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Aims: The objective of this study was to propose a maize–peanut intercropping system for traditional sole maize to increase economic benefits and decrease environmental pollution for dryland farming. Methods: The treatments comprised sole maize, sole peanut, maize–peanut intercropping, maize–peanut intercropping–rotation (rotation of the maize and peanut planting strips every year), and maize–peanut intercropping–rotation with 20% and 40% N reduction in maize planting strip. Soil water and total N stock, photosynthetic traits, yield, greenhouse gas emissions, economic income, and interspecific relationships were evaluated. Results: Intercropped maize absorbed more moisture but lost more N than sole maize. Maize–peanut intercropping had higher economic benefits and less N2O emissions than sole maize, but had no intercropped advantage on land equivalent ratio. In addition, intercropping increased the continuous cropping barriers of peanuts than a sole peanut. Rotation of the planting strips in intercropping increased the peanut yield and economic benefits compared with not rotating the planting strips, and the economic benefits reached the highest level in the third planting year. A 20% N reduction in maize planting strips can decrease the global warming potential without affecting economic benefits. A 40% N reduction in maize planting strips could reduce soil N stock, maize yield, water use efficiency, N use efficiency, land equivalent ratio, and income. Conclusions: A maize–peanut intercropping–rotation system is recommended for dryland farming since it promoted efficient use of N and economic benefits and decreased N2O emission. The proper N reduction in maize planting does not lead to N stress but decreased global warming potential. [ABSTRACT FROM AUTHOR]

Aims: Poor soil aeration can be the result of poor soil drainage, soil compaction, or flooding of the root zone, and tolerance to root hypoxia is determined by rootstock characteristics. Based on this assumption, we aimed to verify whether cherry rootstocks can be classified according to their tolerance to poorly aerated soils based on their root growth traits. Methods: Six cherry rootstocks, 'Mazzard F12/1', 'Gisela 6', 'Colt', 'Maxma 14', 'Maxma 60' and 'Cab 6P', were established in 300L containers under field conditions and they were evaluated. Three soils with different textures were selected to generate different air-filled porosities by controlling the volumetric water content: 21% (Ɛα21%), 16% (Ɛα16%) and 9% (Ɛα9%). Vegetative growth, photosynthetic parameters and fine root growth were measured during the 2013-2014 season. Results: In soils with a low air content, Ɛα9%, 'Colt' and 'Maxma 60' rootstocks increased total fine root production by increasing root growth rates in the last phase. 'Colt' and 'Maxma 60' can be classified as tolerant rootstocks. In contrast, 'Mazzard F12/1' and 'Gisela 6' reduced shoot growth by 51.5% and 42.4% and reduced the maximum rate of photosynthesis (Amax) by 69% and 78%, respectively, compared with contrasting soil aeration, resulting in a reduction in total fine root output in poorly aerated soil. They were classified as sensitive rootstocks. Conclusions: Higher fine root production and lower root mortality were the major root traits of tolerance that improved photosynthetic performance and were associated with high photosynthetic capacity under a prolonged low oxygen content in the soil. [ABSTRACT FROM AUTHOR]

Aims: Multi-elemental stoichiometry can represent the biogeochemical niches of species, which can further guide community assemblage. Mycorrhizae play a key role in plant elemental acquisition. Whether and how mycorrhizal type influences the plant multi-elemental stoichiometries and elemental coordination in above- and belowground organs, however, remain unclear. Methods: We determined the concentrations of C, N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, Na, Pb and Sr and some elemental ratios in the leaves and roots of arbuscular mycorrhizal (AM) trees (Phoebe bournei, Schima superba, Michelia maudiae and Cunninghamia lanceolata) and ectomycorrhizal (ECM) trees (Cyclobalanopsis glauca, Pinus massoniana and P. elliottii) in subtropical China. The effects of root traits and soil abiotic factors on elemental concentrations and ratios were reported. Results: The elemental concentrations and ratios differed substantially between the AM and ECM trees, indicating the their biogeochemical niches' differentiation. The C, P, Mg and Mn concentrations and the K:Mg andCa:Mg ratios for AM and the N, Mn and Na concentrations and the Fe:Mn ratio for the ECM species were strongly correlated between leaves and roots, but the correlations were positive or negative depending on elemental composition and mycorrhizal type. The root branching ratio, branching intensity and length played important roles in the plant elemental stoichiometries. Conclusions: The biogeochemical niche's differentiation between the AM and ECM species emphasizes the important role of mycorrhizal type in the assemblage of co-occurring species. This study offers a new opinion for species choosing in mixed forests from the view of the biogeochemical niche's separation. [ABSTRACT FROM AUTHOR]

