2,4-表油菜素内酯对低温胁迫下辣椒幼苗根系生长及抗氧化酶系统的影响

为探讨外源2,4-表油菜素内酯(2,4-epibrassinolide,EBR)对低温胁迫下辣椒(Capsicum annuum L.)幼苗根系的生长和根系抗氧化系统的影响,本试验采用叶面喷施外源EBR(0、10.0、1.0、0.1、0.01、0.001 μmol·L-1)的方法,比较分析了低温胁迫下幼苗根系形态、根系抗氧化酶活性、过氧化物质含量等生理指标.结果表明,低温抑制了辣椒幼苗根系的生长,低温胁迫下喷施EBR,辣椒幼苗根系的生长受抑制程度减轻,其根系总长、根表面积、分根数较单纯低温处理显著增加;低温胁迫下喷施0.1μmol·L-1EBR辣椒幼苗根系SOD、POD、CAT活性显著提高,MDA含量降低.外源EBR处理可调节辣椒根系形态和提高根系抗氧化酶活性,增强植株抗低温胁迫的能力,并且EBR的浓度以0.1μmol·L-1最佳.说明在低温胁迫下适宜浓度的EBR可缓解辣椒幼苗的根系生长,这对阐明EBR缓解辣椒幼苗低温胁迫的作用机制提供了理论依据.     

渗透胁迫下Ca2+/CaM信使系统对小麦幼苗生理特性的调控效应

为探讨Ca2+/CaM信使系统对渗透胁迫下小麦幼苗生理特性的调控效应,以豫麦49-198为材料,研究了Ca2+通道阻断剂异博啶(VP)和CaM拮抗剂盐酸氯丙嗪(CPZ)对PEG胁迫下小麦幼苗相对含水量、丙二醛(MDA)、超氧阴离子(O2·-)、双氧水(H2O2)、可溶性糖、可溶性蛋白质、脯氨酸和谷胱甘肽(GSH)含量以及超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性的影响.结果表明,随着渗透胁迫时间延长,VP和CPZ处理提高了小麦幼苗MDA、O2·-和H2O2含量,降低了相对含水量、可溶性糖、脯氨酸、可溶性蛋白质和GSH含量,抑制了SOD、POD和CAT活性,而且VP和CPZ复合处理对小麦幼苗的伤害程度更大.试验表明,Ca2+/CaM信使系统可能通过提高渗透调节物质和抗氧化剂含量、增强抗氧化酶活性、降低膜质过氧化水平调节小麦幼苗对渗透胁迫的适应性.     

外源谷胱甘肽对自毒作用下嫁接黄瓜及砧穗幼苗叶片抗氧化系统的影响

为探索外源还原型谷胱甘肽(GSH)对自毒作用下嫁接黄瓜的保护作用及机理,本研究以200g·L-1连作嫁接黄瓜根际土壤浸提液灌根模拟自毒胁迫(CK2),分别以浓度为0、100、200 mg·L-1GSH对幼苗进行叶片喷施和灌根处理,在处理第4、第8、第12、第16天测定嫁接黄瓜、黄瓜、南瓜幼苗生物量、叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)和过氧化氢酶(CAT)活性以及GSH、抗坏血酸(As A)、丙二醛(MDA)含量。结果表明,自毒胁迫下,嫁接黄瓜、黄瓜和南瓜幼苗壮苗指数、叶片SOD、POD、APX、CAT活性降低,As A、GSH含量下降,MDA含量升高。表明连作嫁接黄瓜土壤浸提液能够对3种植物幼苗产生自毒作用。3种植物幼苗T1、T2、T3处理和嫁接黄瓜、南瓜幼苗T4处理的壮苗指数,叶片SOD、POD、APX、CAT活性和GSH、As A含量均显著增加,MDA含量均显著降低。黄瓜幼苗T4处理的壮苗指数,叶片SOD、POD、APX、CAT活性和GSH、As A含量呈下降趋势,MDA含量呈上升趋势。表明施加适宜浓度GSH可以提高抗氧化酶活性和抗氧化剂含量,减轻活性氧对膜脂造成的伤害,从而提高幼苗素质。综上,嫁接黄瓜和南瓜幼苗的T4处理,黄瓜幼苗的T2处理缓解自毒作用效果较为明显。本研究结果为防治嫁接黄瓜连作障碍提供了理论依据。     

