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The persistence of subtropical seasonally dry forests urgently requires the implementation of ex situ conservation and restoration programs. We studied variation in seed traits and dormancy of six native species growing in seasonally dry Chaco forests of Argentina. We documented high intra- and interspecific variability in seed traits and dormancy. Fresh seeds of Geoffroea decorticans and Parasenegalia visco (Fabaceae) were water-permeable and nondormant (ND), while those of Parkinsonia praecox and Vachellia aroma (Fabaceae) were water-impermeable and had physical dormancy (PY). Seeds of Schnopsis lorentzii (Anacardiaceae) and Sarcomphalus mistol (Rhamnaceae) were water-permeable and had physiological dormancy (PD). Mechanical and chemical scarification were the most effective methods to break PY, and dry storage for 3 months was effective in breaking PD. Seeds of large-seeded species were ND or had PD, and those of small-seeded species had PY. Species inhabiting moist habitats had ND seeds, whereas those from seasonally dry habitats had seeds with PY or PD. These results suggest that seed traits and dormancy are species-specific and that intraspecific variation in seed traits is likely associated with high phenotypic plasticity of species in response to local environmental heterogeneity. These findings should be considered at the time of implementation of conservation techniques and for seed sourcing decisions for restoration. [ABSTRACT FROM AUTHOR]

Background and aims: The species of Papilionoideae have floral traits or strategies related to the pollination mechanisms and promote cross pollination such as mechanic barriers, spatial or temporal separation of the maturation of the sexual organs, among others. The aim of this study was to provide a detailed morphological description of the androecium and gynoecium of 17 Papilionoideae species native to Lerma Valley (Salta-Argentina). M&M: We studied on field and laboratory quantitative and qualitative floral traits and analized from a functional point of view those traits that could be related to the reproductive system and to the pollination mechanisms. Results: Most of the species are homogamous and have monadelphous or pseudomonadelphous with basal fenestration androecium, monomorphic anthers, variable forms of the style and stigma, stylar trichomes, peristigmatic trichomes and stigmatic membrane. We registered for the first time some traits in some of the species, such as the spontaneous rupture of the stigmatic membrane during the anthesis and the reduction of anthers-stigma distance after the maturation of both sexual organs. Conclusions: All the studied species have floral traits associated with a reduction in selfpollination. Detailed information on morphology and other traits of the androecium and gynoecium has been obtained, and could be used to describe better their pollination mechanisms and to understand some aspects of their reproductive biology. [ABSTRACT FROM AUTHOR]

Background and aims: The occurrence of seeds with physical dormancy is an obstacle for the use and management of many plant species. Here, we studied the presence of physical dormancy in mericarps (seed-dispersal units) and seeds, the morphoanatomical structures responsible for physical dormancy, and the effects of possible methods for breaking dormancy in seeds of Malvastrum coromandelianum (Malvaceae). M&M: Imbibition essays were used to confirm the presence of physical dormancy in mericarps and seeds, and the morpho-anatomical seed structure was described by using a scanning electron microscopy. The effects of mechanical, chemical and thermal scarifications on seed germination and seed structure were also evaluated. Results: Mericarps and scarified seeds increased > 160% of their initial weight, whereas intact seeds increased < 40% of their initial weight. The presence of a palisade cell layer in seed coat and a water-gaps complex in the chalazal region were observed. Higher germination percentages and lower t50 were registered after mechanical scarification, followed by chemical and thermal scarifications (dry heat). Chemical and thermal scarifications caused the chalazal cap elimination and the contiguous cracks to form around the chalazal region; whereas the formation of a chalazal blister and its elimination were only observed after chemical scarification. Conclusions: Seeds of M. coromandelianum have physical dormancy. Water enters the seeds through a water-gap complex (Type III compound) located in the chalazal region. Mechanical, chemical and thermal scarifications are effective methods for breaking physical dormancy and increase germination. [ABSTRACT FROM AUTHOR]

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Copyright of Boletín de la Sociedad Argentina de Botánica is the property of Sociedad Argentina de Botanica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)