绿色木霉TV41对尖孢镰刀菌FW0在西瓜植株空间分布和枯萎病防控效果的影响

【目的】为进一步探究盆栽试验条件下绿色木霉TV41 (Trichoderma viride TV41)对尖孢镰刀菌FW0 (Fusarium oxysporum FW0)在西瓜植株空间分布的影响以及对西瓜枯萎病的防控效果。【方法】通过定期检测不同处理西瓜根际/根表尖孢镰刀菌的数量、西瓜植株根内/茎内尖孢镰刀菌的数量以及植株侧根被侵染比例和尖孢镰刀菌在植株内的侵染进程,进行多次盆栽试验并统计发病率。【结果】当绿色木霉和尖孢镰刀菌接种量均为5×105孢子/g基质时,绿色木霉TV41在西瓜根际/根表的定殖数量明显高于尖孢镰刀菌FW0的数量,接种了绿色木霉TV41的处理,根际/根表尖孢镰刀菌的数量(103/g基质)显著低于仅接种FW0的对照(104/g基质);绿色木霉TV41不仅能够有效减缓尖孢镰刀菌在西瓜植株内的侵染进程,而且能够有效降低西瓜植株根内、茎内尖孢镰刀菌的数量。与对照(只接种FW0)相比,接种绿色木霉后西瓜枯萎病的发病率从66%降低到27%。【结论】绿色木霉TV41能够通过影响尖孢镰刀菌FW0在西瓜植株的空间分布,从而有效防控西瓜枯萎病的发生,防控效果达到60%。     

不同品种小麦与蚕豆间作对蚕豆枯萎病的防治及其机理

通过田间小区试验和水培试验,研究了3个品种小麦（云麦42、云麦47和绵阳29）与蚕豆间作对蚕豆地上部生物量、枯萎病发生、根际微生物代谢功能多样性和枯萎病病原菌尖孢镰刀菌数量的影响,分析了3个不同小麦品种低分子量根系分泌物组分（糖、氨基酸和有机酸）的差异.结果表明： 云麦42与蚕豆间作（YM42/B）和云麦47与蚕豆间作（YM47/B）使蚕豆地上部生物量分别增加16.6%和13.4%,使蚕豆枯萎病病情指数分别降低47.6%和23.3%,绵阳29与蚕豆间作（MY29/B）对蚕豆地上部生物量和枯萎病病情指数均无显著影响.与单作蚕豆相比,YM42/B和YM47/B处理均显著提高了蚕豆根际微生物的平均颜色变化率（AWCD)及对碳源的总利用强度和Biolog ECO板中各种碳源的利用,明显改变了蚕豆根际微生物群落结构,并显著降低了蚕豆根际的尖孢镰刀菌数量;MY29/B处理对AWCD值、碳源总利用强度和Biolog ECO板中各种碳源的利用及蚕豆根际尖孢镰刀菌数量均无显著影响,也未明显改变蚕豆根际的微生物群落结构.3个小麦品种根系分泌物中可溶性糖、游离氨基酸总量和有机酸总量均表现为MY29＞YM47＞YM42.MY29根系分泌物中丝氨酸、谷氨酸、甘氨酸、缬氨酸、蛋氨酸、苯丙氨酸、赖氨酸的含量均显著高于YM42和YM47;精氨酸为YM42、YM47所特有,而亮氨酸为MY29所特有.MY29和YM47根系分泌物中检出酒石酸、苹果酸、柠檬酸、琥珀酸、延胡索酸和顺乌头酸6种有机酸,而YM42根系分泌物中检出洒石酸、苹果酸、柠檬酸和延胡索酸4种有机酸,且MY29和YM47根系分泌物中苹果酸含量显著高于YM42.小麦与蚕豆间作提高了蚕豆根际微生物的活性和碳源利用强度,改变了根际微生物的群落结构,降低了蚕豆根际尖孢镰刀菌的数量,促进了蚕豆生长,抑制了蚕豆枯萎病的发生,但小麦与蚕豆间作控病效果受小麦品种的影响,表明间作系统中非寄主作物根系分泌物的差异是影响间作对土传病害控制的重要因素.     

