Cheng Y ; Cai ZC ; Zhang JB ; Lang M ; Mary B ; Chang SX .Soil moisture effects on gross nitrification differ between adjacent grassland and forested soils in central Alberta Canada. Plant and Soil 2012 352: 289-301 (IF 2.773 农林科学，一区）

摘要

Background and aims Changes in soil moisture availability seasonally and as a result of climatic variability would influence soil nitrogen (N) cycling in different land use systems. This study aimed to understand mechanisms of soil moisture availability on gross N transformation rates.

Methods A laboratory incubation experiment was conducted to evaluate the effects of soil moisture content (65 vs. 100% water holding capacity WHC) on gross N transformation rates using the N-15 tracing technique (calculated by the numerical model FLUAZ) in adjacent grassland and forest soils in central Alberta Canada.

Results Gross N mineralization and gross NH4+ immobilization rates were not influenced by soil moisture content for both soils. Gross nitrification rates were greater at 100 than at 65% WHC only in the forest soil. Denitrification rates during the 9 days of incubation were 2.47 and 4.91 mg N kg(-1) soil d(-1) in the grassland and forest soils respectively at 100% WHC but were not different from zero at 65% WHC. In the forest soil both the ratio of gross nitrification to gross NH4+ immobilization rates (N-IA) and cumulative N2O emission were lower in the 65 than in the 100% WHC treatment while in the grassland soil the N-IA ratio was similar between the two soil moisture content treatments but cumulative N2O emission was lower at 65% WHC.

Conclusions The effect of soil moisture content on gross nitrification rates differ between forest and grassland soils and decreasing soil moisture content from 100 to 65% WHC reduced N2O emissions in both soils.

 Na ZouBaohai Li Gangqiang Dong Herbert J. Kronzucker and Weiming Shi. Ammonium-induced loss of root gravitropism is related to auxin distribution and TRH1 function and is uncoupled from the inhibition of root elongation in Arabidopsis. J. Exp. Bot. 2012 63 (10): 3777-3788.

Abstract

Root gravitropism is affected by many environmental stresses including salinity drought and nutrient deficiency. One significant environmental stress excess ammonium (NH₄ ⁺) is well documented to inhibit root elongation and lateral root formation yet little is known about its effects on the direction of root growth. We show here that inhibition of root elongation upon elevation of external NH₄ ⁺ is accompanied by a loss in root gravitropism (agravitropism) in Arabidopsis. Addition of potassium (K⁺) to the treatment medium partially rescued the inhibition of root elongation by high NH₄ ⁺ but did not improve gravitropic root curvature. Expression analysis of the auxin-responsive reporter gene DR5::GUS revealed that NH₄ ⁺ treatment delayed the development of gravity-induced auxin gradients across the root cap but extended their duration once initiated. Moreover the β-glucuronidase (GUS) signal intensity in root tip cells was significantly reduced under high NH₄ ⁺ treatment over time. The potassium carrier mutant trh1 displayed different patterns of root gravitropism and DR5::GUS signal intensity in root apex cells compared with the wild type in response to NH₄ ⁺. Together the results demonstrate that the effects of NH₄ ⁺ on root gravitropism are related to delayed lateral auxin redistribution and the TRH1 pathway and are largely independent of inhibitory effects on root elongation.

WEIFENG XU WEIMING SHI LIGUO JIA JIANSHENG LIANG JIANHUA ZHANG. TFT6 and TFT7 two different members of tomato 14-3-3 gene family play distinct roles in plant adaption to low phosphorus stress. Plant Cell and Environment 2012 35: 1393–1406.

Abstract

14-3-3 proteins are a large family of proteins but exact roles of their members in plant response to abiotic stresses are not clear especially under nutrient deficiency. We investigated the expressions of all the tomato 14-3-3 gene family members (TFT1–TFT12) under low phosphorus stress (LP) and found that TFT6 belongs to the later responsive gene while TFT7 belongs to the early responsive gene. When the two genes were separately introduced into Arabidopsis and overexpressed their plant growth under LP was much enhanced compared with wild-type plant. TFT6 overexpressing plants showed reduced starch synthase activity reduced starch content but enhanced sucrose loading into phloem in the shoot under LP. TFT7 overexpressing plants had much enhanced H⁺ flux along their root tip and activity of plasma membrane H⁺-ATPase in the roots under LP. Our results suggest that TFT6 and TFT7 play different roles in plant adaption to LP. TFT6 acts mainly in leaves and is involved in the systemic response to LP by regulating leaf carbon allocation and increasing phloem sucrose transport to promote root growth while TFT7 directly functions in root by activating root plasma membrane H⁺-ATPase to release more protons under LP.

Chunwu Zhu Lewis Ziska Jianguo Zhu Qing Zeng Zubing Xie Haoyan Tang Xiaodong Jia Toshihiro Hasegawa. The temporal and species dynamics of photosynthetic acclimation in flag leaves of rice (Oryza sativa) and wheat (Triticum aestivum) under elevated carbon dioxide. Physiologia Plantarum 2012 145: 395–405.

