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Aim of study: The native species of warm humid climates Ceiba pentandra, Tabebuia rosea, Gliricidia sepium, Enterolobium cyclocar-pum and Brosimum alicastrum are often included in Mexican reforestation programs. We evaluated the growth response in sandy soils of these species that could serve as pioneers in the restoration of coastal areas.Area of study: Alluvial plain in Frontera, Tabasco, Mexico.Material and methods: A total of 1080 plants were planted in 2014 and evaluated for 23 months in 30 plots under a randomized block design with six replications. The sample plots each occupied 36 m2 (each with 16 plants). Survival percentage, stem height (SH), basal diameter (BD) and basal area (BA) were quantified. Survival and growth variables were analyzed using logistic regression and ANOVA for repeated measures, respectively.Main results: At the end of the experiment (2016), high survival was demonstrated in G. sepium (88 %) and in C. pentandra (86 %), while B. alicastrum presented total mortality at six months. The highest values of SH and BD were presented in C. pentandra (2.9 m and 7.8 cm, respectively) and in G. sepium (2.6 m and 4.2 cm, respectively). Gliricidia sepium differed significantly from C. pentandra in terms of BA (5.9 vs. 23 m2 ha-1, respectively).Research highlights: The native species C. pentandra and G. sepium presented high survival and growth in the sandy soils; G. sepiumshowed strong adaptation to the environment and C. pentandra offered suitable coverage, characteristics that are necessary for the success of reforestation and restoration programs.

Annona reticulata is a poorly domesticated native Annonaceae species of the neotropics, commonly found in home gardens and its fruit is of nice flavor. As part of the strategies for germplasm conservation, and, taking into account that certain pregerminative treatments may favor its germination capacity, two objectives were pursued: the morphological characterization of fruits and seeds, and the assessment of its response to pregerminative treatments. Samples were collected in two municipalities of Tabasco State, Mexico. Dimensions of fruits and seeds were measured, and seeds were submitted to six pre-germinative treatments as follows, control (T1), mechanical scarification (T2), soaking in gibberellic acid (GA3 100 mg L-1 for 3 h) (T3), soaking in GA3 (100 mg L-1 for 6 h) (T4), soaking in GA3 a 200 mg L-1 for 3 h (T5), and mechanical scarification + soaking in GA3 (100 mg L-1 for 24 h) (T6). The germination percentage (GP) and rate (GR) were evaluated in a completely randomized design with five replications. The fruit averaged 422.2 g, with 116.8 seeds. The pulp is 69.22 % of the total fruit weight. Epigeal cryptocotylar germination started on day 17 and reached its maximum (76.6 %) on day 31. The mechanical scarification (T2) produced the highest values of GP, and GR, while the use of GA3 tended to result in lower values as the concentrations and soaking times of the product increased., Annona reticulata es una especie nativa del Neotrópico, poco domesticada, común en huertos familiares y su fruto es de sabor agradable. Como una estrategia de conservación del germoplasma, y considerando que determinados tratamientos pregerminativos pueden favorecer su capacidad de germinación, se plantearon dos objetivos: la caracterización morfológica de frutos y semillas, y el estudio de la respuesta a varios tratamientos pregerminativos. Las muestras provienen de Tabasco, México. Se midieron frutos y semillas. Las semillas se sometieron a seis tratamientos pregerminativos: Testigo (T1), escarificación mecánica (T2), remojo en ácido giberélico (AG3 100 mg L-1 por 3 h) (T3), remojo en AG3 (100 mg L-1 por 6 h) (T4), remojo en AG3 a 200 mg L-1 por 3 h (T5), y escarificación mecánica + remojo en AG3 (100 mg L-1 por 24 h) (T6). Se determinó el porcentaje total de germinación (PG) y la tasa de germinación (TG) en un ensayo completamente al azar con cinco repeticiones. El peso promedio del fruto fue de 422,2 g, con 113,8 semillas, de los cuales el 69,22 % estuvo representado por el peso de la pulpa. La germinación criptocotilar epígea inició el día 17 y alcanzó su máximo (76,6 %) el día 31. La escarificación mecánica (T2) promovió los mayores valores de PG y TG, mientras que el uso del AG3 afectó la germinación y produjo los menores valores a medida que se incrementaron las concentraciones y tiempos de remojo del producto.

