Foliar application of silicon can be beneficial to orchid growth, but it may also impair growth depending on the source and solution concentration. Due to the lack of information on silicon toxicity in long-term orchid nutrition, experiment with two different orchid species, Phalaenopsis Golden Peoker and Dendrobium Valentine, were performed. The plants were grown in plastic trays with dry Sphagnum in a greenhouse, being fed the nutrient solution without silicon in the first six months. After that, the plants were transplanted to individual plastic vessels (0.9 L). The treatments followed a completely randomized design with a 5 × 3 factorial consisting of five Si concentrations (control, 14.3, 28.6, 42.9 and 57.2 mmol L −1) and three sources (monosilicic acid, potassium silicate, and potassium silicate and sodium silicate mixture), with five replicates. After 18 months of Si foliar application, the Si, C, N, P, K, Ca, Mg and S levels, lignin content and biometric variables were determined for both species. The application of 27 and 16 mmol L −1 Si (potassium silicate and monosilicic acid) resulted in the highest values for the evaluated biometric parameters for Phalaenopsis and Dendrobium, respectively. The results suggest that silicon foliar application affected nutrient absorption and green color index of Phalaenopsis and Dendrobium, and the lignin content of Phalaenopsis. Application of concentrations greater than 39 and 18 mmol L −1 Si over 18 months was toxic to Phalaenopsis and Dendrobium, respectively, since the orchid dry matter decreased by 10% (critical level due to toxicity). Applying increasing concentrations of Si sources decreased the C:N:P stoichiometric ratio of orchids.

IVCrescimento in vitro e aclimatização de Cattleya loddigesii Lindley (Orchidaceae) com carvão ativado sob dois espectros luminosos

No abstract

Phalaenopsis and Dendrobium do not grow and flower well with 100% ammonium (NH 4-N); and there are detailed studies on the effects of nitrate (NO 3-N) and ammonium ratios on the flowering, but no information about accumulation of other nutrients and the effects of ammonium toxicity on orchids. For this reason, two experiments were carried out with orchids: Phalaenopsis 'Golden Peoker' and Dendrobium 'Valentine'. Six months after acclimatization the plants were transplanted to individual plastic vessels and the treatments consisted of five ratios (%) of nitrate / ammonium (0/100, 25/75, 50/50, 75/25, 100/0). The sources of NO 3-N and NH 4-N were calcium nitrate and ammonium sulfate, respectively. After 12 months treatment, when the plants were beginning to issuance of flower stem, the accumulation of: N, P, K, Ca and Mg in the shoot and biometric variables were evaluated for both species. The NH 4-N ratio of 40% and 50% of the total nitrogen benefited the growth of Phalaenopsis and Dendrobium, respectively. The application of higher proportions of ammonium resulted in decreased N, K, Ca and Mg absorption, index of green color and increased leakage of electrolytes in Phalaenopsis and Dendrobium. NH 4-N proportions greater than 75% for 12 months caused toxicity in Phalaenopsis and Dendrobium.

Dendrobium nobile Lindl. is one of the most cultivated and distributed orchids around the world; however, information on its nutrition is scarce. Our objective was to study the plant development and nutrient accumulation in plants of D. nobile weekly fertilized with 100 mL Sarruge nutrient solution at 75% concentration. One plant per replication was randomly collected every month, along 12 months, totaling four plants. Dry matter (DM) and nutrient accumulation were determined for the different plant parts. Plants had already accumulated nearly 50% of total DM up to the flowering stage (240 days after first fertilization, DAFF). Order and amount of accumulated nutrients, at 360 DAFF, was, in mg per plant: K (701.07) > N (339.44) > Ca (289.03) > Mg (135.44) > P (118.83) > S (23.56); in mg per plant, it was Fe (14,122.35) > Zn (5,277.82) > Mn (3,216.87) > B (1,253.02) > Cu (271.25).

