陳 鋒,孟永杰,帥海威,羅曉峰,周文冠,劉建偉,楊文鈺,舒 凱

(四川農(nóng)業(yè)大學(xué)農(nóng)學(xué)院生態(tài)農(nóng)業(yè)研究所/農(nóng)業(yè)部西南作物生理生態(tài)與耕作重點(diǎn)實(shí)驗(yàn)室 成都 611130)

植物化感物質(zhì)對(duì)種子萌發(fā)的影響及其生態(tài)學(xué)意義*

陳 鋒,孟永杰,帥海威,羅曉峰,周文冠,劉建偉,楊文鈺**,舒 凱**

(四川農(nóng)業(yè)大學(xué)農(nóng)學(xué)院生態(tài)農(nóng)業(yè)研究所/農(nóng)業(yè)部西南作物生理生態(tài)與耕作重點(diǎn)實(shí)驗(yàn)室 成都 611130)

化感現(xiàn)象作為植物之間的一種相互作用方式,在農(nóng)林業(yè)生產(chǎn)中廣泛存在。合理利用植物之間的化感作用,對(duì)于生產(chǎn)實(shí)踐具有重要的指導(dǎo)意義。研究表明,化感物質(zhì)可促進(jìn)或抑制不同物種種子的萌發(fā)過(guò)程,這對(duì)于植物的生長(zhǎng)發(fā)育、植物群落的組成與分布以及生態(tài)系統(tǒng)的平衡有著重要影響。本文從化感物質(zhì)對(duì)種子萌發(fā)的影響與其生態(tài)學(xué)意義兩個(gè)方面進(jìn)行了綜述。一方面,在闡述化感作用影響種子萌發(fā)的基礎(chǔ)上,進(jìn)一步總結(jié)了化感物質(zhì)抑制植物種子萌發(fā)的生理生化機(jī)制。包括:化感物質(zhì)通過(guò)抑制胚根和胚軸的伸長(zhǎng),破壞亞細(xì)胞結(jié)構(gòu),干擾植物激素及活性氧的合成與代謝,造成細(xì)胞損傷,從而阻礙種子萌發(fā);抑制種子中儲(chǔ)存物質(zhì)的代謝,阻礙種子萌發(fā)過(guò)程中的物質(zhì)以及能量轉(zhuǎn)換,導(dǎo)致種子萌發(fā)受阻等。另一方面,本文從化感作用在抑制農(nóng)田雜草及影響生態(tài)系統(tǒng)穩(wěn)定性兩個(gè)方面,闡述了化感物質(zhì)調(diào)控種子萌發(fā)的生態(tài)學(xué)意義。討論了農(nóng)作物的化感抑草作用,農(nóng)林業(yè)生產(chǎn)中的化感自毒作用以及化感作用造成的生物入侵等,以期為農(nóng)林業(yè)生產(chǎn)提供借鑒。最后,根據(jù)目前研究進(jìn)展,對(duì)本領(lǐng)域未來(lái)研究方向進(jìn)行了展望和討論。

化感作用;化感物質(zhì);種子萌發(fā);生態(tài)系統(tǒng)

化感作用(Allelopathy)是植物在長(zhǎng)期進(jìn)化的過(guò)程中形成的一種適應(yīng)機(jī)制,有利于保持本物種在空間和資源競(jìng)爭(zhēng)中的優(yōu)勢(shì)[1]。植物釋放到環(huán)境中的化感物質(zhì)(Allelochemical)通常為次生代謝產(chǎn)物(如酚酸類化合物、萜類化合物以及炔類化合物等),幾乎可以由植物的任何組織或器官合成,例如植物根、莖、葉、果實(shí)、種子等[2-3]。這些化感物質(zhì)進(jìn)入環(huán)境后能夠影響周圍植物的生長(zhǎng)發(fā)育。

植物化感作用與植物自身的生長(zhǎng)特性有關(guān)。由于植物固著生長(zhǎng),其無(wú)法通過(guò)移動(dòng)來(lái)逃避逆境,只能通過(guò)改變自身形態(tài)結(jié)構(gòu)以及生理生化反應(yīng)來(lái)適應(yīng)環(huán)境,或者通過(guò)釋放化學(xué)物質(zhì)來(lái)影響周邊其他植物的生長(zhǎng)發(fā)育,以改變微環(huán)境,使環(huán)境向著更適合自己生長(zhǎng)的方向發(fā)展[4-5]。桉樹(shù)(Eucalyptus robusta)人工林中植被比較稀少[6-7],大豆(Glycine max)連作會(huì)導(dǎo)致嚴(yán)重減產(chǎn)[8-9],外來(lái)植物可能造成生物入侵[10]。這些現(xiàn)象都是植物之間化感作用的表現(xiàn)。

種子萌發(fā)是植物生命周期中的關(guān)鍵環(huán)節(jié),對(duì)植物生長(zhǎng)發(fā)育至關(guān)重要[11-12]。在農(nóng)業(yè)生產(chǎn)方面,種子的正常萌發(fā)與出苗對(duì)作物產(chǎn)量影響很大[13]。種子萌發(fā)率或者出苗率下降都會(huì)導(dǎo)致作物有效株數(shù)下降,進(jìn)而導(dǎo)致產(chǎn)量降低[14]。因此研究化感物質(zhì)對(duì)種子萌發(fā)的影響具有重要意義。本文針對(duì)化感作用的最新研究進(jìn)展進(jìn)行綜述,闡述化感物質(zhì)調(diào)控種子萌發(fā)的機(jī)理,并探討其生態(tài)學(xué)意義,以期為該領(lǐng)域今后理論研究以及生產(chǎn)實(shí)踐提供借鑒。

1 化感作用

1.1 化感作用定義的發(fā)展

歷史上,人們就注意到植物之間存在相生相克的現(xiàn)象,如黑胡桃(Juglans nigra)樹(shù)下其他植物很難生存,鷹嘴豆(Cicer arietinum)可顯著抑制雜草生長(zhǎng)[3],但其背后的具體機(jī)理一直不甚明了,直到最近幾十年,隨著相關(guān)研究的逐漸增多,才取得了重要進(jìn)展。1937年,Molisch將這種植物(包括微生物)之間有益或者有害的化學(xué)相互作用定義為化感作用[15]。隨后,在20世紀(jì)70年代,Rice進(jìn)一步完善了化感定義,即植物(包括微生物)釋放化學(xué)物質(zhì)進(jìn)入環(huán)境中,并對(duì)其他植物產(chǎn)生直接或間接的有害作用[16]。后來(lái),植物之間相互促進(jìn)生長(zhǎng)及自毒現(xiàn)象也被納入化感作用范疇[17-18]。1996年,國(guó)際化感學(xué)會(huì)將化感作用定義為:植物、細(xì)菌、真菌以及藻類的次生代謝產(chǎn)物對(duì)農(nóng)業(yè)以及自然生態(tài)系統(tǒng)生物的生長(zhǎng)發(fā)育產(chǎn)生的影響[19]。

1.2 化感物質(zhì)分類及進(jìn)入環(huán)境的途徑

Rice將化感物質(zhì)分為14類,分別是水溶性有機(jī)酸、直鏈醇、脂肪族醛和醇,簡(jiǎn)單不飽和內(nèi)酯,長(zhǎng)鏈脂肪酸和多炔,萘醌、蒽醌以及復(fù)雜醌類,簡(jiǎn)單酚、苯甲酸及其衍生物,肉桂酸及其衍生物,單寧,萜烯和甾族化合物,氨基酸和多肽,生物堿和氰醇,硫化物和芥子油苷,嘌呤和核酸,香豆素以及類黃酮[18]。這些化感物質(zhì)可以通過(guò)自然揮發(fā)、根系分泌、雨霧淋溶以及植株腐解4種方式進(jìn)入環(huán)境[20-21],影響臨近植物生長(zhǎng),以確保自身獲得足夠的資源(圖1)。

2 化感物質(zhì)對(duì)植物種子萌發(fā)的影響

化感物質(zhì)對(duì)植物種子的影響分為兩個(gè)方面。一方面,化感物質(zhì)抑制種子萌發(fā);另一方面,化感物質(zhì)能促進(jìn)種子萌發(fā)。目前,多數(shù)研究集中在化感物質(zhì)抑制植物種子萌發(fā)方面[22-24]。此外,化感物質(zhì)對(duì)種子萌發(fā)表現(xiàn)為促進(jìn)還是抑制,與化感物質(zhì)種類、濃度以及受體植物種類有很大關(guān)系[25-27]。

2.1 化感物質(zhì)抑制植物種子萌發(fā)

