LIGHT MICROSCOPIC STUDY OF PORELLA PLATYPHYLLA (L.) PFEIFF. CELLS UNDER VARIOUS ABIOTIC STRESS FACTORS

Absztrakt

The leaf cells of the extremely desiccation tolerant leafy liverwort, Porella platyphylla can be studied natively by light microscope due to their one-cell layered structure. The effects of various abiotic stress factors can be also monitored at cell level following the rate of plasmolysis, and the changes in the structure of cell organelles (chloroplasts, vacuoles, oil bodies). Furthermore our aim was to test the applicability of different stains (neutral red, toluidine blue, methylene blue, SudanIII) in Porella platyphylla cells under experimental treatments. Natural drying at room temperature (for 1 day, 1 week, ’62 years’ by checking an old herbarium sample), subsequent rehydration, freezing at -18 and -80°C, heat treatment at 40, 50 and 100°C (for 5 and 10 min), osmotic and salt stress (0.5 M NaCl, 1 M KSCN, 25% PEG8000) were applied. In the course of monitoring the various stress factors the use of neutral red (at pH 7.6) staining proved to be the most optimal. In control plants one big cherry coloured vacuole was discovered after staining. The central vacuole fragmented into small pieces, then ruptured after 10 minutes, due to the strongest osmotic treatment (1 M KSCN). At the same time chloroplasts were irreversibly disrupted. The oil bodies proved to be the most resistant structures against the various stress factors. Plants hardened for 5-month-long cold were able to regenerate their cell structure and metabolism within 24 hours after a 1-day natural drying. The 3 different high temperature treatments (40, 50, 100°C) resulted in similar changes in the cell structure to those induced by the cold treatments. Tissues were coloured by neutral red before freezing and heat treatments suffered less injury compared with the unstained ones. Light microscopic studies are convenient to monitor the regeneration of the cell structure after stress.