ResumoEste trabalho foi realizado com objetivo de estudar a influência da concentração de sacarose no meio de cultura para o crescimento in vitro e aclimatização da orquídea epífita Cattleya loddigesii. Cinco tratamentos (ausência, 10, 20, 30 e 40g L -1 de sacarose) foram utilizados, em delineamento inteiramente casualizado. A semeadura procedeu-se em meio de cultura ½ MS e, após 90 dias as plântulas de 1,0 +/-0,2 cm foram distribuídas entre os tratamentos, em que permaneceram por mais 90 dias. Após 90 dias da transferência dos explantes para o meio contendo os tratamentos foi avaliado o número de raízes, comprimento da maior raiz, comprimento da parte aérea, comprimento da maior folha, número de folhas, massa de matéria seca total e pigmentos fotossintéticos. A porcentagem de sobrevivência foi aferida 75 dias após a aclimatização das plantas em casa de vegetação. Os dados das variáveis biométricas foram submetidos à análise de variância e regressão polinomial (p<0,05) e para os demais as médias foram comparadas pelo teste de Tukey (p<0,05). A concentração de 20g L -1 de sacarose favoreceu o crescimento in vitro, em todos os parâmetros avaliados, apresentou maior produção de clorofila a, clorofilas totais e carotenóides, além de maior sobrevivência em condições ex vitro. A concentração de 20g L -1 de sacarose no meio de cultura foi a de maior eficiência dentre as concentrações estudadas, tanto para o crescimento in vitro quanto estabelecimento ex vitro de Cattleya loddigesii. Palavras-chave: Micropropagação, carboidrato, orquídea brasileira AbstractThis work aimed to study the influence of sucrose in the culture medium for in vitro growth and acclimatization of the epiphytic orchid Cattleya loddigesii. Five sucrose treatments (absence, 10, 20, 30 and 40g L -1 ) were used in a randomic experimental design. Mature seeds were sowed in ½ MS culture medium and after 90 days the plantlets (1.0 +/-0.2 cm) were inoculated between the treatments, whereby they were remained more 90 days. After 180 days of the beginning of the experiment the plantlets were removed from the flasks and evaluated the number of roots, shoot length, number of leafs, total dry weight and photosynthetic pigments. Survival percentage was evaluated after 75 days of acclimatization. The data of biometric variables were analyzed by Anovaand polynomial regression (p<0.05). Theothers data were submitted to the Anova and the means compared by the Tukey test (p<0.05). The sucrose concentration of 20g L -1 favored the in vitro growth in all evaluated parameters, showed higher production of chlorophyll a, total chlorophyll and carotenoids, in addition to increased

RESUMOO presente estudo teve por objetivo analisar os aspectos da germinação e avaliar o efeito de concentrações de sacarose no crescimento in vitro de Cattleya violacea. Sementes provenientes de cápsulas fechadas foram semeadas em meio de cultura Murashige e Skoog (MS) e a morfologia externa da semente à plântula foi fotodocumentada em estereomicroscópio e microscópio eletrônico de varredura. Plântulas com 90 dias após a semeadura foram repicadas em meio de cultura ½ MS (com metade da concentração de macronutrientes) com diferentes concentrações de sacarose (0, 10, 20, 30 e 40 g L -1 ), incubadas nas mesmas condições in vitro por mais 150 dias e em seguida as plântulas foram avaliadas quanto ao número de raízes, comprimento da maior raiz, número de folhas, comprimento da parte aérea, massa fresca e seca total. Os dados biométricos foram submetidos à análise estatística e a eles ajustadas curvas de regressão. As sementes apresentaram testa reticulada com uma extremidade micropilar (aberta) e calazal (fechada); o embrião originou uma estrutura tuberiforme clorofilada denominada protocormo que pode apresentar rizóides, folíolos e quando provido de raiz é considerado plântula. A ausência de açúcar ou a maior concentração avaliada de sacarose foram prejudiciais ao crescimento da planta. A concentração de 27 g L -1 proporcionou maior crescimento in vitro possibilitando maior eficiência para a propagação massal dessa espécie de elevado potencial ornamental. PALAVRAS-CHAVE: Germinação assimbiótica, orquídea nativa, carboidrato. Initial development and in vitro growth of Cattleya violacea (Kunth) Rolfe in different sucrose concentrations ABSTRACTThe aims of this study were to analyze the initial germination aspects and evaluate the effect of sucrose concentrations on in vitro growth of Cattleya violacea. Mature seeds from closed pods were sowed on MS (Murashige and Skoog) culture medium. The external morphology of seed and plantlets were documented by light and scanning electron microscopy. Plantlets with 90 days after sowing were subcultured on ½ MS (with half-strength macronutrients concentrations) culture medium with different sucrose concentrations (0, 10, 20, 30 and 40 g L -1 ), incubated under the same in vitro conditions during more 150 days followed by the evaluation of root number, root length, shoot length, fresh and dry weight. The biometric data were statistically analyzed and regression curves constructed. The seeds showed reticulate seed coat with a micropylar (opened) and chalazal (closed) end; the embryo results a chlorophyllated tuberiforme structure called protocorm, which may have rhizoids, leaflets and is considered plantlet when it has root. Absence of sucrose or the highest evaluated sucrose concentration was detrimental for plant growth. The concentration of 27 g L -1 provided the highest in vitro growth enabling great efficiency for mass propagation of this species of high ornamental potential.

The beneficial effect of silicon on plants is known, but there are no studies demonstrating the effect of this element on protein and lignin production in ornamental plants. This study aimed to assess the effects of monosilicic acid fertigation at 0, 2, 4, and 8 mmol L-1 of Si on protein and lignin production of two ornamental species: Viola x wittrockiana Gams ex Nauenb. & Buttler ‘Majestic Giants II Fire’ e Tagetes erecta L. ‘Hero’ (color mix). The experiment was installed in a 4 × 2 factorial arrangement using a completely randomized design with five replications. After 90 days of the sowing, we assessed N and Si contents in shoot system, Si accumulation in shoot system, root, and total, and lignin and protein production. An increase in lignin followed by its reduction was observed from the concentration of 2.0 (4.29) and 4.3 (5.72) mmol L-1 of Si for Viola and Tagetes species, respectively. Silicon application promoted higher lignin content in T. erecta and V. x wittrockiana.