拟康宁木霉T 51菌株对番茄枯萎病的生物防治及其机理研究

尖孢镰刀菌是番茄枯萎病的致病菌,该研究利用拟康宁木霉T 51菌株对尖孢镰刀菌展开对峙培养试验、防治最适温度、酸碱度筛选试验及生物防治效果试验,并测定防治试验中番茄幼苗叶片的生理生化指标和水杨酸、茉莉酸合成和信号途径关键基因表达量,探讨T 51菌株的生物防治机理。结果表明：(1)T 51菌株可显著抑制对峙培养中尖孢镰刀菌生长;随着环境温度和pH的增加,T 51菌株对尖孢镰刀菌的抑制率先升后降,并且在20 ℃、pH 7环境下效果最佳。(2)T 51菌株和尖孢镰刀菌混合孢子液处理番茄幼苗植株无明显的感病症状,植株生长状态与清水对照组无显著差异,枯萎病发病率和病情指数比单施尖孢镰刀菌孢子液处理显著大幅度降低,相对防效为87.5%。(3)与单施尖孢镰刀菌孢子液处理相比,混合孢子液处理番茄幼苗叶片的叶绿素荧光参数最大光化学效率、光化学淬灭系数和表观光合电子传递速率,以及抗氧化酶SOD、POD、CAT活性均显著增加,而非光化学淬灭系数和过氧化氢含量均显著降低。(4)与单施尖孢镰刀菌孢子液处理相比,混合孢子液处理番茄幼苗叶片的内源水杨酸(SA)显著降低,而茉莉酸(JA)含量显著升高,同时SA信号通路上的PR1和TGA2基因表达量均显著下调,JA合成基因LoxD的表达量显著上调。研究认为,拟康宁木霉T 51菌株对尖孢镰刀菌有显著的防治效果,并在20 ℃、pH 7环境下防治效果最佳;T 51菌株可能通过抑制尖孢镰刀菌侵染,增强番茄叶片抗氧化酶活性,提高叶片光合效率,以及调控水杨酸和茉莉酸合成和信号途径关键基因表达,调节内源水杨酸和茉莉酸含量,进而提高番茄植株的枯萎病抗病性。研究结果为番茄抗枯萎病提供了生防途径的理论依据。     

石灰碳铵熏蒸与施用生物有机肥对连作黄瓜和西瓜枯萎病及生物量的影响

采用稀释涂布平板计数法,研究了石灰碳铵及碳铵熏蒸对黄瓜和西瓜连作土壤尖孢镰刀菌数量的影响,以及熏蒸后施用生物有机肥对黄瓜和西瓜枯萎病的防控效果及植株生长的影响.结果表明:与对照相比,石灰碳铵及碳铵熏蒸后,连作土壤中黄瓜尖孢镰刀菌的数量分别下降95.4%及71.4%,西瓜尖孢镰刀菌的数量分别下降87.2%及64.2%;多因素方差分析表明,熏蒸、施用有机肥及作物种类均对土壤中尖孢菌数量、枯萎病发病率、防控率及生物量有显著影响;与未熏蒸施用普通有机肥对照相比,石灰碳铵熏蒸后施用生物有机肥能显著减少后茬黄瓜或西瓜土壤中尖孢镰刀菌的数量并显著降低枯萎病发病率,防控率高达91.9%及92.5%,同时显著增加了植株的株高、茎粗、SPAD值及干质量.表明石灰碳铵熏蒸及施用生物有机肥能够降低土壤中尖孢镰刀菌数量,有效防控黄瓜和西瓜枯萎病的发生并促进其植株生长.     

