The removal of nitrate reductase phosphorylation enhances tolerance to ammonium nitrogen deficiency in rice

Nitrate reductase(NR) is a key enzyme for nitrogen assimilation in plants, and its activity is regulated by posttranslational phosphorylation. To investigate the effects of dephosphorylation of the NIA1 protein on the growth and the physiological and biochemical characteristics of rice under different forms of nitrogen supplies, the phenotypes, nitrogen metabolism and reactive oxygen metabolism were measured in NIA1 phosphorylation site-directed mutant lines(S532 D and S532 A), an Os Nia1 over-e...     

喷施不同纳米材料对水稻幼苗磷含量的影响

为探究喷施不同纳米材料对水稻幼苗生物量和磷含量的影响,将水稻幼苗培养在不同含磷浓度营养液中,对水稻幼苗叶片喷施不同浓度的不同纳米材料,即粒径40 nm的羟基磷灰石(nHA)、三氧化二铁(nFe2O3)、零价铁(nFe)、二氧化铈(nCeO2)和甲壳素[CH,(C8H13NO5)n]悬浊液,测定水稻地上部和根部含磷量。结果表明:在正常供磷条件下,喷施nHA、nFe2O3、nFe处理,浓度分别在200、100 mg·L^-1和150 mg·L^-1时,地上部生物量达到最大,根部生物量则在150、100 mg·L^-1和100 mg·L^-1处理时达到最高;但大部分处理不会显著提高水稻幼苗磷含量。在供磷1/2条件下,各处理均可不同程度促进水稻幼苗对磷的吸收;喷施nHA、nFe2O3、nFe、nCeO2和CH处理,分别在50、100、100、100 mg·L^-1和150 mg·L^-1的浓度处理时生物量达到最大;nHA、nFe2O3、nFe处理均可显著促进地上部磷含量,地上部磷含量分别在150、100 mg·L^-1和150 mg·L^-1处理时达到最高。研究表明:在不同浓度磷供应条件下,喷施粒径40 nm的nHA、nFe2O3、nFe、nCeO2和CH均可不同程度促进水稻幼苗生长。不缺磷条件下,nHA、nFe处理促进生物量增加明显;缺磷条件下,nHA、nFe2O3、nFe促进磷吸收效果更明显。     

广西喀斯特地区土壤多金属胁迫对水稻重金属积累及生理特性的影响

为了解喀斯特地区农田土壤中重金属复合污染对水稻生长的影响,通过盆栽试验,研究了不同重金属污染程度下,多金属胁迫对水稻植株的株高、生物量、生理指标[超氧化物歧化酶(SOD)、过氧化物酶(POD)活性和叶绿素(Chl)、丙二醛(MDA)含量]的影响及水稻对重金属的积累特征。结果表明,土壤综合污染负荷指数PLI(Pollution load index)与水稻株高、生物量呈显著负相关(P0.05),当PLI为5.96时,水稻植株在苗期逐渐枯黄并死亡。与无污染对照(CK)相比较,重金属污染程度Ⅰ~Ⅴ处理的水稻株高分别降低了32.79%、30.99%、69.14%、63.40%和73.55%,地上生物量分别减少42.89%、37.77%、93.44%、79.98%和85.88%,且差异显著(P0.05)。随PLI增加,水稻对重金属积累增加,水稻植株地下部分重金属含量大于地上部分,且重金属积累量ZnCdPbHgAs,水稻对重金属生物累积系数BCF表现为CdHgZnAsPb。PLI与叶片POD活性呈显著正相关,与SOD活性及MDA含量呈正相关,与Chl含量呈负相关。其中PLI为4.36时,水稻幼苗叶片中SOD活性达最大值235.02 U·g~(-1)FW,PLI为5.96时,水稻幼苗叶片中POD活性和MAD含量达到最大,分别为155.54 U·g~(-1)FW和41.48 nmol·g~(-1)FW。多金属胁迫下,水稻能够通过抗氧化酶系统减少植株受到的损害,但当污染负荷指数过大、影响水稻生长的时候,水稻就会死亡。     

