Germinación de semillas de Crescentia alata (Bignoniaceae) en distintas condiciones de temperatura, luminosidad y almacenamiento

Crescentia alata (Bignoniaceae) es una especie arborescente de gran interés cultural y económico desde México hasta Costa Rica. Sin embargo, la protección de las poblaciones naturales y el establecimiento de plantaciones son limitados por la carencia de información sobre germinación de semillas y crecimiento de plántulas. Este estudio pretende caracterizar los frutos y las semillas, evaluar el proceso de germinación a diferentes temperaturas y niveles de luminosidad, y determinar las condiciones óptimas de temperatura, humedad y almacenamiento para mantener viables las semillas. Se midieron altura, diámetro y masa de frutos, así como largo, ancho y masa de semillas; además, se contó el número de semillas por fruto. Asimismo, se evaluó el porcentaje de germinación a cinco temperaturas (15, 20, 30, 20-30 y 25-30 °C), en condiciones de luz-oscuridad, con almacenamiento a tres temperaturas (5° C, 15 °C y ambiente: 22-24 °C) durante 36 meses. También se observó la viabilidad de las semillas conservadas dentro del fruto. El valor promedio del índice de redondez (IR) fue -1.86; esto indica que los frutos son redondeado-achatados. En promedio el fruto midió 7.90 ± 2.58 cm de altura y 9.62 ± 1.21 cm de diámetro; las semillas midieron 0.75 ± 0.07 cm de largo y 0.67 ± 0.05 cm de ancho. La masa promedio del fruto fue 414.57 g y cada fruto tuvo en promedio ca. 691 semillas, que no germinaron a 15 °C ni a 20 °C; en la oscuridad disminuyó la germinación y la viabilidad de las semillas se redujo cuando se almacenaron a temperatura ambiente (22-24 °C) y cuando permanecieron dentro del fruto. Los resultados indican que las semillas de C. alata germinan mejor a 30 °C, en condiciones de luz y separadas de la pulpa del fruto antes de almacenarse; además, almacenadas a temperaturas bajas (5 °C y 15 °C) los porcentajes de germinación y la viabilidad se mantienen altos (ca. 90 %) hasta por tres años. Estos datos pueden contribuir a mejorar el almacenamiento de semillas y la obtención de plántulas para propagación; así podría aumentar el tamaño de las poblaciones con fines económicos o de conservación, lo que favorecería tanto a la especie estudiada como al bosque tropical seco en que habita.

Crescentia alata is a natural resource with cultural and economic value from Mexico to Costa Rica. Nevertheless, protection of natural populations and establishment of plantations are limited by lack of information on seed germination and plant growth. This study aims to characterize size, weight and number of fruits and seeds, to evaluate the seed germination process at different temperatures and light conditions, and to determine the optimal conditions of temperature, humidity, and storage periods for viable seeds. We measured germination at five different temperatures (15, 20, 30, 20-30, and 25-30 °C), in light-dark conditions, with seed storage at three temperatures (5 °C, 15 °C, and ambient temperature: 22-24 °C) during 36 months. Mean values: fruit roundness index -1.86 (i.e. they are flattened-rounded). Fruit height 7.90 ± 2.58 cm, diameter 9.62 ± 1.21 cm; seeds were 0.75 ± 0.07 cm long and 0.67 ± 0.05 cm wide. Fruit mass 414.57 g; each fruit contained on average ca. 691 seeds. Seeds did not germinate at 15 °C or 20 °C; germination decreased in darkness; germination and viability decreased when seeds were stored at ambient temperature (22-24 °C), and when they were preserved inside fruits. The seeds of C. alata germinate better at 30 °C, exposed to light, and separated from the pulp before storage. When seeds are stored at low temperatures (5 °C and 15 °C), high germination and viability percentages (ca. 90 %) can be maintained for three years, allowing conservation programs for the species.

Drying on the germination and vigor of Crataeva tapia L. seeds / Secagem de sementes de Crataeva tapia L. sobre a germinação e vigor

ABSTRACT: Crataeva tapia L. is a fruit native to the Brazilian savanna, the Caatinga, and is used in the production of soft drinks and other beverages. Given the importance of this species and the lack of knowledge about its seeds, this research aimed to evaluate the physiological quality of C. tapia L. seeds subjected to different environments and drying periods. Seeds were dried for the following time periods: 0 (no drying), 24, 48, 72, 96, and 120 hours, in the laboratory environment (25°C and 90% RH) and in a greenhouse (30°C and 80% RH). After the drying period, seeds from each of the treatments were used for determining the water content, germination, and vigor (using tests for emergence, first count of germination and emergence, rate of germination and emergence, length, and seedling dry weight). The experimental design was completely randomized and a factorial 2×6 scheme (local environment × drying periods) was used with four replicate sets of seeds. The data were subjected to analysis of variance and polynomial regression using quadratic models. The germination and seed vigor reduced as the drying periods increased. For optimum results, the seeds of C. tapia L. must be dried in the laboratory for a period of 48 hours. In addition, their desiccation resistance was classified as intermediate.

