RESPONSE OF Cattleya forbesii ORCHID TO INCREASING SILICON CONCENTRATIONS IN VITRO

Abstract

-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 SiO 2 (0.0, 0.5, 1.0, 1.5, and 2.0 g·L −1 ). 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.Keywords: Micropropagation, Culture medium, Amorphous silica. SILÍCIO NO DESENVOLVIMENTO IN VITRO DA ORQUÍDEA Cattleya forbesiiRESUMO -A adição de silício (Si) aos meios de cultura tem apontado melhor desenvolvimento das plântulas cultivadas in vitro e redução das perdas durante a fase de aclimatização. Objetivou-se avaliar cinco concentrações de SiO 2 (0,0; 0,5; 1,0; 1,5 e 2,0 g·L −1 ) em meio de cultura MS sobre o crescimento in vitro da orquídea Cattleya forbesii. Aos 200 dias, avaliou-se as variáveis: número de raízes, comprimento médio do sistema radicular, área foliar, número de folhas e de brotos, altura da parte aérea, massa fresca e seca de raízes e de parte aérea, conteúdo de água das raízes e da parte aérea, e pH final dos meios de cultura. Para a maioria das variáveis avaliadas observou-se decréscimo em função do aumento da concentração de Si, reduzindo o desenvolvimento vegetativo in vitro da C. forbesii. Além disso, detectou-se acúmulo de Si nos tecidos foliares por meio da microscopia eletrônica de varredura, confirmando a absorção deste pelas plântulas. Para o crescimento in vitro da espécie estudada, a fonte e concentrações de Si testadas, não apresentaram efeito benéfico.Palavras-chave: Micropropagação. Meio de cultura. Sílica amorfa. ________________ *

The Effects of Potassium Silicate as a Component of Nutrient Medium for Selected in Vitro Cultures of Prunus and Corylus Genera

“…It was described that silicon can improve growth characteristics of micropropagated plants and their morphology, although the molecular and biochemical bases of silicon actions on organogenesis remain unknown . Decrease in an occurrence of hyperhydricity and oxidative browning of shoots in plant tissue cultures enriched by silicon was also reported Colombo et al, 2016). This behaviour confirmed also study based on the dispersive X-ray study of Cotoneaster wilsonii leaves (Sivanesan et al, 2011), where no trace of silicon in the hyperhydric leaf samples was observed, while in non-hyperhydric plants silicon was found.…”

Application of silicon sources in yam (Dioscorea spp.) micropropagation

“…Similarly, Asmar et al (2013b) found no significant difference in root number for any silicon sources they used. Colombo et al (2016) found no significant effect of silicon sources and concentrations on the in vitro growth of an orchid (Cattleya forbesii). However, Soares et al (2011) reported a positive effect of sodium silicate on root number.…”

“…Reports of satisfactory in vitro results for Si supplementation include studies of ornithogalum (Ziv et al, 2010), begonia (Lim et al, 2012), water reed (Mathé et al, 2012), rice (He et al, 2013), pear (Reed et al, 2013), orchids Soares et al, 2012;Colombo et al, 2016), banana plants (Asmar et al, 2013a, b), ajuga (Sivanesan and Jeong, 2014), and anthurium (Dias et al, 2014). However, no study has reported the effects of Si addition to yam micropropagation culture media.…”

Silicon and agar on in vitro development of cockscomb (Amaranthaceae)

“…Although various researchers have observed increments in phytotechnical parameters through the use of sources containing silicon, such as an increased number of leaves of the orchid, Cattleya loddigesii Lindl., with the incorporation of sodium silicate and potassium in the culture medium (Soares et al, 2011), it is important to stress that these sources are not pure, presenting other elements in their composition, like sodium and potassium. Therefore, the results achieved cannot be attributed exclusively to silicon, but also to other associated elements, as reported by other authors (Soares et al, 2011;Colombo et al, 2016). In contrast, in the present study, a pure source of silicon was used, silicic acid (H 4 SiO 4 ), which may have been insufficient to ensure a significant result regarding the phytotechnical characteristics, although it has contributed to reduce damage caused by saline stress under in vitro conditions (Rezende et al, 2017 However, some studies show that silicate sources did not affect the in vitro development of various plant species, mainly of ornamentals, such as the C. loddigesii (Soares et al, 2013) and C. forbesii Lindl.…”

“…In contrast, in the present study, a pure source of silicon was used, silicic acid (H 4 SiO 4 ), which may have been insufficient to ensure a significant result regarding the phytotechnical characteristics, although it has contributed to reduce damage caused by saline stress under in vitro conditions (Rezende et al, 2017 However, some studies show that silicate sources did not affect the in vitro development of various plant species, mainly of ornamentals, such as the C. loddigesii (Soares et al, 2013) and C. forbesii Lindl. (Colombo et al, 2016) orchids. Thus, the addition of sodium silicate (Na 2 SiO 3 ) to the Knudson C culture medium did not affect the growth in the number of orchid shoots (C. loddigesii) (Soares et al, 2013).…”