玉米/大豆间作系统的作物资源竞争

通过分析不同分隔方式下[地上地下均不分隔(T1)、地上地下均分隔(T2)、仅地下分隔(T3)、仅地上分隔(T4)]玉米/大豆间作系统的土壤储水量、作物生长发育、生物量及产量,研究了间作作物间的资源竞争.结果表明:T1中玉米行120 cm土层平均土壤含水量比其他处理低3.1%~12.9%,大豆行比其他处理低2.8%~12.5%.与T1相比,T2、T3和T4的玉米生育进程均有所推后,株高、叶面积、生物量累积、籽粒产量及产量构成因素均降低;大豆则与之相反.综上,玉米/大豆间作系统作物生长和产量的变化是由于地上部与地下部综合作用的结果,且地下部作用大于地上部.     

常绿果树地上部与地下部的相互关系（综述）

常绿果树的地上部与地下部存在着相互营养，交替生长，形态对称与生势平衡，菌根作用和激素调控等多种关系，在生产实践中，可以通过综合的栽培技术来调控其平衡关系，达到果树早结丰产优势的目的。     

常绿果树地上部与地下部的相互关系(综述)

常绿果树的地上部与地下部存在着相互营养、交替生长、形态对称与生势平衡、菌根作用和激素调控等多种关系，在生产实践中，可以通过综合的栽培技术来调控其平衡关系，达到果树早结丰产优质的目的。     

玉米,小麦与花间作改善花生铁营养机制的探讨

采用土培盆栽方法模拟研究了玉米／花生、小麦／花生间作对花生铁营养状况的影响及其作用机制。结果表明,禾本科作物与花生间作对花生的铁营养显著影响;当花生与玉米或小麦分别间作时,花生新叶叶色正常,而花生单作则表现出严重的缺铁花化现象,间作花生新叶活性铁、叶绿素含量明显高单作,途中瞳作花生各部位铁含量和吸收量明显高于单作,间作灶促进了铁向花生地上部的转移;在单作花生表现缺铁症状１４ｄ的时间范围内,其根系质     

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。     

玉米、小麦与花生间作改善花生铁营养机制的探讨

采用土培盆栽方法模拟研究了玉米／花生、小麦／花生间作对花生铁营养状况的影响及其作用机制。结果表明,禾本科作物与花生间作对花生的铁营养状况有显著影响：当花生与玉米或小麦分别间作时,花生新叶叶色正常,而花生单作则表现出严重的缺铁黄化现象,间作花生新叶活性铁、叶绿素含量明显高于单作,两种间作花生各部位铁含量和吸收量明显高于单作,间作明显地促进了铁向花生地上部的转移;在单作花生表现缺铁症状１４ｄ的时间范围内,其根系质外体铁含量仅是间作花生的５２％～８０％;而根系还原力则是单作花生在表现缺铁症状后迅速提高,至缺铁第６ｄ时还原力达到最大值,随后花生根系还原力迅速下降,而间作花生在０～１４ｄ内还原力增加速度缓慢,在１０～１４ｄ中其根系还原力明显地高于单作花生根系还原力。其主要原因可能是禾本科作物玉米、小麦根系分泌物（如：麦根酸类植物铁载体）螯合土壤中难溶性铁并被花生吸收利用。     

燕麦/小麦间作对小麦生长和锰营养的影响

通过根系分隔的盆栽试验,研究了燕麦,小麦间作对小麦生长及其锰营养的影响。结果表明：根系不分隔处理,小麦地上部干重和植株吸锰量都高于其他两种分隔方式;而根系完全分隔处理,小麦地上部植株锰含量高于其他两种分隔方式;根系不同分隔方式对川麦28土壤DTPA-Mn含量几乎没有影响,小麦9023土壤DTPA-Mn含量则以完全分隔处理高于另外两种分隔方式。推测在该间作体系中,燕麦可能通过根系分泌物来活化土壤难溶性的锰氧化物,从而促进了小麦的生长,改善了小麦的锰营养,但因其竞争能力不如小麦而消弱了自身的生长。具体原因有待于进一步试验验证。试验还发现,种植燕麦后土壤的DTPA-Mn含量要高于种植小麦后的土壤,而且燕麦地上部植株锰含量也比小麦高,表明燕麦活化、吸收土壤锰的能力强于小麦。不同间作组合时,小麦各项研究指标无一致的规律性,说明在促进小麦生长、改善小麦锰营养的能力方面,本试验采用的3个燕麦品种之间无明显差异。     

