不同磷水平下小麦-蚕豆间作根系形态的变化及其与内源激素的关系

采用水培方法,研究了不同磷水平下小麦-蚕豆间作体系根系形态变化及其与内源激素的相关关系。结果表明: 与单作小麦相比,在低磷(1/2P)水平下,小麦-蚕豆间作能显著增加小麦的根长,显著减少小麦根系的平均直径,显著增加根系的表面积;在常规磷(P)水平下,间作能显著降低小麦根系的平均直径,有增加小麦根长和根表面积的趋势;与单作蚕豆相比,间作能明显促进蚕豆根系的增长,同时增加蚕豆根表面积。在1/2P水平下,间作能显著提高小麦和蚕豆根系中的生长素(IAA)、脱落酸(ABA)、水杨酸(SA)和茉莉酸(JA)含量;在P水平下,间作能显著提高小麦根系中的IAA、ABA和JA含量,单、间作小麦根系中的SA含量没有显著差异,间作显著增加了蚕豆根系中ABA和SA含量,单、间作蚕豆根系中的IAA和JA含量无显著差异。单作条件下,小麦和蚕豆根系中的内源激素(IAA、ABA、SA和JA)含量与其根系形态(根长、根平均直径和根表面积)无显著相关性;间作条件下,小麦和蚕豆根系中的IAA含量与根长和根表面积之间存在明显的正相关关系。由此可见,小麦-蚕豆间作能够诱导小麦和蚕豆根系IAA的增加。这种变化可能是驱动间作系统根系形态变化的重要因子。     

小麦-蚕豆间作对根系分泌低分子量有机酸的影响

通过盆栽试验收集了不同生育期单作和间作小麦、蚕豆的根系分泌物,用HPLC分析了根系分泌物中低分子量有机酸的含量和种类.结果表明: 小麦-蚕豆间作显著提高了有机酸的分泌量,在小麦分蘖期(57 d)、孕穗期(120 d)和灌浆期(142 d),间作使小麦根系有机酸分泌量分别提高155%、35.6%和92.6%;在蚕豆分枝期(57 d)和籽粒膨大期(142 d),间作使蚕豆根系有机酸分泌量提高87.4%和38.7%.小麦-蚕豆间作改变了根系分泌物中有机酸的种类,与单作小麦相比,在分蘖期,间作小麦根系分泌物中增加了乳酸;在拔节期(98 d),间作小麦根系分泌物中增加了柠檬酸,但未检测到乙酸;在蚕豆分枝期,间作蚕豆根系分泌物中增加了乙酸,但未检测到乳酸;在蚕豆籽粒膨大期,间作蚕豆根系分泌物中增加了乳酸.小麦-蚕豆间作提高了小麦根系有机酸的分泌速率,在小麦孕穗期,间作小麦分泌柠檬酸、富马酸的速率是单作小麦的179和184倍;在小麦灌浆期,间作小麦分泌乳酸的速率是单作的2.53倍.总之,小麦-蚕豆间作增加了有机酸的分泌量,改变了根系分泌物中有机酸的种类,提高了小麦根系有机酸的分泌速率.     

小麦蚕豆间作对蚕豆根际微生物群落功能多样性的影响及其与蚕豆枯萎病发生的关系

通过田间小区试验,研究了小麦与蚕豆间作对蚕豆枯萎病发生和根际微生物代谢功能多样性的影响。结果表明,小麦与蚕豆间作使蚕豆枯萎病的发病率和病情指数分别比单作显著降低20%和30.4%。与单作处理相比,间作显著增加了蚕豆和小麦根际微生物对31种碳源的平均利用率（AWCD）,其中间作蚕豆的AWCD值最高,比单作增加82.7%,单作蚕豆最低。间作蚕豆和间作小麦根际微生物的Shannon多样性指数与丰富度指数均显著高于单作,间作使蚕豆和小麦的丰富度指数分别增加29.2%和30.3%。根际微生物对六类碳源的利用强度百分比以糖类、羧酸类和氨基酸最高,分别为41.96%,19.80%和18.13%。主成分分析表明,小麦与蚕豆间作改变了根际微生物的群落组成;相关分析表明,糖类、羧酸类和氨基酸类碳源是区分单间作处理差异的主要碳源,其中氨基酸类碳源是最敏感的碳源。小麦与蚕豆间作增加了根际微生物活性,提高了Shannon多样性指数和丰富度指数,改变了微生物群落功能多样性,是抑制蚕豆枯萎病的有效措施。该研究为阐明根际微生物功能多样性变化在间作体系病害控制中的作用与机制奠定了理论基础。     

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.     