Aim of study: The native species of warm humid climates Ceiba pentandra, Tabebuia rosea, Gliricidia sepium, Enterolobium cyclocarpum and Brosimum alicastrum are often included in Mexican reforestation programs. We evaluated the growth response in sandy soils of these species that could serve as pioneers in the restoration of coastal areas. Area of study: Alluvial plain in Frontera, Tabasco, Mexico. Material and methods: A total of 1080 plants were planted in 2014 and evaluated for 23 months in 30 plots under a randomized block design with six replications. The sample plots each occupied 36 m2 (each with 16 plants). Survival percentage, stem height (SH), basal diameter (BD) and basal area (BA) were quantified. Survival and growth variables were analyzed using logistic regression and ANOVA for repeated measures, respectively. Main results: At the end of the experiment (2016), high survival was demonstrated in G. sepium (88 %) and in C. pentandra (86 %), while B. alicastrum presented total mortality at six months. The highest values of SH and BD were presented in C. pentandra (2.9 m and 7.8 cm, respectively) and in G. sepium (2.6 m and 4.2 cm, respectively). Gliricidia sepium differed significantly from C. pentandra in terms of BA (5.9 vs. 23 m2 ha-1, respectively). Research highlights: The native species C. pentandra and G. sepium presented high survival and growth in the sandy soils; G. sepium showed strong adaptation to the environment and C. pentandra offered suitable coverage, characteristics that are necessary for the success of reforestation and restoration programs.

Background and Aims:Castilla elastica is a Mesoamerican native species associated with different Prehispanic cultures that used their latex for ceremonial purposes. It is considered an emblematic tree, useful in agroforestry systems. This work aimed to evaluate the germination, initial growth and morphology of C. elastica.Methods: Seeds from 30 trees were collected and planted in polyethylene trays. The start of the germination was determined by the sprouting of the epicotyls. The percentage of germination was quantified, and three periods of evaluation were established, every 45 days. Stem length (Lt) and basal stem diameter (Db) were evaluated. Absolute (RGA) and relative (RGR) growth rates were also obtained. Additionally, simple regression tests were made, and a regression was calculated associating RGA from Lt against some climatic variables. Growth evaluation of the plants lasted 205 days.Key results: Germination was obtained in 100%, the process initiated at 12 days. At 205 days, plants reached an average (±1 SD) Lt and Db of 36.5 cm (±5.27) and 8.2 mm (±0.55), respectively. The three evaluation periods showed significant statistical differences. According to regression models, C. elastica grows 0.188 cm day-1 for each millimeter of increase in Db. Conclusions: The use of recently harvested seeds guarantees 100% germination. Different stages of development of the seedling depending on the time (205 days) were obtained. The RGR decreased after the first evaluation, being attributable to the solar radiation. This work demonstrated the feasibility of producing C. elastica plants, reaching the minimal required quality standards in terms of its average Lt and Db, Antecedentes y Objetivos: Castilla elastica es una especie nativa de Mesoamérica asociada a diferentes culturas prehispánicas que utilizaban su látex para fines ceremoniales. Es un árbol emblemático, útil en sistemas agroforestales. Este trabajo tuvo por objetivo evaluar la germinación, crecimiento inicial y morfología de C. elastica. Métodos: Se colectaron semillas de 30 árboles y se sembraron en bandejas de polietileno. El inicio de la germinación se determinó por la emergencia de los epicótilos. Se cuantificó el porcentaje de germinación y se establecieron tres periodos de evaluación del crecimiento cada 45 días. Se evaluaron la longitud de tallo (Lt) y el diámetro de tallo (Db). Se obtuvo la tasa absoluta de crecimiento (TAC) y la tasa relativa de crecimiento (TRC). Adicionalmente, se realizaron pruebas de regresión simple entre Lt y Db y se calculó una regresión asociando la TAC de la Lt con algunas variables climáticas. La evaluación del crecimiento tuvo una duración de 205 días. Resultados clave: Se obtuvo 100% de germinación, el proceso inició a los 12 días. A los 205 días, las plantas alcanzaron una Lt y un Db promedio (±1 DE) de 36.5 cm (±5.27) y 8.2 mm (±0.55), respectivamente. Los tres períodos de evaluación mostraron diferencias estadísticas significativas. De acuerdo con los modelos de regresión, C. elastica crece 0.188 cm día-1 por cada milímetro de incremento en Db. Conclusiones: La utilización de semillas recién cosechadas asegura 100% de la germinación. Se obtuvieron diferentes etapas de desarrollo de la plántula en función del tiempo (205 días). La TRC disminuyó después de la primera evaluación atribuible a la radiación solar. Este trabajo demostró la factibilidad de producir plantas de C. elastica y contar con el requisito mínimo como planta de calidad en cuanto a la Lt y Db promedio.

Aim of study: The objective of this study was to present statistical information pertaining to recurrent inconsistencies found in the literature of the last 25 years that involve calculation of the GR and the errors that this may entail when interpreting the seed vigor of different botanical materials.Materiales y métodos: After filtering articles that did not present numerical results or in which the application of Maguire's formula was not clearly indicated, a total of 124 papers were ultimately used in this study.Main results: Germination rate (GR) represents the potential of seeds to germinate and, along with germination percentage (GP), are the two most important measurements when evaluating seed quality. The correct calculation of GR allows the seeds classification according to their vigor and capacity to produce healthy seedlings, so it is very important to rely on the adequate mathematical formula for this purpose. According to the formula developed by Maguire, this parameter is calculated by the sum of values obtained when dividing the GP at different times (i.e. daily) by the total time elapsed since the start of the test. We have found from the relevant literature that different authors have been using different ways of applying the formula, which makes it difficult to directly compare the results.Research highlights: A total of 54.8 % of the papers reviewed, belonging mainly to the theme of forestry, presented objectionable application of the formula. Publication of this warning may help to reduce the occurrence of this situation in the future.Keywords. Germination percentage, germination speed, Maguire’s formula, seed vigor.