铝胁迫对葡萄苗铝吸收分配及抗氧化系统的影响

为了探明葡萄苗在不同浓度铝胁迫下树体的铝积累特征和生理响应,研究以‘水晶’葡萄为试材,在无土栽培条件下,用1.0~8.0 mmol·L~(-1) KAl(SO4)2处理60 d后测定树体铝含量及相关生理指标。结果表明,过量的铝在葡萄苗中的分配为细根粗根老叶树皮嫩叶木质部新枝,2.0 mmol·L~(-1)铝处理后植株生长旺盛,生物量最大,单株铝积累总量最高,5.0 mmol·L~(-1)铝处理后植株生长较弱,生物量较小,单株铝含量最低;铝浓度超过3.0 mmol·L~(-1)时显著降低葡萄苗叶绿素a、叶绿素b、叶绿素a+b的含量,铝浓度超过4.0 mmol·L~(-1)显著降低葡萄苗类胡萝卜素含量;随着铝浓度的增大,葡萄叶片和根系的脯氨酸含量逐渐升高且显著高于CK;铝浓度达到3.0mmol·L~(-1)时,各处理叶片和根系的丙二醛含量均显著高于CK;铝处理提高了葡萄叶片和根系中的氧自由基产生速率和过氧化氢含量;铝胁迫下,葡萄苗叶片和根系的POD活性高于CK;铝浓度低于4.0 mmol·L~(-1)时,SOD活性高于CK,而浓度达到4.0 mmol·L~(-1)时则显著低于CK。可见,低于3.0 mmol·L~(-1)铝对葡萄苗的伤害较小,甚至还能促进其生长,但超过3.0 mmol·L~(-1)铝将对葡萄苗造成不同程度的伤害。     

水稻黄嘌呤脱氢酶基因OsXDH克隆及表达分析

[目的]克隆水稻黄嘌呤脱氢酶(Xanthine dehydrogenase,XDH)基因(OsXDH),分析其生物信息学特性及表达特性,为研究XDH在水稻生长发育和响应逆境胁迫中的调控机制提供理论依据.[方法]以粳稻品种日本晴为材料,采用同源克隆技术克隆OsXDH基因,应用生物信息学方法对其氨基酸序列进行分析.利用实时荧光定量PCR (qPCR)检测OsXDH基因的组织表达特性及逆境胁迫下的表达情况,并对不同转基因株系乳熟期剑叶OsXDH基因表达量、XDH活性和叶绿素含量进行比较分析.[结果]克隆获得OsXDH基因的开放阅读框序列(ORF)(GenBank登录号LOC4333171),其长度为4110 bp,编码1369个氨基酸.OsXDH蛋白分子量大小为150.23 kD,理论等电点(pI)为6.54,与小麦、高粱、玉米、谷子和油菜等作物XDH蛋白氨基酸序列的相似性分别为84.54%、84.07%、81.52%、76.35%和69.22%,表明XDH蛋白氨基酸序列具有高度保守性.OsXDH基因在水稻不同组织部位均有表达,灌浆期的表达量显著高于苗期和分蘖盛期(P<0.05),且受干旱、黑暗、高温和盐胁迫诱导高效表达.OsXDH过表达水稻转基因株系乳熟期剑叶的XDH活性和叶绿素含量高于野生型,OsXDH干扰转基因株系的XDH活性和叶绿素含量低于野生型.[结论]OsXDH基因受水稻生长发育和逆境胁迫因子诱导表达,推测其是调控水稻生长发育和响应逆境胁迫的关键基因.     

