土壤干旱胁迫对樟树（Cinnamomum camphora (L.) Presl）苗木水力结构特征的影响

植物水力结构特征通常用导水率(Kh)、比导率(Ks)、叶比导率(LSC)、胡伯尔值(Hv)等参数来表征.设置了3种土壤干旱胁迫强度和对照共4种处理,每一处理5个重复,采用"冲洗法"对喀斯特地区造林树种两年生樟树(Cinnamomum camphora (L.) Presl)苗木的水力结构相关参数进行测定.结果表明:樟树苗木在正常水分和不同强度土壤干旱胁迫条件下,其茎段导水率、比导率、叶比导率、胡伯尔值均与茎段直径呈正相关关系,并可以用不同类型函数进行拟合.随着干旱胁迫强度的加剧,不同处理的导水率、比导率、叶比导率降低,胡伯尔值在不同处理间的差异不显著.这说明较粗的茎段,其单位横截面积的导管投入与使用效率明显高于较细茎段,且供给末端叶片水分所需要的压力梯度小于较细茎段.结果为进一步探讨土壤干旱对樟树苗木水力结构作用机理及在石漠化山地造林的适应性提供理论依据.     

胡杨木质部水分传导对盐胁迫的响应与适应北大核心CSCD

解析植物木质部导水率对逆境的响应和适应对促进植物抗逆性机理研究和受损植被恢复具有重要意义。该文以荒漠河岸林建群种胡杨(Populus euphratica)为研究对象,系统分析了胡杨幼株根、茎、叶水分传输通道对不同浓度盐胁迫的响应和适应。结果表明:(1)胡杨幼株根系对盐胁迫的敏感性高于茎和叶,盐胁迫下根系生长和根尖数显著受到抑制,根木质部易于发生栓塞,导水率明显降低。(2)胡杨幼株茎木质部导水率对盐胁迫的响应依盐浓度而定,轻度(0.05 mol·L–1 Na Cl)和中度(0.15 mol·L–1 Na Cl)盐胁迫下,胡杨可以通过协调导管输水的有效性和安全性来调节木质部的导水率,维持植物正常生长;重度(0.30 mol·L–1 Na Cl)盐胁迫下,胡杨茎木质部导管输水有效性和安全性均明显降低,木质部导水率显著下降,并伴随叶片气孔导度的显著降低,从而严重抑制了胡杨的光合和生长。     

黄腐酸和甜菜碱预处理对干旱胁迫下平邑甜茶生理特性及光合的影响

该研究以平邑甜茶[Malus hupehensis(Pamp.)Rehd.]2年生实生苗为材料,通过盆栽试验于干旱处理前3d分别连续喷施黄腐酸(FA)、甜菜碱(GB)和复配(FA+GB),并以清水为对照(CK)进行预处理,比较分析不同预处理对干旱胁迫下平邑甜茶的生理及光合特性变化,探讨FA和GB对平邑甜茶的抗旱生理机制。结果显示:(1)与对照相比,FA、GB和FA+GB预处理均能够显著提高平邑甜茶叶片相对含水量,且FA的保水性效果最佳。(2)3种预处理均可显著促进干旱胁迫下叶片可溶性蛋白、可溶性糖和脯氨酸含量增加,且FA+GB预处理后在干旱胁迫下叶片可溶性糖和脯氨酸累积量显著高于单施FA或GB。(3)3种预处理均可显著提高干旱胁迫下平邑甜茶幼苗的SOD、POD、CAT活性,并显著降低MDA的积累速度及其累积量,且以FA+GB预处理的MDA含量最低、抗氧化酶活性最高。(4)GB和FA+GB预处理下平邑甜茶的净光合速率、瞬时水分利用率显著高于CK和FA,且FA+GB处理下改善光合特性的效果最佳,GB次之。研究表明,单独喷施黄腐酸和甜菜碱及两者配施预处理均能够增加干旱胁迫下平邑甜茶的渗透调节物质和相对含水量,提高叶片的保水性,调节抗氧化物酶活性,降低丙二醛含量,增加细胞膜稳定性,改善光合性能,进而提高平邑甜茶的抗旱能力,且以复配喷施(FA+GB)预处理的效果最好。     

