Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background and aims</jats:title> <jats:p>Iron (Fe) plaque on rice roots is a mixture of Fe oxide and oxyhydroxide minerals thought to protect rice from high levels of arsenic (As) in flooded paddy soils. Silicon (Si), phosphorus (P), and selenium (Se) also exist as oxyanions in rice paddies, but the impacts of Fe plaque on uptake of these nutrients are unknown.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>We used natural variation in paddy soil chemistry to test how Si, P, As, and Se move from porewater to plaque to plant via multiple techniques. In a pot study, we monitored Fe plaque deposition and porewater chemistry in 5 different soils over time and measured plaque/plant chemistry and Fe plaque mineralogy at harvest. We normalized oxyanion concentrations by Fe to determine the preferential retention on plaque or plant uptake.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>Low phosphorus availability increased root Fe-oxidizing activity, while Fe, Si, P, As, and Se concentrations in plaque were strongly correlated with porewater. Plaque did not appreciably retain Si and Se, and the oxyanions did not compete for adsorption sites on the Fe plaque.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusion</jats:title> <jats:p>Root Fe plaque seems to protect rice from As uptake, does not interfere with Si and Se uptake, and roots adapt to maintain P nutrition even with retention of porewater P on plaque.</jats:p> </jats:sec>

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background and Aims</jats:title> <jats:p>Nitrogen (N) is an essential macronutrient that can limit plant development and crop yield through widespread physiological and molecular impacts. In maize, N-starvation enhances biosynthesis and exudation of strigolactones (SLs) in a process reversible by nitrate addition and consequent repression of genes for SL biosynthesis.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>In the present study, a maize mutant deficient in SL biosynthesis (<jats:italic>zmccd8</jats:italic>) allowed an in-depth analysis of SL contributions under low N. Both hydroponic and field conditions were used to better characterize the response of the mutant to N availability.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>The severity of responses to N-limitation by the SL-deficient <jats:italic>zmccd8</jats:italic> mutant extended from growth parameters to content of iron, sulfur, protein, and photosynthetic pigments, as well as pronounced impacts on expression of key genes, which could be crucial molecular target for the SL-mediated acclimatation to N shortage.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Our results demonstrate that SLs are critical for physiological acclimation to N deficiency by maize and identify central players in this action. Further contributions by iron and sulfur are implicated in the complex pathway underlying SL modulation of responses to N-deprivation, thus widening our knowledge on SL functioning and providing new hints on their potential use in agriculture.</jats:p> </jats:sec>

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background and aims</jats:title> <jats:p>Several lines of evidence indicate that arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) associations can have different effects on soil nutrient dynamics. Some lineages of ECM fungi can extract N from organic matter, with varying impacts on decomposers, soil carbon pools, mineral N availability, and plants that lack ECM. However, these effects are not always observed, and it is not clear how they are mediated by environmental factors.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>We used Plant Root Simulator probes to compare soil availability of a wide range of nutrients beneath replicated 30-yr old plantations of Chilean <jats:italic>Nothofagus</jats:italic> (ECM) and Cupressaceae (<jats:italic>Austrocedrus, Fitzroya</jats:italic>: AM) on a lowland temperate site. Probes were buried for two 8-week periods in early spring and late summer. We also compared understorey composition beneath plantations, to test for evidence of different successional trajectories beneath <jats:italic>Nothofagus</jats:italic> and Cupressaceae.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>Soil organic carbon, total N and total phosphorus did not differ significantly between <jats:italic>Nothofagus</jats:italic> and Cupressaceae stands. Redundancy analysis revealed significant effects of both plantation type (<jats:italic>Nothofagus</jats:italic> vs. Cupressaceae) and season on overall mineral nutrient availability. Mineral N availability did not differ significantly between <jats:italic>Nothofagus</jats:italic> and Cupressaceae plots, but pH and calcium availability were significantly lower beneath <jats:italic>Nothofagus</jats:italic>. Manganese (Mn) was much more available beneath <jats:italic>Nothofagus</jats:italic> stands, which might reflect abundant Mn-peroxidase, a key enzyme involved in breakdown of lignin by ECM fungi. Understorey composition varied considerably between individual plantations, but did not differ significantly between <jats:italic>Nothofagus</jats:italic> and Cupressaceae plantations.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Despite an overall effect on the stoichiometry of nutrient availability, we found little evidence of modification of the local N cycle by ECM fungi, or of divergent regeneration patterns beneath AM and ECM plantations. This might reflect the relatively N-rich character of this site, and/or mycorrhizal effects being counteracted by leaf trait differences between Chilean Cupressaceae and <jats:italic>Nothofagus</jats:italic> species.</jats:p> </jats:sec>