不同水、氮条件对水稻苗生长及伤流液的影响

为探明不同水分供应和氮素形态对水稻根苗及伤流液的影响,设正常水分及50 g/L PEG模拟水分胁迫和3种不同质量比例的NH4+-N/NO3--N（9/1,5/5,1/9）氮素营养处理,测定了水稻幼苗生物量,根系形态指标,根系活力及根基伤流量。结果表明,正常水分条件下,NH4+-N促进水稻根系平均直径增大,有利于水稻地上部物质累积;NO3--N则使水稻根系总吸收面积增大,促进根系物质累积;NH4+-N/NO3--N为5/5处理的水稻活跃吸收面积最大,活跃吸收面积比亦最高。水分胁迫条件下,NH4+-N/NO3--N为5/5的处理更有利于水稻地上部分的生长,NO3--N有利于水稻鲜重和干重增加,促进根系平均直径增大,水稻的根系总吸收面积、活跃吸收面积均随NO3--N供应比例的增加呈上升趋势。正常水分条件下,水稻幼苗白天的耗水量随NH4+-N/ NO3--N比例降低呈下降趋势,水分胁迫条件降低了水稻对水分的吸收。水分胁迫显著降低各处理水稻伤流量,正常水分条件下,NH4+-N/NO3--N为5/5处理的水稻伤流量最大;水分胁迫后,9/1处理的水稻伤流量相对较多。     

Role of nitrogen supplementation in alleviating drought‐associated growth and metabolic impairments in Phoebe zhennan seedlings

Drought is one of the major environmental stresses altering forest productivity. However, nutrient availability can modulate drought resistance. Phoebe zhennan (gold Phoebe) is a high‐quality timber‐producing but threatened tree species in China, facing serious anthropogenic disturbances and abiotic constraints that restrict its growth and development. However, little attention has been given to designing adaptive strategies for its management by evaluating the possible role of major nutrients, particularly nitrogen (N), on its morphological and physio‐biochemical responses under water stress. To evaluate these responses, a complete randomized design was followed to investigate the effects of two irrigation levels (well‐watered and drought‐stressed conditions) and N fertilization treatments (with and without N). Drought stress significantly affected the growth of seedlings, as indicated by impaired photosynthesis, pigment degradation, disrupted N metabolism, over‐production of reactive oxygen species and enhanced lipid peroxidation. Nitrogen supplementation under drought stress had remarkable positive effects on the growth through physio‐biochemical adjustments as shown by higher level of nitrogenous compounds and up‐regulation of N‐associated metabolic enzymes activities which might be due to N‐mediated improved leaf relative water contents and photosynthetic efficiency. In addition, N application reduced oxidative stress and membrane damage, and maintained a high accumulation of osmolytes. However, in well‐watered seedlings N fertilization significantly improved root biomass and net CO₂ assimilation rate suggesting high N‐use efficiency of the seedlings. These findings reveal that drought significantly affects the growth of P. zhennan, while N fertilization plays a crucial role in alleviating water stress damage by improving its drought tolerance potential at low metabolic costs. Therefore, N fertilization could be considered as an effective strategy for the conservation and management of P. zhennan in the face of future climate change.     

改性磁性荔枝皮对水及果汁中砷的吸附效果及动力学分析

为探索安全高效实用的果汁类食品砷吸附材料,以天然植物副产物荔枝皮为材料,通过共沉法制备砷吸附材料磁性荔枝皮(magnetic litchi peel,MLP),采用电感耦合等离子体质谱法测定砷含量,以砷清除率为判断指标,研究了MLP对三价砷和五价砷吸附效果及机理。结果表明:改性MLP表面含有粉末状的Fe3O4,与未改性荔枝皮相比部分官能团增加,表面粗糙、更加凹凸不平,结构疏松,微孔数量增加,有利于吸附作用的进行,在砷浓度为0.20 mg/L水溶液中三价砷和五价砷吸附率为88%和90%,对苹果汁中的三价砷和五价砷吸附率为83%和93%;MLP对三价砷和五价砷溶液吸附等温线符合Langmuir等温线模型,拟合决定系数R2均大于0.99,为单分子层吸附,在298 K条件下饱和吸附量三价砷为0.181 mg/g,五价砷为0.225 mg/g;MLP对砷溶液吸附动力学可以通过准二级吸附动力学模型描述,R2均高于0.99;MLP对三价砷和五价砷的吸附过程中吉布斯自由能小于0,吸附反应是自发进行的,焓变小于0,MLP对两种价态砷的吸附都是放热反应。研究结果可为改性荔枝皮在果汁类食品中砷脱除方法和工艺的应用提供理论与数据参考。     