許多化感物質(zhì)能顯著抑制植物種子萌發(fā),并影響種子萌發(fā)后幼苗的生長(zhǎng)發(fā)育。對(duì)加拿大一枝黃花(Solidago canadensis)的研究表明,其地上部的水提取液能顯著抑制雞眼草(Kummerowia striata)、萵苣(Lactuca sativa)、蘿卜(Raphanus sativus)等種子的萌發(fā),根部的水提取液亦能顯著抑制雞眼草種子的萌發(fā),但是對(duì)萵苣以及蘿卜種子萌發(fā)影響不顯著[10,28]。這表明,同一植株的不同部位產(chǎn)生的化感物質(zhì)對(duì)不同植物種子萌發(fā)的生理效應(yīng)有所不同。與加拿大一枝黃花類似,生姜(Zingiber officinale)的莖和葉的水提取液在多個(gè)濃度下均能抑制大豆及北蔥(Allium schoenoprasum)種子萌發(fā),但不同部位的提取液抑制效果有所差異[29]。對(duì)金銀忍冬(Lonicera maackii)的化感作用研究表明,植物的化感抑制效應(yīng)與化感物質(zhì)的濃度有關(guān)。金銀忍冬葉片和根的水提取液對(duì)蔥芥(Alliaria petiolata)以及擬南芥(Arabidopsis thaliana)種子的萌發(fā)均有抑制作用,且抑制效應(yīng)隨著提取液濃度升高而更加明顯[27]。

圖1 植物化感物質(zhì)進(jìn)入環(huán)境的4種途徑Fig.1 Four ways of plant allelochemicals entering into the environment

進(jìn)一步的研究表明,在同一植物提取液中,不同成分的化感物質(zhì)對(duì)種子萌發(fā)的抑制作用也不相同。對(duì)煙草(Nicotiana tabacum)根系滲出液中含有的6種有機(jī)酸(苯甲酸、肉桂酸、月桂酸、肉豆蔻酸、軟脂酸以及鄰苯二甲酸)的研究表明,相同濃度下苯甲酸和肉桂酸對(duì)煙草種子萌發(fā)的抑制作用最明顯[25]。但是,并非所有化感物質(zhì)都會(huì)降低種子萌發(fā)率,有些僅僅是延緩種子的萌發(fā)進(jìn)程。相關(guān)研究表明,美國(guó)杜鵑(Rhododendron maximum)、山月桂(Kalmia latifolia)以及金銀忍冬葉片提取液對(duì)葦狀羊茅(Festuca arundinacea)種子的最終萌發(fā)率無(wú)明顯影響,但是能顯著延緩其種子的萌發(fā)進(jìn)程,即對(duì)照組種子萌發(fā)率于第8 d即達(dá)到最大值,而處理組在12 d才達(dá)到最大值[30]。此外,一些植物會(huì)表現(xiàn)出很強(qiáng)的自毒作用[31-33]。研究表明,連續(xù)種植三七(Panax notoginseng)的土壤能顯著抑制三七種子萌發(fā),且隨種植年限延長(zhǎng),抑制效果越明顯[31]。以上研究表明,化感物質(zhì)對(duì)植物種子萌發(fā)具有強(qiáng)烈的抑制作用,且這種抑制作用與植物種類、植物不同部位以及化感物質(zhì)濃度有關(guān)。

2.2 化感物質(zhì)促進(jìn)植物種子萌發(fā)

雖然大多數(shù)化感物質(zhì)表現(xiàn)為抑制其他植物種子萌發(fā)或者強(qiáng)烈的自毒作用,但是部分化感物質(zhì)也會(huì)促進(jìn)其他植物種子的萌發(fā)。對(duì)14個(gè)大豆栽培品種的化感作用研究表明,大豆三節(jié)期根、莖以及葉的甲醇提取液均能顯著促進(jìn)向日葵列當(dāng)(Orobanche cumana)種子萌發(fā),其中根部提取液的促進(jìn)效果最明顯[34]。與此類似,玉米(Zea mays)、小麥(Triticum aestivum)、馬鈴薯(Solanum tuberosum)、大麻(Cannabis sativa)以及棉花(Gossypium hirsutum)的根際土或者植株提取液能顯著提高列當(dāng)屬植物的種子萌發(fā)率[35-39]。同時(shí),麻風(fēng)樹(shù)(Jatropha curcas)的葉片水提取液對(duì)芝麻(Sesamum indicum)種子的萌發(fā)起促進(jìn)作用[40],小麥和大豆根部滲出原液則能顯著提高黃瓜(Cucumis sativus)種子萌發(fā)率[26]。

化感物質(zhì)促進(jìn)植物種子萌發(fā),是植物之間相互協(xié)作的一個(gè)范例,有助于植物生長(zhǎng)發(fā)育。但是,這種促進(jìn)作用對(duì)于寄主植物可能是有害的,一旦寄主植物釋放化學(xué)物質(zhì)刺激寄生植物種子萌發(fā),寄主植物本身的生長(zhǎng)就會(huì)受到影響。在農(nóng)業(yè)生產(chǎn)上,可以將玉米或大豆與向日葵列當(dāng)?shù)募闹髦参颷例如甜瓜(Cucumis melo)、豌豆(Pisum sativum)、蠶豆(Vicia faba)以及煙草等]進(jìn)行間套作或者輪作,玉米或大豆可以釋放化感物質(zhì)誘導(dǎo)向日葵列當(dāng)種子萌發(fā),而萌發(fā)的向日葵列當(dāng)又不能寄生在玉米或大豆植株上,最后,向日葵列當(dāng)便會(huì)因缺少營(yíng)養(yǎng)而死亡,從而降低向日葵列當(dāng)?shù)叵路N子庫(kù),減少對(duì)寄主植物的危害[34-35]。

3 化感物質(zhì)調(diào)控植物種子萌發(fā)的機(jī)制

3.1 抑制胚的生長(zhǎng)

種胚是由受精卵發(fā)育而成的植物幼體,是種子的重要組成部分。植物種子吸水膨脹,胚根突破種皮和胚乳后,即為種子萌發(fā)[41]。因此,化感物質(zhì)能通過(guò)抑制胚的生長(zhǎng)而抑制種子萌發(fā)。

研究顯示,生姜莖和葉的水提液能抑制大豆和北蔥胚根以及下胚軸的生長(zhǎng),且這種抑制效果隨著提取液濃度升高而增強(qiáng)[29]。與此類似,黑芥(Brassica nigra)的根、莖、葉以及花的水提取液亦能抑制野燕麥(Avena fatua)胚根和下胚軸的伸長(zhǎng),其中胚根對(duì)化感物質(zhì)最為敏感[42]。但并非每類化感物質(zhì)都能通過(guò)同時(shí)抑制胚根和下胚軸的伸長(zhǎng)來(lái)抑制胚的生長(zhǎng)。比如,芳香植物灌木鼠尾草(Salvia leucophylla)揮發(fā)物中的單萜類物質(zhì)(樟腦、1,8-桉葉素、α-蒎烯、β-蒎烯、莰烯)能顯著抑制油菜(Brassica campestris)胚根的生長(zhǎng),但是對(duì)下胚軸沒(méi)有顯著影響;進(jìn)一步研究結(jié)果顯示,單萜類物質(zhì)能通過(guò)抑制胚根頂端分生組織細(xì)胞的增殖,從而抑制胚根生長(zhǎng)[43]。土荊芥(Dysphania ambrosioides)揮發(fā)油能誘導(dǎo)蠶豆根尖細(xì)胞染色體發(fā)生畸變,導(dǎo)致 DNA合成受阻,降低細(xì)胞有絲分裂指數(shù),從而導(dǎo)致胚根生長(zhǎng)受到抑制,而且這種抑制效果具有明顯的濃度效應(yīng)以及時(shí)間效應(yīng)[44]。由此可見(jiàn),化感物質(zhì)能通過(guò)抑制胚的生長(zhǎng),阻礙胚根突破種皮,從而抑制種子萌發(fā)。

3.2 對(duì)細(xì)胞結(jié)構(gòu)的影響

種子萌發(fā)過(guò)程中,幼胚細(xì)胞數(shù)目增加,體積增大,而完整的細(xì)胞結(jié)構(gòu)對(duì)于這個(gè)過(guò)程是必需的。研究表明,化感物質(zhì)會(huì)作用于細(xì)胞,破壞細(xì)胞結(jié)構(gòu),進(jìn)而影響植物種子萌發(fā)。

