  Recent experiments conducted in the International Space Station highlight the
apparent periodicity of leaf oscillations and other biological phenomena
associated with rhythmic variations of lunisolar forces. These events are
similar to those occurring on Earth, but with greater effects over a shorter
period of time. Among the possible disturbances, other than forced or
self-existing oscillations, parametric resonances appear caused by a small
periodic term; such is the case of fluids subjected to small periodic
variations in gravitational forces in microscopic or mesoscopic plant channels
filled with sap and air-vapor. The interface instabilities verify a Mathieu's
second order differential equation resulting from a Rayleigh-Taylor stability
model. These instabilities appear during the Moon's rotation around the Earth
and during the revolution of the International Space Station. They create
impulses of pressure and sap movements in the network of roots, stems and
leaves. The model can explain the effects of the lunar tide on plant growth.
The eccentricity of the lunar orbit around the Earth creates an important
difference between the apogee and perigee of the Moon's trajectory and
therefore the tidal effects can depend on the distance between the Moon and the
Earth.
