与单独供硝（NO₃^-）或者单独供铵（NH₄⁺）相比，混合供氮能够促进苗期玉米的生长。前期研究表明，混合供氮不仅可以提高玉米的光合效率，还可以促进地上部生长素的合成来增强叶片生长，进而为碳和氮的利用构建一个较大的库。然而，该过程是否依赖于氮的吸收还尚不清楚。在此，将玉米幼苗在具有三种供氮形态（单独供硝，75/25硝铵比和单独供铵）的水培实验中进行生长。结果表明，在0-3天，混合供氮下玉米生长速率和地上部含氮量与单独供硝处理间无显著差异，在6-9天，混合供氮下玉米生长速率和地上部含氮量显著高于单独供硝处理。于此同时，虽然混合供氮条件下15NO₃^-与15NH₄⁺的瞬时吸收速率较单独供硝和单独供铵相比皆有所下降，但混合供氮在6-9天具有最高的总氮吸收速率。QRT-PCR结果表明，长期混合供氮条件下根系N吸收的增加可能与长期处理下NO₃^-转运蛋白基因（例如ZmNRT1.1A， ZmNRT1.1B，ZmNRT1.1C， ZmNRT1.2和ZmNRT1.3）的高表达或铵转运蛋白基因（例如ZmAMT1.1A）的高表达有关，尤其是后者。此外，与单独供硝处理相比，混合供氮处理下植株地上部与根系中具有较高的谷氨酰胺合酶（GS）活性以及氨基酸含量。硝酸还原酶酶（NR）和GS酶抑制剂实验进一步证明了混合供氮情况下氮的同化能力对于玉米生长促进是至关重要的。该研究证明了混合供氮能够促进氮素吸收并进一步促进了氮的同化，而该过程可能是促进玉米上生长的主要驱动力。

本研究通过比较基因表达量和有机酸含量，发现了一个P_3A亚家族成员PbPH5基因的表达量与不同梨系统的苹果酸积累呈高度相关，且与白梨系统、西洋梨系统、砂梨系统和秋子梨系统中的相关性分别是0.932**，0.656*，0.900**和0.518*（*P<0.05或** P<0.01）。在梨果实中过表达PbPH5基因后苹果酸含量增加，沉默PbPH5基因后苹果酸含量降低；亚细胞定位结果显示PbPH5定位于液泡膜。此外，系统发育分析结果表明PbPH5基因是PH5的同源基因，与矮牵牛、苹果和柑橘PH5基因归于同一支。综上所述，这些结果表明PbPH5是一个较为保守的基因，而且，梨果实中苹果酸的积累至少部分与PbPH5基因表达量相关。

Leaf area index (LAI) is used for crop growth monitoring in agronomic research, and is promising to diagnose the nitrogen (N) status of crops.  This study was conducted to develop appropriate LAI-based N diagnostic models in irrigated lowland rice.  Four field experiments were carried out in Jiangsu Province of East China from 2009 to 2014.  Different N application rates and plant densities were used to generate contrasting conditions of N availability or population densities in rice.  LAI was determined by LI-3000, and estimated indirectly by LAI-2000 during vegetative growth period.  Group and individual plant characters (e.g., tiller number (TN) and plant height (H)) were investigated simultaneously.  Two N indicators of plant N accumulation (NA) and N nutrition index (NNI) were measured as well.  A calibration equation (LAI=1.7787LAI₂₀₀₀–0.8816, R²=0.870**) was developed for LAI-2000.  The linear regression analysis showed a significant relationship between NA and actual LAI (R²=0.863**).  For the NNI, the relative LAI (R2=0.808**) was a relatively unbiased variable in the regression than the LAI (R²=0.33**).  The results were used to formulate two LAI-based N diagnostic models for irrigated lowland rice (NA=29.778LAI–5.9397; NNI=0.7705RLAI+0.2764).  Finally, a simple LAI deterministic model was developed to estimate the actual LAI using the characters of TN and H (LAI=–0.3375(TH×H×0.01)²+3.665(TH×H×0.01)–1.8249, R²=0.875**).  With these models, the N status of rice can be diagnosed conveniently in the field.

