A contribution to ex-situ conservation of Mediterranean thymes: Germination trials.

• Autores: José Blanco Salas, Trinidad Ruiz Téllez, Francisco María Vázquez Pardo
• Localización: Acta Botanica Malacitana, ISSN-e 2340-5074, ISSN 0210-9506, Nº 34, 2009, págs. 39-55
• Idioma: inglés
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• Resumen
  • español

    Contribución a la conservación ex-situ de los tomillos mediterráneos: ensayos de germinación. Se estudiaron los procesos de germinación de las semillas de siete tomillos endémicos o amenazados de la Región Mediterránea, recolectados en poblaciones silvestres del SO de la Península Ibérica. Se indujeron a germinar 4 réplicas de 50 semillas de cada población con alternancia de temperaturas (6 horas a 20ºC, 18 horas a 30ºC;

    humedad del 40-60%). Se determinaron curvas de porcentajes acumulados de germinación, germinabilidad (en porcentaje) y la velocidad de germinación (mediante el índice de vigor, Iv). Para Thymus caespititius las germinabilidades fueron nulas o bajas y la velocidad de germinación fue lenta (0%-11%; Iv = 0-1.26);

    Thymus mastichina, germinabilidades moderadas o altas y velocidades de germinación rápidas o muy rápidas (59%-92%; Iv = 12.84-35.67); Thymus praecox subsp. penyalarensis, germinabilidades altas y velocidades rápidas (79%; Iv = 19.53); Th. pulegioides, germinabilidades bajas o moderadas y velocidades lentas o medias (2%-41%; Iv = 0.33-7.58); Thymus villosus subsp. lusitanicus, germinabilidades moderadas y velocidades medias (35%; Iv = 9.00); Thymus zygis subsp. sylvestris, germinabilidades lentas, moderadas o altas y Recibido el 20 de febrero de 2009,aceptado para su publicación el 7 de julio de 2009 Publicado "on line" en octubre de 2009 40 J. Blanco Salas et al.

    INTRODUCTION The genus Thymus L., belonging to the Lamiaceae family, is very well represented in the Mediterranean Region with 114 species (91 counting only the binomial level), of which 37 are located in the Iberian Peninsula (Morales, 2000). Thymbra capitata (L.) Cav., which was once included in the Thymus genus, is also a member of the Lamiaceae family, and is a clearly circum-Mediterranean species. The taxa are biologically interesting in terms of their reproduction, taxonomy, ecology, and chorology, and also because of their applications. Information about their germinative capacity would help to understand them from all of these viewpoints.

    Correct seed storage is necessary to maintain genetic resources for subsequent agricultural use or for ex situ conservation in seed banks (Kretschmer, 1989; Caixinhas et al., 1993; Pérez-García et al., 2006). In the context of the potential use of aromatic plants as alternative crops on marginal lands, the physiology of the germination of correctly stored seeds of thymes and other labiates has been studied by many workers (Thanos, 1993;

    Thano, Kadis and Skarou, 1995).

    Most publications on this topic have focused on thymes that are grown for their economic importance as medicinal and culinary plants. A prime example is Th. vulgaris L.

    which is grown in Germany (Kretschmer, 1989), Japan (Ushitani, 1991; Takano et al., 1993), Switzerland (Rey et al., 1993), and the US (Linhart, 1999). Biological studies of this species have dealt with its floral architecture, reproductive processes (Belhassen et al., 1987;

    Belhassen et al., 1989; Belhassen et al., 1990), and ecological biochemistry (Tarayre et al., 1995).

    Published information on the germination conditions of some thymes can be found within the context of more broadly focused studies.

    Some examples are: the investigations of Erikson (1998) on Th. serpyllum L., of Morales (1986) in a taxonomic review of the genus at the level of the Iberian Peninsula, of Vokou and Margaris (1986), Thanos (1993) and Thanos, Kadis and Skarou (1995) who studied Greek populations of Thymbra capitata, and the recent publication of Pérez García (2003) on Th. zygis Loefl.ex L.and Th. mastichina (L.) L. amongst other labiates. The international ISTA (1999) guidelines also contribute interesting data in this sense.

    The species studied in this investigation are plants of great interest biogeographically, since they are Iberian [Th. mastichina, Th. zygis subsp. sylvestris (Hoffmanns. and Link) Brot.

    ex Coutinho, Th. villosus subsp. lusitanicus (Boiss.) Coutinho] or Ibero-Macaronesian (Th.

    caespititius Brot.) endemics, Mediterranean plants of areas in regression (Thymbra capitata), or plants with a marked Atlantic character that only penetrate into the Mediterranean region in mountainous zones or in areas that are especially cool and where the summer drought is not harsh [Th. praecox subsp. penyalarensis (Pau) Rivas Martínez, Fernández González & Sánchez Mata and Th. pulegioides L.].

    This chorological situation is the reason for the importance of the principal objective of the present work � to obtain new information velocidades lentas, medianas o rápidas(2%-68%; Iv = 0.52-19.36); y Thymbra capitata, germinabilidades altas y velocidades rápidas (92%; Iv = 19.07). Se observaron diferencias interespecíficas e interpoblacionales en la capacidad germinativa. Un pretratamiento térmico (7 días a 10-12°C) no produjo alteración significativa en los resultados. También se observó relación entre el peso de las semillas y el porcentaje de germinación.

  • English

    A contribution to ex-situ conservation of Mediterranean thymes: Germination trials. The germination process was studied of the seeds of seven endemic or threatened Mediterranean thymes collected from natural populations of the SW Iberian Peninsula. Four replicates of 50 seeds of each population were induced to germinate by alternating temperatures (6 hours at 20°C, 18 hours at 30°C; 40-60% humidity).

    The accumulated percentage germination curves, the germinability (percentages), and the germination rate (in terms of the vigour index, Iv) were determined. The results were as follows: Thymus caespititius, germinabilities null or low and germination rates slow (0%-11%; Iv = 0-1.26); Thymus mastichina, germinabilities moderate or high and germination rates fast or very fast (59%-92%; Iv = 12.84-35.67);

    Thymus praecox subsp. penyalarensis, germinabilities high and germination rates fast (79%; Iv = 19.53);

    Th. pulegioides, germinabilities low or moderate and germination rates slow or medium (2%-41%; Iv = 0.33-7.58); Thymus villosus subsp. lusitanicus, germinabilities moderate and germination rates medium (35%; Iv = 9.00); Thymus zygis subsp. sylvestris, germinabilities low, moderate, or high and germination rates slow, medium, or fast (2%-68%; Iv = 0.52-19.36); and Thymbra capitata, germinabilities high and germination rates fast (92%; Iv = 19.07). There were both interspecific and interpopulational differences in germinative capacity. Cooling the seeds for 7 days at 10-12°C prior to sowing produced no significant alterations in the results. A relationship was observed between seed weight and germination percentage.