Aims: Phyllostachys praecox is one of the bamboo species that cultivated extensively in southern China. An organic material mulching technique is commonly adopted in winter to increase the yield of bamboo shoots and profits. However, P. praecox is inevitable to be declined when using the technique continuously. Accordingly, we conducted an aeration study to explore the mechanism of the bamboo recession. Methods: P. praecox were subjected to mulching and aeration treatments for 50 days, antioxidant enzymes, anaerobic respiratory metabolizing enzymes, and photosynthesis characteristics were investigated in root and leaf tissues. Results: The mulching treatment led to bamboo hypoxia stress, while the aeration improved bamboo growth. Compared with mulching treatment, the aeration treatment significantly increased the soil oxygen content. Aeration treatment led to increases in the bamboo root respiratory activity by 19.74%, but decreased ADH, LDH, PDC, SOD, CAT, APX, GR activities by 64.98%, 36.58%, 57.78%, 21.57%, 33.33%, 22.60%, and 32.06%, respectively. Moreover, the aeration treatment greatly enhanced chlorophyll synthesis and improved bamboo photosynthesis. Conclusions: Soil hypoxia induced by the organic material mulching inhibited bamboo growth, which might be the critical factor in the bamboo recession. Our results indicated aeration was conducive to preventing the degeneration of the P. praecox bamboo forest. [ABSTRACT FROM AUTHOR]

Aims: This study investigated the influence of soil properties and plant age on the water use pattern of Bambusa rigida at different distances from a river during the dry season. Methods: The oxygen and hydrogen isotope compositions (δ18O and δ2H) of soil water and culm water in B. rigida forests from sites located at different distances from a river (site A: beside the river with high air moisture; site B: 200 m from the river with high clay content; site C: 400 m from the river with low clay content) were measured. Results: Water uptake was not affected by plant age during early summer. Bambusa rigida at site A were able to use water from the soil organic horizon and moist air contributed 26% and 16% of soil water in this layer during winter and early summer. Bambusa rigida mainly took up water from soil layers with a high clay content at a depth < 50 cm due to the high water storage of these layers, although a high clay concentration weakened water uptake of bamboo roots at greater depths. Conclusions: This study is the first to identify the importance of air moisture for water dynamics of riparian bamboo and offers new insights into water use strategies of riparian B. rigida. [ABSTRACT FROM AUTHOR]

Background: In the almost century since the establishment of boron (B) as an essential plant nutrient, its roles in plant growth and development have been identified, and the mechanism for B transportation explained. Scope: This review relates the yield response of crops, measured as B efficiency i.e. productivity when B is limiting relative to when it is not, to the B supply logistics and requirement of different tissues and organs. Conclusions: Yield is depressed by B deficiency in graminaceous cereals primarily by impaired development and function of the stamen and pistil, but in dicots the adverse effects are expressed as structural damage to various organs. Boron-efficient cereal genotypes are readily identifiable by their successful grain set under limited B, while the quantitative trait loci associated with B efficiency provide a useful selection tool for dicots. The relevance to breeding for B efficiency of the numerous BOR1 and NIP genes controlling active B transport identified in many crops will depend on how close their up-regulation in a deficiency is associated with B efficiency. Understanding of the yield impact of B deficiency is useful in dealing with crop choice and the management of germplasm and B fertilizer. [ABSTRACT FROM AUTHOR]