向日葵(Helianthus annuus)葉片提取液處理白芥(Sinapis alba)種子,會(huì)導(dǎo)致白芥種子中電解液滲透率增加,丙二醛(malondialdehyde,MDA)含量升高,細(xì)胞膜受到嚴(yán)重破壞[21]。Sicyos deppei葉片提取液處理菜豆(Phaseolus vulgaris)種子,導(dǎo)致菜豆胚根根冠細(xì)胞液泡內(nèi)陷,染色體紊亂,核仁變小;根邊緣細(xì)胞排列紊亂,細(xì)胞壁以及液泡形狀不規(guī)則[45]。與此類似,土荊芥揮發(fā)油誘導(dǎo)蠶豆根尖細(xì)胞核染色體畸變,導(dǎo)致細(xì)胞微核率顯著增加,細(xì)胞分裂受阻,同時(shí),加劇細(xì)胞凋亡[44]。因此,化感物質(zhì)能通過(guò)影響細(xì)胞結(jié)構(gòu),干擾細(xì)胞正常生命活動(dòng),來(lái)抑制植物種子萌發(fā)。

3.3 干擾種子中活性氧的產(chǎn)生與積累

活性氧(reactive oxygen species,ROS)是生物有氧代謝過(guò)程中產(chǎn)生的一類小分子,參與細(xì)胞內(nèi)許多重要的生理過(guò)程。一方面,作為重要的信號(hào)分子,活性氧在種子萌發(fā)以及植物抗逆性方面具有重要的調(diào)控作用[13,46-47]。另一方面,細(xì)胞內(nèi)積累過(guò)多的活性氧則會(huì)破壞細(xì)胞膜以及細(xì)胞內(nèi)大分子物質(zhì),影響植物生長(zhǎng)發(fā)育以及種子萌發(fā)[48-49]。已有研究表明,環(huán)境脅迫會(huì)干擾植物細(xì)胞內(nèi)部穩(wěn)態(tài),促進(jìn)活性氧積累[48]。而作為一種生物脅迫,化感作用能影響植物種子萌發(fā)過(guò)程中活性氧的產(chǎn)生與消除,進(jìn)而調(diào)控植物種子萌發(fā)[50]。

種子萌發(fā)過(guò)程中,活性氧的產(chǎn)生與清除處于動(dòng)態(tài)平衡中,但受到化感脅迫時(shí),這種平衡關(guān)系被打破,種子萌發(fā)就會(huì)受到抑制。高濃度的香豆素能通過(guò)干擾小麥種子中超氧化物歧化酶(superoxide dismutase,SOD)、脫氫抗壞血酸還原酶(dehydroascorbate reductase,DHAR)和單脫氫抗壞血酸還原酶(monodehydroascorbate reductase,MDHAR)等抗氧化酶的活性,以及抗壞血酸(ascorbic acid,AsA)和谷胱甘肽(glutathione,GSH)等抗氧化劑的含量,進(jìn)而影響小麥種子萌發(fā)過(guò)程中活性氧的含量,抑制小麥種子萌發(fā)[51]。用向日葵葉片提取液處理白芥種子后,白芥種子中H2O2的含量顯著升高,谷胱甘肽還原酶(glutathione reductase,GR)活性受到明顯抑制,雖然處理后期GR、SOD以及過(guò)氧化氫酶(catalase,CAT)的活性都有所增加,但是白芥種子中H2O2含量仍然持續(xù)升高,細(xì)胞膜受到破壞,種子萌發(fā)受到抑制[21]。

很多化感物質(zhì)會(huì)導(dǎo)致植物體內(nèi)活性氧含量增加,進(jìn)而造成細(xì)胞死亡,從而影響植物生長(zhǎng)發(fā)育。非常有趣的是,對(duì)黃酮類化合物Myrigalone A的相關(guān)研究表明,Myrigalone A 能抑制家獨(dú)行菜(Lepidium sativum)種子中活性氧的產(chǎn)生,從而阻礙細(xì)胞分裂,抑制胚根生長(zhǎng),進(jìn)而抑制種子萌發(fā)[52-53]。雖然大多數(shù)化感物質(zhì)對(duì)于植物種子萌發(fā)具有抑制作用,但是不同的化感物質(zhì)抑制種子萌發(fā)的途徑有所差異,因此非常有必要深入研究每類化感物質(zhì)對(duì)種子萌發(fā)的具體作用機(jī)理。

3.4 影響種子萌發(fā)過(guò)程中的代謝途徑

植物種子吸脹完成后,進(jìn)入萌動(dòng)階段,這時(shí)吸水量減少,但是種子內(nèi)部生理生化反應(yīng)異?；钴S,隨后種子胚根生長(zhǎng)突破種皮,種子萌發(fā)[41,50]?；形镔|(zhì)可通過(guò)干擾種子萌發(fā)階段內(nèi)部的生理生化反應(yīng)來(lái)抑制植物種子萌發(fā)。

6-甲氧基-2-苯并唑啉酮(6-methoxy-2-benzoxazolinone,MBOA)對(duì)小麥、水稻(Oryza sativa)、黑麥(Secale cereale)、萵苣以及野胡蘿卜(Daucus carota)等植物種子萌發(fā)具有顯著的抑制作用[54]。進(jìn)一步研究結(jié)果表明,MBOA能抑制 α-淀粉酶活性,降低種子中淀粉的轉(zhuǎn)化利用效率,進(jìn)而抑制植物種子萌發(fā)[54-55]。與此類似,生姜莖和葉的水提液均能抑制大豆或者北蔥種子中脂肪酶活性[29]?；形镔|(zhì)不僅阻礙種子萌發(fā)過(guò)程中物質(zhì)的轉(zhuǎn)化,同樣也干擾其能量代謝。向日葵葉片水提液不僅能抑制白芥種子中肽鏈內(nèi)切酶(endopeptidase)以及異檸檬酸裂解酶(isocitratelyase,ICL)的活性,干擾種子內(nèi)部?jī)?chǔ)存蛋白以及脂肪酸的降解,而且阻礙O2吸收,抑制ATP的產(chǎn)生,干擾種子內(nèi)部能量代謝,進(jìn)而抑制種子萌發(fā)[56]。植物種子萌發(fā)初期會(huì)動(dòng)用種子內(nèi)部?jī)?chǔ)存的蛋白質(zhì)、油脂或者淀粉來(lái)獲取能量,并進(jìn)行活躍的物質(zhì)合成,以滿足種子萌發(fā)所需要的物質(zhì)和能量;而化感物質(zhì)正是通過(guò)干擾種子萌發(fā)過(guò)程中的物質(zhì)代謝以及能量代謝來(lái)抑制植物種子萌發(fā)。

3.5 打破種子內(nèi)源激素平衡

植物種子的萌發(fā)受到一系列機(jī)制的調(diào)節(jié),從而保證幼胚的正常生長(zhǎng)[57]。在眾多調(diào)節(jié)種子萌發(fā)的機(jī)制中,激素扮演著重要的角色。常見(jiàn)的植物激素包括脫落酸(abscisic acid,ABA)、生長(zhǎng)素(auxin)、乙烯(ethylene,ETH)、赤霉素(gibberellin,GA)、細(xì)胞分裂素(cytokinin,CTK)以及油菜素甾醇(brassinosteroid,BR),它們共同協(xié)同或拮抗調(diào)控著植物生長(zhǎng)發(fā)育,其中ABA、GA、ETH以及生長(zhǎng)素能調(diào)控種子萌發(fā)[14,58-60]。

研究表明,GA促進(jìn)種子萌發(fā),而ABA抑制種子萌發(fā)[61-62]。環(huán)境因子通過(guò)調(diào)節(jié)與兩種激素生物合成與分解代謝相關(guān)酶的生物活性來(lái)控制兩者的比例,進(jìn)而調(diào)控植物種子的萌發(fā)[63]。Myrica gale是一種生長(zhǎng)在河邊、湖邊或者沼澤潮濕地帶的落葉灌木[64],其果實(shí)和葉片中含有一種黃酮類化感物質(zhì)Myrigalone A能顯著影響其他植物種子的萌發(fā)[53,65]。Myrigalone A能顯著抑制家獨(dú)行菜種子的胚乳破裂以及胚根伸長(zhǎng),進(jìn)而抑制其種子萌發(fā)[52-53]。進(jìn)一步研究表明,Myrigalone A對(duì)ABA含量沒(méi)有顯著影響,但是能抑制家獨(dú)行菜種子幼胚中 GA3氧化酶的活性,干擾GA代謝及信號(hào)轉(zhuǎn)導(dǎo),進(jìn)而影響GA與ABA比值,從而抑制其種子萌發(fā)[52]。與此類似,在對(duì)向日葵化感作用的研究表明,向日葵葉片提取液能提高白芥種子中 ABA的含量,并通過(guò)干擾 ACC氧化酶以及ACC合成酶的活性來(lái)降低ETH含量,進(jìn)而抑制白芥種子萌發(fā)[66]。綜上所述,化感物質(zhì)能影響植物種子萌發(fā)過(guò)程中激素的含量,打破種子內(nèi)源激素平衡,從而抑制種子萌發(fā)。

