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It was shown in our previous reports that a few spores of moss Venturiella could tolerate the very high pressure of 20 GPa for 30 min and germinated a protonema to the length of 30 μm. However, these spores did not grow any further, and disappeared at around 30 days of incubation after seeded. On the other hand, colonies of blue-green alga Microcystis flos-aquae came to appear about 76 days after the moss spores were seeded. Many of these colonies appeared at the places where the moss spores had disappeared. These colonies were formed by the algae that had adhered to the spore cases of the moss and survived after exposure to the very high pressure of 20 GPa. Though the appearance of the colonies of high pressure exposed algae was delayed by about 50 days compared with that of the control group which was not exposed to high pressure, there seems no difference in their shape and color from those of the control group. The pressure tolerance of blue-green alga is found to be enormously strong, and it can survive after exposure to the high pressure which corresponds to the depth of about 550–600 km from the surface of the Earth, just above the lower mantle.

In our previous studies on the tolerance of living organisms such as planktons and spores of mosses to the high hydrostatic pressure of 7.5 GPa, we showed that all the samples could be borne at this high pressure. These studies have been extended to the extreme high pressure of 20 GPa by using a Kawai-type octahedral anvil press. It was found that the average diameter of the spores of Venturiella exposed to 20 GPa for 30 min was 25.5 μm, which is 16.5% smaller (40.0% smaller in volume) than that of the control group which was not exposed to high pressure. The inner organisms showed a further extent of plastic deformation. As a result, a gap appeared between the outer cover and the cytoplasm. A relationship has been obtained between the survival ratio and plastic deformation of spores of moss Venturiella caused by the application of ultra high pressure.

The experiment on the search for life under very high pressure done on small animal, tardigrade, has been extended to the moss Ptychomitrium. Several spore placentas of the moss Ptychomitrium were sealed in a small Teflon capsule together with fluorinate as liquid pressure medium. The capsule was put in the center of a pyrophillite cube. This cube was compressed by six tungsten–carbide second-stage anvils with a front edge length of 4.0 mm. These anvils were compressed by a first stage, 250 ton press. It was proven that 80–90% of the spores were alive and germinated after being exposed to the maximum 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 6 days. The pressure tolerance of moss is found to be much stronger than tardigrades.

We studied the tolerance of living organisms, such as a small animal (Milnesium tardigradum), a small crustacean (Artemia), non-vascular plants or moss (Ptichomitrium and Venturiella), and a vascular plant (Trifolium) to the extremely high hydrostatic pressure of 7.5 GPa. It turned out that most of the high pressure exposed seeds of white clover were alive. Those exposed to 7.5 GPa for up to 1 day and seeded on agar germinated roots. Those exposed for up to 1 hour and seeded on soil germinated stems and leaves. Considering the fact that proteins begins to unfold around 0.3 GPa, it seems difficult to understand that all the living samples which have been investigated can survive after exposure to 7.5 GPa.

It was shown by the present authors group that tardigrade can survive under high pressure of 7.5 GPa. In the case of land plants, however, no result of such experiment has been reported. We have extended our experiments to moss searching for lives under very high pressure. Spore placentas of moss 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 two-stage cubic anvil press. The pressure was kept constant at the maximum pressure for12, 24, 72 and 144 hours. After the pressure was released, the spores were seeded on a ager medium, and incubated for one week and more longer at 25°C with white light of 2000 lux. It was proved that 70-90% of the spores were alive and germinated after exposed to the maximum pressure of 7.5 GPa for up to 72 hours. However, after exposed to 7.5 GPa for 6 days, only 4 individuals in a hundred were germinated. The pressure tolerance of moss Venturiella is found to be stronger than a small animal, tardigrade.