Aims: There are major knowledge gaps in understanding the translocation leading from nickel uptake in the root to accumulation in other tissues in tropical nickel hyperaccumulator plant species. This study focuses on two species, Rinorea cf. bengalensis and Rinorea cf. javanica and aims to elucidate the similarities and differences in the distribution of nickel and physiologically relevant elements (potassium, calcium, manganese and zinc) in various organs and tissues. Methods: High-resolution X-ray fluorescence microscopy (XFM) of frozen-hydrated and fresh-hydrated tissue samples and nuclear microprobe (micro-PIXE) analysis of freeze-dried samples were used to provide insights into the in situ elemental distribution in these plant species. Results: This study has shown that the distribution pattern of nickel hyperaccumulation is typified by very high levels of accumulation in the phloem bundles of roots and stems. In the leaves, nickel is preferentially located in epidermal cell region, whereas manganese is located mainly in the lower epidermis and zinc in the upper epidermis and palisade mesophyll. The abundant formation of calcium-oxalate crystals, lining the collenchyma, is a prominent feature of both Rinorea cf. bengalensis and Rinorea cf. javanica. Conclusions: Future investigations on Rinorea cf. bengalensis and Rinorea cf. javanica should focus on unravelling the mechanisms of nickel uptake in the root, specifically targeting the identification of nickelspecific membrane transporters. [ABSTRACT FROM AUTHOR]

Background and aims: Serpentine soils typically have low Ca/Mg quotients, low water-holding capacities, and are rich in Ni and Cr, but poor in N and P. To better understand the role of drought and low Ca/Mg quotients in plant adaptation to serpentine soil, we compared the effects of different Ca/Mg quotients (0.18, 2 and 4) and polyethyleneglycol (PEG)-imposed osmotic stress on growth and Ca and Mg uptake and translocation between two Iranian serpentine endemic plant species, the Ni-hyperaccumulator Alyssum inflatum, and the non-accumulator Fortuynia garcinii.Methods: Seedlings were grown in modified Hoagland’s solution with varying Ca/Mg molar quotients (0.18, 2 and 4) and then exposed to PEG (209.7 g L−1) for 8 days.Results: In both species, shoot dry weight was highest at the highest Ca/Mg quotient (4). However, at this Ca/Mg quotient A. inflatum suffered much more from PEG-induced drought (84% mortality and severe growth inhibition in the survivors), compared with the lower Ca/Mg quotients (<20% mortality and no significant growth inhibition). In F. garcinii, the PEG*Ca/Mg interaction was not significant. Shoot Ca concentrations and translocation factors in A. inflatum were higher than in F. garcinii in all the treatments. In both species the Mg translocation factor was highest at the highest Ca/Mg quotient (4) in the PEG treatment.Conclusions: We conclude that a high Ca/Mg quotient stimulated growth in the absence of PEG in both species, but strongly decreased survival and growth in combination with PEG in A. inflatum. In F. garcinii root dry weight and the root to shoot dry weight ratio were significantly decreased at the highest Ca/Mg quotient (4), particularly after PEG treatment, suggesting that F. garcinii also may require a moderate or low Ca/Mg quotient to cope with natural drought. [ABSTRACT FROM AUTHOR]

Aims: To assess the importance of Ni and drought tolerance in serpentine adaptation, the effects of Ni and polyethylene glycol (PEG)-simulated drought, alone and in combination, on growth, water-status, photosynthetic pigments, osmoprotectants, stress markers, and ROS-scavenging enzymes were compared between the serpentine endemic Cleome heratensis and the closely related non-serpentinophyte C. foliolosa. Methods: C. heratensis and C. foliolosa were exposed to combinations of Ni (0, or 20 μM) and PEG (0, −0.3, or −0.9 MPa) in a full factorial, replicated randomized block design. Results were analyzed using 3-way ANOVA. Results: Ni improved growth, enhanced osmoprotectant synthesis, and decreased oxidative stress in C. heratensis, but had insignificant, or deleterious effects on the same parameters in C. foliolosa. The second order Ni*PEG*species interactions were usually significant, demonstrating that the species responded distinctly to combined exposure to PEG and excess Ni. In most cases this was due to additive deleterious effects of Ni in PEG-treated C. foliolosa, i.e. on growth, shoot water status and stress markers, and beneficial effects or no effects of Ni in PEG-treated C. heratensis. Conclusions: In the absence of Ni exposure, the species were approximately equally tolerant to PEG-simulated drought. Under PEG exposure, Ni positively affected the performance of C. heratensis, but had additive deleterious effects in C. foliolosa. C. heratensis does not only exhibit Ni hypertolerance, associated with a strongly decreased root-to-shoot translocation, but also an enhanced requirement for Ni, particularly when under PEG exposure, in comparison with C. foliolosa. [ABSTRACT FROM AUTHOR]