4 化感物質(zhì)影響種子萌發(fā)的生態(tài)學(xué)意義

4.1 抑制雜草種子萌發(fā)

在農(nóng)業(yè)生產(chǎn)中,雜草是造成作物減產(chǎn)的主要因素之一,如何科學(xué)地控制雜草,提高作物產(chǎn)量,是一個(gè)重要的生產(chǎn)問(wèn)題。目前,化學(xué)合成除草劑在抑制雜草方面扮演重要角色,能顯著提高作物產(chǎn)量,但是它對(duì)作物和環(huán)境具有不利影響,威脅人類健康[67-69]。近年來(lái),已經(jīng)發(fā)現(xiàn)很多作物能釋放化感物質(zhì)進(jìn)入環(huán)境,抑制雜草生長(zhǎng)[70-75]。事實(shí)上,作為一種天然的化學(xué)除草劑,化感物質(zhì)的抑草作用在農(nóng)業(yè)生產(chǎn)上受到了越來(lái)越多的關(guān)注[2,76]?；形镔|(zhì)是由植物或者微生物產(chǎn)生的一種天然的化合物,可以在環(huán)境中被生物降解。合理利用作物的化感作用或者以化感物質(zhì)部分代替化學(xué)合成除草劑,對(duì)于保護(hù)環(huán)境,實(shí)現(xiàn)農(nóng)業(yè)可持續(xù)發(fā)展具有重要意義[77-78]。

將能釋放化感物質(zhì)的作物與其他作物進(jìn)行間作、套作或者輪作,能改善農(nóng)田土壤性質(zhì),抑制雜草生長(zhǎng),提高作物產(chǎn)量[79-80]。草木犀(Melilotus officinalis)是一種優(yōu)良的飼草和綠肥,在與豌豆(Pisum sativum)、亞麻(Linum usitatissimum)以及芥菜(Brassica juncea)套作收獲后,草木犀的殘株能顯著降低雜草密度,抑制蒲公英(Taraxacum mongolicum)、苦菜(Lobelia davidii)、地膚(Kochia scoparia)、藜(Chenopodium album)、旱雀麥(Bromus tectorum)等雜草種子萌發(fā),其中對(duì)藜及地膚兩種雜草密度的抑制率達(dá)到 80%,并顯著降低野燕麥的生物量[81-82]。與此類似,經(jīng)濟(jì)作物菊芋(Helianthus tuberosus)的莖和葉混合基質(zhì)能顯著降低雜草密度[83]。因此,利用作物之間的化感作用,合理搭配農(nóng)作物種植方式,有利于抑制農(nóng)田雜草,提高作物產(chǎn)量,同時(shí)保護(hù)生態(tài)環(huán)境。

4.2 生態(tài)系統(tǒng)中的化感作用

生態(tài)系統(tǒng)是指在一定時(shí)間和空間內(nèi),生物群落與環(huán)境構(gòu)成的統(tǒng)一整體,在這個(gè)統(tǒng)一整體中,生物與環(huán)境之間相互影響、相互制約,并在一定時(shí)期內(nèi)處于相對(duì)穩(wěn)定的動(dòng)態(tài)平衡狀態(tài)。生態(tài)系統(tǒng)中每種植物都有自己特定的分布區(qū)域,植物之間相互影響,共同形成穩(wěn)定的群落分布格局。

4.2.1 生物入侵

引入外來(lái)物種會(huì)導(dǎo)致3種結(jié)局:外來(lái)物種不適應(yīng)引入地環(huán)境而逐漸消亡、與引入地物種共同形成穩(wěn)定生物群落以及造成生物入侵(圖2),其中生物入侵會(huì)對(duì)入侵地區(qū)的生態(tài)系統(tǒng)造成嚴(yán)重威脅[84]。生物入侵是指生物由原生存地經(jīng)自然或人為途徑侵入到另一個(gè)新的環(huán)境,對(duì)當(dāng)?shù)氐纳锒鄻有浴⒆匀画h(huán)境以及經(jīng)濟(jì)造成損失。很多植物在離開(kāi)自己原先的生活環(huán)境后,會(huì)表現(xiàn)出極強(qiáng)的侵入能力,例如加拿大一枝黃花[85]、微甘菊(Mikania micrantha)[86]、豚草(Ambrosia artemisiifolia)[87]以及紫莖澤蘭(Ageratina adenophora)[88]等。但是,外來(lái)入侵物種在原有生態(tài)系統(tǒng)中不會(huì)造成生物入侵,其中很大一部分原因是在原有生態(tài)系統(tǒng)經(jīng)過(guò)上百年甚至上千年的協(xié)同進(jìn)化,相互之間達(dá)到一種和諧共生狀態(tài)。一旦這種和諧共生格局被打破,生物之間相互制約關(guān)系被破壞,就容易造成生物入侵。導(dǎo)致生物入侵的原因有很多,化感就是其中一個(gè)方面。

圖2 外來(lái)物種進(jìn)入本地生態(tài)系統(tǒng)后的3種發(fā)展方向Fig.2 Three types of destiny after alien species entering into the local ecosystem

很多外來(lái)入侵物種都能釋放化感物質(zhì)影響其他植物生長(zhǎng),從而增強(qiáng)競(jìng)爭(zhēng)資源的能力,保證自身生長(zhǎng)[89-90]。研究表明,紫莖澤蘭地上部凋落物的不同濃度水提液均能抑制紫花苜蓿(Medicago sativa)和白三葉(Trifolium repens)種子萌發(fā)及幼苗生長(zhǎng)[91]。在對(duì)生長(zhǎng)于原生地(北美)以及侵入地(中國(guó))的加拿大一枝黃花進(jìn)行比較發(fā)現(xiàn),在侵入地生長(zhǎng)的加拿大一枝黃花地上部或地下部提取液中酚類化合物、黃酮類化合物以及皂苷都顯著或者極顯著高于原生地生長(zhǎng)的加拿大一枝黃花,同時(shí),兩者的提取液均能顯著抑制雞眼草種子的萌發(fā),并且侵入地生長(zhǎng)的加拿大一枝黃花的抑制作用更明顯[5]。外來(lái)侵入物種在侵入地能釋放更多化感物質(zhì)進(jìn)入周圍環(huán)境,影響周圍植物生長(zhǎng)發(fā)育,從而為自己迅速蔓延創(chuàng)造條件。一旦外來(lái)物種在侵入地大規(guī)模繁殖,就會(huì)導(dǎo)致當(dāng)?shù)厣鷳B(tài)結(jié)構(gòu)單一,本地生物多樣性減少,容易引發(fā)當(dāng)?shù)厣鷳B(tài)危機(jī)[92]。

4.2.2 對(duì)生態(tài)系統(tǒng)中群落組成與分布格局的影響

雖然外來(lái)入侵植物會(huì)通過(guò)釋放化感物質(zhì)影響其他植物生長(zhǎng),造成生物入侵,對(duì)當(dāng)?shù)厣鷳B(tài)系統(tǒng)穩(wěn)定性造成威脅;但另一方面,化感作用對(duì)于維持生態(tài)系統(tǒng)中群落的組成與分布格局具有重要意義。其中最典型的一個(gè)例子,就是對(duì)美國(guó)南加州灌木叢的化感作用的研究,研究者發(fā)現(xiàn),在每塊灌木叢的周圍都會(huì)出現(xiàn)1～2 m的裸帶,這些裸帶中沒(méi)有任何植物。進(jìn)一步研究發(fā)現(xiàn),灌木釋放的萜類化合物能隨著雨霧進(jìn)入周圍環(huán)境中,抑制草本植物種子萌發(fā)及幼苗生長(zhǎng),從而形成這種穩(wěn)定的分布格局[93]。

自毒作用是化感作用的一個(gè)重要方面,是指一種植物釋放化感物質(zhì)抑制同類植物種子萌發(fā)及植株生長(zhǎng)的現(xiàn)象[94]。研究表明,天山云杉(Picea schrenkiana)、杉木(Cunninghamia lanceolata)、紫花苜蓿以及馬鈴薯等植物都具有明顯的化感自毒作用[95-98]。例如,油松(Pinus tabuliformis)根和葉的水提取液以及乙酸乙酯提取液對(duì)油松種子萌發(fā)及幼苗生長(zhǎng)具有明顯的抑制作用,此外,油松揮發(fā)油亦能顯著抑制油松種子萌發(fā)及幼苗生長(zhǎng)[99]。對(duì)杉木自毒作用的研究表明,杉木根、鮮葉、枯葉、半分解枯葉以及根際土壤浸提液對(duì)杉木種子萌發(fā)及幼苗生長(zhǎng)均有不同程度的抑制作用,其中杉木根際土壤以及非根際土壤浸提液對(duì)杉木種子萌發(fā)的抑制作用隨著杉木栽植代數(shù)增加而更加明顯[100-101]。

