Mattana E.,University of Cagliari |
Pritchard H.W.,Seed Conservation |
Porceddu M.,University of Cagliari |
Stuppy W.H.,Seed Conservation |
Bacchetta G.,University of Cagliari
Plant Biology | Year: 2012
Morphophysiological dormancy was investigated in seeds of Ribes multiflorum Kit ex Roem et Schult. ssp. sandalioticum Arrigoni, a rare mountain species endemic to Sardinia (Italy). There were no differences in imbibition rates between intact and scarified seeds, suggesting a lack of physical dormancy, while methylene blue solution (0.5%) highlighted a preferential pathway for solution entrance through the raphe. Embryos were small at seed dispersal, with an initial embryo:seed ratio (E:S) of ca. 0.2 (embryo length, ca. 0.5mm), whereas the critical E:S ratio for germination was three times longer (ca. 0.6). Gibberellic acid (GA 3, 250mg·l -1) and warm stratification (25°C for 3months) followed by low temperature (<15°C) enhanced embryo growth rate (maximum of ca. 0.04mm·day -1 at 10°C) and subsequent seed germination (radicle emergence; ca. 80% at 10°C). Low germination occurred at warmer temperatures, and cold stratification (5°C for 3months) induced secondary dormancy. After radicle emergence, epicotyl emergence was delayed for ca. 2months for seeds from three different populations. Mean time of epicotyl emergence was affected by GA 3. Seeds of this species showed non-deep simple (root)-non-deep simple (epicotyl) morphophysiological dormancy, highlighting a high synchronisation with Mediterranean seasonality in all the investigated populations. © 2011 German Botanical Society and The Royal Botanical Society of the Netherlands.
Fenu G.,University of Cagliari |
Cogoni D.,University of Cagliari |
Ulian T.,Seed Conservation |
Bacchetta G.,University of Cagliari
Flora: Morphology, Distribution, Functional Ecology of Plants | Year: 2013
In a 5-period study (2007-2011) we examined the effects of human trampling on the last remaining population of Anchusa littorea on its sandy coastal habitat in Sardinia. This species, considered extinct in the wild for several years, was casually rediscovered in a small population at Is Arenas (SW Sardinia). We monthly monitored six trampled and six un-trampled permanent plots, mapping individuals and recording their size and reproductive variables. Trampled and un-trampled plots showed significant differences with respect to plant density, plant size and reproductive performance (flowers and fruits production) of A. littorea. This study demonstrated that human trampling represents a severe threat to the conservation of this species that can be appreciated as a keystone species with concern to human trampling effects on coastal dune plants. In case of A. littorea urgent measures should be undertaken to protect this unique remnant population in the dune system of Is Arenas. In particular, tourist paths should be redirected and confined to others areas in order to promote the natural expansion of A. littorea in its original habitat. A possible integrated strategy for the conservation and management of the species consists in a combination of in situ and ex situ measures. © 2013 Elsevier GmbH.
Ortega-Baes P.,National University of Salta |
Galindez G.,Instituto Nacional de Tecnologia Agropecuaria |
Suhring S.,National University of Salta |
Rojas-Arechiga M.,National Autonomous University of Mexico |
And 2 more authors.
Seed Science and Technology | Year: 2011
The effects of constant and alternating temperatures on seed germination in the Cactaceae have been reported to vary, probably as a result of the different temperature regimes used and the species considered. We determined the cardinal temperatures for, and evaluated the effects of a wide range of constant and alternating temperatures on, seed germination of the South American cactus, Echinopsis schickendantzii Web. The base, optimum and maximum temperatures were 7°C, 26.8°C and 49°C, respectively. The proportion of seeds that germinated and the germination rates were not only significantly different at constant and alternating temperatures but also among all temperature regimes considered. The highest proportion of seeds to germinate occurred at 15°, 20°, 30° and 30/15°C whereas the highest germination rates occurred at 25°, 30°, 30/20°, 35/20° and 40/25°C, with no significant differences between the highest values at constant and alternating temperatures. In the suboptimal temperature range for germination rate, the thermal time to 50% germination was 98°C-days. The results indicate that the seeds have no obligate requirement for alternating temperature for germination.