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1.
Pablo Delgado-Sánchez Juan Francisco Jiménez-Bremont María de la Luz Guerrero-González Joel Flores 《Journal of plant research》2013,126(5):643-649
Fungal attack under light reduces mechanical resistance of the testa of Opuntia seeds, making it easier for the embryo to emerge. However, the effect of fungi on Opuntia seed germination in darkness is unknown. We evaluated the combined effects of light and inoculation with Phoma medicaginis, Trichoderma harzianum, Trichoderma koningii, and Penicillium chrysogenum on germination of O. streptacantha, O. leucotricha, and O. robusta seeds, from central Mexico. We also evaluated the combined effects of seed age (2-, 3-, and 12-year-old seeds) and presence of fungi on the testa on O. streptacantha germination. All fungal species eroded the funicular envelope and promoted seed germination for O. leucotricha and O. streptacantha, but did more so in light than in darkness. For the latter species, younger seeds inoculated with fungi had lower germination than older ones. For O. robusta, we found that seeds inoculated with P. medicaginis and T. harzianum had similar germination in light and in darkness. Our results strongly indicate that deterioration of the testa by fungi is higher in light than in darkness. 相似文献
2.
Orozco-Segovia A Márquez-Guzmán J Sánchez-Coronado ME Gamboa de Buen A Baskin JM Baskin CC 《Annals of botany》2007,99(4):581-592
BACKGROUND AND AIMS: There is considerable confusion in the literature concerning impermeability of seeds with 'hard' seed coats, because the ability to take up (imbibe) water has not been tested in most of them. Seeds of Opuntia tomentosa were reported recently to have a water-impermeable seed coat sensu lato (i.e. physical dormancy), in combination with physiological dormancy. However, physical dormancy is not known to occur in Cactaceae. Therefore, the aim of this study was to determine if seeds of O. tomentosa are water-permeable or water-impermeable, i.e. if they have physical dormancy. METHODS: The micromorphology of the seed coat and associated structures were characterized by SEM and light microscopy. Permeability of the seed-covering layers was assessed by an increase in mass of seeds on a wet substrate and by dye-tracking and uptake of tritiated water by intact versus scarified seeds. KEY RESULTS: A germination valve and a water channel are formed in the hilum-micropyle region during dehydration and ageing in seeds of O. tomentosa. The funicular envelope undoubtedly plays a role in germination of Opuntia seeds via restriction of water uptake and mechanical resistance to expansion of the embryo. However, seeds do not exhibit any of three features characteristic of those with physical dormancy. Thus, they do not have a water-impermeable layer(s) of palisade cells (macrosclereids) or a water gap sensu stricto and they imbibe water without the seed coat being disrupted. CONCLUSIONS: Although dormancy in seeds of this species can be broken by scarification, they have physiological dormancy only. Further, based on information in the literature, it is concluded that it is unlikely that any species of Opuntia has physical dormancy. This is the first integrative study of the anatomy, dynamics of water uptake and dormancy in seeds of Cactaceae subfamily Opuntioideae. 相似文献
3.
When studying congeneric species, it is of reasonable importance to understand different ecophysiological performances which might determine the distribution of species in habitats with different natural resources. Styrax ferrugineus is exclusive and well adapted to the Brazilian Cerrado sensu stricto (s. str.); S. camporum is widely distributed in the Cerrado sensu lato (s. l.) areas, with young trees being observed at the edge of cerradão and other vegetation fragments; and S. pohlii occurs in permanently waterlogged soils of the Cerrado region, such as those of riparian forests. We tested the hypothesis that the higher the soil water content in the physiognomic gradient of the vegetation, the higher is the germination success of S. pohlii, but the lower is the germination success of S. ferrugineus. We also discuss whether gap conditions inside a cerradão fragment imply a high germination rates of seeds of S. camporum. Seeds from each of the three species were buried within nylon bags containing soil from the respective sites. Burial occurred in a Cerrado s. str., in understory and gap conditions of a cerradão, and in the understory of a riparian forest fragment, and lasted for 60, 120, 180 and 240 days, respectively, after the fruit dispersal time of each of the three species. After 60 days, a relationship was found showing that the percentage of germinated seeds diminished, and the percentage of damaged seeds increased as soil water content increased (Cerrado s. str. < cerradão gap < cerradão understory ? riparian forest). S. camporum still showed viable seeds 60 days after burial (DAB), and germinated seeds 120 DAB, indicating that it needed a longer time to germinate, which might be associated to its thicker seed coat, in relation to the other two species. The germination performance of each of the three species was the same in the gap and understory conditions of the cerradão. The higher concentration of adult S. camporum plants at the edge of vegetation fragments is not related to a particular high germination performance and seedling establishment. 相似文献
4.