    The effect of hot air (HA, 45°C, 3.5 h) treatment on reducing gray mold caused by Botrytis cinerea in strawberry fruit and the possible mechanisms were investigated. The results showed that HA treatment significantly reduced lesion diameter and enhanced activities of chitinase (CHI), β-1,3-glucanase and phenylalanine ammonia-lyase (PAL) in strawberry fruit. Total phenolic contents were also increased by HA treatment. The activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) were higher in HA treated strawberry fruit than those in control. Expression of three defense related genes such as CAT, CCR-1 allele and PLA6 was greatly induced in HA treated strawberry fruit with or without inoculation by B. cinerea. In addition, the in vitro experiment showed that HA treatment inhibited spore germination and tube growth of B. cinerea. These results suggested that HA treatment directly activated disease resistance against B. cinerea in strawberry fruit without priming response and directly inhibiting growth of B. cinerea.

Different nitrogen (N) forms may cause changes in the metabolic profiles of plants. However, few studies have been conducted on the effects of amino acid-N on plant metabolic profiles. The main objective of this study was to identify primary metabolites associated with amino acid-N (Gly, Gln and Ala) through metabolic profile analysis using gas chromatography- mass spectrometry (GC-MS). Plants of pakchoi (Brassica campestris L. ssp. chinensis L.), Huawang and Wuyueman cultivars, were grown with different nitrogen forms (i.e., Gly, Gln, Ala, NO3 --N, and N starvation) applied under sterile hydroponic conditions. The fresh weight and plant N accumulation of Huawang were greater than those of Wuyueman, which indicates that the former exhibited better N-use efficiency than the latter. The physiological performances of the applied N forms were generally in the order of NO3 --N>Gln>Gly>Ala. The metabolic analysis of leaf polar extracts revealed 30 amino acid N-responsive metabolites in the two pakchoi cultivars, mainly consisting of sugars, amino acids, and organic acids. Changes in the carbon metabolism of pakchoi leaves under amino acid treatments occurred via the accumulation of fructose, glucose, xylose, and arabinose. Disruption of amino acid metabolism resulted in accumulation of endogenous Gly in Gly treatment, Pro in Ala treatment, and Asn in three amino acid (Gly, Gln and Ala) treatments. By contrast, the levels of endogenous Gln and Leu decreased. However, this reduction varied among cultivars and amino acid types. Amino acid-N supply also affected the citric acid cycle, namely, the second stage of respiration, where leaves in Gly, Gln and Ala treatments contained low levels of malic, citric and succinic acids compared with leaves in NO3 --N treatments. No significant difference in the metabolic responses was observed between the two cultivars which differed in their capability to use N. The response of primary metabolites in pakchoi leaves to amino acid-N supply may serve an important function in pakchoi adaptation to amino acid-N sources.

The purpose of the present study was to survey contents of trace elements of Cu, Mn, Fe, and Zn in the surface layer (0-20 cm) in the soil, pasture and serum of sheep in Huangcheng area of Qilian mountain grassland, China. Also the soil-plant- animal continuum was analyzed. Soil (n=300), pasture (n=60), and blood serum samples from sheep (n=480) were collected from Huangcheng area of Qilian mountain grassland, China. The contents of trace element in the samples were analyzed by atomic absorption spectrophotometer after digestion. The soil trace elements density distribution shows a ladder-like pattern distribution. Equations developed in the present study for prediction of Fe (R2=0.943) and Zn (R2=0.882) had significant R2 values.

Plants need to be efficient in nutrient management, especially when they face the temporal nutrient defficiencies. Understanding how crops respond to nitrogen (N) starvation would help in the selection of crop cultivars more tolerant to N deficiency. In the present work, the physiological responses of two wheat cultivars, Yannong 19 (YN) and Qinmai 11 (QM), to N starvation conditions were investigated. The two cultivars differed in biomass and N rearrangement between shoots and roots during N starvation. QM allocated more N to roots and exhibited higher root/shoot biomass ratio than YN. However, tissue measurement indicated that both cultivars had similar nitrate content in leaves and roots and similar remobilization rate in roots. Microelectrode measurement showed that vacuolar nitrate activity (concentration) in roots of QM was lower than that in roots of YN, especially in epidermal cells. Nitrate remobilization rates from root vacuoles of two cultivars were also identical. Moreover, vacuolar nitrate remobilization rate was proportional to vacuolar nitrate activity. During N starvation, nitrate reductase activity (NRA) was decreased but there were no significant differences between the two cultivars. Nitrate efflux from roots reduced after external N removal and QM seemed to have higher nitrate efflux rate.