胡杨木质部水分传导对盐胁迫的响应与适应

解析植物木质部导水率对逆境的响应和适应对促进植物抗逆性机理研究和受损植被恢复具有重要意义。该文以荒漠河岸林建群种胡杨(Populus euphratica)为研究对象, 系统分析了胡杨幼株根、茎、叶水分传输通道对不同浓度盐胁迫的响应和适应。结果表明: (1)胡杨幼株根系对盐胁迫的敏感性高于茎和叶, 盐胁迫下根系生长和根尖数显著受到抑制, 根木质部易于发生栓塞, 导水率明显降低。(2)胡杨幼株茎木质部导水率对盐胁迫的响应依盐浓度而定, 轻度(0.05 mol·L^-1 NaCl)和中度(0.15 mol·L^-1 NaCl)盐胁迫下, 胡杨可以通过协调导管输水的有效性和安全性来调节木质部的导水率, 维持植物正常生长; 重度(0.30 mol·L^-1 NaCl)盐胁迫下, 胡杨茎木质部导管输水有效性和安全性均明显降低, 木质部导水率显著下降, 并伴随叶片气孔导度的显著降低, 从而严重抑制了胡杨的光合和生长。     

不同抗性苹果砧木叶片抗坏血酸代谢对干旱胁迫的响应

以抗旱性强的苹果砧木新疆野苹果[Malus sieversii (Ledeb.) Roem.]和抗旱性弱的平邑甜茶[M.hupehensis (Panlp.) Reld.]叶片为试材,在20%PEG-6000模拟干旱胁迫条件下,研究了抗坏血酸(AsA)含量、氧化还原状态、合成和代谢相关酶活性对干旱胁迫的响应。结果显示,在正常水分条件下,新疆野苹果和平邑甜茶叶片间AsA含量及代谢相关酶活性差异不显著。干旱胁迫过程中,二者之间叶片AsA、谷胱甘肽(GSH)、总谷胱甘肽和总抗坏血酸含量变化趋势基本一致,但新疆野苹果叶片中的含量增加幅度明显大于平邑甜茶;且与平邑甜茶相比,新疆野苹果叶片具有较高的L-半乳糖酸-1,4-内酯脱氢酶(GalLDH)、脱氢抗坏血酸还原酶(DHAR)和谷胱甘肽还原酶(GR)活性及AsA/DHA(脱氢抗坏酸)和GSH/GSSG(氧化型谷胱甘肽)比率。研究表明,干旱胁迫下,新疆野苹果能够维持较高的AsA合成和再生能力,并具有维持高AsA水平特性,这可能与其具有较强的抗旱性相关。     

干旱低磷胁迫对不同品种小麦根系导水率的影响

控制磷素水平,采用控制灌水量(正常供水、中度及重度干旱胁迫)的盆栽试验法,选择抗旱性小麦品种陕合6号(W1)和水分敏感型品种郑引1号(W2)为供试材料。用压力室法测定了三叶期的两品种小麦根系导水率(LPr)的变化规律。结果表明：陕合6号,在有磷正常供水处理( PH)下具有较高的导水率,干旱胁迫时LPr降低较少,且复水后有较强的恢复能力。郑引1号, PH的LPr值相对较小,干旱导致的根系导水率下降非常突出,复水后的恢复能力也较弱。另外,干旱胁迫对小麦苗期根系导水率的影响大于磷胁迫对其导水率的影响,且两品种小麦无磷止常供水处理(-PH)的LPr分别为 PH的31．9%和53．6％,即磷对前者LPr的影响大于后者。     