玉米、小麦和大麦与蚕豆间作体系不同根系分隔方式对蚕豆结瘤的影响

本实验选取3种对土壤氮素竞争能力不同的禾本科作物大麦(Hordeum vulgare)、小麦(Triticum aestivum)和玉米(Zea mays)分别与蚕豆(Vicia faba)间作, 建立对土壤氮素竞争能力不同的作物组合; 并采用3种分隔方式(塑料膜分隔、尼龙网分隔和无分隔)建立同一作物组合条件下作物种间根系相互作用的不同强度, 来研究不同作物组合及种间根系相互作用强度对蚕豆结瘤的影响。结果如下: (1)蚕豆的结瘤并未随3种禾本科作物氮素竞争能力的增强而增加, 但是3种间作体系蚕豆的结瘤却均表现出无分隔处理多于塑料膜分隔处理, 即同一间作体系种间根系相互作用越强, 越有利于蚕豆结瘤的产生, 存在种间互利作用; (2)在玉米/蚕豆间作体系中, 无分隔处理的蚕豆根瘤数目和根瘤重显著高于塑料膜分隔处理, 分别高出67.5%和70.1%; 在大麦/蚕豆间作体系中也表现出无分隔处理的根瘤重显著高于塑料膜分隔处理(高出46.3%); (3)玉米/蚕豆间作体系与小麦/蚕豆和大麦/蚕豆间作体系相比, 无分隔处理时土壤氮素含量显著高于后2个间作体系, 但是玉米/蚕豆间作体系对蚕豆结瘤的促进作用更强。上述结果表明, 在蚕豆/玉米间作体系中, 玉米促进蚕豆生物固氮除了氮素竞争机制外, 还可能存在其它机制。     

Wheat and faba bean intercropping changes phenolic acids from roots to rhizosphere

The changed phenolic acids (PAs) allelochemicals exuded by the roots induced by interspecific interactions is related to intercropping alleviates soil-borne disease. However, the presence of PAs in roots and root exudations and their rhizodeposition under intercropping are still unclear. Hydroponic and soil experiments of wheat, faba bean, and wheat intercropped with faba bean were conducted, and the major compositions and contents of PAs in roots, root exudations, and rhizospheric soil were determined. The results showed that ρ-hydroxybenzoic, vanillic, and syringic acids were the major components of PAs in roots, root exudations, and rhizospheric soil in a wheat and faba bean intercropping system. The compositions and percentages of PAs in roots of faba bean were altered when faba bean intercropped with wheat. The total exudation rate of PAs in root exudations was decreased by 30%–60% under the wheat and faba bean intercropping (W//F) system as compared to mono-cropped faba bean (MF). ρ-hydroxybenzoic acid was identified in the root exudation of both MF and mono-cropped wheat (MW), but not detected in the intercropping on 60 days after transplanting. Vanillic acid was only detected in the root exudation of MF on 30 days after transplanting. The rhizodepostion of vanillic and cumaric acid were decreased at both branching and pod setting stages in W//F as compared to MF. In conclusion, interspecific interaction changed the compositions and contents of PAs in faba bean roots and root exudations. W//F constrained vanillic acid exuded by roots and decreased vanillic and coumaric acid rhizodeposition by faba bean, which provides insight into root-soil interactions in the intercropping systems.     

小麦与蚕豆间作体系根系形态与磷吸收的定量解析

豆科与禾本科作物间作能够改变作物根系生长,但不同施磷水平下间作-根系形态-磷吸收之间的关系尚未明确.本研究通过田间定位试验和根箱模拟试验,研究不同种植模式(小麦单作、蚕豆单作和小麦-蚕豆间作)和不同磷水平下小麦和蚕豆的产量、生物量、磷吸收及根系形态特征,分析探讨不同施磷条件下小麦-蚕豆间作对根系形态和磷吸收的影响.结果...     