黄花蒿叶水提物对三七根际尖孢镰刀菌生长的抑制作用

田间试验结果表明,在三七土壤表面覆盖黄花蒿可促进三七植株的生长,并且对三七"黄腐型"根腐病有一定的抑制作用,防控效果高达76.6%。通过以水为溶媒提取黄花蒿叶片,研究了其水提物对三七根腐病主要病原菌之一尖孢镰刀菌菌丝生长、孢子产量、菌丝干重、镰刀菌酸产生的作用。结果表明,随着水提物浓度的增大,黄花蒿水提物对尖孢镰刀菌菌丝的生长、孢子产量和镰刀菌酸产生的抑制作用逐渐增强;并且病原菌培养基的粗提物对植株体的致病作用与其镰刀菌酸含量成正相关关系。该研究将为三七根腐病的生态防控以及新农药的开发利用提供重要科学依据。     

两种秸秆醋液对尖孢镰刀菌和立枯丝核菌的抑菌作用

本研究以玉米秸秆醋液、水稻秸秆醋液为供试材料,研究不同稀释度的秸秆醋液对尖孢镰刀菌(Fusarium oxysporum)和立枯丝核菌(Rhizoctonia solani)的抑制作用,测定其可溶性蛋白和可溶性糖。结果表明,50倍稀释液对2种病原菌的抑制率为100%,即2种病原菌在50倍稀释处理的秸秆醋液中不能生长。玉米秸秆醋液对尖孢镰刀菌中可溶性蛋白的影响不显著,对立枯丝核菌中可溶性蛋白的影响表现为先升高后降低。水稻秸秆醋液对尖孢镰刀菌中可溶性蛋白的影响是先升高后降低,对立枯丝核菌中可溶性蛋白的影响是逐渐累积。高浓度的水稻秸秆醋液可提高2种菌体内可溶性糖含量,100倍稀释的玉米秸秆醋液可提高尖孢镰刀菌体内的可溶糖含量,玉米秸秆醋液对立枯丝核菌的可溶性糖含量基本不会产生影响。本研究为秸秆醋液在农业生产上的推广应用等提供科学依据。     

连栽杉木根际土壤镰刀菌属真菌群落变化规律

为探讨连栽对杉木(Cunninghamia lanceolata (Lamb.) Hook.)根际土壤镰刀菌属真菌多样性的影响,本研究应用DGGE技术研究连栽杉木根际土壤镰刀菌属(Fusarium)真菌在一代杉木人工林(first rotation Chinese fir plantation,FCP)、二代杉木人工林(second rotation Chinese fir plantation,SCP)与三代杉木人工林(third rotation Chinese fir plantation,TCP)的组成及含量变化,并结合qRT-PCR技术测定杉木根际土壤病原菌尖孢镰刀菌(Fusarium oxysporum)的绝对含量变化,从而揭示杉木连栽障碍土壤微生态失衡现象。DGGE结果表明,多代连栽后杉木根际土壤镰刀菌属真菌组成及含量均发生显著变化,优势菌尖孢镰刀菌含量随着栽植代数的增加显著上升。主成分分析能较好区分FCP、SCP与TCP根际土壤镰刀菌群落特征。聚类分析结果表明,TCP土壤镰刀属结构组成及百分含量与FCP、SCP差异显著。多样性分析结果显示,连栽杉木土壤镰刀菌多样性与丰富...     

硅和稻瘟病菌接种对水稻植株有机酸含量的影响

以抗病性不同的一对水稻近等基因系——感病CO39和抗病C101LAC(Pi-1)为实验材料,在水培条件下研究了施硅和稻瘟病接菌对水稻根系和叶片抗性物质有机酸含量的影响,揭示硅提高水稻对稻瘟病抗性的机理。结果表明:接菌条件下硅处理显著降低了2个基因型材料的叶片反丁烯二酸、柠檬酸的含量,而增加了叶片中草酸、顺丁烯二酸的含量;加硅显著降低接菌后第3天的CO39叶片酒石酸含量,但增加了C101LAC(Pi-1)接菌后第7天的叶片酒石酸含量;硅处理还显著增加了根系中苹果酸和草酸的含量;各种有机酸在水稻植株体内的分布也不尽相同,如柠檬酸主要分布在叶片中,苹果酸主要分布在根系中,顺丁烯二酸、反丁烯二酸、酒石酸和草酸在叶片和根系中都有分布。研究表明,硅可能通过影响植株体内的有机酸代谢而增强稻瘟病的抗性。     