固沙灌木柠条锦鸡儿和中间锦鸡儿木质部导水与叶片光合能力对土壤水分的响应

水分是干旱沙区植被重建和恢复的主要限制性因子,土壤有效水分含量直接影响植物木质部水分运输能力。但是不同水分条件下不同物种、不同年龄木质部水力特性和叶片气体交换的差异以及土壤水分含量对其影响的相关研究目前尚不明确。因此,该研究以10年和30年树龄人工固沙区的柠条锦鸡儿(Caragana korshinskii)和中间锦鸡儿(C. liouana)为实验材料,研究它们在旱季和雨季下水力特性和光合特性的差异及其关系。研究结果表明,树龄对柠条锦鸡儿和中间锦鸡儿木质部导水率、导水率损失百分比、叶片水势和相对含水量等无显著的影响,而土壤水分含量对其功能性状的影响较显著。树龄和土壤水分含量均对灌木叶片光合作用有显著影响,但在土壤水分条件良好的情况下树龄对其影响不显著。此外,土壤含水量与叶片水分含量和木质部茎比导水率之间呈显著的正相关关系;木质部导水率与叶片水分状态和气孔导度也存在显著的正相关关系,而光合速率与木质部导水率和叶片水分含量存在显著正相关关系,这表明土壤水分含量通过影响木质部导水率和栓塞程度而直接影响了叶片水分状况和光合碳同化能力。总而言之,柠条锦鸡儿和中间锦鸡儿的木质部导水能力和叶片光合...     

外源NO对水分胁迫下平邑甜茶幼苗氧化损伤的缓解效应

以苹果属植物平邑甜茶水培幼苗为试验材料,采用20%PEG-6000模拟水分胁迫,进行了外源NO对水分胁迫下平邑甜茶幼苗氧化损伤的缓解效应研究。结果表明:100~500μmol·L-1外源硝普钠(SNP,NO供体)处理,能在一定程度上提高渗透胁迫下平邑甜茶叶片内SOD、POD、CAT、APX活性和ASA含量,不同程度减轻20%PEG-6000胁迫对平邑甜茶幼苗活性氧的累积和氧化损伤,其中以300μmol·L-1 SNP处理缓解效应最佳,而相对高浓度的700μmol·L-1 SNP处理则不能起到缓解作用,反而有一定的毒害作用。     

聚乙二醇对平邑甜茶叶片气孔器超微结构的影响

 采用透射电镜技术对聚乙二醇（PEG）模拟干旱处理的平邑甜茶(Malus hupehensis Rehd (pingyitiancha))叶片气孔器超微结构进行了观察,并对叶片气孔器超微结构制片方法进行了改进。所观察结果如下：1）PEG胁迫后保卫细胞中叶绿体数量增加,而叶绿体中淀粉粒数量呈下降趋势;2）PEG胁迫降低保卫细胞中线粒体的数量及破坏线粒体的超微结构;3）PEG胁迫使平邑甜茶保卫细胞中的液泡变小以致不明显。     

淹水条件下平邑甜茶根系NO生成及外源硝酸钠对其影响

以2年生平邑甜茶(Malus hupehensis)为试验材料,研究了淹水条件下平邑甜茶根系一氧化氮(NO)的生成规律以及外源硝酸钠(NaNO₃)对NO生物合成的影响.结果表明：3～9 d的淹水处理显著提高了平邑甜茶根系NO生成量;在12 d内,随着淹水时间延长,根系NO生成量、硝酸还原酶(NR)、一氧化氮合酶(NOS)活性和丙二醛(MDA)含量均先上升后下降.10 mmol·L^-1NaNO₃显著抑制了淹水条件下根系MDA含量和NOS活性的提高,但NR活性增强;淹水期间,根系NO生成量在NaNO₃处理的前3天提高,处理第6天后显著降低.     

Formation of ethionine from homocysteine and of S-methylmethionine from methionine in apple tissue

Conversion of l-homocysteine into ethionine and of methionine into S-methylcysteine in apple tissues is demonstrated.     

Characterization of the MLO gene family in Rosaceae and gene expression analysis in Malus domestica

Background

Powdery mildew (PM) is a major fungal disease of thousands of plant species, including many cultivated Rosaceae. PM pathogenesis is associated with up-regulation of MLO genes during early stages of infection, causing down-regulation of plant defense pathways. Specific members of the MLO gene family act as PM-susceptibility genes, as their loss-of-function mutations grant durable and broad-spectrum resistance.

