EfEcto dE difErEntEs agEntEs gElificantEs En la gErminación y dEsarrollo in vitro dE plántulas dE Echinocactus platyacanthus link Et otto (cactacEaE)EffEct of diffErEnt gElling agEnts on in vitro gErmination and sEEdling dEvElopmEnt of Echinocactus platyacanthus link Et otto (cactacEaE) a
A simple and efficient protocol has been developed in order to obtain healthy seedlings by asymbiotic germination of seeds from Laelia autumnalis. Seeds from mature capsules were germinated asymbiotically after being cultured on full- or half-strength Murashige and Skoog's (MS) medium, without plant growth regulators and with 3.0% or 1.5% of sucrose. The percentage of germinated seeds (% GS) was recorded during 6 weeks using three different conditions of incubation: light (80% GS, p < 0.05), darkness (30% GS) and white light photoperiod (100% GS, p < 0.05). The best seed germination percentages were found on the light and white light photoperiod conditions. Moreover, we also investigated the vasorelaxant action of the methanolic extracts from wild L. autumnalis (roots, pseudobulbs and leaves) and plantlets generated in vitro. Results showed that the methanolic extract of roots and pseudobulbs produced a significant vasodilator effect, in a concentration-dependent and endothelium-independent manner on norepinephrine (NE) and potassium chloride (KCl)-induced contractions in rat aortic thoracic rings. Nevertheless, the methanolic extract of leaves and plantlets showed no relevant vasorelaxant activity. Therefore, the results suggest that pseudobulbs and roots were the main tissues of the plant where vasorelaxant compounds are stored.
Zygotic embryos of Picea chihuahuana MartõÂ nez were cultivated in vitro to determine the time of organogenic competence and to maximize adventitious bud induction. The induction medium consisted of modi®ed B5 substrate supplemented with N 6 -benzyladenine (with or without naphthalene acetic acid) or kinetin (with or without 2-4, dichlorophenoxyacetic acid) at dierent concentrations and induction times. The minimum induction time required for bud formation was 14 d with kinetin and 17 d with N 6 -benzyladenine. After induction embryos were transferred to the proliferation medium (modi®ed B5 substrate with 50 % of its components and without growth regulators) for 30 d. The subsequent buds were transferred every 15 d to Schenk and Hildebrandt medium at half its concentration without growth regulators. The most eective treatments were 3 and 5 mg l À1 kinetin or N 6 -benzyladenine which produced ®ve to seven buds per embryo. The largest shoots were subjected to rooting trials with pulses of dierent concentrations of indole butyric acid resulting in only one bud developing a root. Histological analysis revealed clusters of three to four cells that became more evident as induction time increased. Kinetin promoted the development of an organized structure prior to adventitious buds formation sooner than N 6 -benzyladenine. # 2000 Annals of Botany Company
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