ABSTRACT
En el bosque tropical seco, el árbol Crescentia alata (Bignoniaceae) es un recurso cultural y económico, pero han fracasado algunos intentos para establecer plantaciones, que podrían satisfacer la producción comercial y, así, evitar el impacto en las poblaciones naturales. Por tanto, existe la necesidad de generar información biológica sobre esta especie para obtener plantas en condiciones de invernaderos. El objetivo de este trabajo fue evaluar la tasa de crecimiento de plantas de C. alata obtenidas de semillas que se almacenaron en diferentes períodos y a varias temperaturas, y determinar el efecto de la intensidad de la luz sobre el crecimiento de las plántulas. Se recolectaron frutos en Liberia (Guanacaste, Costa Rica) y se almacenaron semillas por 0, 4, 8 y 14 meses a 5 °C, 15 °C y a temperatura ambiente (22-24 °C). Las plántulas de las semillas almacenadas por 0, 4, 8 y 14 meses se trasplantaron para evaluar el crecimiento después de 8 días, 2 y 16 meses, y en dos condiciones de luminosidad. La morfología de las plántulas de 8 días cambió según el tiempo de almacenamiento. El análisis de componentes principales de la evaluación de 2 meses indica que las variables más significativas fueron biomasa total seca, biomasa seca de hojas, de raíz-vástago, de tallo y de raíz, mientras que en el análisis de la evaluación de 16 meses tales variables fueron biomasa seca de raíz, de raíz-vástago y de hojas, también número de hojas y longitud del vástago. El área foliar específica de plantas con 16 meses de edad obtenidas de semillas almacenadas 14 meses no cambió con la temperatura de almacenamiento. Además, dos condiciones de luminosidad influyeron en la altura, el diámetro del tallo o el número de hojas. El almacenamiento de semillas a 5 °C y 15 °C favoreció el desarrollo de los cotiledones, así como la longitud de la raíz y del hipocótilo. Plantas de 2 meses obtenidas de 0 y 8 meses asignaron mayor biomasa a raíces que a tallos, mejorando así la absorción de agua. Plantas de 16 meses provenientes de semillas no almacenadas desarrollaron el mayor número de hojas, y aquellas de semillas de 8 meses a 5 °C y 15 °C mostraron tallos más cortos. Las semillas almacenadas hasta 14 meses se convirtieron en plantas bien desarrolladas. Se recomienda a futuros investigadores evaluar la viabilidad a diferentes temperaturas de secado de las semillas y en niveles de intensidad lumínica más contrastantes durante el crecimiento.
The dry tropical forest tree Crescentia alata is a cultural and economical resource, but efforts to establish plantations, which could satisfy commercial production and avoid impact on natural populations, have been unsuccessful. So there is a need to generate biological information on this species for obtaining plants in greenhouses. The aim of this work was to evaluate the vigor and growth rate of C. alata seedlings born from seeds that were stored at different periods and temperatures, and to determine the effect of light intensity on the seedlings. Fruits were collected in Liberia (Guanacaste, Costa Rica) and seeds stored for 0, 4, 8, and 14 months at 5 °C, 15 °C, and ambient temperature (22-24 °C). Seedlings from seeds stored for 0, 4, 8 and 14 months were grown to evaluate growth after 8 days, 2 months, and 16 months, and in two different light conditions. Morphology of 8-day-seedlings changed according to storage time. Principal component analysis of 2-month evaluation indicates that the most significant variables were total dry biomass, dry biomass of leaves, root-shoot, stem, and root, while for the analysis of 16-month evaluation these variables were dry biomass of root, root-shoot, and leaves, also leaf number, and shoot length. Specific leaf area of 16-month plants from seeds stored for 14 months did not change with storage temperature. In addition, two different light conditions influence seedling height, stem diameter or leaf number. Seed storage at 5 °C and 15 °C favored development of seedling cotyledons, and length of both root and hypocotyl. Two month-seedlings from 0M and 8M allocated most biomass to roots and less to stems, enhancing this way water absorption. Sixteen-month-plants from non-stored seeds developed the highest leaf numbers, and those plants from 8M seeds at 5 °C and 15 °C showed shorter stems. Seeds stored up to 14 months kept viable, becoming healthy seedlings. We recommend that future researchers evaluate seed viability at different drying temperatures and more contrasting light levels.