Overexpression of a Cytosolic Ascorbate Peroxidase Gene,OsAPX2, Increases Salt Tolerance in Transgenic Alfalfa

Alfalfa (Medicago sativa L.) is an important forage crop in the world and it is of great significance for the improvement of its salt tolerance. To improve salt tolerance in alfalfa, a rice ascorbate peroxidase gene (OsAPX2) was introduced into alfalfa using Agrobacterium tumefaciens-mediated transformation with marker gene bar. The different T-DNA insertions in T₁ transgenic alfalfa were identified by Southern hybridization. Three independent T₂ transgenic lines were selected for stress analysis and the results showed that all of them were salt tolerant compared with wild-type plants. The transgenic plants had low levels of H₂O₂, malondialdehyde and relative electrical conductivity under salt and drought stresses. Moreover, the contents of chlorophyll and proline, and APX activity were high in transgenic plants under salt and drought stresses. Taken together, the overexpression of OsAPX2 enhances salt tolerance in alfalfa through scavenging reactive oxygen species.     

海桐(Pittosporum tobira)对污染土壤中镉的耐受和吸收特征

通过盆栽实验研究了海桐对土壤中镉(Cd)的耐受和吸收特征。动态取样研究结果表明,当土壤中Cd含量为9.6 mg·kg-1时可对海桐生长产生促进作用,当Cd含量为24.6 mg·kg-1时对海桐产生抑制作用;海桐对污染土壤中Cd有一定吸收能力,吸收量随土壤中Cd含量增加而增加。培养154 d后,与对照处理(土壤Cd含量为3.6 mg·kg-1)相比,当土壤中Cd含量为9.6 mg·kg-1时,海桐根、茎、叶干重,叶片中叶绿素a、叶绿素b和类胡萝卜素含量及丙二醛含量没有明显变化;当Cd含量达到24.6 mg·kg-1时,海桐根、茎、叶干重分别降低了38.7%、5.2%和52.5%,叶片中叶绿素a、叶绿素b及类胡萝卜素含量分别是对照处理的71.3%、68.2%和75%,丙二醛含量为对照处理的1.52倍。研究表明,海桐可作为Cd污染土壤修复的备选植物,在修复土壤的同时改善环境景观。     

大气臭氧胁迫对稻季土壤Cd生物有效性的影响

为明确大气O_3浓度升高对稻季土壤Cd生物有效性的影响,利用开顶式气室(OTCs)设置正常大气和臭氧浓度升高(比周围大气高40 nmol·mol-1)处理,土壤设置外源加入0、5、50 mg·kg~(-1)Cd处理,研究水稻生长期间不同深度土壤Cd含量的动态变化以及成熟期植株生物量和体内Cd含量的变化情况。在水稻分蘖期、拔节期、抽穗期和成熟期分别采集耕层0~5、5~10、10~15 cm深度土样,同时利用BCR连续提取法和DTPA提取法评价盆栽水稻土壤Cd生物有效性。结果表明,臭氧熏蒸显著降低了无污染土壤处理水稻籽粒生物量,降幅达2.92%,但却有增加植株各器官Cd含量的趋势,中度和重度污染土壤处理水稻的籽粒Cd含量较对照分别增加了20.20%和6.67%,差异不显著;臭氧熏蒸加剧了水稻生长对残渣态Cd的活化,营养生长时期更加明显,臭氧熏蒸不利于水稻的生长,在Cd污染土壤上会加剧Cd对作物的毒害,可能增加其通过生物富集进入食物链的风险。     