小麦/蚕豆间作作物生长曲线的模拟及种间互作分析

物种间的相互作用与间作产量优势的形成密切相关,但很少有人注意到种间互作动态.本研究通过2年田间定位试验,运用Logistic分析模拟了不同种植模式(小麦单作、蚕豆单作和小麦/蚕豆间作)和不同磷水平下[P₀,施磷量(P₂O₅)为0 kg·hm^-2(对照);P₁,施磷量(P₂O₅)为45 kg·hm^-2;P₂,施磷量(P₂O₅)为90 kg·hm^-2]单间作小麦、蚕豆的生长模型,分析了作物种间互作的动态变化.结果表明: 小麦/蚕豆间作使小麦产量提高了10.5%~18.6%,蚕豆产量却降低了4.8%~12.3%,但间作系统仍具有产量优势,土地当量比(LER)和相对拥挤系数(K)分别为1.01~1.15 和1.12~3.20.小麦和蚕豆的产量及关键生长参数均受磷水平调控,但LER和K并不受磷水平影响.与单作相比,间作小麦的最大生长速率(R_max)和最初生长速率(r)分别提高21.8%~38.7%和20.7%~38.9%,但间作对蚕豆的关键生长参数无影响.在小麦、蚕豆的生长初期,不同磷水平下,单间作作物的生长曲线无差异;间作群体以种间竞争为主,无间作生物量优势(LER<1,K<1).当蚕豆达到最大生长速率(T_max)后,间作显著提高了小麦的生长速率,降低了小麦的种内竞争压力,表现出间作生物量和产量优势(LER>1,K>1).总之,在不同的生长发育阶段,小麦、蚕豆的相互作用不同,间作提高了中后期小麦的生长速率,为间作优势的形成奠定了基础.     

Crop nitrogen use and soil mineral nitrogen accumulation under different crop combinations and patterns of strip intercropping in northwest China

Increasing crop nitrogen use efficiency while also simultaneously decreasing nitrogen accumulation in the soil would be key steps in controlling nitrogen pollution from agricultural systems. Long-term field experiments were started in 2003 to study the effects of intercropping on crop N use and soil mineral N accumulation in wheat (Triticum aestivum L. cv 2014)/maize (Zea mays L. cv Shendan16), wheat/faba bean (Vicia faba L. cv Lincan No. 5) and maize/faba bean intercropping and monocropping systems. Monocropping was compared with two types of strip intercropping: continuous intercropping (two crops intercropped continuously on the same strips of land every year) and rotational intercropping (two crops grown adjacently and rotated to the other crop??s strip every year). Maize/faba bean intercropping had greater crop N uptake than did wheat/faba bean or wheat/maize. Wheat/maize accumulated more mineral N in the top 140 cm of the soil profile during the co-growth stage from maize emergence to maturity of wheat or faba bean. Continuously intercropped maize substantially decreased soil mineral N accumulation under wheat and faba bean rows (60?C100 cm soil depth) at maize harvest. Soil mineral N accumulation under wheat rows increased with rotational intercropping with faba bean. Rotational intercropping may potentially alleviate the adverse effects of wheat on N use by other crops and increase the nitrogen harvest index of wheat, maize and faba bean. Intercropping using species with different maturity dates may be more effective in increasing crop N use efficiency and decreasing soil mineral N accumulation.     

施氮对间作蚕豆根际微生物区系和枯萎病发生的影响

通过田间小区试验,研究了小麦、蚕豆间作条件下4个施氮水平(0,56.25,112.5kg.hm-2和168.75kg.hm-2)对蚕豆根际微生物区系和蚕豆枯萎病发生的影响。结果表明,单作和间作条件下,施氮显著增加了蚕豆根际的微生物数量,在N2(112.5kg.hm-2)水平下达到最高值;施氮对土壤微生物多样性无显著影响,但减轻了单、间作蚕豆枯萎病的发生,且在N2水平下发病最轻。与单作相比,间作显著增加了蚕豆根际的细菌、真菌、放线菌数量、微生物总数和微生物多样性,尤其在N0、N1(56.25kg.hm-2)和N2(112.5kg.hm-2)水平下间作对蚕豆根际微生物的促进效应明显,且以真菌和放线菌的增幅较大.N0、N1和N2水平下间作显著降低了蚕豆枯萎病的发病率和病情指数。小麦蚕豆间作下适量施氮能有效调节蚕豆根际微生物区系,是抑制蚕豆枯萎病发生的有效措施。     

