When a water deficit was induced in a mature fully turgid leaf of Ricinus communis L. the tissues could completely regain full turgidity by absorption of water at around 1° C. This was true of large water deficits (40%) which greatly exceeded the cell wall volume (12%). This uptake therefore included movement into the protoplasts and was not restricted to the cell walls alone as had been previously supposed (Weatherley, 1963).

However, resaturation of leaf tissues taken from plants which had suffered from drought for more prolonged periods, could be separated into two fractions. An uptake at 1° C was attributable as before to recovery of turgor; an extra uptake at 25° C seemed to be a growth phenomenon inhibited at the lower temperature. This represented a rapid cell expansion following a period of growth arrestment due to water stress.

The implications of these findings for the measurement of relative water content are discussed.