Among nanomaterials, silver nanoparticles (AgNPs) are cost-effective and exhibit unique physicochemical properties that enable them to become the most used agents for the manufacture of various products known as nano-enabled, including those for personal care, drugs, fabrics, sprays, disinfectants, vacuum cleaners, and air conditioners, with a continuous expansion to different sectors. Industrial discharges, the disposal of wastewater treatment effluents, and indirect runoff from the soil are some factors that are increasing the accumulation of AgNPs in aquatic and wetland ecosystems. Herewith, we critically analyze the progress in the research of the uptake and translocation of AgNPs in aquatic and wetland plants and their phytotoxic effect that depends on the concentration, size, distribution, morphological shape, surface characteristics and chemical composition of the nanoparticles, as well as the plant genotypes, among other factors. Due to biological plasticity, the toxicity level of AgNPs may vary among plant species, which may be further affected by the mode of application, time of exposure, and plant conditions (e.g., agronomic management, growth rate, phenological stage, etc.). Therefore, it is possible to identify and select competent plants for phytoremediation purposes, including superior capabilities for phytoextraction, phytofiltration, and phytostabilization. The review also identifies the main gaps that require attention in future research in order to elucidate a more integrative map aimed to reduce the potential threats to the environment and living organisms including humans.

La propagación asexual por hijuelos jóvenes de rizoma parece ser la forma natural más común y exitosa de propagación de plantas de Agave spp. silvestres y en plantaciones comerciales. Sin embargo, la reproducción sexual es importante porque incrementa la variabilidad genética. El objetivo de esta investigación fue caracterizar las semillas de las variantes ‘Blanco’, ‘Chino’ y ‘Liso’ del maguey A. salmiana que crecen en San Luis Potosí, México, en cuanto a sus dimensiones (longitud, anchura y peso), potencial de emergencia y crecimiento inicial. La emergencia se evaluó en invernadero en tres ocasiones, verano e invierno del 2008 y verano del 2009. Se registró el progreso de la emergencia de la hoja cotiledonar y su número, el tiempo de desdoblamiento y peso de las hojas laterales. Las semillas de ‘Blanco’ fueron las de menor longitud (7.1 mm), anchura (5.4 mm) y peso (10.7 mg), las de ‘Chino’ fueron las de mayor longitud y anchura (8.4 mm y 6.5 mm, respectivamente), y la ‘Liso’ fueron las más pesadas (14.5 mg) (P ≤ 0.05). Las hojas cotiledonares iniciaron la emergencia a los 13 d después de la siembra (DDS) en promedio, y la mayor emergencia de plántulas (hojas cotiledonares) en las tres variantes se presentó entre los 21 y 51 DDS. Las hojas laterales se desarrollaron en promedio a los 33 DDS, 18 d después de la emergencia de la hoja cotiledonar. La variante ‘Blanco’ tiene las semillas más chicas y las de mayor emergencia inicial. Después de la emergencia de las hojas cotiledonares, el desarrollo de las plántulas con hojas laterales parece no estar relacionada con las características de las semillas.

Endemic populations of Hechtia perotensis have been described in Puebla and Veracruz, Mexico. Good quality seed collections can be used in conservation, research and ecological restoration. To evaluate seed quality of wild and endemic species, some compounds are used as effective promoters of germination, such as potassium nitrate (KNO3) and gibberellic acid (AG3), because they increase seed germination capacity and reduce latency. The triphenyl tetrazolium chloride (tetrazolium) test correlates seed viability because it is based on the activity of dehydrogenases in live tissues that catalyze mitochondrial respiration. The objective of this study was to obtain information on size and weight of capsules and seeds and seed germination and viability of H. perotensis, collected in Veracruz in the year 2012 and 2015. The hypotheses were 1) that seed germination and viability are independent of the year of collection, 2) that there is a tetrazolium concentration that can identify seed viability better than others, and 3) that pretreatment with KNO3 or AG3 improves seed germination. Seed germination was assessed using a completely randomized design with three treatments (control and the germination promoters 0.2 % KNO3 and 500 mg/L AG3), four treatments for the viability test (control, 0.2, 0.5 and 1.0 % of tetrazolium) and six replicates for each treatment. A total of one hundred seeds for germination experiments, and 25 seeds for the viability test were used. The results between and within years were analyzed with ANOVA and multiple comparison with the Tukey test. The proportion of non-germinated seeds was quantified along with the number of normal and abnormal seedlings, seeds with viable embryo, seeds without embryo, and seeds with low or no viability. On average, for the 2012 collected sample, 36 % had viable embryos, 7 % had low viability, 24 % were not viable and 33 % had no embryo. This result was significantly different from the 2015 sample, for which 87 % of seed showed viable embryos, 10 % had low viability, 0 % was not viable and 3 % had no embryo. Seed germination was also significantly different between years (22 and 92 %) Pregerminative treatments did not improve germination. Seed germination and viability of H. perotensis significantly varied between years of seed collection.