Vanessa Favetta

SILÍCIO NO DESENVOLVIMENTO IN VITRO DA ORQUÍDEA Cattleya forbesii

Addition of Silicon (Si) to culture media has been shown to improve the development of seedlings grown in vitro, and to reduce losses during the acclimatization phase. The objective of this study was to evaluate the in vitro growth of Cattleya forbesii (Orchidaceae) in MS medium containing five different concentrations of SiO2 (0.0, 0.5, 1.0, 1.5, and 2.0 g·L ). At day 200, the following variables were measured: number of roots, average length of the root system, leaf area, number of leaves and shoots, shoot height, fresh and dry masses of roots and shoots, water content of roots and shoots, and pH of the culture medium. Most variables decreased as the concentration of Si increased, reducing the in vitro vegetative growth of C. forbesii. Accumulation of Si in leaf tissues was detected by scanning electron microscopy, confirming uptake by plants. The Si source and concentrations tested showed no beneficial effect on in vitro growth of C. forbesii.

Cultivo in vitro de Vanda tricolor Lindl. em meios de cultura simplificados

As orquideas do genero Vanda sao apreciadas pela exuberância de suas floradas e, diferentemente de outras orquideas, essas plantas, de crescimento lento e monopodial, nao apresentam brotacoes laterais que dao origem a novas mudas, caracteristicas estas que lhes conferem alto valor de mercado. Entao, para produzi-las em escala comercial, e preciso recorrer as tecnicas de propagacao in vitro, em que o meio de cultura adequado e um dos fatores mais importantes para o desenvolvimento das plântulas. Plântulas de Vanda tricolor, aos 150 dias de idade, foram subcultivadas em meio MS e meios de cultura a base de fertilizantes comerciais, com e sem adicao de polpa de banana ‘Nanica’ (100 g L–1). O delineamento experimental adotado foi o inteiramente casualizado, composto por 12 tratamentos e seis repeticoes, com sete plântulas. Aos 180 dias, avaliaram-se as variaveis: area foliar; numero de folhas e raizes; comprimento medio do sistema radicular e a materia seca das folhas, raizes e total. Conclui-se que e possivel utilizar o meio simplificado a base de fertilizante Biofert® (08-09-09) acrescido de polpa de banana em substituicao ao meio MS para o desenvolvimento in vitro de V. tricolor

Collect Seasons, Indolebutyric Acid and Substrates on Rooting of ‘Bengal’ Lychee Cuttings

Lychee ( Litchi chinensis Sonn.) propagation by cuttings is a promising alternative in commercial production of seedlings, since it is an easy procedure, in addition to enabling the standardization in the field and the reduction in production costs. Therefore the objective of this work was to evaluate ‘Bengal’ lychee cuttings rooting, collected in spring and summer, using different concentrations of indolebutyric acid (IBA) and substrates. The experimental design was completely randomized, in a 3 × 3 factorial arrangement, with 5 replications and 10 cuttings per plot, and the following factors were adopted: IBA concentrations (0; 1,000 and 2,000 mg L -1 ) and types of substrates (carbonized rice husk, vermiculite medium granules and coconut fiber). At 140 days, the following variables were evaluated: cuttings survival; leaf maintenance; cuttings unrooted with calli; cuttings rooted; roots number per cutting; root length and root dry mass. In addition, the pH, electrical conductivity, density and water retention capacity of the substrates were evaluated. There was no difference in IBA concentrations applied in both evaluated periods. However, in the spring, the carbonized rice husk provided highest mean for the measured variables. On the other hand, in the summer, the rooting percentage presented a lower average in all substrates (< 1%), independent of the IBA concentrations. It was concluded that the ‘Bengal’ lychee propagation by cutting can be carried out in the spring, using carbonized rice husk as substrate, without IBA.

Substrates and irrigation levels for growing desert rose in pots

In the past decades, desert rose has become a very popular ornamental plant, especially among collectors, due to its exotic and sculptural forms. However, it has been grown on a commercial scale only recently, and little is known about how to best manage it as a container-grown plant, or even which potting medium (substrate) to recommend. Therefore, the aim of this study was to investigate the interactions between potting media and irrigation levels for growing desert rose as a potted ornamental plant. The experiment was conducted in a greenhouse using a 6 x 2 factorial arrangement with six replications, six potting media and two irrigation levels. The mixes were characterized by measuring their physical properties, specifically the density and water retention capacity (WRC), as well as chemical properties, such as the pH and electrical conductivity (EC). After 210 days, plant growth and plant water consumption were evaluated and measured. A lower dry density for the vermiculite mixes was observed in comparison to that for the sand mixes. However, WRC ranged from 428 to 528 mL L-1 among the mixes, values considered close to ideal. In general, plant growth exhibited higher increases in mixes consisting of coconut fiber + sand or vermiculite, regardless of the irrigation level. Mixes of vermiculite + coconut fiber and sand + coconut fiber can be used to grow desert rose in pots, as long as irrigation is used to maintain the moisture content of the potting medium (mix) between 60-70% and 80-90% of the WRC.