Enxertia e propagação in vitro de fáfia [Pfaffia glomerata (Spreng.) Pedersen]

• Autor(a) principal: Iarema, Lourdes
• Data de Publicação: 2008
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/352
• topic: Pfaffia glomerata; Enxertia in vitro; β-ecdisona; Propagação fotoautotrófica; Pfaffia glomerata; In vitro micrografting; β-ecdysone; Photoautotrophic propagation; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA

Pfaffia glomerata, popularly known as Brazilian Ginseng, is an important medicinal species whose market demand and extractivism form led to its inclusion in the priority conservation species list. It presents great genetic diversity among its natural populations, being this variability expressed both in root biomass production, organ of interest of the species, as in the active principle content (β-ecdysone). Thereby, the present work aimed: (a) to evaluate in vitro micrografting efficiency in two P. glomerata accessions to establish a compatible combination between a low- (2202) and a high-producing (2209) β-ecdysone accessions, in order to increase the production of the commercial interest compound; and (b) to evaluate the photoautotrophic capacity of P. glomerata propagated in vitro by comparison of physiological and structural parameters under heterotrophic, photomixotrophic and photoautotrophic conditions. In in vitro micrografting, internodal segments and stem apexes, obtained from in vitro propagated plants, were used as rootstock and as scion, respectively, in order to establish reciprocal combinations between the accessions, self-micrografting, and comparisons with non-micrografted counterparts. Evaluations were made concerning the connection percentage and growing features of graftings during in vitro stage (at 30 days) and survival and growing of micrografted plants both in vitro as in ex vitro conditions, being monitored throughout 360 days after micrografting. The acclimatization process was monitored by physiological parameters, such as chloroplastidic pigments tenors, chlorophyll fluorescence, and photossynthetic rates. The time course of grafting connections was monitored by histological analyses in the periods of 7, 14, 21, 28, 35, 70 and 100 days after the in vitro grafting. Well-formed micrografting connections achieved indexes varying from regular to excellent in 80% of plants in all combinations. The micrografted plants had lower in vitro growth rates as compared to the non-grafted ones. Mortality rates (2.5-17.5%) were only observed during the phase of in vitro establishment. Analyzing the physiological patterns statistical differences were not detected among the treatments, however considering the cultivation conditions which plants were submitted, the greenhouse was the best environment tested. Under field conditions, the phenology difference between both accessions tested was very expressive, especially concerning root and inflorescence production, as well as susceptibility to insects attack. Accession 2202 plants presented higher active principle concentration in leaves, and higher number of injuries resulting from insect attack to the shoots. The accessions considered the greatest active principle producer was susceptible to nematode attack and exhibited gall symptoms, while the other access was resistant. Interestingly, the nematodes positively influenced β-ecdysone production in roots, but did not commit plants development. Micrografting promoted higher active principle concentration when constituted by accession 2202 as scion and accession 2209 as rootstock, proving the existence of physiological interactions between grafting components. Anatomical evaluations indicated that formation of calli in graft union region occurred as an immediate response to injury, and vascular reconnection of graftings occurred 21 days after micrografting performance. There was no structural difference in healing process among treatments. Results indicated efficiency of in vitro micrografting application in establishing different accession combinations of P. glomerata and obtainment of higher concentrations of β- ecdysone on roots. Nodal segments were used for propagation in sucrose-containing (0 to 30 g L-1) medium combined with closure types: 1. one polyvinyl chloride transparent film layer (PVC); 2. polypropylene rigid lid (LWH); 3. LWH with one orifice (L1H); and 4. LWH with 2 orifices (L2H) covered by gas exchanging permeable membranes. The experiment was maintained in growth room at 25 ± 2 °C under 16 hours of photoperiod with 50 µmol m-2 s-1 irradiance. Significant morphological differences were observed among treatments; plants cultivated with sucrose and membrane closure were the most vigorous. However, analyzing growing patterns plants cultivated without sucrose and with membranes closure did not differ statistically from other heterotrophic cultivation treatments. Sucrose influenced physiological responses, with highest content of chloroplastidic pigments and higher amount of fresh mass with this carbohydrate, while photosynthetic rates were higher in sucrose-lacking medium. Leaf structural analysis demonstrated influence of carbohydrate source on cell wall formation, supporting tissues and vascular bundles differentiation. Plants cultivated without both sucrose and membrane closure presented poorly formed stomata and hypertrophic cells, while with this carbohydrate source, despite closure types used, leaves presented well defined organization. Plants cultivated without sucrose and with two membranes closure presented typical in vitro organization. However, this treatment presented the highest leaf area between treatments, without growth compromising. Therefore, P. glomerata has potential for photoautotrophic propagation.