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Dormant Seeds (dormant + seed)
Selected AbstractsAssessing the benefits of frugivory for seed germination: the importance of the deinhibition effectFUNCTIONAL ECOLOGY, Issue 1 2006A. W. ROBERTSON Summary 1Many studies have examined the effects of frugivores on the germination of seeds of fleshy fruited plants. However, three key issues are rarely addressed: the need to measure germination of seeds in intact fruits; the effect of germination conditions on results; and the distinction between dead vs dormant seeds. 2A literature review including 51 plant species from 28 families found that the often-measured scarification effect (germination of bird-defecated vs hand-cleaned seeds) is significantly smaller than the rarely-measured deinhibition effect (germination of hand-cleaned seeds vs those in intact fruits). 3Both the literature review and new experimental data show that germination conditions affect germination. In particular, seeds in intact fruits have much lower germination percentages in Petri dishes than in the field. Poor germination from intact fruits in Petri dishes may be an artefact. 4A field experiment with three New Zealand species showed variable effects of non-removal of the fruit pericarp. The retention of the pericarp had no effect on germination in Nestegis cunninghamii; increased the proportion of seeds entering dormancy in Melicytus lanceolatus; and greatly increased seed mortality in Pennantia corymbosa. 5Germination experiments must be designed carefully to evaluate accurately the risks for plants of frugivory mutualism failures. [source] Fruit dispersal and seed banks in Atriplex sagittata: the role of heterocarpyJOURNAL OF ECOLOGY, Issue 2 2001Bohumil Mandák Summary 1Atriplex sagittata, an arly succesional, annual species of disturbed habitats in Central Europe, produces three types of fruits. We studied the differences in dispersal between the fruit types in order to investigate their ecological roles. 2The typical positive relationship between dispersal ability and germinability is not found in this species. Type A (ebracteate) fruits produced deeply dormant seeds and had the lowest dispersal potential, but of the two fruits with bracts, type B, with dormant seeds, was better dispersed by both water and wind than type C, which produces non-dormant seeds. 3Wind, temperature and precipitation have significant effects on fruit release but their effects differ between fruit types. The release of fruit types with bracts was positively correlated with wind whereas all fruit types tended to be negatively correlated with precipitation and temperature range. 4Type C fruit, which contains non-dormant seed, are absent from the soil in summer and have a Type II transient seed bank. Type A and B fruits, containing dormant seeds, form a persistent seed bank. 5Heterocarpy, where fruit types show distinct ecological behaviour, enables colonizing species such as A. sagittata to survive both major disturbance (by ensuring that some seeds persist) and unfavourable conditions (by spreading germination over a long period). 6In A. sagittata, seed dynamics can be explained by the germination behaviour of seeds produced by the three types of fruit. All fruit types mature in autumn, but few of Type A fall from the mother plant until spring, when germination is probably inhibited because of insufficient stratification. Type C fruit, however, show peak dispersal in winter and the majority of these non-dormant seeds are able to germinate as soon as conditions become more suitable. [source] A protein phosphatase 2A from Fagus sylvatica is regulated by GA3 and okadaic acid in seeds and related to the transition from dormancy to germinationPHYSIOLOGIA PLANTARUM, Issue 1 2006Mary Paz González-García Several gibberellic acid (GA3)-induced cDNA fragments encoding putative serine/threonine protein phosphatase (PP) 2A catalytic subunits were obtained by means of differential reverse transcriptase-PCR approach. The full-length clone, named FsPP2A1, isolated from a beechnut cDNA library, exhibited all the features of and homology to members of the PP2A family. By transient expression of FsPP2A1 in tobacco and Arabidopsis cells as a green fluorescent fusion protein, we have obtained evidence supporting the subcellular localization of this protein in both the cytosol and the nucleus. Analysis of FsPP2A1 expression during seed stratification shows that these transcripts increase in the presence of