Nitrogen- and helium-induced anoxia: different lethal effects on rye seeds.

Prolonged exposures to acute anoxia caused progressive reductions in the viability of hydrated seeds of Prolific rye. For equal exposures of 9 days or longer, mortality was significantly higher in helium than in nitrogen. The findings suggest that prolonged use of helium as a component of atmospheres in manned space capsules may be harmful.