坡向与植物群落对水蚀风蚀交错带土壤有机碳氮的影响

以黄土高原北部水蚀风蚀交错带六道沟流域内的1个支沟为对象,通过植被调查和采样分析,研究了坡向和植物群落类型对土壤有机碳(SOC)、全氮(TN)含量、碳氮比(C/N)和有机碳氮密度(SOCD、TND)的影响。结果表明:(1)坡向对0—20cm土壤SOC和TN含量及0—60cm C/N均有显著影响。SOC、TN含量及C/N分别表现为:半阴坡半阳坡沟头半阴坡半阳坡=沟头及半阳坡半阴坡≥沟头的趋势;(2)植物群落对0—10cm SOC和TN含量及0—20cm C/N均有显著影响。半阴坡分布的3种豆科群落达乌里胡枝子、紫花苜蓿及白花草木樨间土壤碳氮差异不显著,但均显著高于禾本科的长芒草群落;半阳坡分布的达乌里胡枝子和紫花苜蓿群落SOC和TN含量相当,均显著高于茵陈蒿群落(菊科)和长芒草群落;沟头的达乌里胡枝子群落SOC、TN显著高于长芒草。豆科草本植物更有利于促进土壤碳氮的积累;(3)坡向主要影响表层0—20cm SOCD和TND,其对60cm剖面SOCD和TND贡献率分别为45%～55%和47%～53%。不同植物群落下土壤表层及整个剖面SOCD和TND均有显著差异。研究支沟内SOCD平均为2.13kg/m2,远低于黄土高原其他地区。上述结果对于水蚀风蚀交错带土壤碳氮储量的精确评估及植被合理建造有一定指导价值。     

外源氮输入对黄河口碱蓬湿地土壤碳氮含量动态的影响

2014年4—11月,选择黄河入海口北部滨岸高潮滩的碱蓬湿地为研究对象,基于野外原位氮输入模拟试验,研究了不同氮输入梯度下(N0,无氮输入;N1,低氮输入;N2,中氮输入;N3,高氮输入)湿地土壤碳氮含量动态特征及其差异。结果表明,不同氮输入处理下土壤的SOC、TN、NH_4~+—N和NO_3~-—N含量整体上均随着土层深度的增加而逐渐降低,各土层的SOC和NO_3~-—N含量在N2处理最高,而TN和NH_4~+—N含量在N3处理最高。尽管不同氮输入处理并未改变湿地土壤中TN和NH_4~+—N含量的动态变化模式,但随氮负荷增强二者含量均呈增加趋势。不同的氮输入处理明显改变了土壤中SOC和NO_3~-—N的动态变化模式,适量氮输入(N1和N2)明显提高了土壤中的NO_3~-—N含量,过量氮输入(N3)则不利于NO_3~-—N的累积;不同氮输入处理下(特别是N2和N3处理)湿地表层土壤(0—20cm)的SOC含量在7月中旬后远大于N0处理(P0.05),说明持续的氮输入可能不利于表层土壤中SOC的转化。研究发现,当未来黄河口湿地氮养分达到N1和N2水平时将有利于土壤氮矿化,而这将使得土壤氮养分的供给更为充足;但氮负荷持续增强可能使土壤表层的SOC转化受到抑制,而这将有助于提升土壤的储碳功能。     

秸秆覆盖方式和施氮量对河套灌区夏玉米氮利用及产量影响

为探究夏玉米氮素转运利用规律、产量及土壤NO₃^--N含量分布对秸秆覆盖方式和施氮量的响应,在河套灌区开展2 a不同秸秆覆盖方式(秸秆表覆B处理、秸秆深埋S处理)和不同施氮水平(不施氮N0、低氮N1、中氮N2、高氮N3)的田间试验,以传统耕作模式为对照(CK处理)。结果表明:在0～100 cm土层,各处理NO₃^--N含量随施氮量增加而增大,成熟期B和CK处理随土层加深呈先减后增趋势,而S处理呈先增后减趋势;B处理提高0～20cm土层NO₃^--N含量,而S处理提高20～40 cm土层NO₃^--N含量(P<0.05);秸秆覆盖可减少0～100 cm土层NO3--N累积损失量,且显著提高氮肥利用率及夏玉米氮素转运量对籽粒产量的贡献率,SN2处理效果较佳。相比CK处理,成熟期的SN2处理2a平均NO₃^--N累积损失量降低39.6%,氮肥利用率较提高28.5%,夏玉米氮素转运...     

