Giant reed (Arundo donax L.) has great potential for phytoremediation of N balance-disrupted soils due to its large plant biomass production and strong N use efficiency. Soil properties and the artificial modification in agricultural production cause a heterogeneous distribution of N. However, little is known about the differential responses of A. donax at varying N abundances. Herein, giant reed seedlings were grown in solutions with low, moderate and high N supply under hydroponic culture system. We found that both nonoptimal N inhibited the growth and biomass accumulation of A. donax, which was severely repressed by high N. While phytophysiological assays showed that N stress decreased photosynthetic rate and Fv/Fm by increasing reactive oxygen species (ROS) accumulation and lipid peroxidation, the activity of antioxidant enzymes and redox poise in leaves and roots was promoted to minimize excessive ROS accumulation and oxidative stress. High-throughput transcriptomic profiling revealed a total of 19,848 and 16,736 differentially expressed genes (DEGs) under low N and high N conditions, respectively. Based on the results of DEG function annotation and enrichment analyses, varying N abundances up-regulated the expression of a number of genes involved in ROS production and antioxidant defense systems and down-regulated most genes related to photosynthesis, which may contribute to plant response. The expression of 76 and 64 transcription factors (TFs) in leaves, 88 and 110 TFs in roots were up-regulated under low N and high N conditions, respectively, which may contribute to alleviating damage caused by varying N treatment. Our findings would enrich our understanding of the growth and development changes of A. donax plants under low N or high N conditions, and might also provide suitable gene resources and important implications for the genetic improvement of plant N resistance and accumulation through molecular engineering of these genes under varying N abundances in soils.

Moderately volatile elements (MVE) are key tracers of volatile depletion in planetary bodies. Zinc is an especially useful MVE because of its generally elevated abundances in planetary basalts, relative to other MVE, and limited evidence for mass-dependent isotopic fractionation under high-temperature igneous processes. Compared with terrestrial basalts, which have delta Zn-66 values (per mille deviation of the Zn-66/Zn-64 ratio from the JMC-Lyon standard) similar to some chondrite meteorites (similar to+0.3 parts per thousand), lunar mare basalts yield a mean delta Zn-66 value of +1.4 +/- 0.5 parts per thousand (2 st. dev.). Furthermore, mare basalts have average Zn concentrations similar to 50 times lower than in typical terrestrial basaltic rocks. Late-stage lunar magmatic products, including ferroan anorthosite, Mg- and Alkali-suite rocks have even higher delta Zn-66 values (+3 to +6 parts per thousand). Differences in Zn abundance and isotopic compositions between lunar and terrestrial rocks have previously been interpreted to reflect evaporative loss of Zn, either during the Earth-Moon forming Giant Impact, or in a lunar magma ocean (LMO) phase. To explore the mechanisms and processes under which volatile element loss may have occurred during a LMO phase, we developed models of Zn isotopic fractionation that are generally applicable to planetary magma oceans. Our objective was to identify conditions that would yield a delta Zn-66 signature of similar to+1.4%0 within the lunar mantle. For the sake of simplicity, we neglect possible Zn isotopic fractionation during the Giant Impact, and assumed a starting composition equal to the composition of the present-day terrestrial mantle, assuming both the Earth and Moon had zinc 'consanguinity' following their formation. We developed two models: the first simulates evaporative fractionation of Zn only prior to LMO mixing and crystallization; the second simulates continued evaporative fractionation of Zn that persists until similar to 75% LMO crystallization. The first model yields a relatively homogenous bulk solid LMO delta Zn-66 value, while the second results in a stratification of delta Zn-66 values within the LMO sequence. Loss and/or isolation mechanisms for volatiles are critical to these models; hydrodynamic escape was not a dominant process, but loss of a nascent lunar atmosphere or separation of condensates into a proto-lunar crust are possible mechanisms by which volatiles could be separated from the lunar interior. The results do not preclude models that suggest a lunar volatile depletion episode related to the Giant Impact. Conversely, LMO models for volatile loss do not require loss of volatiles prior to lunar formation. Outgassing during planetary magma ocean phases likely played a profound role in setting the volatile inventories of planets, particularly for low mass bodies that experienced the greatest volatile loss. In turn, our results suggest that the initial compositions of planets that accreted from smaller, highly differentiated planetesimals were likely to be severely volatile depleted. (C) 2017 Elsevier Inc. All rights reserved.

Low energy secondary ions ejected by the solar wind are an important component of tenuous exospheres surrounding airless bodies, since these ions carry information on the planetary surface composition. In this work we examine the dependence of secondary-ion abundance, as a function of energy and mass, on surface composition. The surface compositions of two Apollo soils (10084 and 62231) and a synthetic Corning glass lunar simulant were measured with X-ray photoelectron spectroscopy and correlated with the spectra of secondary-ions ejected from the same soils by 4 key He ions. XPS spectra for lunar soils show that the surface compositions are similar to the bulk, but enriched in Fe and 0, while depleted in Mg and Ca. 4 keV He irradiation on the lunar soils and a glass simulant preferentially removes 0 and Si, enriching the surface in Al, Ti, Mg, and Ca. Secondary-ion species ejected from the Apollo soils by 4 keV He include: Na+, Mg+, Al+, Si+, Ca+, Ca++, Ti+, Fe+, and molecular species: NaO+, MgO+ and SiO+. Secondary ion energy distributions for lunar soil 10084 and 62231 rise rapidly, reach a maxima at similar to 5 eV for molecular ions and Na+, similar to 7.5 eV for Fe+, and similar to 10 eV for Mg+, Al+, Si+, Ca+ and Ti+, then decrease slowly with energy. We present species-dependent relative conversion factors for the derivation of atomic surface composition from secondary-ion count rates for 4 keV He irradiation of lunar soils 10084 and 62231, as well as the Corning glass lunar simulant. (c) 2014 Elsevier Inc. All rights reserved.