Results

We carried out a genome-wide characterization of the MLO gene family in apple, peach and strawberry, and we isolated apricot MLO homologs through a PCR-approach. Evolutionary relationships between MLO homologs were studied and syntenic blocks constructed. Homologs that are candidates for being PM susceptibility genes were inferred by phylogenetic relationships with functionally characterized MLO genes and, in apple, by monitoring their expression following inoculation with the PM causal pathogen Podosphaera leucotricha.

Conclusions

Genomic tools available for Rosaceae were exploited in order to characterize the MLO gene family. Candidate MLO susceptibility genes were identified. In follow-up studies it can be investigated whether silencing or a loss-of-function mutations in one or more of these candidate genes leads to PM resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-618) contains supplementary material, which is available to authorized users.     

Apple polygalacturonase inhibiting protein1 expressed in transgenic tobacco inhibits polygalacturonases from fungal pathogens of apple and the anthracnose pathogen of lupins

Extracts from apple fruit (cultivar "Granny Smith") inhibited the cell-wall degrading polygalacturonase (PG) activity of Colletotrichum lupini, the causal agent of anthracnose on lupins, as well as Aspergillus niger PG. Southern blot analysis indicated that this cultivar of apple has a small gene family of polygalacturonase inhibiting proteins (pgips), and therefore heterologous expression in transgenic tobacco was used to identify the specific gene product responsible for the inhibitory activity. A previously isolated pgip gene, termed Mdpgip1, was introduced into tobacco (Nicotiana tabacum) by Agrobacterium-mediated transformation. The mature MdPGIP1 protein was purified to apparent homogeneity from tobacco leaves by high salt extraction, clarification by DEAE-Sepharose and cation exchange HPLC. Purified MdPGIP1 inhibited PGs from C. lupini and PGs from two economically important pathogens of apple trees, Botryosphaeria obtusa and Diaporthe ambigua. It did not inhibit the A. niger PG, which was in contrast to the apple fruit extract used in this study. We conclude that there are at least two active PGIPs expressed in apple, which differ in their charge properties and ability to inhibit A. niger PG.     

变叶海棠及其伴生植物峨眉小檗的水分利用策略

变叶海棠(Malus toringoides)是分布在我国四川省甘孜州炉霍县亚高山地区的野生植物种,其嫩叶可制茶,为一种纯正的天然保健珍品。它根系发达、抗逆性强,也是川西亚高山干旱地区退化植被生态恢复的良好树种。运用氢稳定同位素示踪技术,比较分析了变叶海棠和伴生植物峨眉小檗(Berberis aemulans)茎水与其潜在水源(降水、土壤水和河水)的δD值,结果表明:变叶海棠与峨眉小檗植物水主要来源于降水和深层土壤水。生长在河边的变叶海棠并不利用河水。在干季,降水10-20 mm后,变叶海棠对降水的利用率为33.50%-70.06%,而峨眉小檗为26.17%-45.17%;在雨季,降水10-25 mm后,变叶海棠对降水的利用率为40.64%-69.01%,而峨眉小檗为28.44%-71.41%;无论干季还是雨季,两种植物在雨后对降水利用的格局相似,但变叶海棠对降水的利用率皆显著高于峨眉小檗(P<0.01)。两种植物水分利用策略与其根系分布相一致。为川西甘孜州亚高山干旱地区退化植被生态恢复的树种选择以及变叶海棠的扩繁与利用提供科学理论依据。     

