| Abstract: | Tissue culture under conditions of boron deficiency Cambium tissue from sunflowers and carrots were cultured in nutrient solution according to Murashige and Skoog with graduated supplies of boron. A light-coloured and well growing callus was formed only in the presence of boron. Explants on a boron-deficient medium agglutinated at the edges, had only small areas of cell division and revealed appositions on the walls of some cells. Deficient tissues also became noticeably darker. Callus grown on normal medium and then transferred to boron-deficient medium slowed down in growth rate – at the latest after 4 weeks – and also turned dark. In contrast to normal calli, the deficient cultures could not be easily separated in water into individual cells or small cell groups. Moreover, the cells were smaller on the average and often revealed grainy contents and (in the case of carrots) accumulation of plasma at the ends of the cells. A large number of deficient cells were plasmolyzed. An accumulation of undifferentiated cells in the cambium region is particularly striking in dicotyledons under conditions of boron deficiency. If this symptom should be the result of cell division activity, then isolated cambium should react to boron deficiency with intensive cell division. Contrary to expectation, isolated cambium of sunflowers and carrots in tissue culture did not reveal a promotion of cell division under conditions of boron deficiency. These results indicate that the symptom of “increased cambium growth” in intact dicotyledons is due to a secondary effect of boron deficiency. |