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。     

种间互作和施氮对蚕豆/玉米间作生态系统地上部和地下部生长的影响

为河西走廊绿洲灌区豆科/禾本科间作体系的养分管理提供科学依据,于2007年在武威绿洲农业试验站应用田间原位根系行分隔技术研究了蚕豆/玉米种间互作和施氮对玉米抽雄期的根系空间分布、根系形态和作物地上部生长的影响。研究结果表明:种间互作和施氮均增加了玉米和蚕豆在纵向和横向两个尺度上的根重密度、根长密度、根表面积、根系体积。根长密度和根表面积与两种作物产量和氮素吸收均呈正相关,而与蚕豆的根瘤重呈负相关;抽雄期的土壤含水量与玉米产量和养分吸收呈显著的负相关。玉米根系可以占据蚕豆地下部空间,但蚕豆的根却较少到间作玉米的地下部空间,也就是间作后增加了玉米根系水平尺度的生态位。蚕豆和玉米根系主要分布分别在0-40 cm浅土层和0-60 cm 土层,且间作玉米根系在60-120 cm比单作和分隔的多。因此,种间互作和施氮扩大了两作物根系纵向和横向的空间生态位,改变了作物根系形态,即扩展了两者水分和养分吸收的生态位,增加了作物吸收养分的有效空间,从而提高了间作生态系统的生产力。     

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.     

两种光强下木质藤本与树木幼苗的竞争关系

 为了探讨木质藤本和树木幼苗的相互作用关系,对两种光强(4%和35%的光强)、4种竞争处理下(全竞争、地上竞争、地下竞争和无竞争),一种 需光木质藤本(刺果藤(Byttneria grandifolia))和3个树种(耐荫种：五桠果木姜子(Litsea dilleniifolia)和绒毛番龙眼(Pometia tomentosa);需光种：羊蹄甲(Bauhinia variegata))幼苗的地上部分和地下部分的竞争关系进行了研究。结果表明：木质藤本的竞争显著影响 着3种树木幼苗的光合能力、形态特征和生长,但生长环境的不同光强影响地上部分竞争和地下部分竞争的相对强度。在低光下,地上部分竞争 比地下部分竞争对3种树木幼苗的相对生长速率(Relative growth rate,RGR)和光合能力造成更大的影响;而高光下,地下竞争对树木幼苗的 生长有更强的抑制作用。不同的竞争处理和光强对树木幼苗的生物量积累造成显著的影响。光强对3种树种的比叶面积(Specific leaf area, SLA)和叶面积比(Leaf area ratio,LAR)有显著的抑制作用,但竞争只对需光的羊蹄甲的SLA和LAR有显著影响。不同的光照和竞争处理之间, 同种植物表现出不同的表型特征。由于竞争的影响,苗木在形态上较为矮小、叶片数目较少、叶面积减小,但是长细比改变较少 。     

民勤荒漠绿洲过渡带优势植物地上和地下生物量的估测模型

荒漠优势物种生物量的定量测量是荒漠土壤管理的重要依据。为精确估计民勤典型绿洲-荒漠过渡带中优势物种生物量,我们用随机选取的82个10 m×10 m的样方进行优势物种调查。结果显示试验地物种结构简单,而且总盖度仅为16.12%。选取5种荒漠优势物种(白刺(Nitraria tangutorum)、沙拐枣(Calligonum mongolicum)、梭梭(Haloxylon ammodendron)、沙蓬(Agriophyllum squarrosum)和盐生草(Halogeton arachnoideus)),利用全挖法测定其地上和地下生物量。用测定生物量80%的数据分析每一种植物地上和地下干、鲜生物量与其自身的形态参数地径、高度和冠幅之间的相关关系,再利用线性回归分析方法,以相关性显著的形态参数为自变量确定了预测试验地每一优势物种最适宜的地上及地下干、鲜生物量的回归模型。研究结果证实包括地茎(除白刺)和盖度为自变量的回归方程和5种优势荒漠植物的生物量拟合度很好,用测定生物量20%的数据对所有模型进行检验,证实所有生物量的估测模型能够精确预测优势荒漠物种生物量。     