GA3, a treatment proved to be efficient in breaking the dormancy of Fagus sylvatica seeds, but they are almost undetectable in dormant seeds or when dormancy is maintained after treatment with either abscisic acid or the gibberellin biosynthesis inhibitor paclobutrazol. The PP inhibitor okadaic acid (OKA) has a clear effect in decreasing both seed germination and FsPP2A1 expression. Furthermore, FsPP2A1 is specifically expressed in seed tissues, not being detected in other vegetative tissues examined. These results show the regulation of this PP by GA3 and OKA in these seeds. Its relationship with the processes taking place during the transition from dormancy to germination is also discussed. [source] Bet-hedging and germination in the Australian arid zone shrub Acacia ligulataAUSTRAL ECOLOGY, Issue 4 2000MIKE LETNIC Abstract The diaspore of the Australian arid zone shrub Acacia ligulata is dispersed by birds and ants. To investigate the benefits of providing a dispersal structure attractive to both groups, we compared the germination response and viability of seeds eaten by birds, handled by ants or collected from trees to simulated precursors of germination: scarification, fire and rainfall were simulated. Seed germination and viability were related to the degree of preheating disturbance to the seed coat. Heating increased the germinability of seeds not scarified or eaten by birds. In the absence of heating, ingestion by birds increased germinability. Heating increased the mortality of seeds. Our results suggest that ingestion of seeds by birds may break seed dormancy and hence enable some seeds to germinate soon after dispersal. Alternatively, seeds not eaten by birds are likely to remain dormant until sufficiently scarified by soil or stimulated by fire. Consequently, in areas such as the Simpson Desert, A. ligulata may be able to use a range of seedling establishment ,windows' provided by monsoon rains, post-fire environments and unseasonal winter rains, and also spread the risk of unsuccessful seedling establishment by retaining dormant seeds in the seedbank. [source] Disturbance Effects on the Seed Bank of Mexican Cloud Forest Fragments,BIOTROPICA, Issue 3 2005C. Alvarez-Aquino ABSTRACT The density and floristic composition of the soil seed bank was assessed in six cloud forest fragments with different levels of human disturbance in central Veracruz, Mexico. A total of 8416 seeds germinated in 60 soil samples, at 5-cm depth, corresponding to 107 species, 85 genera, and 48 families. Significant differences were found among study sites in seed densities with values ranging from 873 to 3632/m2. Tree species contributed 20 percent of the total soil seed bank in four sites and herbs accounted for the majority of the species in each site. Among tree species, Trema micrantha displayed the highest seed density, accounting for 84 percent of the germinated seeds. In general, the tree species composition of the soil seed bank did not closely reflect the composition of the tree community. Results suggest that disturbance produced by human activities (trail use, selective cutting of trees, livestock) may influence the size and composition of the soil seed bank in forest fragments. Sites where human activity has been reduced showed the highest proportion of dormant seeds. RESUMEN La densidad y composición florística del banco de semillas del suelo se determinó en seis fragmentos de bosque de niebla con distinto nivel de alteración humana, en Veracruz, México. Un total de 8416 semillas germinaron en 60 muestras de suelo, correspondientes a 107 especies, 85 géneros y 48 familias. Se encontraron diferencias significativas entre los sitios de estudio, con valores desde 873 a 3632 semillas/m2. La mayoria de las especies fueron hierbas y en cuatro de los sitios las especies arbóreas contribuyeron un 20 por ciento al total de semillas del banco del suelo. Entre las especies arbóreas, Trema micrantha (L.) Blume (Ulmaceae) presentó la mayor densidad de semillas (84% de las semillas germinadas). En general, la composición de especies arbóreas en el banco del suelo no reflejó la composición de la comunidad de árboles en cada sitio. Los resultados sugieren que la alteración causada por actividad humana (uso de senderos, tala selectiva y pastoreo) puede influir en el tamaño y composición del banco de semillas del suelo en fragmentos de bosque. Los sitios donde la actividad humana es reducida tienen la mayor proporción de semillas latentes. [source] | ||||||||||