在生態(tài)系統(tǒng)中,具有自毒作用的植物能釋放化感物質(zhì)抑制同種植物種子萌發(fā)與幼苗生長(zhǎng),起到自疏的作用。植物通過(guò)這種方式降低種群密度,一方面避免了過(guò)多幼苗競(jìng)爭(zhēng)養(yǎng)分,影響成株生長(zhǎng);另一方面,避免同一地區(qū)形成單一植物群落,從而增加地區(qū)生物多樣性,穩(wěn)定生態(tài)系統(tǒng)。自毒作用是植物對(duì)環(huán)境的一種適應(yīng)機(jī)制,有利于生態(tài)系統(tǒng)的穩(wěn)定與發(fā)展。但是在生產(chǎn)實(shí)踐上,自毒作用會(huì)導(dǎo)致嚴(yán)重的減產(chǎn)。現(xiàn)在已經(jīng)發(fā)現(xiàn)很多經(jīng)濟(jì)作物、糧食作物以及園藝植物,都存在著嚴(yán)重的自毒作用[9,31,102-103]。盡管自毒作用是植物與環(huán)境長(zhǎng)期作用的結(jié)果,在生產(chǎn)實(shí)踐上我們也無(wú)法避免,但是我們可以通過(guò)合理的種植制度安排減少自毒作用造成的損失[104]。例如,可以將作物合理的間混套作或者輪作,避免化感自毒作用;育種工作者可以選育優(yōu)良抗自毒作物品種;在園藝植物方面,可以選擇優(yōu)良砧木進(jìn)行嫁接;也可以通過(guò)合理施肥的方式減輕化感自毒作用。

5 展望

盡管人們很早就注意到植物之間的化感作用,但是直到最近幾十年才真正重視化感作用的研究。而化感物質(zhì)對(duì)植物種子萌發(fā)的影響作為本領(lǐng)域的重要方面,近年來(lái)取得了一些重要的進(jìn)展。在已有研究的基礎(chǔ)上,特提出以下重點(diǎn)研究方向及建議。

首先,在自然界中,化感物質(zhì)一般是溶于雨水后進(jìn)入環(huán)境,進(jìn)而影響植物種子萌發(fā)和植物生長(zhǎng)。然而,在目前的很多研究中,常使用甲醇、乙酸乙酯以及丙酮等有機(jī)溶劑提取植物組織內(nèi)的化感物質(zhì),這種提取方法雖然可以將化感物質(zhì)提取出來(lái),但是這樣也會(huì)把植物內(nèi)部的非化感物質(zhì)提取出來(lái),而且提取濃度與自然界中也會(huì)有差異。這也是為什么有些試驗(yàn)表明某些植物具有化感作用,但是在自然界中化感作用不是很明顯,其中一個(gè)原因就是提取液中有很多物質(zhì)不是化感物質(zhì)。因此,在之后的試驗(yàn)中,提取化感物質(zhì)盡量以水為介質(zhì),模擬自然界中化感物質(zhì)進(jìn)入環(huán)境的形式,這樣才能更好更準(zhǔn)確地解釋化感現(xiàn)象。

其次,化感物質(zhì)可以通過(guò) 4種方式進(jìn)入環(huán)境,除了自然揮發(fā)之外,其余3種途徑釋放的化感物質(zhì)都會(huì)隨著雨水進(jìn)入土壤,然后作用于臨近植物?；形镔|(zhì)進(jìn)入土壤以后,在土壤微生物以及土壤介質(zhì)的作用下,會(huì)發(fā)生一些改變,同時(shí),化感物質(zhì)也會(huì)影響土壤微生物的群體結(jié)構(gòu)以及土壤環(huán)境。不同的化感物質(zhì)進(jìn)入土壤以后會(huì)發(fā)生怎樣的變化以及不同的化感物質(zhì)會(huì)影響哪些特異的微生物的群體結(jié)構(gòu)？深入研究這些科學(xué)問(wèn)題對(duì)于理解連作障礙以及化感抑草作用具有重要的理論與實(shí)際意義。

再次,已有研究表明,ABA、GA、ETH等激素以及 ROS在種子萌發(fā)過(guò)程中具有重要的調(diào)節(jié)作用,而化感物質(zhì)能干擾種子萌發(fā)過(guò)程中激素以及ROS的平衡,從而影響種子萌發(fā)。因此,深入探討化感物質(zhì)干擾激素和 ROS的分子機(jī)理,以及在這個(gè)過(guò)程中ROS如何參與到激素的調(diào)節(jié)通路中,將是非常有意義的。

最后,現(xiàn)在化感作用研究多集中在理論研究階段,如何將化感作用研究成果應(yīng)用于實(shí)踐,是目前亟待解決的問(wèn)題之一。我們現(xiàn)在已經(jīng)知道很多植物具有化感作用,但是能應(yīng)用到實(shí)際生產(chǎn)中的成果很少。因此,要進(jìn)一步思考如何在現(xiàn)有研究成果的基礎(chǔ)上,探討合理的農(nóng)作物間套作搭配方式,開(kāi)發(fā)新型綠色除草劑,使化感作用真正促進(jìn)農(nóng)業(yè)的發(fā)展。

References

[1]郭蘭萍,黃璐琦,蔣有緒,等.藥用植物栽培種植中的土壤環(huán)境惡化及防治策略[J].中國(guó)中藥雜志,2006,31(9):714–717 Guo L P,Huang L Q,Jiang Y X,et al.Soil deterioration during cultivation of medicinal plants and ways to prevent it[J].China Journal of Chinese Materia Medica,2006,31(9):714–717

[2]Farooq M,Jabran K,Cheema Z A,et al.The role of allelopathy in agricultural pest management[J].Pest Management Science,2011,67(5):493–506

[3]Weir T L,Park S W,Vivanco J M.Biochemical and physiological mechanisms mediated by allelochemicals[J].Current Opinion in Plant Biology,2004,7(4):472–479

[4]Callaway R M,Pennings S C,Richards C L.Phenotypic plasticity and interactions among plants[J].Ecology,2003,84(5):1115–1128

[5]黃喬喬,沈奕德,李曉霞,等.外來(lái)入侵植物在中國(guó)的分布及入侵能力研究進(jìn)展[J].生態(tài)環(huán)境學(xué)報(bào),2012,21(5):977–985 Huang Q Q,Shen Y D,Li X X,et al.Research progress on the distribution and invasiveness of alien invasive plants in China[J].Ecology and Environmental Sciences,2012,21(5):977–985

[6]Chu C J,Mortimer P,Wang H C,et al.Allelopathic effects ofEucalyptuson native and introduced tree species[J].Forest Ecology and Management,2014,323:79–84

[7]Bughio F A,Mangrio S M,Abro S A,et al.Physiomorphological responses of nativeAcacia niloticato eucalyptus allelopathy[J].Pakistan Journal of Botany,2013,45(S1):97–105

[8]Liu X B,Herbert S J.Fifteen years of research examining cultivation of continuous soybean in northeast China:A review[J].Field Crops Research,2002,79(1):1–7

[9]杜英君,靳月華.連作大豆植株化感作用的模擬研究[J].應(yīng)用生態(tài)學(xué)報(bào),1999,10(2):209–212 Du Y J,Jin Y H.Simulations of allelopathy in continuouscropping of soybean[J].Chinese Journal of Applied Ecology,1999,10(2):209–212

[10]Yuan Y G,Wang B,Zhang S S,et al.Enhanced allelopathy and competitive ability of invasive plantSolidago canadensisin its introduced range[J].Journal of Plant Ecology,2013,6(3):253–263

[11]Barrero J M,Downie A B,Xu Q,et al.A role for barley CRYPTOCHROME1 in light regulation of grain dormancy and germination[J].The Plant Cell,2014,26(3):1094–1104

[12]Ishibashi Y,Koda Y,Zheng S H,et al.Regulation of soybean seed germination through ethylene production in response to reactive oxygen species[J].Annals of Botany,2012,111(1):95–102

[13]El-Maarouf-Bouteau H,Sajjad Y,Bazin J,et al.Reactive oxygen species,abscisic acid and ethylene interact to regulate sunflower seed germination[J].Plant,Cell &Environment,2015,38(2):364–374