硼调控干旱胁迫下马铃薯生长发育及抗性的生理机制

为了探讨叶面喷施硼（Na₂B₄O₇·10H₂O溶液）对马铃薯植株在干旱胁迫下生长发育及抗性的影响及其生理机制,在甘肃省景泰县条山集团马铃薯种植基地,对中度干旱和轻度干旱处理的两垄地,每隔3 m进行一个硼浓度（Na₂B₄O₇·10H₂O）喷施处理,浓度依次为0、10、20、30、40、60 g·L^-1,每个浓度（3 m长）的喷施量为166.7 ml。结果表明：叶面喷施硼相对增加了干旱胁迫下马铃薯的块茎产量及生物量,使干旱胁迫下叶片含水量和色素含量下降幅度减小;叶面喷施硼还从整体上表现为抗氧化酶活性的提高,并抑制了超氧阴离子产生速率的增加。通过去花与不去花植株生长发育的比较,发现去花后马铃薯植株地上部分重和地下部分重均有所下降,但施硼相对提高了块茎产量及地下部分重。可见,叶面喷施硼能促进马铃薯植株在干旱胁迫下的生长发育,提高其抗旱性及块茎产量,且这种变化可能与其促进光合产物向地下部分输送密切相关。     

Physiological and Biochemical Changes of IrlVHA-c gene Transgenic Tobacco Seedlings and Self-crossed Progeny Under NaHCO3 Stress

In order to study the alkali resistivity of VHA-c in Iris lacteal. (IrlVHA-c), the transgenic tobacco seedlings harboring IrlVHA-c gene from Iris lactea (T0), the self-crossed progeny (T1), and the non-transgenic lines of tobacco seedlings were grown in Hoagland nutrient solutions supplemented with 0, 100, 200, 300, 400 mmol·L-1 NaHCO3 . The MDA content, CAT, POD and SOD activity, electrical conductivity, chlorophyll content, soluble sugar content, proline content and polyphenol oxidase activity of the seedlings were determined. The results showed that the transgenic lines of tobacco maintained a high activity up to 200 mmol·L-1 NaHCO3 , and activity was slightly lower at 300 mmol·L-1 NaHCO3 . When the concentration of NaHCO3 was as high as 400 mmol·L-1 the seedlings were badly hurt. In addition, the activity of T0 and T1 transgentic tobacoo was maintained more or less. While the non-transgenic lines of tobacco could maintain viably up to 100 mmol·L-1 NaHCO3 , and they could not survive at 400 mmol·L-1 NaHCO3 . The conclusion was drawn that the alkali resistance of the tobacoo transformed IrlVHA-c was noticeably improved.     

卡马西平对小球藻生长的影响和氧化损伤

为了考察药品及个人护理品(Pharmaceuticals and Personal Care Products,PPCPs)对水生生物及生态环境的影响,以典型的PPCPs化合物卡马西平(Carbamazepine,CBZ)为目标化合物,研究其对普通小球藻(Chlorella)的生长、叶绿素含量、超氧化物歧化酶(Superoxide Dismutase,SOD)活性、过氧化氢酶(Catalase,CAT)活性和丙二醛(Malondialdehyde,MDA)含量的影响。结果表明,CBZ对小球藻的96 h半最大效应浓度(EC_(50))为154.42 mg·L~(-1),对小球藻具有一定的毒性作用,能抑制小球藻的生长。CBZ影响小球藻的叶绿素含量,低浓度(0.1 mg·L~(-1))的CBZ对小球藻的叶绿素a和b的含量有抑制作用,使其分别降低到2.16 mg·L~(-1)和0.38 mg·L~(-1),随着CBZ浓度的升高,抑制作用逐渐减弱;小球藻SOD的活性随CBZ浓度的升高表现出先激活后抑制的状态,CAT活性表现出中低浓度激活的状态;CBZ对MDA含量的影响较弱,处理组含量在2.06~2.32 nmol·g~(-1)范围之间,略高于对照组。由冗余分析(RDA)可知,CBZ对小球藻CAT、SOD活性和叶绿素a含量的影响更显著。     