供肥对小麦间作蚕豆群体产量及根系的调控

利用田间,池栽,盆栽等方法,对不同N,P水平下小麦间作蚕豆群体根系的时空分布及产量效应进行了研究。结果表明,供P对小麦-蚕豆间作系统有明显的增产作用,与不供P相比,田间试验中供P处理间作小麦和蚕豆分别提高了48.39%和16.69%,池栽试验中群体产量增产幅度为20.07%-43.14%。间作蚕豆经济产量增幅为58.46%-78.78%,小麦间作蚕豆多作系统2种作物根密度生长高峰期交错出现,小麦的峰值出现早于蚕豆,其中,小麦和蚕豆根干重最大值分别出现在抽穗期和成熟期,而根长的最大值分别出现在拔节期和成熟期,这在一定程度上减轻了共生期2种作物对水肥的竞争,也是此群体增产增效的原因之一,施P处理间作小麦的根重,根长和根表面积分别比不施P处理提高54.33%,48.88%和47.00%;施N处理间作小麦的根重,根长和根表面积分别比不施N的增加15.25%,11.61%和11.46%。间作小麦根重的57.61%和蚕豆的69.20%分布在0-30cm土层,随施P水平的提高,总根干重及根密度都趋于增加,且深层土壤中根系增加明显。     

The role of maize root size in phosphorus uptake and productivity of maize/faba bean and maize/wheat intercropping systems

Interspecific root/rhizosphere interactions affect phosphorus (P) uptake and the productivity of maize/faba bean and maize/wheat intercropping systems. The aim of these experiments was to determine whether manipulation of maize root growth could improve the productivity of the two intercropping systems. Two near isogenic maize hybrids (the larger-rooted T149 and smaller-rooted T222) were intercropped with faba bean and wheat, under conditions of high- and low-P availability. The larger-rooted T149 showed greater competitive ability than the smaller-rooted T222 in both maize/faba bean and maize/wheat intercropping systems. The higher competitive ability of T149 improved the productivity of the maize/faba bean intercropping system in P-sufficient conditions. In maize/wheat intercropping systems, root growth, shoot biomass, and P uptake of maize were inhibited by wheat, regardless of the P-supply. Compared with T222, the larger-rooted T149 suffered less in the intercropping systems. The total biomass of the maize/wheat intercropping system was higher for wheat/T149 than for wheat/T222 under low-P conditions. These data suggested that genetic improvement of maize root size could enhance maize growth and its ability to compete for P resources in maize/faba bean and maize/wheat intercropping systems. In addition, depending on the P availability, larger maize roots could increase the productivity of intercropping systems.     

Nitrogen Fixation of Faba Bean (Vicia faba L.) Interacting with a Non-legume in Two Contrasting Intercropping Systems

A field experiment was carried out to quantify biological nitrogen fixation (BNF) using the ¹⁵N isotope natural abundance method in maize (Zea mays L.)/faba bean (Vicia faba L.) and wheat (Triticum aestivum L.)/faba bean intercropping systems. Faba bean was yielding more in the maize/faba bean intercropping, but not in the wheat/faba bean intercropping. Biomass, grain yield and N acquisition of faba bean were significantly increased when intercropped with maize, and decreased significantly with wheat, irrespective of N-fertilizer application, indicating that the legume could gain or lose productivity in an intercropping situation. There was yield advantage of maize/faba bean intercropping, but no in wheat/faba bean intercropping. The grain yield of the faba bean intercropped with maize was greater than that of faba bean monoculture due to increases of the stems per plant and the pods per stem of faba bean. N fertilization inhibited N fixation of faba bean in maize/faba bean and wheat/faba bean intercropping and faba bean monoculture. The responses of different cropping systems to N-fertilizer application, however, were not identical, with competitive intercropping (wheat/faba bean) being more sensitive than facilitative intercropping (maize/faba bean). Intercropping increased the percentage of N derived from air (%Ndfa) of the wheat/faba bean system, but not that of the maize/faba bean system when no N fertilizer was applied. When receiving 120 kg N/ha, however, intercropping did not significantly increase %Ndfa either in the wheat/faba bean system or in the maize/faba bean system in comparison with faba bean in monoculture. The amount of shoot N derived from air (Ndfa), however, increased significantly when intercropped with maize, irrespective of N-fertilizer application. Ndfa decreased when intercropped with wheat, albeit not significantly at 120 kg N/ha. Ndfa was correlated more closely with dry matter yield, grain yield and competitive ratio, than with %Ndfa. This indicates that that total dry matter yield (sink strength), not %Ndfa, was more critical for the legume to increase Ndfa. The results suggested that N fixation could be improved by yield maximization in an intercropping system.     

