Osmotic and Atmospheric Dehydration Effects in the Lichens Hypogymnia Physodes,Lobaria Pulmonaria,and Peltigera Aphthosa: An in vivo Study of the Chlorophyll Fluorescence Induction |
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Authors: | Jensen M Chakir Samira Feige GB |
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Institution: | 1.Universit?t-GII Essen, FB 9, Botanik, Universit?tsstr. 5, D-45117, Essen, Germany e-mail ; |
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Abstract: | Inactivation of photosynthesis during atmospheric and osmotic (highly concentrated NaCl or sucrose solutions) dehydration
was monitored by measurement of chlorophyll fluorescence induction (OIP-phase, Kautsky-curves) in three lichen species. The
induction curves were changed in a very similar way by all three treatments. All dehydration effects were rapidly reversible
after rehydration. At relatively mild water stress, the rise time to the transient peak Fp was prolonged, and the variable part of fluorescence was diminished. In addition, at severe water stress, a considerable
decline of the F0 value was observed. For NaCl treatment this effect started at water potentials <-8.5 MPa in P. aphthosa, <-12 MPa in H. physodes, and <-21 MPa in L. pulmonaria. Above these water potentials, our observations are in agreement with values from desiccation-tolerant algae, higher plants,
and lichens, where an inactivation on the photosystem 2 (PS2) donor side has been postulated. At very low water potentials,
the decrease in F0 probably monitors changes in the organization of the antenna apparatus of PS2.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | green algae NaCl sucrose water potential water stress |
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