不同基因型玉米间作对叶片衰老、籽粒产量和品质的影响

 采用大田试验, 研究了不同基因型玉米(Zea mays)间作对叶片衰老、籽粒产量和品质的影响。结果表明, ‘豫玉19’(YY19)与‘周单 041’(ZD041)、‘郑单958’(ZD958)与‘鲁单981’(LD981)间作, 可提高叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)的活 性, 降低丙二醛(MDA)含量, 延缓叶片衰老。具体表现为, 在吐丝后10 d, 4个玉米品种叶片中的SOD和POD活性均有所提高或显著提高, ZD041和 ZD958叶片中的CAT活性提高或显著提高, YY19和LD981变化不显著; 4个玉米品种叶片中的MDA含量降低。在吐丝后40 d, SOD和POD活性及MDA含 量的变化与吐丝后10 d基本一致, CAT活性均有所提高, 其中以YY19较为显著。研究还表明, 间作增加了复合群体产量, 土地当量比(Land equivalent ratio, LER)均大于1, 籽粒品质也有所改善。     

LEGUME-GRASS INTERCROPPING PHYTOREMEDIATION OF PHTHALIC ACID ESTERS IN SOIL NEAR AN ELECTRONIC WASTE RECYCLING SITE: A FIELD STUDY

A field experiment was conducted to study the phytoremediation of phthalic acid esters (PAEs) by legume (alfalfa, Medicago sativa L.)-grass (perennial ryegrass, Lolium perenne L. and tall fescue, Festuca arundinacea) intercropping in contaminated agricultural soil at one of the largest e-waste recycling sites in China. Two compounds, DEHP and DnBP, were present in the soil and in the shoots of the test plants at much higher concentrations than the other target PAEs studied. Over 80% of ‘total’ (i.e., all six) PAEs were removed from the soil across all treatments by the end of the experiment. Alfalfa in monoculture removed over 90% of PAEs and alfalfa in the intercrop of the three plant species contained the highest shoot concentration of total PAEs of about 4.7 mg kg^?1 DW (dry weight). Calculation of phytoextraction efficiency indicated that the most effective plant combinations in eliminating soil PAEs were the three-species intercrop (1.78%) and the alfalfa monocrop (1.41%). Phytoremediation with alfalfa was effective in both monoculture and intercropping. High bioconcentration factors (BCFs) indicated the occurrence of significant extraction of PAEs by plants from soil, suggesting that phytoremediation may have potential for the removal of PAEs from contaminated soils.     

HOST–PARASITE GENETIC INTERACTIONS AND VIRULENCE-TRANSMISSION RELATIONSHIPS IN NATURAL POPULATIONS OF MONARCH BUTTERFLIES

Evolutionary models predict that parasite virulence (parasite-induced host mortality) can evolve as a consequence of natural selection operating on between-host parasite transmission. Two major assumptions are that virulence and transmission are genetically related and that the relative virulence and transmission of parasite genotypes remain similar across host genotypes. We conducted a cross-infection experiment using monarch butterflies and their protozoan parasites from two populations in eastern and western North America. We tested each of 10 host family lines against each of 18 parasite genotypes and measured virulence (host life span) and parasite transmission potential (spore load). Consistent with virulence evolution theory, we found a positive relationship between virulence and transmission across parasite genotypes. However, the absolute values of virulence and transmission differed among host family lines, as did the rank order of parasite clones along the virulence-transmission relationship. Population-level analyses showed that parasites from western North America caused higher infection levels and virulence, but there was no evidence of local adaptation of parasites on sympatric hosts. Collectively, our results suggest that host genotypes can affect the strength and direction of selection on virulence in natural populations, and that predicting virulence evolution may require building genotype-specific interactions into simpler trade-off models.     

TEMPERATURE EFFECTS AND GENOTYPE-BY-ENVIRONMENT INTERACTIONS IN HYBRIDS: HALDANE'S RULE IN FLOUR BEETLES

When males of the flour beetle, Tribolium castaneum, are crossed to females of its close relative T. freemani, the sex ratio of the hybrids is female biased, owing in part to hybrid male mortality. Morphological abnormalities are also frequent in the surviving hybrid males, but not in the hybrid females. The finding that the heterogametic sex (male) is more adversely affected in interspecific crosses than the homogametic sex is consistent with Haldane's rule, which predicts that hybrid dysfunction should emerge as an indirect byproduct of divergent adaptation to differing environments. If so, environmental effects and genotype-by-environment interactions (GEI) should characterize the expression of Haldane's rule and interspecific hybrid traits in general. We used two wild-collected populations of T. castaneum (from Infantes, Spain, and Madagascar) to investigate the effects of environmental variation on the expression of Haldane's rule. Males from each population were mated to several T. freemani females and the half-sibling hybrid progenies were reared across a series of temperature regimes. For both populations, we found that hybrids raised at higher temperatures exhibited a more extreme expression of Haldane's rule: The hybrid sex ratios were more biased toward females and hybrid males had a much higher incidence of morphological abnormalities. The average response to temperature, the norm of reaction for Haldane's rule, varied between the two populations, and we found considerable and significant GEI for both hybrid traits within both populations. The evolutionary implications of these findings are discussed in the context of speciation arising as an indirect effect of local adaptation.     