The role of rhizobacteria in rice plants: Growth and mitigation of toxicity

Allelopathic compounds reduce the growth and productivity of upland rice plants, especially in consecutive plantations. The rhizobacteria Pseudomonas fluorescens BRM-32111 and Burkholderia pyrrocinia BRM-32113 have been recorded as growth promoters in rice. This study was developed to understand the effect of the application of rhizobacteria on upland rice plants in consecutive plantations. Experiments were conducted in a completely randomized design with four replications of four treatments: rice seed inoculated with P. fluorescens BRM-32111, rice seed inoculated with B. pyrrocinia BRM-32113 (both sown on soil with rice residue), non-inoculated plants sown on soil with rice residue (control with residue (WR)), and non-inoculated plants on soil with no residue (NR). Roots and seedling growth were adversely affected by allelopathic compounds in control WR plants. Plants inoculated with rhizobacteria P. fluorescens BRM-32111 or B. pyrrocinia BRM-32113 induced an increase of 88% in biomass, 3% in the leaf area, 40% in length, 67% in root biomass, 21% in chlorophyll a, 53% in chlorophyll (a+b), 50% in rate of carbon assimilation (A), 227% in A/rubisco carboxylation efficiency (C_i) and 63% in water use efficiency (WUE) compared to control WR plants. These results indicate that rhizobacteria P. fluorescens BRM-32111 and B. pyrrocinia BRM-32113 increase the tolerance of rice plants to stress from allelochemicals. There are possible practical agricultural applications of these results for mitigating the effects of environmental allelochemistry on upland rice.     

Effects of potassium deficiency on photosynthesis,chloroplast ultrastructure,ROS, and antioxidant activities in maize (Zea mays L.)

Potassium(K)deficiency significantly decreases photosynthesis due to leaf chlorosis induced by accumulation of reactive oxygen species(ROS).But,the physiological mechanism for adjusting antioxidative defense system to protect leaf function in maize(Zea mays L.)is unknown.In the present study,four maize inbred lines(K-tolerant,90-21-3 and 099;K-sensitive,D937 and 835)were used to analyze leaf photosynthesis,anatomical structure,chloroplast ultrastructure,ROS,and antioxidant activities.The results showed that the chlorophyll content,net photosynthetic rate(P_n),stomatal conductance(G_s),photochemical quenching(q_P),and electron transport rate of PSII(ETR)in 90-21-3 and 099 were higher than those in D937 and 835 under K deficiency treatment.Parameters of leaf anatomical structure in D937 that were significantly changed under K deficiency treatment include smaller thickness of leaf,lower epidermis cells,and vascular bundle area,whereas the vascular bundle area,xylem vessel number,and area in 90-21-3 were significantly larger or higher.D937 also had seriously damaged chloroplasts and PSII reaction centers along with increased superoxide anion(O_2~-·)and hydrogen peroxide(H_2O_2).Activities of antioxidants,like superoxide dismutase(SOD),catalase(CAT),and ascorbate peroxidase(APX),were significantly stimulated in 90-21-3 resulting in lower levels of O_2~-·and H_2O_2.These results indicated that the K-tolerant maize promoted antioxidant enzyme activities to maintain ROS homeostasis and suffered less oxidative damage on the photosynthetic apparatus,thereby maintaining regular photosynthesis under K deficiency stress.     

转铁蛋白基因水稻抗Fe2+能力分析

[目的]研究转铁蛋白基因水稻对Fe2+胁迫的生理响应。[方法]采用溶液培养法,对参试水稻进行Fe2+胁迫(200 mg/L)处理,测定其株高、生物量、Fv/Fm及质膜伤害。[结果]Fe2+胁迫下,参试水稻生长受到明显抑制,株高和生物量下降,Fv/Fm下降,MDA含量和电解质渗漏增加。与非转基因对照相比,转铁蛋白植株各测定参数受Fe2+胁迫影响较小,差异显著(P0.05)。[结论]水稻中铁蛋白的表达可降低过量Fe2+对植株光合作用的影响和对叶片质膜的损伤,从而减轻Fe2+胁迫对植株生长的抑制作用,提高了植物抗铁毒的能力。     