表油菜素内酯对镉胁迫下番茄幼苗生长及镉累积的影响

采用盆栽试验研究不同浓度(0、0.02、0.1、0.5、2.5 mg/L)的表油菜素内酯(EBR)对镉胁迫下番茄幼苗生长及镉累积的影响。结果表明,镉处理后番茄幼苗的生物量、叶绿素含量、抗氧化酶(POD和CAT)活性均下降,丙二醛(MDA)含量、相对电导率和渗透调节物质含量均升高;喷施一定浓度的EBR(0.5 mg/L)后,番茄幼苗的生物量、叶绿素含量、抗氧化酶(POD和CAT)活性及脯氨酸含量均显著增加,可溶性蛋白、MDA含量和相对电导率有所下降,番茄幼苗根系和地上部分的镉含量分别上升了50.0%和93.4%,镉转运系数最低,为0.45。综上,喷施EBR能够增强番茄幼苗对镉胁迫的耐受性,促进幼苗生长,降低镉的转运系数,其中,EBR浓度为0.5 mg/L时效果最好。     

2,4-表油菜素内酯对NaCl胁迫下紫花苜蓿幼苗根系生长抑制及氧化损伤的缓解效应

为探讨外源2,4-表油菜素内酯(2,4-epibrassinolide,EBR)提高紫花苜蓿(Medicago sativa L.)耐盐性的生理调控机制,采用营养液水培法,以紫花苜蓿品种‘中苜3号’和‘陇中苜蓿’为材料,研究Na Cl胁迫下添加外源EBR对紫花苜蓿幼苗根系生长、渗透调节物质含量、抗氧化酶活性、非酶抗氧化物质、活性氧及MDA含量的影响。结果表明:150 mmol·L?1 Na Cl胁迫下,‘中苜3号’、‘陇中苜蓿’幼苗根系的生长显著受到抑制,根系干重和根系活力显著降低,幼苗根系中的可溶性蛋白含量和抗氧化酶活性显著降低,活性氧和MDA含量显著增加,根系脂质过氧化程度加剧,细胞质膜完整性受到破坏。添加0.1μmol·L?1外源EBR显著增加了2个品种苜蓿幼苗的主根长、根系总长度、根系总表面积、根体积、根尖数、根系干重和根系活力,幼苗根系中的可溶性蛋白含量、抗氧化酶(SOD、APX、GPX、CAT、GR)活性、非酶抗氧化物质(As A、GSH)含量均显著增加,超氧阴离子自由基(O2·?)产生速率、羟自由基(OH·)浓度、H2O2含量和膜脂过氧化产物MDA含量显著降低,有效缓解了根系脂质过氧化程度,提高了细胞质膜的完整性。说明外源EBR能够有效缓解Na Cl胁迫对紫花苜蓿幼苗根系生长的抑制作用,增强紫花苜蓿幼苗根系的渗透调节能力和抗氧化系统活性,降低活性氧的积累和膜脂过氧化水平,减小Na Cl胁迫对紫花苜蓿幼苗根系造成的氧化伤害,促进根系生长,增强苜蓿幼苗的抗盐性。     

外源硫化氢对PEG模拟干旱胁迫下玉米种子萌发及幼苗生长的影响

为明确干旱胁迫下外源硫化氢(H2S)对植物幼苗的缓解作用,以玉米自交系郑58为试验材料,研究了不同浓度(0、0.3、0.6、0.9、1.2及1.5 mmol·L-1)的H2S供体硫氢化钠(Na HS)对15%PEG模拟干旱胁迫下玉米种子萌发的影响,并以筛选到的最佳Na HS浓度对幼苗进行叶面喷施,研究其对幼苗叶片抗氧化酶活性、抗氧化剂含量、游离脯氨酸(Pro)和活性氧(ROS)的积累特征及膜质过氧化水平的影响。结果表明,不同浓度的Na HS处理在一定程度上提高了干旱胁迫下玉米种子的发芽势、发芽率及幼苗的生物量,其中以0.6 mmol·L-1的Na HS处理效果最佳。叶面喷施0.6 mmol·L-1Na HS溶液显著增强了叶片中超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)及抗坏血酸过氧化物酶(APX)活性,提高了叶片中抗坏血酸(As A)和谷胱甘肽(GSH)的含量。同时,外源H2S处理增强了玉米叶片中△1-吡咯啉-5-羧酸合成酶(P5CS)的活性,提高了叶片中游离Pro含量,显著降低了叶片中过氧化氢(H2O2)及丙二醛(MDA)含量。综上,外源H2S处理通过提高幼苗的抗氧化水平,减少干旱胁迫对玉米叶片造成的氧化损伤,在一定程度上提高了玉米幼苗对干旱胁迫的适应能力。本研究为进一步探索H2S缓解玉米干旱胁迫的机理提供了理论依据。     