氮肥利用率的问题与改进

传统差减法计算氮肥利用率变异较大,影响了氮肥利用率的应用,科学的氮肥利用率计算方法对氮肥的合理施用十分重要。本文概述了氮肥利用率50多年的研究过程,并划分为3个创新研究阶段,提出差减法计算氮肥利用率各个创新研究阶段的主要创新点。采用常规计算方法和定位试验研究资料计算了氮肥利用率,阐明常规计算方法计算的氮肥利用率结果存在的问题;归纳了氮肥利用率变异较大的主要原因:1)采用土壤氮素养分系统没有达到平衡或接近平衡的试验结果;2)常规计算方法仅考虑氮肥用量和作物吸收氮量,没有考虑土壤残留氮(或消耗土壤氮)。建立了2个氮肥利用率计算的新方法:1)土壤氮素养分系统平衡状态计算公式:氮肥利用率=(施肥作物吸收氮-报酬递减系数×对照作物吸收氮)/施肥氮;2)土壤氮素养分未达到平衡状态计算公式:氮肥利用率=(施肥作物吸收氮-报酬递减系数×对照作物吸收氮)/(施肥氮+施肥处理土壤氮素消耗量-对照处理土壤氮素消耗量)。     

大孔树脂对紫甘薯色素的吸附与解吸特性研究

为了选择紫甘薯色素粗提液纯化性能较好的树脂,采用AB-8型、S-8型、NKA-II型和NKA-9型4种大孔树脂对紫甘薯色素进行了吸附与解吸试验,研究了大孔树脂对紫甘薯色素的静态吸附动力学曲线、吸附等温曲线及解吸特性。结果表明：在4种树脂中,AB-8型树脂吸附平衡的速率常数为最大,对紫甘薯色素的吸附量和解吸量分别是S-8、NKA-II及NKA-9的119%,139%,118%和105%,116%,118%,因而AB-8型大孔树脂是用于纯化紫甘薯色素较为合适的吸附剂,解吸时宜选用60%乙醇溶液。     

Nutrient limitation of alpine plants: Implications from leaf N : P stoichiometry and leaf δ15N

Nitrogen (N) deposition can affect grassland ecosystems by altering biomass production, plant species composition and abundance. Therefore, a better understanding of the response of dominant plant species to N input is a prerequisite for accurate prediction of future changes and interactions within plant communities. We evaluated the response of seven dominant plant species on the Tibetan Plateau to N input at two levels: individual species and plant functional group. This was achieved by assessing leaf N : P stoichiometry, leaf δ¹⁵N and biomass production for the plant functional groups. Seven dominant plant species—three legumes, two forbs, one grass, one sedge—were analyzed for N, P, and δ¹⁵N 2 years after fertilization with one of the three N forms: NO$ _3^- $ , NH$ _4^+ $ , or NH₄NO₃ at four application rates (0, 7.5, 30, and 150 kg N ha^–1 y^–1). On the basis of biomass production and leaf N : P ratios, we concluded that grasses were limited by available N or co‐limited by available P. Unlike for grasses, leaf N : P and biomass production were not suitable indicators of N limitation for legumes and forbs in alpine meadows. The poor performance of legumes under high N fertilization was mainly due to strong competition with grasses. The total above‐ground biomass was not increased by N fertilization. However, species composition shifted to more productive grasses. A significant negative correlation between leaf N : P and leaf δ¹⁵N indicated that the two forbs Gentiana straminea and Saussurea superba switched from N deficiency to P limitation (e.g., N excess) due to N fertilization. These findings imply that alpine meadows will be more dominated by grasses under increased atmospheric N deposition.