亚热带地区水稻(Oryza sativa L.)气孔臭氧通量和产量的响应关系

基于开放式臭氧浓度升高O_3-FACE(Free-Air Concentration Elevation of O_3)实验平台,利用前期水稻O_3-FACE试验的基础数据,通过建立水稻产量与不同评价指标(累积气孔O_3吸收通量PODY和O_3浓度指标AOTX)的响应关系,比较了水稻产量损失与各评价指标的相关性差异,通过对暴露剂量、吸收通量相关参数取值与产量损失的观察和分析结果的比较,找出更为合理的农作物臭氧风险评估阈值。结果表明:随着通量阈值Y[0~11 nmol O_3·m~(-2)PLA·s~(-1)(PLA:projected leaf area,投影叶面积)]和暴露浓度阈值X(0~50 n L·L~(-1))的增加,回归分析R~2值逐渐增加,当Y为11 nmol O_3m~(-2)PLA·s~(-1)和X为50 n L·L~(-1)时,气孔臭氧吸收通量POD11和累积暴露剂量AOT50与水稻相对产量的相关性最大,当通量阈值Y为8~13 nmol O_3·m~(-2)PLA·s~(-1)和暴露阈值X为46~58 n L·L~(-1)时,可获得较高的R~2值取值范围,分别为0.70~0.75和0.70~0.745。参考文献发现,目前地表臭氧污染可能引起的水稻产量损失范围为5%~8%,对照圈中POD9~10和AOT40~45产量损失的预测值亦在这区间,但前者R~2值(0.73~0.74)明显高于后者R~2值(0.64~0.69),表明基于气孔臭氧通量的评价指标能更好地反映水稻产量的变化。通过进一步分析发现,当通量阈值Y为9 nmol O_3·m~(-2)PLA·s~(-1)时,能更准确地评估水稻产量损失,且其R~2值(0.73)高于通量指标POD6(0.57)。以上研究结果表明,通量指标POD9更适合评估亚热带地区O_3污染对水稻作物的影响。     

24-表油菜素内酯对盐碱胁迫下大豆生育、生理及细胞超微结构的影响

【目的】探讨外源EBR(24-表油菜素内酯)对盐碱复合胁迫下大豆的生长指标、生理特性及超微结构的影响,为改善大豆生长、保障粮食安全、实现农业可持续发展奠定基础。【方法】以大豆品种黑农44号为试材,分别在110 mmol·L~(-1)的盐碱复合胁迫条件下培养3 d和7 d进行取材,研究1.2 mg·L~(-1)外源EBR对大豆株高、根系生长,叶片3种抗氧化酶超氧化物歧化酶(superoxide dismutase,SOD)、过氧化物酶(peroxidase,POD)及抗坏血酸过氧化物酶(ascorbate peroxidase,APX)活性,相对电导率、超氧阴离子(O_2~-)产生速率、过氧化氢(H_2O_2)和丙二醛(malondialdehyde,MDA)含量、游离脯氨酸和叶绿素含量以及叶片和根尖细胞超微结构的影响。【结果】盐碱胁迫处理3 d和7 d时,与对照组相比,3种抗氧化酶(SOD、POD、APX)的活性、游离脯氨酸含量、相对电导率、O_2~-产生速率、H_2O_2和MDA含量均升高;各项生长指标、叶绿素含量均降低;叶片细胞结构中叶绿体和线粒体遭到严重破坏;根尖细胞中线粒体、内质网结构破坏较重,液泡破裂。盐碱胁迫条件下,施加外源EBR使大豆的株高、根长和根鲜重分别提高了6.45%、9.60%和19.85%;使大豆叶片SOD、POD、APX的活性显著升高,在3 d和7 d时分别增加了16.92%和9.68%、48.85%和61.44%、19.05%和20.36%;相对电导率、O_2~-产生速率、H_2O_2和MDA的含量显著降低,分别降低了19.58%和28.26%、28.06%和40.92%、28.62%和31.21%、31.03%和37.17%;脯氨酸和叶绿素含量显著升高,分别升高了3.67%和15.96%、13.34%和16.87%;同时维护了大豆叶片和根尖细胞超微结构的稳定性,延缓了细胞的衰老、解体。【结论】在盐碱胁迫下,施加外源EBR通过提高抗氧化酶活性和脯氨酸及叶绿素含量,降低了活性氧(ROS)的积累,维护了细胞结构的完整,促进了幼苗生长,增强了大豆幼苗耐盐碱胁迫的能力。     

