6533b7d6fe1ef96bd1266eae

RESEARCH PRODUCT

Factors affecting shoot proliferation and vitrification inDigitalis obscura cultures

subject

description

Variations of composition and consistency of the culture medium and time of exposure to growth regulators were assayed to optimize normal caulogenic response ofDigitalis obscura hypocotyls cultured in vitro. The effects of the culture conditions on physiologic changes related to vitrification of the regenerated plants were also investigated. Liquid medium increased the bud-forming capacity of the explants but induced buds failed to develop into shoots and showed symptoms of vitrification. On agar-solidified media, maximum multiplication rates were achieved with 0.7% agar. Increasing agar concentration reduced vitrification but lowered the propagation rate. Changes in the strength of the macronutrients of Murashige and Skoog did not significantly affect the bud-forming capacity of the explants. In contrast, a drastic inhibitory effect on both bud formation and shoot elongation was produced when NH4NO3 was omitted. Reduction of NH4NO3 to one-half or one-fourth of the level of the original formulation not only increased the bud-forming capacity ofD. obscura hypocotyls but also resulted in less vitrification. Modifications of time and method of exposure to growth regulators neither improved the multiplication rates nor overcame vitrification. Cardenolide content was lower in vitrified than in normal cultures and coincided with an overall reduction of photosynthetic pigments, lignin, and dry matter.