Background and Aims: We characterized the relationship between soil and leaf concentrations of selenium in a hyperaccumulator and a non-accumulator to test the hypothesis that hyperaccumulators take up selenium while non-accumulators exclude it. We examined plant performance metrics and the ability of selenium to protect against herbivory by spider mites. Methods: Known hyperaccumulator and non-accumulator species within the genus Astragalus were grown under a range of selenium concentrations and measured for tissue selenium, extent of herbivory, and vigor. Results: Both hyperaccumulators and non-accumulators either failed to meet even the lenient threshold or exceeded even the strict threshold for hyperaccumulation depending on soil concentration. Both had decreased herbivory with increasing leaf selenium, and both grew larger at higher levels of selenium regardless of herbivory, despite a negative impact of higher relative uptake. Conclusions: The relationships between selenium dosage and tissue concentrations matched only some model predictions. Under these conditions, the bioconcentration factor was a better delimiter between species than the absolute tissue concentration. We provide evidence that despite the apparent cost of uptake, selenium can enhance the growth of hyperaccumulators even when herbivory is not a significant factor. We propose the term 'elemental stimulation' for this phenomenon. [ABSTRACT FROM AUTHOR]

Background and Aims: In communities, plants often simultaneously interact with intra- and inter-specific neighbours and heterogeneous nutrients. How plants respond under these conditions and then affect the structure and function of communities remain important questions. Methods: Maize ( Zea mays L.) was intercropped with potatoes ( Solanum tuberosum L.). In the field experiment, we applied fertilizer both homogeneously and heterogeneously under monocropping and intercropping conditions. The heterogeneous nutrient treatment in intercropping was designed with different fertilizer placements, at intraspecific and interspecific rows, respectively. In the pot experiment, crops were grown under both homogeneous and heterogeneous nitrogen conditions with single plant, intraspecific and interspecific competition. Shoot and root biomass and yield were measured to analyse crop performance. Results: In the field experiment, the heterogeneous nitrogen, compared with the homogenous one, enhanced the performance of the intercropped crop. Importantly, this effect of heterogeneous nitrogen was greater when fertilizer was applied at interspecific rows, rather than at intraspecific rows. Moreover, in pot experiments, the root foraging precision of the two crops was increased by interspecific neighbours, but only that of potatoes was increased by intraspecific neighbours. Conclusions: The integrated responses of plants to heterogeneous neighbours and nutrients depend on the position of nutrient-rich patches, which deepen our understanding of the function of plant diversity, and show that fertilizer placement within multi-cropping systems merits more attention. Moreover, the enhanced utilization of heterogeneous nitrogen could drive overyielding in multi-cropping systems. [ABSTRACT FROM AUTHOR]

Aims: With a high growth rate and biomass production, bamboos are frequently used for industrial applications and recently have proven to be useful for wastewater treatment. Bamboos are considered as Si accumulators and there is increasing evidence that silicon may alleviate abiotic stresses such as metal toxicity. The aim of this study was to investigate the extent of metal concentrations and possible correlations with Si concentrations in plants. Methods: This study presents, for the first time, reference values for silicon (Si), copper (Cu) and zinc (Zn) concentrations in stems and leaves of various bamboo species grown under the natural pedo-climatic conditions of the island of Réunion (Indian Ocean). Results: A broad range of silicon concentrations, from 0 (inferior to detection limit) to 183 mg g dry matter (DM), were found in stems and leaves. Mean leaf Cu and Zn concentrations were low, i.e. 5.1 mg kg DM and 15.7 mg kg DM, respectively. Silicon, Cu and Zn concentrations increased over the following gradient: stem base < stem tip < leaves. Significant differences in Si, Cu and Zn contents (except Zn in the stem) were noted between bamboo species, particularly between monopodial and sympodial bamboo species, which differ in their rhizome morphology. Sympodial bamboos accumulated more Si and Cu than monopodial bamboos, in both stems and leaves, whereas sympodial bamboos accumulated less Zn in leaves than monopodial bamboos. Conclusions: The findings of this study suggest that a genotypic character may be responsible for Si, Cu and Zn accumulation in bamboo. [ABSTRACT FROM AUTHOR]

