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São Paulo, Brazil

Tavares A.R.,IBt | Young J.L.M.,IBt | Ori S.S.,IBt | Kanashiro S.,IBt | And 3 more authors.
Horticultura Brasileira | Year: 2012

In vitro cultivation is the main propagation method for the family Orchidaceae, whereas nitrogen is the most important nutrient in the culture media. This work was carried out to study the influence of different nitrogen concentrations on the in vitro growth of the orchid Phalaenopsis amabilis. Nitrogen concentrations varied by altering the ionic balance of the Murashige & Skoog (MS) culture medium. Plants, 360 days old, were cultivated in liquid MS, modified with 7.5, 15, 30, 45, and 60 mM N. After 180 days, we assessed plant and root length, number of leaves and roots, and fresh and dry weight of leaves, roots and plants. Treatments were assigned to completely randomized plots, with four replications. Plots consisted of five three-plant flasks. The lowest nitrogen level (7.5 mM) in the medium induced root development in length, number, and fresh and dry weight. The concentration 30 mM N stimulated both emission and dry weight accumulation of leaves. The original nitrogen concentration in the MS medium (60 mM) was excessive for the in vitro growth of P. amabilis. Source

Seeds intolerant to desiccation, such as those from Eugenia species, must be stored with a high water content which can contribute to microorganism development and lead to rapid seed deterioration. However, normal chemical control is unsuitable considering the use of these seeds in the natural environment. Thermal (seeds in water at 35 °C to 75 °C/ 30 to 150 min) and osmotic (seeds stored in an osmotic solution varying from -1,5MPa to -4,0 MPa) treatments, as well as controlled drying, could be used but there is little information about them and this gave origin to the present study. Results showed that chemical treatments (carboxin+thiram, captan and carbendazim+thiram) were the most efficient for controlling the most frequent fungal species, including Penicillium sp., Cladosporium sp., Fusarium sp., Pestalotiopsis sp. and Alternaria sp. in seeds of Eugenia brasiliensis ("grumixameira"), E. uniflora ("pitangueira") and E. pyriformis ("uvaieira"). Thermal and osmotic treatments show significant potential for the control of these fungi but specific methodology must be developed, considering the inter-relationships of these treatments and the need to make successive application during seed storage. Source

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