滁菊连作土壤中尖孢镰刀菌的分离、鉴定及变化特征

采用传统平板培养法及尖孢镰刀菌专性培养基对滁菊连作土壤的真菌和尖孢镰刀菌进行分析测定,结果表明,在滁菊连作条件下,土壤中真菌和尖孢镰刀菌的数量显著增加,平均分别达到8.71×105 cfu/g干土和3.12×104cfu/g干土,各自是对照土壤的2.24倍和5.57倍。土壤中尖孢镰刀菌数量显著增加可能是导致滁菊连作障碍的重要因素。     

防风根际真菌的分离鉴定及其生防潜力评价

作为世界性分布的镰刀属常见病原真菌,尖孢镰刀菌（Fusarium oxysporum）和木贼镰刀菌（F. equiseti）对包括经济作物及药用植物等的生长均有较大危害。利用源自于植物根际土壤的有益微生物防控尖孢镰刀菌和木贼镰刀菌引起的真菌性病害,是目前较为理想的植物病害管理策略。为获得可有效抑制尖孢镰刀菌和木贼镰刀菌的生防菌源,于防风根际土壤中分离纯化真菌104株,基于平板对峙法筛选获得1株对尖孢镰刀菌和木贼镰刀菌具有显著抑制效果的菌株MR-43,结合形态特征、ITS序列分析,将其确定为Sirastachys castanedae（GenBank登录号：OK287148.1）,隶属于Sirastachys组进化分支,发现其可宿生于植物根际土壤。基于盆栽试验法,探究MR-43在防风栽培土壤中的定殖能力,评价MR-43对由尖孢镰刀菌引起的防风枯萎病和由木贼镰刀菌引起的防风根腐病的防病能力,及其对防风植株的促生能力。结果显示,Sirastachys castanedae MR-43对尖孢镰刀菌、木贼镰刀菌的抑菌率为57%以上,且经多次验证抑菌效果稳定;菌株MR-43可稳定定殖于防风栽培土壤并实现有效扩繁;菌株MR-43的孢子悬液可有效控制防风枯萎病和防风根腐病,平均防效达68.52%,与多菌灵、代森锰锌的防病效果无显著性差异（P>0.05）;此外,MR-43对防风植株生长具有明显促进作用。因此,Sirastachys castanedae MR-43在防风枯萎病、根腐病等真菌性病害管理方面具有较好的开发价值及应用潜力。     

根结线虫对文冠果苗木根系结构与生长及矿质养分分布特性的影响北大核心CSCD

以根结线虫侵染的文冠果一年生苗木为材料,观察分析苗木根系的形态和显微结构,植株生长发育以及主要矿质养分在苗木中的分布特性,并分析不同矿质元素与线虫侵染的关联关系,以揭示根结线虫对文冠果苗木生长发育的影响机制。结果表明:(1)受根结线虫侵染的文冠果苗木根系形成根结,依据根结发生程度分为0(对照,正常植株)、2、3、4级;与对照相比,具有根结的文冠果苗木根系解剖结构特征主要表现为皮层相对较厚,木质部排列扭曲,导管较少,射线数目较少且分布不均匀;韧皮细胞内含物明显较多;多个巨细胞及细胞空腔主要存在于韧皮部。(2)具根结的苗木株高和地径较对照均增加,且株高增幅达显著水平(P<0.05)。(3)具根结苗木根、茎、叶部位的N、P含量均较对照下降,根部降幅达显著水平(P<0.05),其中具2~4级根结的根部N含量分别较对照显著下降7.8%、16.0%和29.5%,P含量分别显著下降15.6%、7.1%和43.3%;根部Fe含量、Zn含量显著上升,2~4级根结根系中Fe含量较对照分别增加1.56倍、0.81倍和3倍,Zn含量分别增加1.11倍、1.56倍和1.78倍;具3和4级根结的苗木根系中K含量较对照显著增加(P<0.05),具2和4级根结的苗木叶片中K含量较对照分别显著下降61.5%和47.0%。(4)苗木根部、茎部N元素含量对于根结线虫侵染的响应最明显,且其含量随侵染程度的增大而降低,叶部Mg元素含量与根结线虫侵染率、K元素含量与整株苗木生物量均呈显著负相关关系(P<0.05)。该研究为根结线虫对文冠果苗木养分吸收利用及运转的影响提供了一定的理论依据。     

