Effects of Desiccation on Net Photosynthetic Activity in the Basidiomycete Lichen Cora pavonia E. Fries from the Cloud/Mist Zone of the Tropical Volcano La Soufrière (Guadeloupe)

Abstract

The recovery of net photosynthetic (NP) activity following pretreatment desiccation of 4, 24, 72, and 240 hr duration is described for thalli of Cora pavonia E. Fries from the cloud/mist zone of La Soufridre. Rates of NP activity (as measured by rates of CO2 uptake) recovered rapidly following 4 hr pretreatment desiccation, reaching half their maximum value (Pma) of 14.3 mmol CO2 m-2 s-' (x 10-4) only 10 minutes after thallus rehydration. NP recovery was marginally slower after 24 and 72 hr pretreatment desiccation exposure, with half maximal values of NP activity respectively reached after 16 and 14 minutes thallus rehydration, although Pmax fell to 12.8 mmol CO2 m-2 s-' (x 10-4) in the 72 hr pretreatment group. An abrupt decline in rates ofNP activity was seen after 240 hr desiccation pretreatment, with Pmax reaching only 0.8 mmol CO2 m-2s-' (x 10-4). These response patterns, although pointing to the extreme sensitivity ofC. pavonia thalli to extended periods of desiccation exposure, also underline the rapid recovery of NP activity expected following most shorter periods of desiccation exposure. This pattern of rapid short term rehydration recovery stands in contrast to previously observed patterns of rehydration response in lichens from north temperate mesic environments as well as those previously documented for populations of Stereo- caulon virgatum, also from the cloud/mist zone of La Soufridre. The differential response of blue- green (cyanobacterial) versus green algal phycobionts to periods of desiccation exposure is discussed in context of these response patterns.