种间互作的生态效应 Ⅱ.与蚕豆间作对作物生长的影响

在2种不同土壤条件下,测定3种间作系统(蚕豆/小麦、蚕豆/油菜和蚕豆/大蒜)和4种单作系统(蚕豆、小麦、油菜和大蒜)生物量、株高、荚数、经济产量的变化。结果表明,在胶泥土和砂壤土中与大蒜间作均能促进蚕豆生物量增加;而与小麦和油菜间作时,只有在砂壤土中才对蚕豆生长具有促进作用。在2种土壤条件下,3种作物均不同程度抑制蚕豆的株高,尤以大蒜抑制作用最强。在胶泥土中,大蒜促进蚕豆结荚作用最强,小麦促进蚕豆结荚作用最弱;大蒜对蚕豆经济产量促进作用最弱,小麦对蚕豆经济产量促进作用最强。在砂壤土中,大蒜对蚕豆生物和经济产量的促进作用均为最强。在2种土壤条件下,小麦间作蚕豆以后,小麦除生物产量稍有降低外,经济产量、株高和分蘖数均有少量提高;油菜间作蚕豆后,油菜经济产量和株高均得到提高;大蒜间作蚕豆后,蒜薹与蒜瓣产量下降,而株高增加。以上结果表明,在农田生态系统中,种间相互作用或强化作物间的竞争或强化物种间的化感效应,影响间作系统中不同植被类型的生长潜力。     

不同化感潜力水稻品种对低钾的生理与分子响应

选择国际公认的化感水稻品种“P1312777”和非化感水稻品种“Lemont”为材料,在K元素为5mg·L^-1（低K）和40mg·L^-1（正常K）2个水平的营养液中培养,通过水稻形态学指标（根长、株高、根冠比和生物量）、生理生化指标（SOD、POD、CAT、根系活力及植株中N、P、K含量）,评价不同化感潜力水稻品种对低K胁迫的生理响应,并采用实时荧光定量PCR（Realtime Fluorescent Quantitative PCR,FQ-PCR）,分析了低K胁迫下水稻根和叶中与N、P、K吸收利用相关的12个关键酶的基因表达差异。结果表明,低K促进了化感水稻“P1312777”根的生长,根冠比加大,生物量增加,但对株高的影响不显著;而该条件下非化感水稻“Lemont”的上述指标均受到不同程度的抑制。低K对两种水稻的保护酶系（SOD、POD、CAT）和根系活力均有一定程度的抑制作用,植株中N、P、K含量降低,但非化感水稻“Lemont”受抑制的程度远大于化感水稻“P1312777”。FQ-PCR检测结果表明,低K胁迫下两种水稻根、叶中的12个关键酶的基因均呈现上调表达,而化感水稻“P1312777”的基因表达上调倍数均明显大于非化感水稻“Lemont”。低K胁迫下两种水稻品种的形态学差异、生理与分子响应均表明,化感水稻“P1312777”比非化感水稻“Lemont”具有更强的适应K匮乏的能力。     

不同供氮水平下间甲酚对玉米的化感作用

通过发芽和管栽试验研究了不同供氮水平下,小麦根系分泌物间甲酚对玉米的化感作用。结果表明,间甲酚对玉米幼苗根系产生的化感作用较弱,对地上组织的化感作用较强,其中苗高受间甲酚的影响最明显。氮素与间甲酚对玉米生物产量和根重均存在显著的互作作用,施氮量与间甲酚对成熟期玉米生物产量产生的化感作用呈显著负相关,施N量为300mg·kg^-1（土）时,浓度为300×10^-6mol·kg^-1（土）的间甲酚对玉米生物产量表现为化感抑制作用,但施N量为150mg·kg^-1（土）时,相同浓度的间甲酚对玉米生物产量表现为促进作用。间甲酚可增大玉米的根重,施氮可显著提高间甲酚增加根重的作用。农田生态系统中,当存在化感物质时,选择适宜的施肥水平十分重要。     