Fusaric acid accelerates the senescence of leaf in banana when infected by Fusarium

Fusarium oxysporum f.sp. cubense (FOC) is a causal agent of vascular wilt and leaf chlorosis of banana plants. Chloroses resulting from FOC occur first in the lowest leaves of banana seedlings and gradually progress upward. To investigate the responses of different leaf positions to FOC infection, hydroponic experiments with FOC inoculation were conducted in a greenhouse. Fusarium-infected seedlings exhibited a decrease in net photosynthesis rate, stomatal conductance, and transpiration rate of all leaves. The wilting process in Fusarium-infected seedlings varied with leaf position. Measurements of the maximum photochemical efficiency of photosystem II (F _V/F _max) and visualization with transmission electron microscopy showed a positive correlation between chloroplast impairment and severity of disease symptoms. Furthermore, results of malondialdehyde content and relative membrane conductivity measurements demonstrated that the membrane system was damaged in infected leaves. Additionally, the activities of phenylalanine ammonia-lyase, peroxidase and polyphenol oxidase were increased and total soluble phenolic compounds were significantly accumulated in the leaves of infected plants. The structural and biochemical changes of infected plants was consistent with plant senescence. As the FOC was not detected in infected leaves, we proposed that the chloroplast and membrane could be damaged by fusaric acid produced by Fusarium. During the infection, fusaric acid was first accumulated in the lower leaves and water-soluble substances in the lower leaves could dramatically enhance fusaric acid production. Taken together, the senescence of infected banana plants was induced by Fusarium infection with fusaric acid production and the composition of different leaf positions largely contribute to the particular senescence process.     

Ferulic acid may prevent infection of Cicer arietinum by Sclerotium rolfsii

High performance liquid chromatography analysis of different parts of Sclerotium rolfsii-infected and healthy seedlings of chickpea (Cicer arietinum) was carried out to examine the status of phenolic compounds. Three major peaks that appeared consistently were identified as gallic, vanillic and ferulic acids. Gallic acid concentrations were increased in the leaves and stems of infected plants compared to healthy ones. Vanillic acid detected in stems and leaves of healthy seedlings was not detected in infected seedlings. There was a significant increase of ferulic acid in those stem portions located above the infected collar region compared to minimal amounts in the roots of healthy seedlings. In vitro studies of ferulic acid showed significant antifungal activity against S. rolfsii. Complete inhibition of mycelial growth was observed with 1000 g of ferulic acid/ml. Lower concentrations (250, 500 and 750 g/ml) were also inhibitory and colony growth was compact in comparison with the fluffy growth of normal mycelium. Higher amounts of phenolics were found in the stems and leaves of S. rolfsii-infected seedlings in comparison to the healthy ones. A role for ferulic acid in preventing infections by S. rolfsii in the stems and leaves of chickpea plants above the infection zone is therefore feasible.     

Effect of Co-infection by Fusarium oxysporum and Cowpea Mosaic Virus on the Growth and Colonization of Cowpea Seedlings (Vigna unguiculata [L.] Walp.)

