Light is more important than nutrient ratios of fertilization for cymodocea nodosa seedling development

Restoration of seagrass beds through seedlings is an alternative to the transplantation of adult plants that reduces the impact over donor areas and increases the genetic variability of restored meadows. To improve the use of Cymodocea nodosa seedlings, obtained from seeds germinated in vitro, in restoration programs, we investigated the ammonium and phosphate uptake rates of seedlings, and the synergistic effects of light levels (20 and 200 mu mol quanta m(-2) s(-1)) and different nitrogen to phosphorus molar ratios (40 mu M N:10 mu M P, 25 mu M N:25 mu M P, and 10 mu N:40 mu M P) on the photosynthetic activity and growth of seedlings. The nutrient content of seedlings was also compared to the seed nutrient reserves to assess the relative importance of external nutrient uptake for seedling development. Eighty two percent of the seeds germinated after 48 days at a mean rate of 1.5 seeds per day. All seedlings under all treatments survived and grew during the 4 weeks of the experiment. Seedlings of C. nodosa acquired ammonium and phosphate from the incubation media while still attached to the seed, at rates of about twice of adult plants. The relevance of external nutrient uptake was further highlighted by the observation that seedlings' tissues were richer in nitrogen and phosphorus than non-germinated seeds. The uptake of ammonium followed saturation kinetics with a half saturation constant of 32 mu M whereas the uptake of phosphate increased linearly with nutrient concentration within the range tested (5 - 100 mu M). Light was more important than the nutrient ratio of fertilization for the successful development of the young seedlings. The seedlings' photosynthetic and growth rates were about 20% higher in the high light treatment, whereas different nitrogen to phosphorus ratios did not significantly affect growth. The photosynthetic responses of the seedlings to changes in the light level and their capacity to use external nutrient sources showed that seedlings of C. nodosa have the ability to rapidly acclimate to the surrounding light and nutrient environment while still attached to the seeds. C. nodosa seedlings experiencing fertilization under low light levels showed slightly enhanced growth if nourished with a balanced formulation, whereas a slight increase in growth was also observed with unbalanced formulations under a higher light level. Our results highlight the importance of high light availability at the seedling restoration sites.Department of the Environment, Heritage and Climate Change of Gibraltar; FCT, the Portuguese Foundation for Science and Technology [SFRH/BPD/91629/2012]; FCT [UID/Multi/04326/2013

Mónica Ruiz Bañuls, El huehuetlatolli como discurso sincrético en el proceso evangelizador novohispano del siglo XVI. Pról. de fray Francisco Morales OFM. Bulzone Editore, Roma, 2009; 285 pp.

Se reseña el libro: El huehuetlatolli como discurso sincrético en el procesoevangelizador novohispano del siglo xvi

Effects of temperature, salinity and seed age on induction of Zostera japonica germination in North America, USA

Seagrasses can colonize unstructured mudflats either through clonal growth or seed germination and survival. Zostera japonicais an introduced seagrass in North America that has rapidly colonized mudflats along the Pacific Coast, leading to active management of the species. Growth and physiology have been evaluated; however, there is little information about the factors influencing seed germination. We examined the effects of storage and induction temperature (10, 15, 20°C) and salinity (0, 10, 20, 30), and storage period (1.5 and 26 months) on germination of seeds of the seagrass Z. japonicacollected from Yaquina Bay, Oregon, USA. Seed germination at 15 and 20 ◦C was 1.24 times higher than at 10°C. Cumulative seed germination at salinity 0 during the first 28 days was 6.5 times greater than at a salinity of 10; similarly, initial seed germination at a salinity of 10 was 7.3 times greater than that observed for salinity 20 and 30. The proportion of germinated seeds collected in 2011 and stored for 26 months was 1.24 times greater than seeds collected in 2013 that were stored for only 6 weeks. Overall average germination rates were 21.6% and 17.1% for 2011 and 2013, respectively. Our experimental results indicate that salinity had a much stronger control over Z. japonica germination than temperature, and the long storage period suggests that Z. japonica is capable of developing a persistent seed bank. We hypothesize that Z. japonica uses seasonal variations in temperature and salinity to avoid competition between generations favoring germination under conditions that are not optimal for the growth of mature plants

Effects of temperature, salinity and seed age on induction of Zostera japonica germination in North America, USA

Seagrasses can colonize unstructured mudflats either through clonal growth or seed germination and survival. Zostera japonicais an introduced seagrass in North America that has rapidly colonized mudflats along the Pacific Coast, leading to active management of the species. Growth and physiology have been evaluated; however, there is little information about the factors influencing seed germination. We examined the effects of storage and induction temperature (10, 15, 20°C) and salinity (0, 10, 20, 30), and storage period (1.5 and 26 months) on germination of seeds of the seagrass Z. japonicacollected from Yaquina Bay, Oregon, USA. Seed germination at 15 and 20 ◦C was 1.24 times higher than at 10°C. Cumulative seed germination at salinity 0 during the first 28 days was 6.5 times greater than at a salinity of 10; similarly, initial seed germination at a salinity of 10 was 7.3 times greater than that observed for salinity 20 and 30. The proportion of germinated seeds collected in 2011 and stored for 26 months was 1.24 times greater than seeds collected in 2013 that were stored for only 6 weeks. Overall average germination rates were 21.6% and 17.1% for 2011 and 2013, respectively. Our experimental results indicate that salinity had a much stronger control over Z. japonica germination than temperature, and the long storage period suggests that Z. japonica is capable of developing a persistent seed bank. We hypothesize that Z. japonica uses seasonal variations in temperature and salinity to avoid competition between generations favoring germination under conditions that are not optimal for the growth of mature plants

Systems Modeling to Improve the Hydro-Ecological Performance of Diked Wetlands

Water scarcity and invasive vegetation threaten arid-region wetlands and wetland managers seek ways to enhance wetland ecosystem services with limited water, labor, and financial resources. While prior systems modeling efforts have focused on water management to improve flow-based ecosystem and habitat objectives, here we consider water allocation and invasive vegetation management that jointly target the concurrent hydrologic and vegetation habitat needs of priority wetland bird species. We formulate a composite weighted usable area for wetlands (WU) objective function that represents the wetland surface area that provides suitable water level and vegetation cover conditions for priority bird species. Maximizing the WU is subject to constraints such as water balance, hydraulic infrastructure capacity, invasive vegetation growth and control, and a limited financial budget to control vegetation. We apply the model at the Bear River Migratory Bird Refuge on the Great Salt Lake, Utah, compare model-recommended management actions to past Refuge water and vegetation control activities, and find that managers can almost double the area of suitable habitat by more dynamically managing water levels and managing invasive vegetation in August at the beginning of the window for control operations. Scenario and sensitivity analyses show the importance to jointly consider hydrology and vegetation system components rather than only the hydrological component

Muertos y maltratados

El estudio que se presenta a continuación explora en cuatro cuentos la manera en que los personajes infantiles de Manuel Gutiérrez Nájera demuestran los problemas sociales de su época.</jats:p