[14]帥海威,孟永杰,羅曉峰,等.生長(zhǎng)素調(diào)控種子的休眠與萌發(fā)[J].遺傳,2016,38(4):314–322 Shuai H W,Meng Y J,Luo X F,et al.The roles of auxin in seed dormancy and germination[J].Hereditas,2016,38(4):314–322

[15]Chon S U,Jang H G,Kim D K,et al.Allelopathic potential in lettuce (Lactuca sativaL.) plants[J].Scientia Horticulturae,2005,106(3):309–317

[16]倪利曉,陳世金,任高翔,等.陸生植物化感作用的抑藻研究進(jìn)展[J].生態(tài)環(huán)境學(xué)報(bào),2011,20(6/7):1176–1182 Ni L X,Chen S J,Ren G X,et al.Advance research on the allelopathy of terrestrial plants in inhibition of algae[J].Ecology and Environmental Sciences,2011,20(6/7):1176–1182

[17]Rice E L.Allelopathy-An update[J].The Botanical Review,1979,45(1):15–109

[18]Rice E L.Allelopathy[M].New York:Academic Press,1984:1–267

[19]Dias L S,Pereira I P,Dias A S.Allelopathy,seed germination,weed control and bioassay methods[J].Allelopathy Journal,2016,37(1):31–40

[20]Zhang D J,Zhang J,Yang W Q,et al.Potential allelopathic effect ofEucalyptus grandisacross a range of plantation ages[J].Ecological Research,2010,25(1):13–23

[21]Oracz K,Bailly C,Gniazdowska A,et al.Induction of oxidative stress by sunflower phytotoxins in germinating mustard seeds[J].Journal of Chemical Ecology,2007,33(2):251–264

[22]Bauer J T,Shannon S M,Stoops R E,et al.Context dependency of the allelopathic effects ofLonicera maackiion seed germination[J].Plant Ecology,2012,213(12):1907–1916

[23]Valera-Burgos J,Díaz-barradas M C,Zunzunegui M.Effects ofPinus pinealitter on seed germination and seedling performance of three Mediterranean shrub species[J].Plant Growth Regulation,2012,66(3):285–292

[24]Wang C Y,Xiao H G,Zhao L L,et al.The allelopathic effects of invasive plantSolidago canadensison seed germination and growth ofLactuca sativaenhanced by different types of acid deposition[J].Ecotoxicology,2016,25(3):555–562

[25]Yu H Y,Hongbo L,Guoming S,et al.Effects of allelochemicals from tobacco root exudates on seed germination and seedling growth of tobacco[J].Allelopathy Journal,2014,33(1):107–120

[26]Wang Y Y,Wu F Z,Liu S W.Allelopathic effects of root exudates from wheat,oat and soybean on seed germination and growth of cucumber[J].Allelopathy Journal,2009,24(1):103–112

[27]Dorning M,Cipollini D.Leaf and root extracts of the invasive shrub,Lonicera maackii,inhibit seed germination of three herbs with no autotoxic effects[J].Plant Ecology,2006,184(2):287–296

[28]Butcko V M,Jensen R J.Evidence of tissue-specific allelopathic activity inEuthamia graminifoliaandSolidago canadensis(Asteraceae)[J].The American Midland Naturalist,2002,148(2):253–262

[29]Han C M,Pan K W,Wu N,et al.Allelopathic effect of ginger on seed germination and seedling growth of soybean and chive[J].Scientia Horticulturae,2008,116(3):330–336

[30]Mcewan R W,Arthur-Paratley L G,Rieske L K,et al.A multi-assay comparison of seed germination inhibition byLonicera maackiiand co-occurring native shrubs[J].Flora-Morphology,Distribution,Functional Ecology of Plants,2010,205(7):475–483

[31]Yang M,Zhang X D,Xu Y G,et al.Autotoxic ginsenosides in the rhizosphere contribute to the replant failure ofPanax notoginseng[J].PLoS One,2015,10(2):e0118555

[32]Asaduzzaman M,Asao T.Autotoxicity in beans and their allelochemicals[J].Scientia Horticulturae,2012,134:26–31

[33]Li Z F,Yang Y Q,Xie D F,et al.Identification of autotoxic compounds in fibrous roots of Rehmannia (Rehmannia glutinosaLibosch.)[J].PLoS One,2012,7(1):e28806

[34]Zhang W,Ma Y Q,Wang Z,et al.Some soybean cultivars have ability to induce germination of sunflower broomrape[J].PLoS One,2013,8(3):e59715

[35]Ma Y Q,Jia J N,Yu A,et al.Potential of some hybrid maize lines to induce germination of sunflower broomrape[J].Crop Science,2013,53(1):260–270

[36]Lins R D,Colquhoun J B,Mallory-Smith C A.Investigation of wheat as a trap crop for control ofOrobanche minor[J].Weed Research,2006,46(4):313–318

[37]王鐘,馬永清,賈錦楠,等.馬鈴薯對(duì)瓜列當(dāng)種子萌發(fā)的化感作用研究[J].中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào),2013,21(3):333–339 Wang Z,Ma Y Q,Jia J N,et al.Allelopathic effect of potato onOrabanche aegyptiacaPers.seed germination[J].Chinese Journal of Eco-Agriculture,2013,21(3):333–339

[38]余蕊,馬永清.大麻對(duì)瓜列當(dāng)和向日葵列當(dāng)種子萌發(fā)誘導(dǎo)作用研究[J].中國(guó)農(nóng)業(yè)大學(xué)學(xué)報(bào),2014,19(4):38–46 Yu R,Ma Y Q.Melon broomrape and sunflower broomrape seeds germination induced by hemp (Cannabis sativaL.) plants[J].Journal of China Agricultural University,2014,19(4):38–46

[39]郎明,馬永清,董淑琦,等.苗期棉花對(duì)向日葵列當(dāng)種子萌發(fā)誘導(dǎo)作用初探[J].生態(tài)環(huán)境學(xué)報(bào),2011,20(1):79–83 Lang M,Ma Y Q,Dong S Q,et al.Allelopathic effect ofcotton in seedling stage on sunflower broomrape[J].Ecology and Environmental Sciences,2011,20(1):79–83

[40]Rejila S,Vijayakumar N.Allelopathic effect ofJatropha curcason selected intercropping plants (green chilli and sesame)[J].Journal of Phytology,2011,3(5):1–3

[41]Weitbrecht K,Müller K,Leubner-Metzger G.First off the mark:Early seed germination[J].Journal of Experimental Botany,2011,62(10):3289–3309

[42]Turk M A,Tawaha A M.Allelopathic effect of black mustard (Brassica nigraL.) on germination and growth of wild oat (Avena fatuaL.)[J].Crop Protection,2003,22(4):673–677

[43]Nishida N,Tamotsu S,Nagata N,et al.Allelopathic effects of volatile monoterpenoids produced bySalvia leucophylla:Inhibition of cell proliferation and DNA synthesis in the root apical meristem ofBrassica campestrisseedlings[J].Journal of Chemical Ecology,2005,31(5):1187–1203

[44]胡琬君,馬丹煒,王亞男,等.土荊芥揮發(fā)油對(duì)蠶豆根尖細(xì)胞的化感潛力[J].生態(tài)學(xué)報(bào),2011,31(13):3684–3690 Hu W J,Ma D W,Wang Y N,et al.Allelopathic potential of volatile oil fromChenopodium ambrosioidesL.on root tip cells ofVicia faba[J].Acta Ecologica Sinica,2011,31(13):3684–3690

[45]Cruz-Ortega R,Anaya A L,Hernández-Bautista B E,et al.Effects of allelochemical stress produced bySicyos deppeion seedling root ultrastructure ofPhaseolus vulgarisandCucurbita ficifolia[J].Journal of Chemical Ecology,1998,24(12):2039–2057

[46]Xiong L M,Schumaker K S,Zhu J K.Cell signaling during cold,drought,and salt stress[J].The Plant Cell,2002,14(S1):S165–S183

[47]Miller G,Suzuki N,Ciftci-Yilmaz S,et al.Reactive oxygen species homeostasis and signalling during drought and salinity stresses[J].Plant,Cell &Environment,2010,33(4):453–467

[48]Sharma P,Jha A B,Dubey R S,et al.Reactive oxygen species,oxidative damage,and antioxidative defense mechanism in plants under stressful conditions[J].Journal of Botany,2012,2012:217037

