Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Drought stress and revival of mosses (cytological effects of de- and rehydration)

Auteur : Reimann, Jakob

Université de soutenance : Universität Wien

Grade : Masterarbeit 2022

Résumé
This work aims to elucidate the effects of drought stress on the morphology and physiology of a small selection of bryophyte species as droughts are becoming more common and mosses could serve as very easy to handle model organisms. Four different bryophyte species were compared in their dehydration and rehydration behaviour. The mosses were compared in terms of shrinkage and regain of their leaf area, as well as, cell size (area), length and width and their photosynthetic activity. This study investigated the effects of dehydration and the ability to recover from this severe dehydration on different moss species. Those species were, Atrichum undulatum, Conocephalum conicum, Funaria hygrometrica and Physcomitrium patens. Light stereo microscopy was used for the leaf area and the cell area/width/length measurement. The photosynthetic activity measurement was determined with a “chlorophyll fluorometer IMAGING-PAM”. In all experiments the leafy gametophyte was examined. The tested species showed significant differences in their reaction to dehydration and the following rehydration. The tested moss species differed significantly in their ability to withstand drought stress. Those results were proven by the photosynthesis activity measurement. Overall, there were unexpected differences between the almost randomly picked species in their reaction to dehydration and rehydration. All mosses were very resilient to dehydration but some more than others. The statement that bryophytes can withstand dehydration to a high degree by (Proctor and Pence, 2002) is confirmed by this study. Different coping mechanisms of the moss species were found, some lost all their water within the cells very quickly while others contained their water relatively well within their cells. The same results were found in the photosynthesis activity measurement. Some species lower the photosynthesis activity very quickly and regain it quickly while others lower it much slower and do not regain it that fast. Significant correlations between the photosynthesis activity and the ability to survive severe drought were found. In the 3D recordings some species showed cytorrhysis, those species were also the most drought resilient species in the other experiments. No correlation was found between cell shape and their ability to withstand dehydration or recover from it. It was found that the only tested multilayered species (C. conicum) had the biggest problems in terms of coping with drought stress.

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