24-表油菜素内酯对镉胁迫下大豆苗期生理特性的影响

为探讨外源EBR缓解大豆幼苗Cd毒害的机理,以大豆品种黑农48为试材,采用营养液水培法,以不同浓度(0.01、0.05、0.1、0.2、0.5mg·L-1)的24-表油菜素内酯(24-epibrassinolide,EBR)处理10mg·L-1Cd胁迫下的大豆幼苗,研究外源EBR对Cd胁迫下大豆幼苗株高及根系生长,过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)3种抗氧化酶活性,丙二醛(MDA)含量和叶绿素含量的影响。结果表明,Cd胁迫下,喷施0.01~0.1mg·L-1EBR对大豆各项生长指标的影响较单独Cd胁迫差异不显著;在0.2~0.5mg·L-1EBR范围内喷施0.5mg·L-1EBR明显提高大豆的株高、根长、地下鲜重、地下干重,较单独Cd胁迫分别提高了17.9%、9.5%、33.3%、38.1%。低浓度EBR(0.01mg·L-1和0.05mg·L-1)对3种抗氧化酶活性、叶绿素含量的提高作用及MDA含量的降低作用不显著;在0.1~0.5mg·L-1范围内喷施0.5mg·L-1EBR,Cd胁迫处理2d和8d后POD、CAT、APX活性及叶绿素含量较单独Cd处理升高42.6%和48.1%,20.2%和67.7%,97.3%和64.8%,29.7%和15.6%,MDA含量较单独Cd处理降低19.7%和27.8%。因此,0.1~0.5mg·L-1EBR是较适宜的喷施浓度,0.5mg·L-1EBR是最佳的喷施浓度。适宜浓度的外源EBR能促进Cd胁迫下大豆的生长,提高其抗氧化酶活性,减轻膜脂过氧化的程度和光合系统的损伤,有利于增强植株耐Cd胁迫能力。本研究为阐明EBR缓解Cd胁迫对大豆幼苗伤害的作用机理提供理论依据。     

高温干旱共胁迫下外源甜菜碱和CaCl2对烟草生理响应的影响

以烤烟品种云烟85为材料,采用盆栽试验研究了对高温干旱共胁迫的反应,以及外源甜菜碱（GB）和CaCl2对烟草抗高温干旱共胁迫方面的作用。结果表明,叶面喷施GB和CaCl2能显著提高烟草植株生物量。在高温干旱共胁迫下,叶面喷施GB较蒸馏水处理能极显著提高烟草叶片叶绿素含量、SOD和POD活性,维持较高的脯氨酸含量及较低的丙二醛（MDA）含量和质膜相对透性;叶面喷施CaCl2较蒸馏水处理能极显著提高烟草叶片叶绿素含量、SOD和POD活性,极显著降低质膜相对透性,显著降低丙二醛（MDA）含量,维持较高的脯氨酸含量。高温干旱共胁迫恢复生长后,GB、CaCl2和蒸馏水处理的烟草其叶绿素含量、SOD和POD活性均有不同程度回升,丙二醛含量、脯氨酸含量、细胞质膜透性都有所下降。因此,GB和CaCl2对有效减轻双逆境胁迫引起的伤害,提高烟草的抗高温干旱胁迫能力具有积极的作用。     

水杨酸对栝楼AsA-GSH循环系统及耐寒性的影响

以耐寒性较强的三门峡栝楼和耐寒性较弱的安庆栝楼为对比试验材料,分析低温(4℃)胁迫下喷施不同浓度(0,0.5,1,2 mmol/L)水杨酸对栝楼幼苗叶片的生长特性、抗氧化物质含量以及抗氧化酶活性的影响.结果表明:栝楼幼苗在低温胁迫下,对照组,2个栝楼品种幼苗的冷害指数、MDA含量、H2 O2含量、APX活性均明显增加;DHA、GSH、GSSG含量以及GR、MDHAR、DHAR活性呈升—降—升的趋势;AsA含量、GSH/GSSG、AsA/GSH比则在胁迫5d时呈相反的变化趋势,显示出2个栝楼品种的耐寒性差异;而喷施适宜浓度的SA能够降低植株的冷害指数、细胞内的MDA、H2 O2、DHA和GSSG含量,增加AsA、GSH含量和AsA/DHA、GSH/GSSG比,维持较高且相对协调平衡的APX、GR、MDHAR和DHAR活性.由隶属函数分析得出,适宜浓度的SA具有缓解栝楼低温胁迫的效果,但不能消除低温胁迫对栝楼生长的抑制作用.通过灰色关联分析可知,喷施SA对栝楼的AsA/GSH比影响很大.     

