Revista de Biología Tropical (Sep 1998)
Germinación, dispersión y establecimiento de plántulas de Mimosa tenuiflora (Leguminosae) en México
Abstract
Mimosa tenuiflora (Willd.) Poir. es un recurso natural importante para México debido a sus diversos usos. Sin embargo, hasta ahora no se había estudiado la germinación, la dispersión y el establecimiento de plántulas de esta especie. Se recolectaron frutos y semillas de esta planta en el estado de Chiapas, México (S. L. Camargo et al. 118, UAMIZ). Las pruebas de germinación se hicieron después de cuatro años de almacenamiento; se sembraron en total 1 935 semillas en cajas de Petri con papel filtro Wathman humedecido. Se determinaron las temperaturas óptimas usando un gradiente de 5-40°C, con luz continua, para semillas escarificadas mecánicamente y no escarificadas. Se realizaron tres pruebas de fotoperíodo: a) luz continua, b) oscuridad constante y c) luz 12hr/oscuridad 12 hr. Se aplicaron tres tratamientos pregerminativos: a) escarificación mecánica, b) ácido sulfúrico concentrado, c) fuego directo y d) ningún tratamiento. Para cada variable y pretratamiento se hicieron tres repeticiones, cada una con 15 semillas. Se aplicaron las pruebas estadísticas correspondientes: desviación estandar (S), análisis de varianza de una vía (ANOVA) y comparación de medias (Prueba de Scheffé) (pMimosa tenuiflora (Willd.) Poir. is an important natural resource in Mexico, due to its diverse uses. However, seed germination, dissemination and seedling establishment of this species had not been studied up to date. Fruits and seeds were collected in the State of Chiapas, Mexico (S. L. Camargo et al. 118, UAMIZ). Germination experiments were carried out after four years of seed storage; 1 935 seeds were sown in Petri dishes containing moistened Wathman filter paper. Optimum temperatures were determined in a gradient 5-40 0C, with continuous light for mechanically scarified and non scarified seeds. Three photoperiod experiments were made: a) continuous light, b) constant darkness and c) 12 hr light/12 hr darkness. Three germinate pretreatments were applied: a) mechanical scarification, b) sulfuric acid scarification, c) fire scarification and d) control. Three replicates of 15 seeds each were made for each variable and pretreatment. Standard deviations (S) were determined, a one-way analysis of variance (ANOVA) and media comparison (Scheffé’s test) were applied (p<0.05). Analysis of fruit and seed dissemination and seedling establishment was made qualitatively on the basis of field and laboratory observations; radius of dissemination of the fruits from the mother plant was measured; development of laboratory grown seedlings was followed during three months. Seeds germinated at 10-30°C; however, the highest percentages of germination were obtained at 20°C (84.44%) and 25°C (95.55%); seeds are indistinctly photoblastic and percentages of germination, after the three germinate pretreatments, were: control (24.44-35.55%), mechanical scarification (84.44-88.88%), sulfuric acid scarification (73.33-91.11%) and fire scarification (0%). Fruits and seeds are disseminated by the wind in a radius of 5-8 m from the mother plant; rain carries them from slopes to lower plains and human activities contribute to their dissemination. Growth of seedlings is fast; they develop a paripinnate protophyll and ten biparipinnate pronomophylls; the first nomophyll develops during the weeks 12 to 14. It is concluded that optimum temperatures for seed germination of M. tenuiflora are 20 °C and 25 °C; seeds are indistinctly photoblastic; percentage and rate of germination are highly increased by coat scarification. This species has certain advantages for its establishment in open areas, given by the abundant production of seeds, their small size, the rate of germination and the fast growth, as well as by its seedling characters: the tap root system, the hypocotyl-epicotyl axis woody at the base and, the compound leaves with linear-oblong leaflets having changes in orientation in response to light. Our results confirm the invasive and typically secondary character of this species.