ABSTRACT
The purpose of this study was to evaluate the influence of different levels of shading on the development of seedlings of three mangrove species (Avicennia germinans (L.) Stearn., Rhizophora mangle L. and Laguncularia racemosa (L.) Gaertn. f.). The experiment was conducted at the community of Tamatateua, Ajuruteua peninsula, Bragança, PA, Brazil. For seedling production, the propagules and seeds of the mangrove species were planted in polyethylene bags (17 x 27 cm), filled with a typical mangrove substrate. The seedlings of the three species were grown under full sun (0), 30% and 60% shading, in a completely randomized design, a 3 x 3 factorial (three species and three shading levels), with eight seedlings per replication. After nine months under shading, plant samples were taken. The variables evaluated were: the shoot/height ratio, stem diameter, shoot dry matter, stem mass, root dry matter, total dry mass matter and morphological indices. Growth of seedlings of R. mangle occurred at all light levels. Seedlings of A. germinans grew faster at full sun and at 30% shading. Whereas, seedlings of L. racemosa were able to grow at 30 and 60% shading, but they also grew faster at full sunlight.
O objetivo do estudo foi avaliar a influência de diferentes níveis de sombreamento sobre o desenvolvimento de mudas das espécies arbóreas de mangue Avicennia germinans (L.) Stearn., Rhizophora mangle L. e Laguncularia racemosa (L.) Gaertn. f. O experimento foi conduzido na comunidade de Tamatateua, na península de Ajuruteua, município de Bragança. Para a produção das mudas, os propágulos das espécies arbóreas de mangue foram semeados em embalagens de polietileno (17 x 27 cm), preenchidas com substrato típico de manguezal. As mudas das três espécies foram testadas a pleno sol, 30% e 60% de sombreamento em delineamento experimental inteiramente casualizado em esquema fatorial (3 x 3) x 3 (3 espécies arbóreas e 3 níveis de sombreamento). Após as plantas atingirem a idade de nove meses, retiraram-se amostras de oito mudas por repetição de cada tratamento. As variáveis avaliadas foram: altura da parte aérea, diâmetro do coleto, massa da parte aérea, massa seca do caule, matéria seca das raízes e matéria seca total e índices morfológicos. O crescimento das mudas de R. mangle ocorreu em todos os níveis de luminosidade. As mudas de A. germinans apresentaram maior crescimento a pleno sol e a 30% de sombreamento. Já as mudas de L. racemosa foram tolerantes a 30% e 60% de sombra, mas se desenvolveram melhor a pleno sol.
ABSTRACT
In vitro asymbiotic seed germination potential of its immature seeds (36 weeks after pollination) of G. calceolaris was successfully tested on three different agar gelled nutrient media i.e. Murashige and Skoog (MS), Mitra et al. (M) and potato dextrose agar (PDA). Seeds germinated within 15.75±0.75 to 35.75±0.75 days in the three different media. The protocorms developed therefrom subsequently differentiated into first leaf and root primordia, and complete seedlings were obtained within 111.25±1.25 to 141.25±1.25 days on MS and M media. The protocorms, though failed to differentiate further on basal PDA medium, despite repeated subculturings, incorporation of peptone (P; 1gl-1), yeast extract (YE; 2 gl-1) and coconut water (CW; 20%) in the medium proved beneficial in inducing differentiation, in these germinating entities. Additional use of growth additives (P/YE/CW), in general, favoured better germination, protocorm formation and seedling development. The optimal nutritional combination during seed germination, protocorm growth and multiplication and seedling development was found to be CW (10%) enriched MS medium.