化感小麦种质资源的筛选与评价

以国内外90份不同小麦为材料,采用土壤-琼脂三明治法和田间杂草调查法,对不同小麦种质资源进行化感潜力评价,筛选出具有较强化感潜力的小麦品种。土壤-琼脂三明治法测试结果表明,不同小麦品种的化感潜力存在明显差异,对莴苣根长抑制率IR在10．1％和69．1％之间;筛选出“115／青海麦”、“92L89”、“百泉3199”、“81-214”和“92H31”5个强化感潜力的小麦品种,其对莴苣根长抑制率依次为69．1％、68．5％、68．7％、69．1％和65．2％,筛选出“抗10103（80）”和“A246”2个弱化感潜力的小麦品种,抑制率IR依次为10．1％和12．2％;田间杂草调查评价和土壤-琼脂三明治法表现出相似趋势,检测结果也得到了琼脂迟播共培法的佐证,表明采用土壤-琼脂三明治法筛选化感小麦种质资源是可行的。这为小麦化感作用研究提供了重要的种质资源,也为化感小麦种质资源的筛选提供方法借鉴。     

黄连须根浸提液对无机磷细菌的负化感效应

黄连(Coptis chinensis)是我国人工栽培的传统大宗中药材,种植面积大,连作障碍严重,了解黄连对土壤微生物的化感效应,有益于揭示黄连连作障碍的发生机理,为减轻连作障碍提供科学依据。试验利用固、液培养技术,以3株能溶解无机磷的伯克霍尔德氏菌(Burkholderia Yabunchi B05、B07和B09)为材料,研究了黄连须根浸提液(Extracts of fibrous roots of Coptis chinensis,ERC)对其生长繁殖和溶磷的化感作用。结果表明,在固体培养时,随ERC浓度提高,无机磷细菌(Inorganic phosphorus-dissolving bacteria,i PDB)的菌落直径、溶磷圈直径和溶磷指数降低。在液体培养基中,ERC不同程度地抑制i PDB繁殖生长,数量减少35.98%~52.98%。供试菌株均能分泌氢离子、草酸和柠檬酸,B05和B09还能分别分泌乙酸和苹果酸,B07能分泌乙酸和丁二酸,三株i PDB溶磷量平均值(mg L~(-1))分别为228.31(B05)、311.64(B07)和174.89(B09)。有机酸和氢离子分泌总量分别与溶磷量呈显著正相关,相关系数依次为0.877和0.604(p≤0.05,n=12)。在ERC抑制iPDB分泌有机酸和氢离子的同时,溶磷量降低21.68%~60.55%。因此,在集约化种植黄连的土壤中,其根系分泌的化感物质可能影响iPDB的种群结构和生理生态功能,降低土壤无机磷的生物有效性,可视为发生连作障碍的潜在原因之一。     

Biodiversity of endophytic bacteria which colonize red clover nodules, roots, stems and foliage and their influence on host growth

The aim of this study was to identifiy the endophytic bacteria recovered from the foliage, tap roots and nodules of red clover plants (Trifolium pratense L.); and to assess the effects of the nodule bacteria, alone and in combination with Rhizobium spp., on the growth and development of red clover seedlings. Thirty-one bacteria species from 14 different genera were recovered from within the foliage, roots and nodules of red clover plants cv. AC Charlie. Genera diversity and species number were greatest in foliage tissues. Pantoea agglomerans (59.6%) was the most frequent species recovered in foliage tissues, Agrobacterium rhizogenes A in the tap root (49.2%) and Rhizobium leguminosarum BV phaseoli and R. loti B in the nodules (27.2% each). Recovery of Rhizobium species was not restricted to the nodules, and species of this genus were systemic throughout the plant. Clover root nodules were host to 12 bacteria species other than rhizobia, of which 8 were specific to this tissue. Using non-selective media, R. leguminosarum BV trifolii constituted only 8.8% of all the root nodule bacteria recovered. In root bacterization experiments, species of nodule bacteria promoted growth of red clover more often when applied in combination with R. leguminosarum BV trifolii than when applied singly. However, Bacillus megaterium, Bordetella avium and Curtobacterium luteum consistently promoted growth either individually or in combination with R. leguminosarum BV trifolii. Nodulation was promoted when R. leguminosarum BV trifolii was coinoculated with Bacillus insolitus, B. brevis or A. rhizogenes A. Single isolate applications of Rhizobium species to roots always led to the depression of clover growth, but mixtures of R. leguminosarum BV trifolii and R. leguminosarum BV phaseoli resulted in growth promotion. The latter is considered further evidence of the beneficial allelopathic side effect of strain competition for the same ecological niche. Received: 27 June 1996     

