Modern agriculture is based on the notion that nitrate is the main source of nitrogen (N) for crops, but nitrate is also the most mobile form of N and easily lost from soil. Efficient acquisition of nitrate by crops is therefore a prerequisite for avoiding off-site N pollution. Sugarcane is considered the most suitable tropical crop for biofuel production, but surprisingly high N fertilizer applications in main producer countries raise doubt about the sustainability of production and are at odds with a carbon-based crop. Examining reasons for the inefficient use of N fertilizer, we hypothesized that sugarcane resembles other giant tropical grasses which inhibit the production of nitrate in soil and differ from related grain crops with a confirmed ability to use nitrate. The results of our study support the hypothesis that N-replete sugarcane and ancestral species in the Andropogoneae supertribe strongly prefer ammonium over nitrate. Sugarcane differs from grain crops, sorghum and maize, which acquired both N sources equally well, while giant grass, Erianthus, displayed an intermediate ability to use nitrate. We conclude that discrimination against nitrate and a low capacity to store nitrate in shoots prevents commercial sugarcane varieties from taking advantage of the high nitrate concentrations in fertilized soils in the first three months of the growing season, leaving nitrate vulnerable to loss. Our study addresses a major caveat of sugarcane production and affords a strong basis for improvement through breeding cultivars with enhanced capacity to use nitrate as well as through agronomic measures that reduce nitrification in soil.

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The substituted 2,6-dinitroanilines were first reported as herbicides in 1960. At the present time, there are 14 2,6-dinitroaniline herbicides in various stages of product development. Literature on absorption, translocation, and mode of action of the dinitroaniline herbicides refers almost entirely to trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) and nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline]. These herbicides do not directly inhibit the germination of seed. Inhibition of lateral root development is the most characteristic growth response. Swelling of the root tip is a universally recognized morphological effect caused by these compounds. The cells in this region are multinucleate, indicating that the mitotic process has been disrupted. Examination of these cells shows an increase in the percentage of cells in arrested metaphase due to the disruption of spindle microtubules. Inference is made that the dinitroaniline herbicides affect chromosomes in a manner similar to colchicine, but research with pig brain (Sus scrofa) microtubules has shown that effects of the herbicide on microtubular protein is different.Injury to the top of plants is recognized by stunting, development of dark green color, and swelling and brittleness of the stem or hypocotyl. The major sites of uptake are the shoot of monocots and the hypocotyl or hypocotyl hook for dicots. Exposure of seedling roots to the dinitroaniline herbicides does not kill the plant, but exposure of the young shoot will result in death. Available data indicate that the dinitroaniline herbicides are either absorbed or adsorbed by the roots due to the proximity of the roots to the herbicide, but that translocation from the root to the top is minimal. When a dinitroaniline was found in the plant, the parent compound was the major product present with metabolites equal to 5% or less.Insufficient information is available to accurately describe effects of these herbicides on plant carbohydrates, lipids, and nitrogenous compounds. The effect of trifluralin on RNA and DNA varies with the plant species, treatment time, concentration of herbicide, and plant part investigated, but differences observed do not correlate with dinitroaniline-susceptible and resistant species. Enzyme activity does not appear to be greatly inhibited by the dinitroaniline herbicides. However, the dinitroaniline herbicides interfere with photosynthesis and respiration in vivo and in vitro.The phytotoxic action of trifluralin can be antidoted with the organophosphorus insecticides, phorate [0,0-diethyl-S-(ethylthiomethyl)-phosphorodithioate], disulfoton [0,0-diethyl-S-2-(ethylthioethyl)-phosphorodithioate], and externally applied lipids such as D-α-tocopherol. There is a strong correlation that seeds with a high lipid content are resistant to trifluralin and those with a low lipid content are susceptible. Despite all the work that has been conducted, the mode of action of the dinitroaniline herbicides is still unclear.

We introduce the AusTraits database - a compilation of measurements of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 375 traits across 29230 taxa from field campaigns, published literature, taxonomic monographs, and individual taxa descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological parameters (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual-, species- and genus-level observations coupled to, where available, contextual information on site properties. This data descriptor provides information on version 2.1.0 of AusTraits which contains data for 937243 trait-by-taxa combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data to increase our collective understanding of the Australian flora.

We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field campaigns, published literature, taxonomic monographs, and individual taxon descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological attributes (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual- and species-level measurements coupled to, where available, contextual information on site properties and experimental conditions. This article provides information on version 3.0.2 of AusTraits which contains data for 997,808 trait-by-taxon combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data, which also provides a template for other national or regional initiatives globally to fill persistent gaps in trait knowledge.

