Ptychomitrium and Venturiella were found to be much stronger than tardigrade. The experiments were extended to the ultra-high pressure range up to 20 GPa, and a few spores of Venturiella were germinated up to the length of 30 μm. The mechanisms for such strong tolerance of moss spores will be discussed on the bases of the quality of the applied hydrostatic pressure, degree of the physical deformation and extremophiles.