间作缓解蚕豆连作障碍的根际微生态效应

通过田间小区试验,研究了3个品种蚕豆(92-24、云豆324、凤豆6号)与小麦间作对蚕豆产量、枯萎病病情指数、根际镰刀菌数量、根际真菌代谢功能多样性和土壤酶活性的影响。结果表明:与单作蚕豆相比,云豆324与小麦间作(YD324/W)和凤豆6号与小麦间作(FD6/W)处理均显著提高了蚕豆地上部干重、籽粒产量和百粒重。YD324/W和FD6/W处理使蚕豆枯萎病发病初期病情指数分别降低57.14%和41.67%,镰刀菌数量分别降低32.06%和29.88%,而92-24与小麦间作(92-24/W)处理蚕豆产量、枯萎病病情指数和镰刀菌数量与单作蚕豆均无显著差异。YD324/W和FD6/W处理显著提高了蚕豆根际真菌的多样性指数和丰富度指数,并使蚕豆根际真菌的AWCD值分别比单作蚕豆提高了61.75%和46.49%;YD324/W和FD6/W处理明显改变了蚕豆根际真菌的群落结构。而92-24/W处理对蚕豆根际真菌的多样性指数、丰富度指数和AWCD值均无显著影响,也未明显改变真菌的群落结构。不同发病时期,YD324/W和FD6/W处理均显著提高了蚕豆根际土壤的蔗糖酶、脲酶和过氧化氢酶活性;而92-24/W处理蚕豆根际蔗糖酶、脲酶和过氧化氢酶活性与单作蚕豆均无显著差异。总之,小麦与不同品种蚕豆间作改变了蚕豆根际的真菌群落结构,提高了蚕豆根际真菌的活性、多样性和丰富度,提高土壤酶活性并改善蚕豆生长,增加了蚕豆产量。表明小麦与蚕豆间作改善了根际土壤的微生态环境,降低了镰刀菌的数量,缓解了蚕豆连作障碍,但蚕豆品种的差异影响间作控病效果。     

小麦-蚕豆间作条件下氮肥施用量对根际微生物区系的影响

通过田间小区试验,研究了小麦/蚕豆间作条件下4种施氮水平(0、90、180和270 kg·hm^-2)对根际微生物区系和多样性的影响.结果表明：在整个生育期,微生物数量有一定的波动,但均以开花期数量最高.与单作相比,间作显著增加了小麦和蚕豆根际的细菌、真菌、放线菌数量和微生物总量,而显著降低了开花期和成熟期蚕豆根际的微生物多样性.在不施氮（N₀）和低氮（N₉₀）水平下,间作与单作在微生物数量上的差异较大.间作对土壤微生物数量的促进效应在分蘖期和开花期最大,成熟期显著降低.小麦根际的微生物数量随施氮量的增加先增加后降低,以常规施氮处理（N₁₈₀）的微生物数量最多,氮肥用量对单作小麦的影响大于间作小麦. 施氮量对蚕豆根际细菌、真菌、放线菌数量和微生物多样性无显著影响,但降低了间作蚕豆根际微生物总量.适量施用氮肥能有效调节根际微生物区系,间作系统地上部植物多样性与地下部微生物区系间存在紧密联系.     

Root distribution and interactions between intercropped species

Even though ecologists and agronomists have considered the spatial root distribution of plants to be important for interspecific interactions in natural and agricultural ecosystems, few experimental studies have quantified patterns of root distribution dynamics and their impacts on interspecific interactions. A field experiment was conducted to investigate the relationship between root distribution and interspecific interactions between intercropped plants. Roots were sampled twice by auger and twice by the monolith method in wheat (Triticum aestivum L.)/maize (Zea mays L.) and faba bean (Vicia faba L.)/maize intercropping and in sole wheat, maize, and faba bean up to 100 cm depth in the soil profile. The results showed that the roots of intercropped wheat spread under maize plants, and had much greater root length density (RLD) at all soil depths than sole wheat. The roots of maize intercropped with wheat were limited laterally, but had a greater RLD than sole-cropped maize. The RLD of maize intercropped with faba bean at different soil depths was influenced by intercropping to a smaller extent compared to maize intercropped with wheat. Faba bean had a relatively shallow root distribution, and the roots of intercropped maize spread underneath them. The results support the hypotheses that the overyielding of species showing benefit in the asymmetric interspecific facilitation results from greater lateral deployment of roots and increased RLD, and that compatibility of the spatial root distribution of intercropped species contributes to symmetric interspecific facilitation in the faba bean/maize intercropping. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Dynamics of phosphorus fractions in the rhizosphere of common bean (Phaseolus vulgaris L.) and durum wheat (Triticum turgidum durum L.) grown in monocropping and intercropping systems

