Aeroterrestrial green algae are exposed to desiccation in their natural habitat, but their actual volume changes have not been investigated. Here, we measure the relative volume reduction (RVRED ) in Klebsormidium crenulatum and Zygnema sp. under different preset relative air humidities (RH). A new chamber allows monitoring RH during light microscopic observation of the desiccation process. The RHs were set in the range of ∼4 % to ∼95% in 10 steps. RVRED caused by the desiccation process was determined after full acclimation to the respective RHs. In K. crenulatum, RVRED (mean ± SE) was 46.4 ± 1.9%, in Zygnema sp. RVRED was only 34.3 ± 2.4% at the highest RH (∼95%) tested. This indicates a more pronounced water loss at higher RHs in K. crenulatum versus Zygnema sp. By contrast, at the lowest RH (∼4%) tested, RVRED ranged from 75.9 ± 2.7% in K. crenulatum to 83.9 ± 2.2% in Zygnema sp. The final volume reduction is therefore more drastic in Zygnema sp. These data contribute to our understanding of the desiccation process in streptophytic green algae, which are considered the closest ancestors of land plants.
Green algae living on the surface of soil are potentially exposed to drying. When they lose water, the volume of the alga is changed, but currently no measurements of these changes are available. We here investigate two green algae from different classes. The algae are exposed to defined relative air humidities in a specially constructed microscopic chamber, and the volume changes are measured. A distinct behaviour of the two investigated algae gives new insights in the lifestyle of terrestrial algae, the closest relatives of land plants.
Keywords: Desiccation; Streptophyta; hydraulic parameter; light microscopy; water loss.
© 2016 The Authors. Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.