Savanna ecosystems are a major source of nitrogen (N) trace gases that influence air quality and climate. These systems are experiencing widespread encroachment by woody plants, frequently associated with large increases in soil N, with no consensus on implications for trace gas emissions. We investigated the impact of encroachment by N‐fixing tree Prosopis glandulosa on total reactive N gas flux (Nt = NO + N2O + NOy + NH3) from south Texas savanna soils over 2 years. Contrary to expectations, upland Prosopis groves did not have greater Nt fluxes than adjacent unencroached grasslands. However, abiotic conditions (temperature, rainfall, and topography) were strong drivers. Emissions from moist, low‐lying Prosopis playas were up to 3 times higher than from Prosopis uplands. Though NO dominated emissions, NH3 and NOy (non‐NO oxidized N) comprised 12–16% of the total summer N flux (up to 7.9 µg N m−2 h−1). Flux responses to soil wetting were temperature dependent for NO, NH3, and NOy: a 15 mm rainfall event increased flux 3‐fold to 22‐fold after 24 h in summer but had no effect in winter. Repeated soil wetting reduced N flux responses, indicating substrate depletion as a likely control. Rapid (<1 min) increases in NO emissions following wetting of dry soils suggested that abiotic chemodenitrification contributes to pulse emissions. We conclude that temperature and wetting dynamics, rather than encroachment, are primary drivers of N flux from these upland savannas, with implications for future emission patterns under altered precipitation regimes.

While importance of amino acids as a nitrogen source for plants is increasingly recognised, other organic N sources including small peptides have received less attention. We assessed the capacity of functionally different species, annual and nonmycorrhizal Arabidopsis thaliana (L.) Heynh. (Brassicaceae) and perennial Lobelia anceps L.f. (Campanulaceae), to acquire, metabolise and use small peptides as a N source independent of symbionts. Plants were grown axenically on media supplemented with small peptides (2-4 amino acids), amino acids or inorganic N. In A. thaliana, peptides of up to four amino acid residues sustained growth and supported up to 74% of the maximum biomass accumulation achieved with inorganic N. Peptides also supported growth of L. anceps, but to a lesser extent. Using metabolite analysis, a proportion of the peptides supplied in the medium were detected intact in root and shoot tissue together with their metabolic products. Nitrogen source preferences, growth responses and shoot-root biomass allocation were species-specific and suggest caution in the use of Arabidopsis as the sole plant model. In particular, glycine peptides of increasing length induced effects ranging from complete inhibition to marked stimulation of root growth. This study contributes to emerging evidence that plants can acquire and metabolise organic N beyond amino acids.

The mechanistic links between nitrogen (N) availability and investment in plant phosphorus (P) acquisition have important implications for plant growth, species distributions, and responses to CO2 fertilization under global change, especially in P‐poor tropical ecosystems. Currently, it is unclear whether investment in strategies that enhance plant P acquisition (arbuscular mycorrhizal, AM; colonization or root phosphatase activity, RPA) are determined primarily by phylogeny, or whether these strategies differ among N2‐fixing legumes and nonfixing plants as a result of differing N availability. We hypothesized that plant N status, which can vary widely independent of N fixation, correlates with investment in P acquisition, because: (a) N and P concentrations scale in plant tissue indicative of coupled demand and (b) plants with more N may have more resources available to allocate to acquisition strategies. We grew seedlings of eight tropical tree species from three families (including three N2‐fixing and one nonfixing legume) under greenhouse conditions in native forest soil for four months. Species represented almost the full range of foliar N observed in tropical trees. Neither foliar N nor P concentrations correlated with investment in P acquisition. Across all species, we found an inverse relationship between investment in AM colonization and RPA, but this trade‐off was unrelated to foliar N or P and did not differ between functional types (i.e., N2 fixers vs. nonfixers). Within legumes (family Fabaceae), two strategies were evident that were unrelated to fixation status. High‐fixing Inga and nonfixing Dialium displayed high foliar N and P concentrations and greater proportional investment in RPA versus AM, while lower fixing Ormosia species were characterized by lower foliar nutrient concentrations and proportionally more investment in AM. Synthesis.Investment in P acquisition strategies in tropical trees is not dependent on foliar N or functional group, but instead may be controlled in part by resource trade‐offs. High diversity in nutrient strategies between related species cautions again the use of simple functional groupings to draw conclusions about nutrient acquisition in tropical trees.