[49]Chen C M,Letnik I,Hacham Y,et al.ASCORBATE PEROXIDASE6 protectsArabidopsisdesiccating and germinating seeds from stress and mediates cross talk between reactive oxygen species,abscisic acid,and auxin[J].Plant Physiology,2014,166(1):370–383

[50]Pergo é M,Ishii-Iwamoto E L.Changes in energy metabolism and antioxidant defense systems during seed germination of the weed speciesIpomoea trilobaL.and the responses to allelochemicals[J].Journal of Chemical Ecology,2011,37(5):500–513

[51]Abenavoli M R,Cacco G,Sorgonà A,et al.The inhibitory effects of coumarin on the germination of durum wheat (Triticum turgidumssp.durum,cv.Simeto) seeds[J].Journal of Chemical Ecology,2006,32(2):489–506

[52]Oracz K,Voegele A,Tarkowsk D,et al.Myrigalone A inhibitsLepidium sativumseed germination by interference with gibberellin metabolism and apoplastic superoxide production required for embryo extension growth and endosperm rupture[J].Plant and Cell Physiology,2012,53(1):81–95

[53]Voegele A,Graeber K,Oracz K,et al.Embryo growth,testa permeability,and endosperm weakening are major targets for the environmentally regulated inhibition ofLepidium sativumseed germination by myrigalone A[J].Journal of Experimental Botany,2012,63(14):5337–5350

[54]Kato-Noguchi H,Macías F A.Inhibition of germination and α-amylase induction by 6-methoxy-2-benzoxazolinone in twelve plant species[J].Biologia Plantarum,2008,52(2):351–354

[55]Kato-Noguchi H,Macías F A.Effects of 6-methoxy-2-benzoxazolinone on the germination andα-amylase activity in lettuce seeds[J].Journal of Plant Physiology,2005,162(12):1304–1307

[56]Kupid?owska E,Gniazdowska A,St?pień J,et al.Impact of sunflower (Helianthus annuusL.) extracts upon reserve mobilization and energy metabolism in germinating mustard (Sinapis albaL.) seeds[J].Journal of Chemical Ecology,2006,32(12):2569–2583

[57]Miransari M,Smith D L.Plant hormones and seed germination[J].Environmental and Experimental Botany,2014,99:110–121

[58]Shu K,Meng Y J,Shuai H W,et al.Dormancy and germination:How does the crop seed decide?[J].Plant Biology,2015,17(6):1104–1112

[59]Shu K,Chen Q,Wu Y R,et al.ABI4 mediates antagonistic effects of abscisic acid and gibberellins at transcript and protein levels[J].The Plant Journal,2015,85(3):348–361

[60]Linkies A,Leubner-Metzger G.Beyond gibberellins and abscisic acid:How ethylene and jasmonates control seed germination[J].Plant Cell Reports,2012,31(2):253–270

[61]Shu K,Zhang H W,Wang S F,et al.ABI4 regulates primary seed dormancy by regulating the biogenesis of abscisic acid and gibberellins in Arabidopsis[J].PLoS Genetics,2013,9(6):e1003577

[62]Holdsworth M J,Bentsink L,Soppe W J J.Molecular networks regulatingArabidopsisseed maturation,afterripening,dormancy and germination[J].New Phytologist,2008,179(1):33–54

[63]Finkelstein R,Reeves W,Ariizumi T,et al.Molecular aspects of seed dormancy[J].Annual Review of Plant Biology,2008,59(1):387–415

[64]Skene K R,Sprent J I,Raven J A,et al.Myrica galeL.[J].Journal of Ecology,2000,88(6):1079–1094

[65]Popovici J,Bertrand C,Jacquemoud D,et al.An allelochemical fromMyrica galewith strong phytotoxic activity against highly invasiveFallopia x bohemicataxa[J].Molecules,2011,16(3):2323–2333

[66]Gniazdowska A,Oraczr K,Bogatek R.Phytotoxic effects of sunflower (Helianthus annuusL.) leaf extracts on germinating mustard (Sinapis albaL.) seeds[J].Allelopathy Journal,2007,19(1):215–226

[67]Zhu Y,Li Q X.Movement of bromacil and hexazinone in soils ofHawaiian pineapplefields[J].Chemosphere,2002,49(6):669–674

[68]Roeleveld N,Bretveld R.The impact of pesticides on male fertility[J].Current Opinion in Obstetrics and Gynecology,2008,20(3):229–233

[69]Dayan F E,Cantrell C L,Duke S O.Natural products in crop protection[J].Bioorganic &Medicinal Chemistry,2009,17(12):4022–4034

[70]Schulz M,Marocco A,Tabaglio V,et al.Benzoxazinoids in rye allelopathy-from discovery to application in sustainable weed control and organic farming[J].Journal of Chemical Ecology,2013,39(2):154–174

[71]Kato-Noguchi H,Peters R J.The role of momilactones in rice allelopathy[J].Journal of Chemical Ecology,2013,39(2):175–185

[72]Weston L A,Alsaadawi I S,Baerson S R.Sorghum allelopathy-From ecosystem to molecule[J].Journal of Chemical Ecology,2013,39(2):142–153

[73]Bogatek R,Gniazdowska A,Zakrzewska W,et al.Allelopathic effects of sunflower extracts on mustard seed germination and seedling growth[J].Biologia Plantarum,2006,50(1):156–158

[74]Fragasso M,Iannucci A,Papa R.Durum wheat and allelopathy:Toward wheat breeding for natural weed management[J].Frontiers Plant in Science,2013,4:375

[75]王建花,陳婷,林文雄.植物化感作用類型及其在農(nóng)業(yè)中的應(yīng)用[J].中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào),2013,21(10):1173–1183 Wang J H,Chen T,Lin W X.Plant allelopathy types and their application in agriculture[J].Chinese Journal of Eco-Agriculture,2013,21(10):1173–1183

[76]Vyvyan J R.Allelochemicals as leads for new herbicides and agrochemicals[J].Tetrahedron,2002,58(9):1631–1646

[77]Jabran K,Mahajan G,Sardana V,et al.Allelopathy for weed control in agricultural systems[J].Crop Protection,2015,72:57–65

[78]Macías F A,Molinillo J M,Galindo J C G,et al.The use of allelopathic studies in the search for natural herbicides[J].Journal of Crop Production,2001,4(2):237–255

[79]Khanh T D,Chung M I,Xuan T D,et al.The exploitation of crop allelopathy in sustainable agricultural production[J].Zeitschrift fur Acker-und Pflanzenbau,2005,191(3):172–184 [80]Dilipkumar M,Chuah T S.Is combination ratio an important factor to determine synergistic activity of allelopathic crop extract and herbicide?[J].International Journal of Agriculture &Biology,2013,15(2):259–265

[81]Blackshaw R E,Moyer J R,Doram R C,et al.Yellow sweetclover,green manure,and its residues effectively suppress weeds during fallow[J].Weed Science,2001,49(3):406–413

[82]Moyer J R,Blackshaw R E,Huang H C.Effect of sweetclover cultivars and management practices on following weed infestations and wheat yield[J].Canadian Journal of Plant Science,2007,87(4):973–983

[83]Tesio F,Vidotto F,Ferrero A.Allelopathic persistence ofHelianthus tuberosusL.residues in the soil[J].Scientia Horticulturae,2012,135:98–105

[84]鞠瑞亭,李慧,石正人,等.近十年中國(guó)生物入侵研究進(jìn)展[J].生物多樣性,2012,20(5):581–611 Ju R T,Li H,Shi Z R,et al.Progress of biological invasions research in China over the last decade[J].Biodiversity Science,2012,20(5):581–611

[85]Schittko C,Wurst S.Above- and belowground effects of plant-soil feedback from exoticSolidago canadensison nativeTanacetum vulgare[J].Biological Invasions,2014,16(7):1465–1479

[86]Shen S C,Xu G F,Clements D R,et al.Suppression of the invasive plant mile-a-minute (Mikania micrantha) by local crop sweet potato (Ipomoea batatas) by means of higher growth rate and competition for soil nutrients[J].BMC Ecology,2015,15:1

[87]Hodgins K A,Lai Z,Nurkowski K,et al.The molecular basis of invasiveness:Differences in gene expression of native and introduced common ragweed (Ambrosia artemisiifolia) in stressful and benign environments[J].Molecular Ecology,2013,22(9):2496–2510

[88]張敏,付冬梅,陳華保,等.紫莖澤蘭葉片對(duì)小麥、油菜幼苗的化感作用及化感機(jī)制的初步研究[J].浙江大學(xué)學(xué)報(bào):農(nóng)業(yè)與生命科學(xué)版,2010,36(5):547–553 Zhang M,Fu D M,Chen H B,et al.Preliminary study on allelopathic effects and mechanism ofEupatorium adenophorumto wheat and rape seedlings[J].Journal of Zhejiang University:Agriculture &Life Sciences,2010,36(5):547–553

