摘要：

Hyperhydricity can cause significant loss in the in vitro propagated plantlets. In order to predict and control its occurrence, a better understanding of the structural aspects and physiological features of hyperhydric plantlets is required. In this study, the ultrastructural and physiological changes associated with hyperhydric red beet plantlets were investigated. Our objective was to establish a correlation between the ultrastructural aspects of Beta vulgaris var. Conditiva leaflets and hypocotyls and the content of chlorophyll pigments extracted in N,N-dimethylformamide (DMF) of two type of plantlets: hyperhydric from a basal culture medium Murashige and Skoog (JAMA 15:473–497, 1962) prepared with distilled water (DW—155ppm Deuterium) and non-hyperhydric, cultivated on identical medium where distilled water was replaced with deuterium depleted water (DDW- 25ppm Deuterium) as a method of preventing hyperhydricity. Cell ultrastructure in hyperhydricity, both from the leaves, but especially from hypocotyls, showed denatured chloroplasts in a myxoplasm mass formed by the damage of the tonoplast and the mixing of the cytoplasm with the vacuolar juice. The nuclei were picnotic, presenting paranucleolar corpuscles. The amount of assimilating pigments was significantly reduced in the plantlets grown on medium prepared with DW as compared to the normal, non-hyperhydric ones from medium prepared with DDW. Both evaluations showed that, in red beet, DDW also prevents the appearance of hyperhydricity.

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