The latitudinal distribution of mangrove species is limited mainly by low temperature. Leaf scorch and massive leaf fall are the predominant symptoms of frost damage. Nutrient resorption during leaf senescence is an important adaptation mechanism of mangroves. Abnormal defoliation disturbs nutrient resorption. We evaluated the effects of frost on nutrient loss of mangroves and the protective effects of warmer seawater inundation on reducing nutrient loss. On January 14, 2009, the most cold-tolerant mangrove Kandelia obovata at its naturally latitudinal limit (Fuding, China, 27°17′N) was exposed to freezing temperature (−2.4°C) for 4 h (minimum −2.8°C). The freezing air temperature occurred during flood tide, resulting that the flooded shoots were protected by warmer seawater. Frost caused 31.3% and 13.0% defoliation on the exposed shoots and the flooded shoots, respectively. Frost restricted nutrient resorption during leaf senescence. K. obovata resorbed 61% N and 42% P during normal leaf senescence, respectively. However, frost-damaged leaves only resorbed 13% N and 10% P during the course, respectively. Foliar N:P molar ratios were <31, suggesting N limitation. Tidal inundation can partially protect mangroves from frost damage. Reduced nutrient resorption efficiency and massive leaf fall caused by frost add pressure to mangroves under nutrient limitation at their latitudinal limits. [ABSTRACT FROM AUTHOR]

In Mediterranean countries, forage grasses and legumes are commonly grown in mixture because of their ability to increase herbage yield and quality compared with monocrop systems. However, the benefits of intercropping over a monocrop system are not always realized because the efficiency of a grass-legume mixture is strongly affected by agronomic factors. The present study evaluated productivity, N fixation, N transfer, and N recovery of berseem clover ( Trifolium alexandrinum) grown in pure stand and in mixture with annual ryegrass ( Lolium multiflorum) under high or low defoliation frequencies and varying plant arrangements (sowing in the same row or in alternating rows). On average, the berseem-ryegrass mixtures resulted in a greater yield and N yield than the monocrops. When mixed together, ryegrass was more efficient than berseem at absorbing soil N, increasing the reliance of berseem on N fixation. Both defoliation management and plant arrangement affected forage yield and the quality of the mixture, modifying the proportion of the two components, the N content of the forage, and the symbiotic N fixation of the legume. Reducing the proximity between plants of the two species may benefit the weaker component of the mixture. No apparent transfer of fixed N from berseem to ryegrass was detected. [ABSTRACT FROM AUTHOR]

Throughout the savanna biome, woody vegetation is cleared to increase productivity of herbaceous pasture. While clearing can result in increased pasture production of semi-arid dystrophic savannas in the short term, it is uncertain whether production is sustained in the long term. There is insufficient knowledge of how clearing affects soil nutrient and organic carbon (SOC) stocks. Using cleared-uncleared site pairs, we evaluated techniques for time-integrated assessment of nutrient and carbon relations in Australian savanna. Short-term in situ resin incubation showed that soil at cleared sites had a higher time-integrated availability of ammonium and nitrate, indicating that nitrogen (N) may turn over faster and/or is taken up slower at cleared sites than uncleared savanna. Nitrate and ammonium availability was approximately 2-fold higher in spring than in summer, likely due to greater uptake and/or loss of nitrate during summer rains. Nitrate was a prominent N source for evergreen trees, especially before summer rain, pointing to a role of trees as permanent N sinks. Stable isotope signatures of soil and vegetation indicate that N input occurs via N2 fixing microbiotic crusts and Acacia species. 30 years after clearing, SOC contained more C4 grass-derived carbon than uncleared savanna, but this shift in C source was not associated with the net C gain often observed in grasslands. Interactions between altered nutrient and C relations and composition of the understorey should be assessed in context of introduced buffelgrass ( Cenchrus ciliaris) which had higher macronutrient concentrations than native grasses. Heterogeneity of the studied soils highlights the need for replication at several spatial scales to infer long-term dynamics with space-for-time chronosequences. We conclude that the techniques presented here are useful for gaining knowledge of the biogeochemical processes governing savannas and the systems that result from clearing. [ABSTRACT FROM AUTHOR]

