Carbohydrate status of in vitro grown trillium rhizomes
Date
2006
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Publisher
University of Delaware
Abstract
Trilliums are herbaceous perennials and forest understory geophytes that grow from underground rhizomes commonly producing only a single new shoot each year. Reasonable protocols need to be further developed for the micropropagation of trilliums. Excision of apical shoots from tissue-cultured rhizomes caused the generation of more mini-rhizomes (MR) in Trillium sulcatum but had no affect on T. decumbens. The following studies focused on field establishment and maturation of tissue-cultured rhizomes of T. decumbens, T. discolor, and T. maculatum by analyzing for carbohydrate status using both qualitative (Lugol's iodine staining) and quantitative colorimetic starch assays, and by quantitating the soluble sugars glucose, fructose, ribose and sucrose via HPLC. To study the effect of carbohydrate changes on the successful reestablishment and growth of trillium, a series of both in vitro and ex vitro treatments were initiated on tissue-cultured rhizomes. Growth regulator experiments {maintenance medium augmented with auxin [1% solution of Dip 'N Grow (5 μM indole-3-butyric acid (IBA) and 2.7 μM 1-naphthaleneacetic acid (NAA)], cytokinin [benzyl adenine (BA) adjusted to 0, 4.4 (control) or 8.8 μM], or gibberellic acid [(GA) 5 μM]; followed by ex vitro coldroom (4°C) storage for 8 weeks} failed to induce a carbohydrate concentration increase in trillium rhizomes. Greenhouse and coldroom experiments to understand starch fluctuation confirmed the depletion of starch after 9 weeks. When trillium rhizomes were placed in 4-, 6-, or 8-week offset cold-warm stratification periods starch was clearly detectable after 12 (6-week stratification) and 16 (4- and 8-week stratifications) weeks. Field-grown rhizomes were also examined to profile natural carbohydrate fluctuations associated with seasonality. Trillium rhizomes displayed a pattern similar to that of other geophytes whose seasonal carbohydrate fluctuations are known.