[89]Jarchow M E,Cook B J.Allelopathy as a mechanism for the invasion ofTypha angustifolia[J].Plant Ecology,2009,204(1):113–124

[90]Greer M J,Wilson G W,Hickman K R,et al.Experimental evidence that invasive grasses use allelopathic biochemicals as a potential mechanism for invasion:Chemical warfare in nature[J].Plant and Soil,2014,385(1/2):165–179

[91]萬(wàn)歡歡,劉萬(wàn)學(xué),萬(wàn)方浩.紫莖澤蘭葉片凋落物對(duì)入侵地4種草本植物的化感作用[J].中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào),2011,19(1):130–134 Wan H H,Liu W X,Wan F H.Allelopathic effect ofAgeratina adenophora(Spreng.) leaf litter on four herbaceous plants in invaded regions[J].Chinese Journal of Eco-Agriculture,2011,19(1):130–134

[92]類延寶,肖海峰,馮玉龍.外來(lái)植物入侵對(duì)生物多樣性的影響及本地生物的進(jìn)化響應(yīng)[J].生物多樣性,2010,18(6):622–630 Lei Y B,Xiao H F,Feng Y L.Impacts of alien plant invasions on biodiversity and evolutionary responses of native species[J].Biodiversity Science,2010,18(6):622–630

[93]彭少麟,邵華.化感作用的研究意義及發(fā)展前景[J].應(yīng)用生態(tài)學(xué)報(bào),2001,12(5):780–786 Peng S L,Shao H.Research significance and foreground of allelopathy[J].Chinese Journal of Applied Ecology,2001,12(5):780–786

[94]Singh H P,Batish D R,Kohli R K.Autotoxicity:Concept,organisms,and ecological significance[J].Critical Reviews in Plant Sciences,1999,18(6):757–772

[95]Ruan X,Li ZH,Wang Q,et al.Autotoxicity and allelopathy of3,4-dihydroxyacetophenone isolated fromPicea schrenkiananeedles[J].Molecules,2011,16(10):8874–8893

[96]Chen L C,Wang S L,Wang P,et al.Autoinhibition and soil allelochemical (cyclic dipeptide) levels in replanted Chinese fir (Cunninghamia lanceolata) plantations[J].Plant and Soil,2014,374(1/2):793–801

[97]Chon S U,Coutts J H,Nelson C J.Effects of light,growth media,and seedling orientation on bioassays of alfalfa autotoxicity[J].Agronomy Journal,2000,92(4):715–720

[98]張文明,邱慧珍,張春紅,等.連作馬鈴薯不同生育期根系分泌物的成分檢測(cè)及其自毒效應(yīng)[J].中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào),2015,23(2):215–224 Zhang W M,Qiu H Z,Zhang C H,et al.Identification and autotoxicity of root exudates of continuous cropping potato at different growth stages[J].Chinese Journal of Eco-Agriculture,2015,23(2):215–224

[99]李登武,王冬梅,姚文旭.油松的自毒作用及其生態(tài)學(xué)意義[J].林業(yè)科學(xué),2010,46(11):174–178 Li D W,Wang D M,Yao W X.Autotoxicity ofPinus tabulaeformisand its ecology significance[J].Scientia Silvae Sinicae,2010,46(11):174–178

[100]林思祖,黃世國(guó),曹光球,等.杉木自毒作用的研究[J].應(yīng)用生態(tài)學(xué)報(bào),1999,10(6):661–664 Lin S Z,Huang S G,Cao G Q,et al.Autointoxication of Chinese fir[J].Chinese Journal of Applied Ecology,1999,10(6):661–664

[101]馬祥慶,劉愛(ài)琴,黃寶龍.杉木人工林自毒作用研究[J].南京林業(yè)大學(xué)學(xué)報(bào),2000,24(1):12–16 Ma X Q,Liu A Q,Huang B L.A study on self-poisoning effects of Chinese fir plantation[J].Journal of Nanjing Forestry University,2000,24(1):12–16

[102]Wu H W,Pratley J,Lemerle D,et al.Autotoxicity of wheat (Triticum aestivumL.) as determined by laboratory bioassays[J].Plant and Soil,2007,296(1/2):85–93

[103]Mondal M F,Asaduzzaman M,Kobayashi Y,et al.Recovery from autotoxicity in strawberry by supplementation of amino acids[J].Scientia Horticulturae,2013,164:137–144

[104]張重義,林文雄.藥用植物的化感自毒作用與連作障礙[J].中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào),2009,17(1):189–196 Zhang C Y,Lin W X.Continuous cropping obstacle and allelopathic autotoxicity of medicinal plants[J].Chinese Journal of Eco-Agriculture,2009,17(1):189–196

Effect of plant allelochemicals on seed germination and its ecological significance*

CHEN Feng,MENG Yongjie,SHUAI Haiwei,LUO Xiaofeng,ZHOU Wenguan,LIU Jianwei,YANG Wenyu**,SHU Kai**
(Key Laboratory of Crop Ecophysiology and Farming Systems in Southwest China,Ministry of Agriculture /Institute of Ecological Agriculture,College of Agronomy,Sichuan Agricultural University,Chengdu 611130,China)

As a form of plant interaction,allelopathy plays a critical role in agriculture and forestry production,including biological invasion,continuous cropping obstacle and weed suppression.Consequently,it is important to guide production if we take advantage of plant allelopathy in crop production.Seed germination is a key stage of a plant and the regulatory mechanism of this physiological process by allelopathy has been paid more and more attention.Numerous studies demonstrated that allelochemicals could promote or inhibit seed germination of different plant species,which had an importantinfluence on the plant growth and development,the composition and distribution of plant communities and the balance within the ecosystem.In this review,the effect of allelochemicals on seed germination and its ecological significance were summarized.On the one hand,the physiological and biochemical mechanisms underlying the inhibition effect of allelochemicals on seed germination were summarized.For example,allelochemicals restrained seed germination through inhibition of radicle and hypocotyl elongation.Allelochemicals also hindered seed germination by damaging subcellular structures,disturbed the synthesis and metabolism of both phytohormones and reactive oxygen species (ROS).Furthermore,allelochemicals delayed seed germination by mediating metabolism of protein,oil and starch,which provide energy during seed germination.On the other hand,we discussed the ecological significance of allelochemicals to seed germination from two perspectives,weeds control of farmland and ecosystem stabilization.Here,we summarized the effects of allelochemicals on weed suppression in natural settings,autotoxicity in agriculture and forestry,and biological invasion caused by allelopathy.Finally,based on current research progresses,future research directions in the field of allelopathy and autotoxicity were proposed and discussed.

Allelopathy;Allelochemical;Seed germination;Ecosystem

Q945.34

:A

:1671-3990(2017)01-0036-11

10.13930/j.cnki.cjea.160632

陳鋒,孟永杰,帥海威,羅曉峰,周文冠,劉建偉,楊文鈺,舒凱.植物化感物質(zhì)對(duì)種子萌發(fā)的影響及其生態(tài)學(xué)意義[J].中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào),2017,25(1):36-46

Chen F,Meng Y J,Shuai H W,Luo X F,Zhou W G,Liu J W,Yang W Y,Shu K.Effects of plant allelochemicals on seed germination and its ecological significance[J].Chinese Journal of Eco-Agriculture,2017,25(1):36-46

* 四川省教育廳基金項(xiàng)目(16ZB0040)、中國(guó)博士后科學(xué)基金項(xiàng)目(2014M552377,2016T90868)和國(guó)家重點(diǎn)基礎(chǔ)研究發(fā)展計(jì)劃(973計(jì)劃)項(xiàng)目(2011CB100402)資助

** 通訊作者:舒凱,主要從事植物遺傳學(xué)及分子生物學(xué)研究,E-mail:kshu@sicau.edu.cn;楊文鈺,主要從事大豆栽培生理研究,E-mail:mssiyangwy@sicau.edu.cn

陳鋒,主要從事植物分子生物學(xué)、遺傳學(xué)研究。E-mail:cffuyang@hotmail.com

2016-07-17接受日期:2016-09-14

* This work was supported by the Project of Education Department of Sichuan Province (16ZB0040),the China Postdoctoral Science Foundation of China (2014M552377,2016T90868) and the National Basic Research Program of China (2011CB100402).

** Corresponding authors:SHU Kai,E-mail:kshu@sicau.edu.cn;YANG Wenyu,E-mail:mssiyangwy@sicau.edu.cn

Received Jul.17,2016;accepted Sep.14,2016