Marathrum schiedeanum and Marathrum rubrum are annual Podostemaceae, thus their seeds are important to their dispersal and persistence in their habitat. We assessed the effect on germination of (1) light (white, red and far red) and darkness, (2) temperature (15, 20, 25, 30 °C and alternating 20/30 °C), (3) osmotic potential (0 to −0.8 MPa), (4) proximity to moisture sources and (5) seed storage. Seeds of M. schiedeanum and M. rubrum were non-dormant and had a high germination capacity (96%). Seeds were positive photoblastic; at 15 °C germination drop to zero, and germination rate was slower at 20 °C and at 20/30 °C than at 25 °C. A small proportion of seeds of both species germinated even at osmotic potentials as low as −0.6 MPa (11%) for M. rubrum and −0.8 MPa (70%) for M. schiedeanum. Seeds germinated only when near to the source of moisture (91.3–87.1% and 53.3–35.6% for M. schiedeanum and M. rubrum, respectively) and 2 years in dry storage did not modify their capacity to germinate. At the beginning of the rainy season, light and temperature in the rivers may be high enough for germination. The ability to germinate at low osmotic potential may be related to early germination during the rainy season. This may be because the seed mucilage assists in diffusion of water from the substrate to the seed. Both species germinated faster at −0.06 MPa, than in distilled water, which may indicate appropriate conditions for germination of these short-lived species. 相似文献
5.
Pablo Delgado-Sánchez María Azucena Ortega-Amaro Aída Araceli Rodríguez-Hernández Juan Francisco Jiménez-Bremont Joel Flores 《Plant signaling & behavior》2010,5(10):1229-1230
Recently, we found that fungi are involved in breaking seed dormancy of Opuntia streptacantha, and that the effect of fungi on seeds is species-specific. However, the effect of fungi on seed germination from other Opuntia spp. has not been evaluated. Thus, we evaluated the effect of four fungal species (Penicillium chrysogenum, Phoma sp., Trichoderma harzianum, Trichoderma koningii) on the germination of Opuntia leucotricha, an abundant species in the Chihuahuan Desert, Mexico. We found that seeds inoculated with the four fungal species had higher germination than control seeds. Trichoderma spp. were the most effective. Our results strongly indicate that fungi are involved in breaking seed dormancy of O. leucotricha. Thus, we suggest that these fungi could promote seed germination from other Opuntia species.Key words: cactaceae, Opuntia leucotricha, Penicillium chrysogenum, Phoma sp., physiological dormancy, prickly pear, seed germination, Trichoderma spp.Seeds in the soil interact with microorganisms that could help them break seed dormancy. Fungi attack the testa, eroding or cracking the hard/stony endocarp, and could reduce the mechanical resistance to germination in seeds with physiological dormancy.1 In arid environments, the effects of fungi on breaking seed dormancy in cacti have received very little attention. Recently, our work group found that Phoma sp. and Trichoderma koningii, and in less proportion Penicillium chrysogenum, help break seed dormancy of Opuntia streptacantha, maybe by the action of enzymes that degrade the testa.2 However, the effect of fungi on seed germination from other Opuntia species has not been evaluated.In this study, we test the effects of four fungal species (two isolated from O. streptacantha testa) in breaking seed dormancy of Opuntia leucotricha; a perennial arborescent cactus of economic interest distributed on the semiarid lands of central Mexico.Since seeds of Opuntia spp. have physiological dormancy, they need a period of after-ripening to break dormancy, and the embryos have low growth potential; we used two-year-old seeds, assuming that old seeds have broken physiological seed dormancy and that fungi can reduce mechanical resistance to germination.2
O. leucotricha seeds were collected from mature fruits in 2008 and stored in paper bags at room temperature during two years.Penicillium chrysogenum, Phoma sp., Trichoderma harzianum and T. koningii were grown on PDA plates at 28°C for three days. The spores (P. chrysogenum, T. harzianum and T. koningii) and mycelia (Phoma sp.) were collected in sterile distilled water and counted in a Neubauer chamber for later inoculation of O. leucotricha seeds. Sterilized seeds were grown on water-agar plates and inoculated with 2 µl of spore solution or mycelium (6 × 107 ml−1) from each fungus. Seeds were incubated in water-agar plates for 35 days in an automatic germination chamber with a 16 h light and 8 h dark photoperiod at 25°C ± 2°C. There were five replicates per treatment and 20 seeds per replicate.After one-way ANOVA, we found a significant effect of fungal species (F = 52.198, p < 0.0001) on O. leucotricha seed germination. Seeds inoculated with the four fungal species had higher germination than control, although Trichoderma spp. promoted higher seed germination than the other fungi examined (Treatment Germination percentage (± S.E.) Control 0%c Penicillium chrysogenum 15% (± 3.35)b Phoma sp. 10% (± 2.23)b Trichoderma harzianum 40% (± 8.94)a Trichoderma koningii 37% (± 8.27)a