Abstract

In this study we tested for the temporal occurrence of photosynthetic acclimation to elevated [CO₂] in the flag leaf of two important cereal crops rice and wheat. In order to characterize the temporal onset of acclimation and the basis for any observed decline in photosynthetic rate we characterized net photosynthesis g_s g_m C_i-C_a C_i-C_c V_cmax J_max cell wall thickness content of Rubisco cytochrome (Cyt) f N chlorophyll and carbohydrate mRNA expression for rbcL and petA activity for Rubisco sucrose phosphate synthase (SPS) and sucrose synthase (SS) at full flag expansion mid-anthesis and the late grain-filling stage. No acclimation was observed for either crop at full flag leaf expansion. However at the mid-anthesis stage photosynthetic acclimation in rice was associated with RuBP carboxylation and regeneration limitations while wheat only had the carboxylation limitation. By grain maturation the decline of Rubisco content and activity had contributed to RuBP carboxylation limitation of photosynthesis in both crops at elevated [CO₂]; however the sharp decrease of Rubisco enzyme activity played a more important role in wheat. Although an increase in non-structural carbohydrates did occur during these later stages it was not consistently associated with changes in SPS and SS or photosynthetic acclimation. Rather over time elevated [CO₂] appeared to enhance the rate of N degradation and senescence so that by late-grain fill photosynthetic acclimation to elevated [CO₂] in the flag leaf of either species was complete. These data suggest that the basis for photosynthetic acclimation with elevated [CO₂] may be more closely associated with enhanced rates of senescence and as a consequence may be temporally dynamic with significant species variation.

  Wu YH ; Li TL ; Yang LZ . Mechanisms of removing pollutants from aqueous solutions by microorganisms and their aggregates: A review. Bioresource Technology 2012 107:10-18 (IF 4.365 工程技术，一区）

摘要 

With the public’s enhanced awareness of eco-safety environmentally benign measures based on microorganisms and microbial aggregates have become more accepted as methods of removing pollutants from aquatic systems. In this review the application of microorganisms and microbial aggregates for removing pollutants from aqueous solutions is introduced and described based on mechanisms such as assimilation adsorption and biodegradation. The advantages of and future studies regarding the use of microorganisms and microbial aggregates to remove pollutants are discussed. Due to the limitation of a single microorganism species in adapting to heterogeneous conditions this review demonstrates that the application of microbial aggregates consisting of multiple photoautotrophic and heterotrophic microorganisms is a promising method of removing multiple pollutants from complex wastewaters and warrants further research. (C) 2011 Elsevier Ltd. All rights reserved.

    2012年2月23日-25日，中科院战略性先导专项课题“中国农田土壤固碳潜力与速率研究”课题在南京召开2011年度工作总结暨经验交流会。应邀出席此次会议的专家和领导有赵其国院士，朱兆良院士，中科院资环局生态处业务主管杨萍，南京土壤研究所所长沈仁芳、副所长蒋新、科技处处长李忠佩等，项目首席科学家史学正研究员以及课题12个参加单位的100多名骨干成员参加了此次会议。会议由史学正研究员主持。

    首先，9个子课题负责人分别详细汇报了2011年度任务完成情况、2012年工作计划以及2012年预期阶段性成果。与会专家和领导对各子课题的报告进行了广泛讨论，提出了许多建设性意见。赵其国院士肯定了此课题野外工作的艰苦性和分析任务的艰巨性，并建议集中目标和建立典型示范样板，由点向面逐步开展工作。朱兆良院士指出由点拓展到区域再拓展到全国的方法是固碳潜力和速率估算的关键，沈仁芳所长强调了数据共享和样品保存的问题。蒋新副所长认为野外实地调查获得的大量样品和数据是难能可贵的，希望各子课题开展自主研究的同时，充分考虑本课题的整体性。项目首席史学正研究员在会议总结中充分肯定了各子课题2011年所取得的进展和成绩，并部署了2012年工作计划和时间节点。他说，4月中下旬将组织研讨会，专门讨论如何计算典型县土壤有机碳的变化速率、近30年来农田土壤有机碳变化的原因分析、典型县的结果如何拓展到全国、如何应用过程研究和模型研发结果等问题，希望各子课题负责人提前做好准备。

    业务主管杨萍代表中科院资环局在此次年度工作总结会议上作了发言。她说，在课题启动时担心子课题负责人是否有足够的时间投入该课题的研究工作中，但听完报告后，她认为过去的一年，各课题投入了大量的时间和精力，很好地完成了年度工作任务，同时充分肯定了课题的管理方法和任务布置的有效性。最后建议子课题之间能够多加强沟通和交流，子课题之间尽早实现数据共享，土壤所领导在土壤样品建库保存方面给予大力支持。希望各子课题在自主探索研究方面能够关注研究热点问题“地下生物碳”，本课题完成后所取得的成果能切实为农业管理提供帮助和支撑，在项目结束后能出版一本关于土壤学领域的新专著。

DENG Mei-Hua SHI Xiao-Jun TIAN Yu-Hua YIN Bin ZHANG Shao-Lin ZHU Zhao-Liang and S. D. KIMURA. Optimizing Nitrogen Fertilizer Application for Rice Production in the Taihu Lake Region China. Pedosphere 2012 22(1): 48–57.

Abstract

To determine the optimal amount of nitrogen (N) fertilizer for achieving a sustainable rice production at the Taihu Lake region of China two-year on-farm field experiments were performed at four sites using various N application rates. The results showed that 22%–30% of the applied N was recovered in crop and 7%–31% in soils at the rates of 100–350 kg N ha⁻¹. Nitrogen losses increased with N application rates from 44% of the applied fertilizer N at the rate of 100 kg N ha⁻¹ to 69% of the N applied at 350 kg N ha⁻¹. Ammonia volatilization and apparent denitrification were the main pathways of N losses. The N application rate of 300 kg N ha⁻¹ which is commonly used by local farmers in the study region was found to lead to a significant reduction in economic and environmental efficiency. Considering the cost for mitigating environmental pollution and the maximum net economic income an application rate of 100–150 kg N ha⁻¹ would be recommended. This recommended N application rate could greatly reduce N loss from 199 kg N ha⁻¹ occurring at the N application rate of 300 kg N ha⁻¹ to 80–110 kg N ha⁻¹ with the rice grain yield still reaching 7 300–8 300 kg DW ha⁻¹ in the meantime.