外源水杨酸(SA)对NaCl胁迫下棉花幼苗生理生化特性的影响

以棉花幼苗为试验材料,在液培条件下,研究叶面喷施0.1mmol/L SA对100mmol/L NaCl胁迫下棉花幼苗生理特性的影响。结果表明:每隔一天向叶面喷施0.1mmol/L SA较每天和每隔两天喷施更能显著缓解NaCl胁迫对棉花幼苗造成的伤害,可明显提高抗氧化酶的活性、可溶性蛋白含量和游离脯氨酸含量;降低叶片的超氧阴离子产生速率、H2O2含量以及丙二醛(MDA)含量。但是每天喷施导致过量SA对棉花幼苗盐胁迫的缓解作用显著降低甚至加剧盐伤害。因此,每隔一天喷施SA可以通过提高抗氧化酶活性等途径提高棉花幼苗的抗盐性,减轻和缓解NaCl胁迫对棉花幼苗的伤害。     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Einfluss der düngungsmethoden auf die entwicklung von zuckerrübenkrankheiten

Während neunjähriger (1994-2002) Untersuchungen in der Versuchsanstalt Ba?cyny (Fahlerde, Fall-Gleyboden, ausgebildet aus leichtem Lehmboden) wurde der Befall mit Krankheiten an der Zuckerrübe in Abhängigkeit von der Düngungsmethode bewertet. Folgende Methoden wurden angewendet: A - Mineraldünger, B - Stalldung und Mineraldünger, C - Stroh-, Gründung und Mineraldünger, D - Kompostdünger und Biopräparate (ökologische Düngung). Auf den Objekten A, B, C wurden bei konstanter Phosphor-Kalium-Düngung die Stickstoffgaben von 0 bis 180 kg.ha^?1 differenziert. Auf dem ökologischen Objekt D ohne Mineraldünger wurden statt Stickstoff die Biopräparate P₅₀₀ und P₅₀₁ verabreicht. Der geringste Befall von Krankheiten wurde an der Zuckerrübe auf jenem Objekt festgestellt, das mit Kompost und den Biopräparaten gedüngt worden war. Im Rahmen der konventionellen Düngungsmethoden wurde allgemein die höchste Intensität der Krankheiten an der mit Stroh, Gründung und Mineraldünger gedüngten Zuckerrübe beobachtet. Ausnahmen von dieser Regel bildete das Vorkommen von echtem Mehltau und Keimlingsfäule. Auf den Objekten A, B, C nahm die Intensität der Krankheiten mit der Steigerung der Stickstoffgabe zu. Auch die auf Objekt D verabreichten Biopräparate stimulierten die Entwicklung der Krankheiten. The effect of various fertilization methods on the diseases of sugar beet was estimated on the basis of nine-year studies (1994-2002) conducted in the Experimental Production Farm in Ba?cyny on loess-based, sedimentary-gley, light-clay soil. The following fertilization methods were applied: A - mineral fertilization, B - mineral and manure fertilization, C - straw, green manure and mineral fertilization, D - ecological compost and biodynamic preparations fertilization. In the objects A, B and C fertilized with phosphorus and potassium, various doses of nitrogen ranging from 0 to 180 kg/ha^?1 were used. In the ecological object D, where mineral fertilization was not used, biodynamic preparations P₅₀₀ and P₅₀₁ were applied instead of nitrogen. The lowest ratio of the diseases of sugar beet was observed in the object fertilized with the compost and biodynamic preparations. In view of the conventional fertilization methods, generally the highest incidence of diseases was noted in the sugar beet fertilized with straw, green manure and mineral fertilizers. The exception was the occurrence of powdery mildew and the black leg. In objects A, B and C the incidence of the diseases increased with the increase in nitrogen doses. The applied biodynamical preparations in the object D stimulated the development of diseases too.     

Prospects for control of Pythium damping-off of lettuce with Trichoderma,Gliocladium and Enterobacter spp.

Summary Damping-off of lettuce (Lactuca sativa) caused by Pythium ultimum was studied in pots containing a non-sterile potting mix in the glasshouse. Fifty P. ultimum sporangia g^-1 compost reduced the plant stand to 15% and shoot dry weight to 18%, but this reduction was totally prevented by applying Trichoderma harzianum at 2×10⁵ viable propagules g^-1 potting mix. Gliocladium virens and Enterobacter cloacae also alleviated the damping-off. E. cloacae did not adversely affect the action of the fungal antagonists. The co-existence of the bacterial and fungal antagonists was revealed on the root surface and inner surface of the testa by scanning electron microscopy, indicating the compatibility of the biocontrol agents.     

细菌、真菌及植物氮营养信号研究进展

氮素吸收代谢是所有生物生命活动的核心部分,因此,各种生物对氮的吸收与同化过程都有精细的调节。这种调节依赖于生物对体内氮素状况信号及体外（生长介质中）氮素信号的感受。过去几十年中,在细菌、真菌中已经对氮素营养信号有了较好的研究,而植物中则相对缓慢,但也有了一定的认识。本文重点比较细菌、真菌及植物中氮信号系统的组成,以期为进一步认识植物中的氮信号接受与转导系统提供启示。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。