In a previous paper [Bedoussac L, Justes E () Plant Soil, doi: ], we showed that intercropping of durum wheat and winter pea increased the yield and protein concentration of durum wheat when early N availability was less than 120 kg N ha−1. The aim of the present work was to understand these results by analysing intercrop species dynamics for growth, light and N acquisition. A 2-year field experiment was carried out in southwest France with different fertilizer-N levels in order to compare wheat ( Triticum turgidum L.) and pea ( Pisum sativum L.) grown as sole crops and as an intercrop in a row substitutive design. The advantages of intercropping in low N conditions were due mainly to: (1) better light use (up to 10%), thanks to species dynamic complementarity for leaf area index and height; (2) growth complementarity over time (higher growth rate of wheat until pea flowering and then of pea until wheat flowering); and (3) dynamic complementary N acquisition associated with better wheat N status throughout growth. Disadvantages, underlining poorer complementarity within the intercrop stand, were observed with ample available N in early growth. This induced higher cereal growth during winter, which led to increase interspecies competition by reducing pea light absorption and, consequently, its biomass production. [ABSTRACT FROM AUTHOR]

In intensive horticultural crops, the choice of growing media and the adequate management of irrigation must ensure an optimal trade-off between aeration and water supply to roots. The proportion of gas-filled pores and their composition can be strongly affected by the water status and hence by irrigation. In this context, continuous measurement of gas exchange and water status of the growing medium could bring out some insights into how irrigation events affect root activity and aeration in a time scale of minutes to several hours. For this purpose, a measuring system was developed that measured the CO2 efflux rate from the entire substrate root system of pot plants while their shoots were kept outside, undisturbed. It was able to monitor four plants at a time for several weeks at a rate of one measurement per plant every 10 min, thus tracing the dynamics of CO2 efflux through a great many irrigation cycles. The results showed a marked pattern of CO2 efflux around each irrigation event, consisting mainly of a sharp, conspicuous peak followed by a depression until a threshold in substrate water potential was reached. Analysis of these data suggests that the pattern is imposed mainly by the effects of irrigation and water content on the mobility of gases in the growing medium. The peak can be explained by the CO2-enriched air being displaced by the water added to the growing medium in the pot, and the following depression can be the result of the reduced mobility of gases when substrate water content is high. In spite of the great variation in the instantaneous efflux rate of CO2, the integration of these CO2 values for the entire day provides a rather predictable value given the root biomass and does not seem to be affected by the number of irrigation events that occur in a given day. [ABSTRACT FROM AUTHOR]

Pantropical species of the genera Phyllanthus and Euphorbia and the Cuban endemic genus Leucocroton from the Euphorbiaceae family, were selected for nickel localization microanalysis. Scanning Electron Microscopy coupled with Energy Dispersive X-ray Microanalysis (SEM-EDX) was used for qualitative detection of nickel in the selected Ni-hyperaccumulator species: Euphorbia helenae, Leucocroton linearifolius, L. flavicans Phyllanthus orbicularis, P. discolor and P. xpallidus, all collected from Cuban ultramafic soils. The leaves and stems from the Euphorbiaceae species analyzed were the organs with higher nickel accumulation. Elemental mapping of leaves and stem tissues from these species have been compared. The highest Ni concentrations were found in the laticifer tubes of stems and the epidermis tissues of leaves in all the analyzed species, suggesting a general pattern of the Euphorbiaceae family for nickel accumulation. The high nickel concentrations and its rather homogeneous distribution found in leaves of these Ni-hyperaccumulating plants suggest a possible role in protection mechanisms against environmental stress, such as UV irradiation. [ABSTRACT FROM AUTHOR]