Interferometrische Untersuchungen zur Dynamik von Hydratur und Trockenmassegehalt während der lichtabhängigen Keimung der Akineten vonAnabaena variabilis KÜTZING

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Abstract
Calculations following interference-microscopical measurements performed on akinetes (A), heterocyts (H), and "vegetative" cells (F) of the Cyanobacterium (blue-green alga) Anabaena variabilis resulted in significant higher values of mean absolute dry matter content of the akinetes (2.06 . 10(-10) g; as compared to 0.46 . 10(-10) g and 0.31 . 10(-10) g for H and F, respectively). tthe water content of these resting cells (63%) was significantly lower than in the other two types of cells (H: 85%, F: 77%). Light exposition of the akinetes in fresh nutrition medium (i. e., conditions allowing germination within 30--50 h) resulted in a decrease of the relative dry matter content so that already in the period preceding the outgrowth of the germling the water content of the vegetative cells was achieved. Simultaneously their volume increased by the uptake of water; whereas the absolute content of dry matter remained constant or was even temporarily diminished during the first period. Only in the second period the values increased in some cases and then remained constant up to germination. The increased dry matter content, however, was not a precondition necessary for the germination of the akinetes. In darkness under otherwise unaltered conditions the values remained unchanged or, after a light period, came back to the initial level. The results demonstrate that formation and germination of the resting cells of Cyanobacteria as well are connected with an alteration in the hydratation level, i. e., in cells which continuously are kept under water saturated conditions. This increase by hydratation during the germination period is, as the germination process itself, strictly controlled by light.