Membrane integrity, oxidative damage and chlorophyll fluorescence during dehydration of the thalloid liverwort Monoclea forsteri Hook.

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Monoclea forsteri Hook. is a thalloid liverwort species that is found in damp habitats and can, therefore, be expected to be sensitive to dehydration. It does, however, have some unique chemical constituents and anatomical features that could play a role in dealing with the adverse effects of water deficits. Corresponding to the habitat, M. forsteri lost its turgor at high relative water content (RWC≈0.90) and did not survive drying below 20% RWC. Moreover, the gametophytes showed an increase in malondialdehyde content and a depletion of the ascorbate pool during dehydration, indicating oxidative damage. Cellular constituents did not affect turgor pressure during drying and electrolyte leakage from the cells was greatly increased at RWC<0.20. Photosynthetic processes seemed not to be affected by the loss of turgor, but a decline appeared to correlate with an increase in electrolyte leakage. A speedy and fully sustained recovery from dehydration was realized from water contents above 30% and seemed only to be possible if membrane integrity could be preserved. Anatomical characteristics within M. forsteri gametophytes deserve further investigation to better understand their physiological functions.