棉隆对苹果连作土壤微生物及平邑甜茶幼苗生长的影响

以生产上常用苹果砧木——平邑甜茶为试材,盆栽条件下研究了棉隆微粒剂对苹果连作土壤微生物及平邑甜茶幼苗生长的影响。结果表明:与重茬(对照CK)相比,棉隆处理极显著(P0.01)降低了连作土壤中真菌数量,降幅达58.8%,细菌和放线菌数量分别显著(P0.05)降低15.3%、8.5%,细菌/真菌增加108.8%,放线菌/真菌增加124.2%;棉隆使连作条件下平邑甜茶单株幼苗根系长度、根表面积、根体积和根系活力分别提高421.4%、426.5%、171.7%、48.8%。平邑甜茶植株叶面积以及叶片中叶绿素a、b含量、净光合速率均极显著提高,分别增加162.6%、14.9%、15.0%、24.0%,叶片同化能力增强;植株长势增强,株高和地径均极显著提高,植株地上干鲜重和地下干鲜重也得到了极显著性增加,最高增加幅度达2.2倍。综上,棉隆处理后苹果连作土壤中微生物数量降低,而细菌与真菌比值、放线菌与真菌比值增加,平邑甜茶幼苗植株长势增强,棉隆可有效减轻苹果连作障碍发生。     

Morphological Variation in Xiphinema spp. from New York Orchards

Xiphinema specimens were collected from orchards in southeastern, northeastern, and western New York. Total length, distance of vulva from anterior end, spear length (odontostyle plus odontophore), body diameter at vulva, tail length, anal body diameter, and length and diameter of hyaline tail tip were measured on fixed, glycerol-infiltrated adult females. Most specimens were identified as X. americanum or X. rivesi, but one western New York population was identified as X. californicum (a new record for New York). Multivariate analyses indicated that, with one exception, western New York populations of both X. americanum and X. rivesi were smaller and slimmer than their eastern counterparts. Regional differences were generally larger than differences attributed to host species.     

Methionine metabolism in apple tissue in relation to ethylene biosynthesis

A comparison of the rate of ethylene production by apple fruit to the methionine content of the tissue suggests that the sulfur of methionine has to be recycled during its continuous synthesis of ethylene. The metabolism of the sulfur of methionine in apple tissue in relation to ethylene biosynthesis was investigated. The results showed that in the conversion of methionine to ethylene the CH₃S-group of methionine is first incorporated as a unit into S-methylcysteine. By demethylation, S-methylcysteine is metabolized to cysteine. Cysteine then donates its sulfur to form methionine, presumably through cystathionine and homocysteine. This view is consistent with the observation that cysteine, homoserine and homocysteine were all converted to methionine, in an order of efficiency from least to greatest. For the conversion to ethylene, methionine was the most efficient precursor, followed by homocysteine and homoserine. Based on these results, a methionine-sulfur cycle in relation to ethylene biosynthesis is presented.     

Effect of Three Plant Species on Population Densities of Xiphinema americanum and X. rivesi

A taxonomic revision of the Xiphinema americanum species complex has necessitated a reexamination of the host range of species in the complex before recommendations can be made with confidence on the likelihood that specific crops will be damaged. Toward this end, populations of X. americanum and X. rivesi collected from apple orchards in eastern and western New York state were evaluated after 3 months in pots planted with cucumber, apple, or dandelion seedlings. Eastern and western New York populations of both nematode species declined on cucumber but increased to similar final densities on apple and dandelion.     

Apple aminopropyl transferase, MdACL5 interacts with putative elongation factor 1-alpha and S-adenosylmethionine synthase [corrected

Several lines of evidence suggest different allocations of the physiological roles of aminopropyl transferase genes, SPMS and ACL5 in plants. To get deeper insights into the physiological role of apple ACL5 (MdACL5), we performed yeast two-hybrid (Y2H) assay to identify proteins which interact with MdACL5. After intense screening processes, including the swapping of the bait and prey vectors and in vitro coimmunoprecipitation, we identified three MdACL5-interacting proteins: putative translation elongation factor 1A (eEF-1A), putative S-adenosyl-l-methionine synthetase (SAMS) and an unknown protein. Results from Y2H and RNA gel blot analysis suggested the involvement of MdACL5 and eEF-1A or SAMS complexes in the plant growth and development of the organized tissues and/or organs.