The main objective of the present study was to investigate phosphorus (P) dynamics in the rhizosphere of durum wheat (Triticum turgidum durum L.) and common bean (Phaseolus vulgaris L.) grown in monocropping and intercropping systems with nitrate supply. Wheat and common bean were grown either alone or in association in a cropping device with a thin (1 mm) soil layer sandwiched between large root mats. Wheat intercropped with common bean exhibited a 33% increase in shoot biomass and a 22% increased root biomass, without significantly affecting common bean growth. After 12 days of culture, rhizosphere pH decreased by 1.66 and 1.13 units in monocropping system of common bean and intercropping system, respectively. Wheat increased intercropped common bean proton release by 36% compared with monocropped beans. Common bean and wheat exhibited different behaviors in rhizosphere P dynamics. Monocropped wheat decreased Resin-P, NaHCO₃-P and NaOH-P in its rhizosphere by 24, 96 and 10%, respectively. However, NaHCO₃-P and NaOH-P were increased by 61 and 10% in the rhizosphere of intercropping. Almost all values about P fraction in intercropping system were between those in monocropped common bean and monocropped wheat. Through taping different P fraction, different plants species possibly can alleviate competition for phosphorus in intercropping system.     

小麦/蚕豆，玉米/蚕豆和小麦/玉米间作对根际细菌群落结构的影响

利用PCR-DGGE技术研究了小麦/蚕豆、玉米/蚕豆和小麦/玉米间作对作物根际细菌群落结构的影响.结果表明：间作能够提高作物根际细菌群落多样性、改变根际细菌群落结构组成.其中,小麦/蚕豆间作对根际细菌群落结构的影响最为突出,作物花期时小麦/蚕豆间作显著提高和改变两种作物根际细菌多样性和群落结构组成.玉米/蚕豆间作主要表现出对苗期玉米根际细菌多样性的显著提高和群落结构组成的改变.小麦/玉米间作对作物根际细菌群落结构的影响程度较弱.同时,3种间作体系都具有不同程度的产量优势.结果证明了间作体系中地上部植物多样性与地下部微生物多样性存在紧密联系.     

The Dynamic Process of Interspecific Interactions of Competitive Nitrogen Capture between Intercropped Wheat (Triticum aestivum L.) and Faba Bean (Vicia faba L.)

Wheat (Triticum aestivum L.)/faba bean (Vicia faba L.) intercropping shows significant overyielding and high nitrogen (N)-use efficiency, but the dynamics of plant interactions have rarely been estimated. The objective of the present study was to investigate the temporal dynamics of competitive N acquisition between intercropped wheat and faba bean with the logistic model. Wheat and faba bean were grown together or alone with limited N supply in pots. Data of shoot and root biomass and N content measured from 14 samplings were fitted to logistic models to determine instantaneous rates of growth and N uptake. The superiority of instantaneous biomass production and N uptake shifted from faba bean to wheat with their growth. Moreover, the shift of superiority on N uptake occurred 7–12 days earlier than that of biomass production. Interspecific competition stimulated intercropped wheat to have a much earlier and stronger superiority on instantaneous N uptake compared with isolated wheat. The modeling methodology characterized the temporal dynamics of biomass production and N uptake of intercropped wheat and faba bean in different planting systems, which helps to understand the underlying process of plant interaction for intercropping plants.     

Enhancement of nitrogen fixation in lentil,faba bean,and soybean by dual inoculation with Rhizobia and mycorrhizae

The combined effect of Vesicular Arbuscular Mycorrhizae (VAM) and Rhizobium on the cold season legumes, lentil and faba bean, as well as on summer legume, soybean, were studied in soils with low indeginous VA mycorrhizal spores. Inoculation of the plant with VA mycorrhizal fungi increased the level of mycorrhizal root infection of lentil, faba bean and soybean. The inoculation with Rhizobium had no significant effect on VA mycorrhizal infection percent, but VA mycorrhizal inoculation increased nodulation of the three legumes. The inoculation with Rhizobium alone significantly increased plant dry weight and N content of lentil and faba bean as well as seed yield of soybean. VA mycorrhizal inoculation also significantly increased plant dry weight and phosphorus content of the plants as did fertilization with superphosphate. Rock phosphate fertilization, however, had no significant effect on plant growth or phosphorus uptake. The addition of rock phosphate in combination with VA mycorrhizal inoculation significantly increased plant dry weight and P uptake of the plants. The dual inoculation with both rhizobia and mycorrhizae induced more significant increases in plant dry weight, N and P content of lentil and faba bean as well as seed yield of soybean than inoculation with either VA mycorrhizae or Rhizobium alone.