Orchid seeds viability identification by tetrazolium test

Abstract

The knowledge of germinal potential optimizes the practice of in vitro germination of Orchidaceae. This work evaluated of the type and concentrations of tetrazolium solutions on reaction time and on the identification of viable orchid seeds. Were used seeds of the species Brassavola tuberculata Rchb f., Cattleya labiata Lindley var Amoema, Cattleya intermedia and Dendrobium antenatum and of two primary hybrids of Cattleya labiata autumnalis x Cattleya labiata Lindley var. Alba. The seeds (0.01g) of each species or hybrid were soaked in 3 mL of aqueous and neutral solutions of 2, 3, 5 triphenyltetrazolium chloride at 0.0625%, 0.125%, 0.25%, 0.5% ou 1,0% concentrations and stored in a light-free environment at 25±2 °C, being evaluated every 30 minutes for identification of the time needed for embryos coloring and later counting of the number of viable seeds by milligram of seed. A completely randomized design was used, in a factorial scheme 6 x 2 x 5 (six genotypes of orchids, two types of tetrazolium solutions and five concentrations) with 3 replications. The genotypes responded differently response both for viable seeds by milligram of seed and for the time required for embryos coloring and C. intermedia not respond to the test. Irrespective of solution type, concentrations only interfered in reaction time for the hybrids. It is recommended, therefore, the use of neutral tetrazolium solution at 0.5% for indentification of viable seeds of hybrids of Cattleya labiata autumnalis x Cattleya labiata var. Alba and use of aqueous solution at 0.125% for Brassavola tuberculata, Cattleya labiata var Amoema e Dendrobium antenatum.