RESUMO: Crataeva tapia L. é uma frutífera nativa da caatinga, cujos frutos são utilizados para a produção de refresco e bebida vinosa. Devido à importância da espécie e a inexistência de informações sobre suas sementes, objetivou-se avaliar a qualidade fisiológica das mesmas quando submetidas a diferentes ambientes e períodos de secagem. As sementes foram submetidas à secagem pelos seguintes períodos 0 (sem secagem), 24, 48, 72, 96 e 120 horas em ambiente de laboratório (25°C e 90% UR) e casa de vegetação (30°C e 80% UR). Após cada período de secagem as sementes foram submetidas à determinação do teor de água e a testes de germinação e vigor (emergência, primeira contagem de germinação e de emergência, índice de velocidade de germinação e de emergência, comprimento e massa seca de plântulas). O delineamento experimental utilizado foi o inteiramente ao acaso, em esquema fatorial 2×6 (locais e períodos de secagem), em quatro repetições. Os dados foram submetidos à análise de variância e de regressão polinomial, utilizando os modelos linear e quadrático. A germinação e o vigor das sementes são reduzidos com a secagem, principalmente em casa de vegetação. As sementes de Crataeva tapia L. podem ser secas em ambiente de laboratório por um período de 48 horas e são classificadas como intermediárias.

Proposta de modelagem não-linear do desempenho germinativo de sementes de milho híbrido / Nonlinear proposal modeling of seed germination performance of hybrid corn seeds

Este trabalho foi desenvolvido com o objetivo de ajustar um modelo de regressão não-linear para estimar o desempenho germinativo de sementes de três lotes comerciais de milho híbrido OC 705, submetidas ao teste de envelhecimento acelerado, à temperatura de 43ºC. Utilizou-se o modelo logístico y(t)=C/(1+exp(B(t-M))) para ajustar os dados. As medidas de viés de Box e de curvaturas paramétrica e intrínseca foram usadas para o diagnóstico do modelo. O modelo proposto ajusta-se adequadamente aos dados de percentuais germinativos de sementes de milho híbrido OC 705, para todos os lotes. Com base nas estimativas dos parâmetros e qualidade de ajuste, o lote três foi identificado como sendo o melhor para comercialização, por apresentar menor redução no poder germinativo ao longo do tempo.

This research was developed with the goal to adjust a nonlinear regression model to estimate seed germination performance of three commercial seed lots of hybrid maize OC 705, subjected to accelerated aging test at a temperature of 43oC. The logistic model y(t)=C/(1+exp (B (t-M))) was used to fit the data. Measures of bias Box and parametric intrinsic bends were used for the diagnosis of the model. The proposed model fits properly to seed germination percentage data of hybrid corn seeds for OC 705, for all seed lots. Based on estimates of the parameters and fit quality, the seed lot three was identified as being the best for marketing, by presenting less reduction in seed germination power over time.

Samara size versus dispersal and seedling establishment in Ailanthus altissima (Miller) Swingle.

We have specifically carried out a greenhouse experiment to assess relationship between samara weight and seed success. Relationship assessed as dispersal potential, germination level, germination rate and early seedling mass for the invasive species Ailanthus altissima. For this purpose, we considered two close stands as seeds source. We found no correlation between samara size and neither germination level, germination rate, nor seedling mass, but a positive correlation with samara projected area. These results suggest that samara weight is not directly related to germination, dispersal and invasion potential neither. Nevertheless, stands differed in the invasion potential of their samaras; one stand presented samaras with higher projected area per weight unit whereas the other one presented samaras that produced heavier seedlings. Whatever the origin, (genetic or environmental) of this differences it should be advantageous for a colonizing invader species such as A. altissima since it could imply a wider range of habitats susceptible to invasion.

Studies on the Seed Storage Behaviour of Panax quinquefolius / 中草药

Seeds of Panax quinquefolius L. with original moisture content of 5.9%, together withthat desiccated over silica gel to moisture contents of 3.4% and 1.7%, were stored at ambient tempera-ture,-5 ℃C, -18 ℃C and -196 ℃C (liquid nitrogen) for 6 months. Influences of desiccation and storage on seed viability were tested by TTC staining, before and after desiccation, and their vigour were evaluatedon tests of seed esterase isozyme isoelectric focusing (IEF), and field test on their rate of splitting and e-mergence,length of bud and root. Results showed that there was no effects on seed viability by desiccationto 3.4% and 1.7% of moisture content, as the TTC staining rates were 100% for all seeds tested immedi-ately after desiccation. No significant differences in seed viability and vigour were detected among seedsstored at defferent temperature as there are no significant difference in vairance analysis for seed split rateand seed emergency rate.

Study on viability of Cistanche deserticola seeds / 中草药

Objective To improve the 2,3,5-triphenyl tetrazolium chloride (TTC) solution method for measuring the viability of Cistanche deserticola seeds and investigate the change in viability during storage at 5 ℃. Methods The effect of the testa,TTC concentration,sodium hypochlorite concentration (NaClO),and staining time were studied,and seed viability during storage at 5 ℃ was measured with the improved method. Results Seeds were kept for 48 h in 0.5% TTC solution at 40 ℃,and then for 2 h in 0.2% NaClO solution;Seed viability was measured under a stereomicroscope. Storing seeds of C. deserticola for 1 to 2 years at 5 ℃ had no significant effects on their viability. However,the percentage of seeds with high viability was increased with the extension of the storage time at 5 ℃. Conclusion A convenient and rapid method for measuring the viability of C. deserticola seeds is developed. Storing C. deserticola seeds at 5 ℃ could improve their viability