Combined infection of cowpea seedlings (c. v. ‘California Blackeye”) by cowpea mosaic virus (CPMV) and Fusarium oxysporum induced greater losses in leaf area, fresh and dry weights than infection by either pathogen alone. The growth of seedlings infected by F. oxysporum f. sp. tracheiphilum was less than that of comparable seedlings infected by F. oxysporum f. sp. phaseoli. The virus infectivity of extracts of the trifoliate leaves of dual-infected plants was significantly higher than that of comparable extracts from the leaves of plants singly infected with CPMV. The nature of the effects of multiple infection in cowpea is discussed.     

Isolation of Endophytic Actinomycetes From Roots and Leaves of Banana (Musa Acuminata) Plants and Their Activities Against Fusarium oxysporumf. sp. cubense

Two hundred and forty-two actinomycete strains were isolated from the interior of leaves and roots of healthy and wilting banana plants. Most of them were streptomycetes, Streptomyces griseorubiginosus-like strains were the most frequently isolated strains. Community analysis demonstrated increased actinomycete diversity in wilting leaves compared to that in healthy leaves, similar actinomycete communities were found in wilting and healthy roots. Screening of the isolates for antagonistic activity against Fusarium oxysporumf. sp. cubenserevealed that the proportion of antagonistic streptomycetes in healthy roots was higher than that in wilting roots (P < 0.01), but no difference was found between antagonistic strains isolated from healthy and wilting leaves. The potential biological control of Panama disease of banana by endophytic streptomycetes, especially Streptomyces griseorubiginosus-like strains was discussed.     

白桦Trihelix家族全基因组鉴定及抗病表达模式分析北大核心CSCD

Trihelix家族是植物中特有的一类转录因子家族,在植物生长发育、抗逆反应中具有重要的调控作用。该研究基于白桦基因组数据库,对白桦Trihelix家族基因的表达特性以及抗病功能等进行分析,为Trihelix家族成员在白桦抗病过程中的功能研究奠定基础。结果显示:(1)共筛选到白桦8个Trihelix家族成员(BpTrihelix1~BpTrihelix8),分布在6条染色体上;氨基酸分子量在35 633.96~81 871.27 Da之间,等电点在5.32~8.67之间,均为疏水性氨基酸。(2)组织特异性表达分析表明,8个家族成员在白桦根、茎、叶中均有不同程度的表达,且BpTrihelix3在根、茎、叶中的表达量均最高。(3)病原菌侵染试验结果发现,链格孢霉菌(Alternaria alternata)感染白桦植株叶片48 h和立枯丝核菌(Rhizoctonia solani)感染白桦幼苗根部24 h时,BpTrihelix3、BpTrihelix4和BpTrihelix7均显著上调,其余家族基因表达量无明显变化,说明该家族基因成员中的BpTrihelix3、BpTrihelix4和BpTrihelix7响应了病原菌的感染,推测三者在白桦抗病过程中可能发挥重要作用。     

Alleviation of Changes in Protein Metabolism in NaCl-Stressed Wheat Seedlings by Thiamine

NaCl-stress induced a pronounced suppression in growth of wheat seedlings. The most abundant amino acids (cysteine, arginine, methionine) constituting about 55 % of total free amino acid content in control wheat were reduced in 100 mM NaCl-treated plants. However, valine, isoleucine, aspartic acid and proline accumulated in response to NaCl stress and NaCl-treated wheat seedlings showed 1.6 fold increase in total free amino acids compared to the control. Addition of 2 [micro ]M thiamine alleviated the effects of NaCl on the amino acid composition and the amount of total free amino acids decreased to that in the control. Content of 26 kDa protein increased in NaCl-treated plants, stimulation was more pronounced in roots than in shoots. In contrast, the contents of 13 and 20 kDa proteins decreased. After addition of thiamine, the 24 kDa protein, which disappeared with NaCl treatment, has been initiated again. Moreover, thiamine treatment stimulated the accumulation of the 20 kDa protein.     