GRAZING IMPACT OF,AND INDIRECT INTERACTIONS BETWEEN MESOGRAZERS ASSOCIATED WITH KELP (LAMINARIA DIGITATA)1

Little is known about the indirect effects of nonlethal grazing impacts in mesograzer–seaweed interactions. Using laboratory experiments, the effect of grazing by the seasonally abundant kelp‐associated gastropod Lacuna vincta on subsequent kelp consumption by one kelp‐associated (Idotea granulosa) and one nonassociated species of isopod (I. emarginata) was determined. Measurements of the toughness and elemental composition of different parts of the sporophyte of Laminaria digitata (Huds.) J. V. Lamour., as well as grazer‐induced changes in the palatability of the blade, were conducted to explore possible mechanisms of indirect effects. In situ grazing pressure was the highest between July and September, with the blade being the preferred part of the kelp sporophyte, despite missing differences in the elemental composition among kelp parts. The laboratory experiments supported our hypotheses in that kelp consumption by both species of isopods was lower on intact than on L. vincta–damaged areas of the blade. This pattern was not caused by grazing‐induced changes in blade palatability. Instead, the observed increase in isopod consumption following grazing by L. vincta resulted more likely from the combined effects of a reduction in the toughness of L. vincta–damaged kelp blades and some unknown gastropod cue(s). These results suggest that kelp‐associated and nonassociated mesograzers may benefit from the nonlethal grazing impact of L. vincta due to changes in physical traits of the seaweed. Thus, the nonlethal grazing impact by one species of mesograzer can positively modify the trophic interactions between kelp and other potential competitors, suggesting that the interactions among mesograzers might be more complex than previously assumed.     

神经内分泌因子调控鱼类生殖和生长的相互作用

脊椎动物的生长与生殖活动有着密切的联系并相互作用。许多调节生长和代谢活动的内分泌因子对青春期或者性腺的发育产生影响。同样,调节生殖活动的许多激素亦同时对生长和代谢产生影响。近年来,我们和其他学者对鱼类生长和生殖的神经内分泌调节的相互作用进行了研究,主要的进展是：①在促进性腺的激素影响生长方面,发现促性腺激素释放激素（ＧｎＲＨ）和多巴胺都能和脑垂体生长激素细胞的特异性受体结合而刺激生长激素释放,并能     

GENETICS OF INCIPIENT SPECIATION IN DROSOPHILA MOJAVENSIS: II. HOST PLANTS AND MATING STATUS INFLUENCE CUTICULAR HYDROCARBON QTL EXPRESSION AND G × E INTERACTIONS

We performed a quantitative trait locus (QTL) analysis of epicuticular hydrocarbon variation in 1650 F₂ males from crosses of Baja California and mainland Mexico populations of Drosophila mojavensis cultured on two major host cacti. Principal component (PC) analysis revealed five PCs that accounted for 82% of the total epicuticular hydrocarbon variation. Courtship trials with mainland females were used to characterize hydrocarbon profiles of mated and unmated F₂ males, and logistic regression analysis showed that cactus substrates, two PCs, and a PC by cactus interaction were associated with mating success. Multiple QTLs were detected for each hydrocarbon PC and seven G × E (cactus) interactions were uncovered for the X, second, and fourth chromosomes. Males from the courtship trials and virgins were used, so "exposure to females" was included as a factor in QTL analyses. "Exposed" males expressed significantly different hydrocarbon profiles than virgins for most QTLs, particularly for the two PCs associated with mating success. Ten QTLs showed G × E (exposure) interactions with most resulting from mainland genotypes expressing altered hydrocarbon amounts when exposed to females compared to Baja genotypes. Many cactus × exposure interaction terms detected across QTL and all PCs confirmed that organ pipe-reared males expressed significantly lower hydrocarbon amounts when exposed to females than when reared on agria cactus. Epicuticular hydrocarbon variation in D. mojavensis is therefore a multigenic trait with some epistasis, multiple QTLs exhibited pleiotropy, correlated groups of hydrocarbons and cactus substrates determined courtship success, and males altered their hydrocarbon profiles in response to females.