化感作用研究中渗透势对生物测定结果的影响

在不同渗透势的甘露醇溶液培养条件下研究了厚壳桂等对萝卜、黄瓜和白菜化感作用的影响试验结果表明,随渗透势的升高,萝卜幼苗根长和苗高逐渐降低,黄瓜幼苗受抑更明显,而白菜影响极小,未达显著水平。对厚壳桂、锥木和藜蒴的生化他感作用研究中分别以蒸馏水和相同渗透势的甘露醇溶液为对照,其结果化感作用程度普遍降低,有些还发生赁变(化感作用在显著与不显著间转换),故化感生物测定分析中应注意渗透势的影响,以保证结果正确性。     

Crude extract of Astragalus mongholicus root inhibits crop seed germination and soil nitrifying activity

Astragalus mongholicus has been of medicinal use within the traditional Chinese system for centuries. However, little information is available on its allelopathic effects on other crop plants and soil biochemical properties. Field experiment showed that the extracted residues of A. mongholicus root inhibited seed germination of wheat. Inhibition of seed germination was further confirmed in laboratory using the same crude extract. When the crude extract was applied to soil at various rates and incubated for 30 days, soil urease activity and denitrifying enzyme activity were significantly increased while soil nitrification rate was significantly decreased at 10% amendment rate as compared to the control. Soil respiration rate was significantly increased by the crude extract when measured at the start of incubation but returned to basal levels after 30 days of incubation. The crude extract supplemented to NB medium significantly decreased the colony numbers of Agrobacterium tumefaciens C58, Paraccocus denitrificans and soil bacteria. The stimulating effects of crude extract observed in the amended soil was attributed to the easily-available carbohydrates in the extract, which might served as external energy sources for heterotrophic microbial activities. It was concluded that A. mongholicus contained some compounds that inhibited seed germination, soil nitrification and bacterial growth in general. Possible links between allelochemicals responsible for the inhibitory effects observed in the present study and the medically bioactive compounds are discussed based on information reported in other fields. Further work is needed to specify and verify the allelochemicals produced by this herbal plant.     

番茄种质资源的化感作用

以莴苣为受体材料,研究了番茄不同品种间化感作用的差异,结果表明:番茄不同品种间化感作用的差异较为明显,并通过综合隶属函数值评价了品种间的化感作用大小,得出00-10-1B品种的化感作用最大,98-3C-32品种的化感作用最小,最后对不同番茄品种进行Q型聚类分析,其分析的结果与综合隶属函数值得出的结果一致。     

乌头酸对尖孢镰刀菌百合专化型抑制作用分析

乌头酸是兰州百合一种重要的根系分泌物,为探究乌头酸对尖孢镰刀菌（Fusarium oxysporum）百合专化型的作用效果,测定外源乌头酸对F.oxysporum生长及抗氧化酶活性基因表达量的影响。结果表明,浓度为1.175~1 175 mg·L^-1时,乌头酸对F.oxysporum的生长具有抑制作用,且随着浓度增加,抑菌作用显著。浓度为1 175 mg·L^-1时,与CK相比,乌头酸对F.oxysporum抑菌率、产孢量抑制率和孢子萌发抑制率分别达到91.95%、77%、93%。乌头酸处理引起菌丝体电导率增大,随着浓度和时间的增加,SOD、POD活性呈现先增加后降低的趋势。SOD酶合成基因在转录水平上于11.75~1 175 mg·L^-1处理下调表达, 1.175 mg·L^-1处理时SOD酶合成基因出现上调,与CK差异不显著。POD酶合成基因在转录水平上所有处理均下调表达。可见,乌头酸可以作为化感抑制剂应用于植物土传病害的防治。