Changes in protein and amino acid contents in two cultivars of rice seedlings with different apparent tolerance to cadmium

Changes in protein and amino acid contents in Cd-treated rice (Oryza sativa L.) seedlings of two cultivars were investigated. By assessing the decrease in chlorophyll content in the second leaves as an indicator of Cd toxicity, it was seen that cv. Tainung 67 (TNG 67) seedlings were apparently more tolerant to Cd than cv. Taichung Native 1 (TN 1). Following treatment with CdCl₂, protein content decreased with a progressive and substantial increase of protease activity and total amino acids in TN 1, but not in TNG 67. The patterns of individual amino acids in Cd-treated leaves of both cultivars were examined and, only in cv. TN 1 a substantial increase in the content of all amino acids analysed, except for methione, was recorded. The role of these changes in endogenous amino acids in Cd toxicity of TN 1 leaves is discussed.     

Isolation and characterization of a cDNA-clone coding for potato type A phytochrome

We have isolated and sequenced a cDNA clone encoding the apoprotein of a potato phytochrome. Based on the deduced amino acid sequence, which shows 78% amino acid identity to the Arabidopsis phyA and 50% identity to the Arabidopsis phyB open reading frame, we have classified this cDNA clone as potato phyA phytochrome. The amino acid immediately preceding cysteine 323, which is the homologue of oat cystein 321, to which the chromophore has been shown to be attached, is a tyrosine residue. This contrasts with six other type A phytochrome sequences from both monocots and dicots that encode serine in this position. As already observed in three other cDNAs isolated from dicot species, the potato phyA clone encodes a short open reading frame (13 amino acids) preceding the phyA open reading frame (1123 amino acids), supporting the idea that this type of leader sequence might be involved in the regulated expression of the phytochrome apoprotein. Southern blot analysis revealed a single phyA gene as well as other related phytochrome sequences in the potato genome. phyA mRNA levels varied in different organs and were modulated by white light; in seedlings and sprouts, highest levels of mRNA were detected in the etiolated stage. Upon illumination with white light, mRNA levels decreased to the amount found in leaves of re-etiolated plants. Lowest expression was observed in leaves of plants grown in the light, in tubers irrespective of light treatment, and in roots of plants grown in the dark. In roots of plants grown in the light, elevated levels of phyA mRNA were detected. Using a monoclonal antibody generated against pea phytochrome as an immunochemical probe, the protein was only detectable in protein extracts from etiolated seedlings and sprouts.     

缺氮和复氮对菘蓝幼苗生长及氮代谢的影响

对基质育苗后水培的菘蓝进行缺氮与复氮处理,分析其生长情况及氮代谢产物含量的变化,探讨缺氮和复氮对菘蓝幼苗生长及氮代谢的影响,以提高菘蓝产量和品质以及栽培过程中的氮素利用效率。结果显示:(1)正常供氮条件下,菘蓝幼苗的叶绿素含量、谷氨酰胺合成酶(GS)活性、硝态氮含量、靛玉红含量为最高,而其株高、主根直径、根的鲜重与干重、叶的鲜重与干重、根系活力均最小。(2)缺氮处理增加了菘蓝幼苗的主根直径和根干重,提高其根系活力和硝酸还原酶(NR)活性,促进游离氨基酸在叶中的积累;但降低了GS的活性,也降低了叶中硝态氮、可溶性蛋白、靛玉红及根中游离氨基酸的含量;缺氮对叶中靛蓝的含量无明显影响。(3)复氮处理增加了菘蓝幼苗的株高、主根长、根鲜重、叶鲜重、叶干重,提高了其根系活力,降低了NR和GS的活性;与对照相比,复氮降低了叶中硝态氮含量,提高了叶中可溶性蛋白、靛蓝及根中游离氨基酸的含量,但对叶中游离氨基酸和靛玉红含量影响较小。研究表明,缺氮后再复氮有利于菘蓝幼苗叶的生长,同时有利于增加其叶内靛蓝含量,从而提高其产量和品质。