Nitrogen Dioxide-Induced Responses in Brassica campestris Seedlings： The Role of Hydrogen Peroxide in the Modulation of Antioxidative Level and Induced Resistance

This article investigates the responses of Brassica campestris seedlings to an acute level of nitrogen dioxide (NO₂) exposure in a plant growth chamber, and examines whether pretreating plants with hydrogen peroxide (H₂O₂) will alleviate NO₂-caused injury. Twenty-eight-day-old B. campestris plants sprayed with 10 mmol L⁻¹ H₂O₂ aqueous solution (corresponding to approximate 1.0 mg H₂O₂ per single plant) were exposed to different concentrations of NO₂ (0.25, 0.5, 1.0, and 2.0 μL L⁻¹, respectively) for 24 h under controlled environment. To measure the plant biomass, the plants were fumigated with the same NO₂ concentrations as mentioned above for 7 h per day (8.00-15.00) for 7 days. As a control, charcoal filtered air alone was applied. Data were collected on plant biomass, total chlorophyll, photosynthetic rate, stomatal conductance, nitrate and nitrate reductase (NR), antioxidative enzymes, ascorbate (ASA), and malondialdehyde (MDA), immediately after exposure. The results showed that exposure to a moderate dose of NO₂ (e.g., 0.25 μL L⁻¹) had a favorable effect on plants, and the dry weight of the above-ground part increased, whereas the exposure to high NO₂ concentrations (e.g., 0.5 μL L⁻¹ or higher) caused a reduction in the plant biomass and the total chlorophyll, when compared with the control. In addition, at 0.5 μL L⁻¹ or higher NO₂ concentrations, prominent increases in the MDA level and superoxide dismutase (SOD) and NR activities were observed. Exposure to 1 μL L⁻¹ and higher NO₂ resulted in necroses appearing on older leaves, and an increase in catalase (CAT) activity, decrease in ASA content, increased accumulation of NO₃, and reduction in photosynthesis, when compared with the controls. No changes were detected in stomatal conductance under NO₂ fumigation. The pretreatment with 10 mmol L⁻¹ H₂O₂ alleviated significantly NO₂-caused biomass decrease and photosynthetic inhibition when compared with H₂O₂-untreated plants. Under NO₂ fumigation, further induction in SOD and CAT activities occurred in H₂O₂ treated plants when compared with H₂O₂-untreated plants. The effect of NO₂ on the ASA and MDA contents was also absent in H₂O₂-treated plants. However, the H₂O₂ treatment did not alter the nitrate content and NR activity in plants under NO₂ fumigation. The H₂O₂ treatment caused a lower rate of stomatal conductance. Taken together, these data suggest that fumigation with an acute level of NO₂ causes oxidative damage to B. campestris seedlings. The H₂O₂ pretreatment markedly protects plants against NO₂ stress and this may be associated with inducible antioxidative level. NO₂ fumigation contributes, at least in part, to the enhanced levels of nitrate in B. campestris leaves.     

