Leaf anatomy of orchids micropropagated with different silicon concentrations

Abstract

Research on anatomical modifications under m fitro culture is essential to the definition and understanding ofthe development of micropropagated plants. Likewise, such research is essential to improve the steps ofthe acclimatization process. Accordingly, the objective ofthe present study is to verify the differences in the leaves anatomical traits of micropropagated orchids under calcium silicate concentrations. Seedlings of in i/iiro-germinated seeds, measuring 0.5 cm in length, were inoculated in 250 cm' pots with 60 mL MS culture medium and different silicon concentrations (0, 0.5, 1.0 and 2.0 mg L"') in different culture environments (natural environment, in a greenliouse and an artificial environment in a growth chamber) and in all statistical combinations. The pH ofthe culture medium was fixed at 5.8 ±0.1 and gelified with 5.5 g L'' of agar before autoclaving at 121°C and 1 atm for 20 min. After 150 days, an anatomical analysis was performed on crosssections of the plant leaves. A complete randomized design was used. Modifications occurred on the plants of those treatments containing silicon compared to those without silicon, and between environment fo artificial and natural light. Plants showed larger growth at the artificial light treatment with 0.5 and 2.0 mg L"' of calcium silicate respectively for the native and hybrid plants Treatments without silicate application induced chlorenchyma and epidermis deformation compared to silicon containing treatments, this effect can affect directly or indirectly plant growth at no silicon conditions. Keywords: microscopy, Orchidaceac, in vitro culture, calcium silicate.Anatomía foliar de orquídea mícropropagada com diferentes concentraçôes de silicio RESUMO. A realizaçâo de pesquisas a respeito das modificaçôes anatómicas decorrentes do cultivo in vitro sâo fundamentáis para o melhor entendimento e elucidaçlo do desenvolvimento das plantas micropropagadas. Dessa forma, tal pesquisa é essencial para melhorar as etapas do processo de aclimatizaçâo. Sendo assim, o objetivo deste trabalho foi identificar diferenças nas características anatómicas em folhas de orquídeas micropropagadas sob concentraçôes de silicato de calcio. Plántulas oriundas de sementes gemiinadas in vitro com aproximadamente 0,5 cm de comprimento foram inoculadas em frascos com capacidade para 250 cm^ contendo 60 mL de meio de cultura MS, acrescido de silicato de calcio (0; 0,5; 1,0 e 2,0 mg L"') em ambientes de cultivo (natural, em casa de vegetaçâo e artificial e, cm sala de crescimento), em todas as combinaçôes possiveis. O meio de cultura teve seu pH ajustado para 5,8 ± 0,1 e geleificado com 5,5 g L"' de ágar, previamente ao processo de autoclavagem (121°C) por 20 minutos. Após 150 dias de cultivo, as follias das plantas foram submetidas à avaliaçao anatómica por meio de secçoes transversais. O delineamento experimental foi o inteiramente casualizado. Ocorreram modificaçôes nos tratamentos contendo silicio em comparaçâo com aqueles isentos de silicio, e entre os ambientes de luz artificial e natur...

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