La presente Tesis Doctoral tiene por objetivo contribuir al conocimiento de los procesos de producción de planta y de la reforestación forestal con especies nativas. Se muestran los resultados de los procesos de germinación de una especie en peligro de extinción (Ormosia macrocalyx), bajo dos experimentos independientes: 1) germinación de semillas obtenidas de frutos en tres etapas de maduración y 2) germinación de semillas almacenadas por 17 meses en condiciones de refrigeración, bajo tratamientos pregerminativos (control, escarificación mecánica, remojo por 24 horas y escarificación mecánica + Ácido giberélico al 1%). Además, se evaluó el crecimiento de seis especies nativas tropicales (Calophyllum brasiliense, Bravaisia integerrima, Dialium guianense, Piscidia piscipula, Tabebuia donnell-smithii y Enterolobium cyclocarpum), bajo 50% de sombra, las variables analizadas fueron: longitud de tallo, diámetro basal y tasas relativas de crecimiento durante seis meses. Paralelamente, se estableció un experimento en campo sobre un suelo arenoso para obtener el porcentaje de supervivencia y el crecimiento de cinco especies arbóreas (Tabebuia rosea, Enterolobium cyclocarpum, Gliricidia sepium, Ceiba pentandra y Brosimum alicastrum) en un diseño de bloques al azar. Las mediciones de la longitud de tallo y diámetro basal por 23 meses, sirvieron para obtener las tasas relativas de crecimiento y las áreas basimétricas., Departamento de Producción Vegetal y Recursos Forestales, Doctorado en Conservación y Uso Sostenible de Sistemas Forestales

We evaluated the germination and survival in situ and ex situ of seedlings of Aspidosperma megalocarpon, Eugenia sp., Lonchocarpus castilloi, Manilkara zapota, Ormosia macrocalyx and Rollinia mucosa. We established nine blocks of 5 m x 20 m in the field, in which 360 seeds of each species were established in three successional conditions with three repetitions: mature tropical forest, advanced fallows and young fallows. The experiment was replied in a tree nursery using 40, 60 and 80% shade. We found no significant differences in the rates of germination and neither in growth due to variation in the natural cover. However, the rates of germination of A. megalocarpon and O. macrocalyx, and the rates of depredation of M. zapota and L. castilloi were affected by the coverage. Seeds sown in young fallows showed higher depredation, whereas seedling survival was higher here than in the other successional stages. In the tree nursery, no significant difference was found in the proportion of germinated seeds, the rates of germination and in growth. However, R. mucosa showed low survival (42%). The environmental conditions of the forests in Tabasco are under various stages of degradation and it is appropriate to start a rehabilitation program by introducing native species. This study indicates that this could be done by sowing the seeds directly in the forests without first producing seedlings in nurseries, which in turn would reduce the costs. It is recommend continuing research on the seed and seedling performance of other species that could be used to rehabilitate and restore the tropical forest., Se evaluó la germinación y supervivencia in situ y ex situ de plántulas de Aspidosperma megalocarpon, Eugenia sp., Lonchocarpus castilloi, Manilkara zapota, Ormosia macrocalyx y Rollinia mucosa. En campo se sembraron 2 160 semillas en nueve bloques de 5 m x 20 m distribuidos en bosque tropical, acahual maduro y acahual joven. El experimento se replicó en condiciones de vivero bajo sombra de 40, 60 y 80%. Los tipos de cobertura vegetal no mostraron diferencias significativas en las tasas de germinación y de crecimiento; sin embargo, estos sí influyeron en la capacidad de germinación de A. megalocarpon y O. macrocalyx, y en las tasas de depredación de M. zapota y L. castilloi. En el acahual joven se presentó la mayor depredación de semillas, sin embargo, las plántulas remanentes presentaron mayor supervivencia que en las otras coberturas vegetales. En el vivero no se encontró diferencia en la proporción de semillas germinadas, ni en las tasas de germinación y de crecimiento. R. mucosa, fue la única especie que presentó menor supervivencia (42%). Las condiciones ambientales de las diferentes clases de cobertura vegetal en el área de estudio mantienen condiciones adecuadas para el proceso de germinación, crecimiento y establecimiento de plántulas de las especies estudiadas, lo cual permite sugerir su utilización en la rehabilitación de áreas degradadas del bosque original sembrando de manera directa, siempre y cuando se realice de manera inmediata después de la recolecta. Es necesario continuar con estos estudios para promover el uso de especies nativas en la rehabilitación y restauración de bosques tropicales.