拟南芥PMRP基因在叶绿体淀粉粒积累和抗寒性中的作用

【目的】分析推测的膜蛋白（putitave membrane realated protein,PMRP）在拟南芥叶绿体发育过程的作用,明确PMRP对拟南芥光合能力的影响及抗寒性分析,为改善作物光合性能及增强抗逆性提供理论依据。【方法】构建PMRP的RNAi和过表达载体,转化农杆菌EHA105,采用花絮侵染法转化野生型拟南芥（Columbia,Col-0）,获得PMRP RNAi和过表达转基因拟南芥;以野生型和PMRP RNAi、过表达转基因拟南芥为材料,利用细胞生物学方法,观察PMRP表达量对拟南芥叶肉细胞叶绿体的结构和淀粉粒积累的影响;利用红外CO₂分析法测定拟南芥的光合速率,分析PMRP对拟南芥光合能力的影响。选取16 h光照、21℃条件下培养的21 d的野生型Col-0、3个过表达PMRP转基因拟南芥株系,3个PMRP-RNAi转基因拟南芥株系,用冷光源培养箱培养,先在4℃培养7 d,然后在-8℃培养1.5 h,取出放到16 h光照、21℃条件培养7 d后,分析PMRP转基因拟南芥对寒害的抗性。选取14 d的野生型Col-0、3个过表达PMRP转基因拟南芥株系和3个PMRP-RNAi转基因拟南芥株系,对其莲座叶细胞渗出液电导率进行测定。【结果】获得PMRP RNAi和过表达转基因拟南芥株系;通过测定野生型和转基因株系的莲座叶光合速率,野生型Col-0的光合速率为7.3 μmol·m^-2·s^-1,PMRP-RNAi转基因拟南芥的光合速率分别为8.8、7.8和8.5 μmol·m^-2·s^-1,PMRP表达量的降低略增强了拟南芥的光合速率。野生型Col-0的绿叶率为48%,过表达PMRP转基因拟南芥的3个株系绿叶率分别为48.6%、47.8%和49.2%,3个PMRP-RNAi转基因拟南芥的绿叶率分别为65.9%、67.4%和68.3%,表明PMRP表达量的降低增强了植物的耐寒性。在-8℃下处理30 min,野生型Col-0拟南芥莲座叶的渗出液电导率为70.67 μS·cm^-1,PMRP-RNAi拟南芥莲座叶渗出液电导率分别为48.57、45.40和52.10 μS·cm^-1。表明PMRP表达量的降低明显降低了逆境对细胞膜的损伤。通过对PMRP-RNAi转基因拟南芥和野生型拟南芥完全展开的莲座叶,进行超微结构分析,发现野生型拟南芥莲座叶细胞中,叶绿体为椭圆形,而PMRP-RNAi转基因拟南芥莲座叶细胞叶绿体变为近似圆形;在光照情况下,PMRP-RNAi转基因拟南芥叶绿体中淀粉粒的积累与野生型相似,均有明显的淀粉粒积累,但在黑暗环境中,PMRP-RNAi转基因拟南芥叶绿体中淀粉粒积累明显增多。【结论】PMRP表达量降低造成叶绿体形状由梭型变为圆球型,淀粉粒明显增多,增强了拟南芥的抗寒性。     

高氯酸钾浸种对水稻种子萌发及幼苗生理特性的影响

以水稻为实验材料,在水培及控制条件下,探讨不同浓度（0、20、50、100和300 mg·L^-1）的高氯酸钾浸种胁迫对水稻种子萌发及幼苗生长生理的影响。结果表明,低浓度胁迫（20 mg·L^-1）对种子萌发有一定的刺激作用,萌发率、根长和根数均大于对照,随着胁迫浓度和时间的增加,种子萌发及幼苗生长受抑制程度逐渐增大,并且茎的生长比根受影响程度更大。与对照相比,幼苗叶片叶绿素、蛋白质和MDA含量均随胁迫浓度的增高而下降,而SOD活性呈先升后降的趋势,POD活性持续增强,CAT则明显下降。综合各指标的变化及相关性分析结果表明,高氯酸钾抑制水稻种子萌发及导致的幼苗生理伤害与活性氧代谢失调有关,其伤害机制尚待进一步探讨。