周　晶,趙　亮,江丹丹,常朝陽(yáng)

(西北農(nóng)林科技大學(xué) 生命科學(xué)學(xué)院,陜西楊陵 712100)

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太原黃耆(豆科)花器官及胚珠發(fā)育研究

周晶,趙亮,江丹丹,常朝陽(yáng)*

(西北農(nóng)林科技大學(xué) 生命科學(xué)學(xué)院,陜西楊陵 712100)

摘要:太原黃耆是新近發(fā)表的物種,分布于中國(guó)陜西和山西。該實(shí)驗(yàn)利用掃描電子顯微鏡對(duì)太原黃耆的花器官發(fā)生和發(fā)育過(guò)程進(jìn)行觀察研究。結(jié)果顯示:(1)太原黃耆的各輪花器官都是從遠(yuǎn)軸端向近軸端單向連續(xù)發(fā)生,在不同輪之間存在花器官重疊發(fā)生的現(xiàn)象。(2)在花的發(fā)育過(guò)程中,出現(xiàn)2種共同原基,即初級(jí)共同原基和次級(jí)共同原基,由初級(jí)共同原基發(fā)育成對(duì)萼雄蕊原基和次級(jí)共同原基,再由次級(jí)共同原基發(fā)育成花瓣原基和對(duì)瓣雄蕊原基。(3)雄蕊管近軸端基部開口是在進(jìn)化過(guò)程中產(chǎn)生的特殊結(jié)構(gòu),是一種對(duì)傳粉者的適應(yīng)機(jī)制,從而有利于傳粉活動(dòng)的進(jìn)行。(4)胚珠為倒生胚珠,具有2層珠被,認(rèn)為倒生胚珠是內(nèi)外2層珠被共同作用的結(jié)果。

關(guān)鍵詞:黃耆屬;花發(fā)育;共同原基;胚珠發(fā)育

黃耆屬(AstragalusL.)是被子植物最大的屬之一[1],包含了超過(guò)2 500種一年生和多年生植物[2],主要分布于北半球、南美洲及非洲。中國(guó)400余種,主要分布于西藏(喜馬拉雅山區(qū))、亞洲中部和東北[3]。黃耆屬為典型的蝶形花類植物,具有典型的兩側(cè)對(duì)稱的蝶形花冠?；ㄝ嗦?lián)合形成花萼筒,花瓣分離(龍骨瓣上部粘合),二體雄蕊,除了對(duì)旗瓣雄蕊外其他9枚雄蕊花絲聯(lián)合成雄蕊管,單心皮?；ǖ奶卣鲗?duì)于黃耆屬的分類很重要[4-6],然而黃耆屬花的發(fā)育特征卻少有研究。最近,伊朗學(xué)者先后研究了AstragaluscaspicusBieb.、AstragaluslagopoidesLam.和Astragaluscompactus花的發(fā)生發(fā)育過(guò)程[7-9],但這些黃耆屬物種均產(chǎn)自西亞,東亞黃耆屬花發(fā)育的研究尚屬空白。太原黃耆(AstragalustaiyuanensisS.B.Ho)隸屬于脹萼黃耆亞屬兔尾狀組(Subgen.Calycocystis Bunge Sect.Laguropsis Bunge),分布于中國(guó)陜西和山西,是新近發(fā)表的物種,目前對(duì)其的研究都比較少[10]。本研究對(duì)太原黃耆花的發(fā)育過(guò)程進(jìn)行研究,以期填補(bǔ)這方面的空白。

1材料和方法

自2013年4月至2014年5月,在陜西咸陽(yáng)市禮泉縣趙鎮(zhèn)北山分別采集太原黃耆不同發(fā)育階段的花芽,用FAA固定液(福爾馬林∶冰醋酸∶70%乙醇=5∶5∶90)固定保存。憑證標(biāo)本(Zhoujing SX2014001,alt.616 m)存放于西北農(nóng)林科技大學(xué)植物標(biāo)本館(WUK)。用于電鏡觀察的材料,在體視顯微鏡下進(jìn)行剝離,剝制好的標(biāo)本在乙醇和乙酸異戊酯中進(jìn)行梯度脫水,CO2臨界點(diǎn)干燥,噴金鍍膜,在日立S-3400掃描電子顯微鏡下觀察拍照?；ǖ男螒B(tài)特征在野外直接將花解剖,用尼康D-600相機(jī)拍攝。

2結(jié)果與分析

2.1花形態(tài)特征

太原黃耆為總狀花序,各小花在花序軸上呈螺旋狀排列(圖版Ⅰ,1)。每朵小花具有1枚小苞片。花萼上密被毛,萼齒長(zhǎng)約為萼片的一半(圖版Ⅰ,2),萼筒在果期膨脹(圖版Ⅰ,1)。旗瓣較大,翼瓣和龍骨瓣近等長(zhǎng)(圖版Ⅰ,3～5)。二體雄蕊(圖版Ⅰ,6),子房密被毛,具子房柄,花柱較長(zhǎng),上部彎成鉤狀(圖版Ⅰ,7),柱頭乳突狀。

2.2花器官發(fā)生過(guò)程

太原黃耆各輪花器官的發(fā)生順序都是由遠(yuǎn)軸端向近軸端單向連續(xù)發(fā)生,器官發(fā)生過(guò)程中不同輪器官表現(xiàn)出高度的重疊發(fā)生現(xiàn)象和共同原基現(xiàn)象。第1枚萼片從遠(yuǎn)軸端開始發(fā)生(圖版Ⅱ,1),隨后側(cè)面的2枚萼片相繼發(fā)生(圖版Ⅱ,1、2),此時(shí)初級(jí)共同原基開始從遠(yuǎn)軸端和兩側(cè)發(fā)生(圖版Ⅱ,2),隨后近軸端的2枚萼片發(fā)生(圖版Ⅱ,3)。遠(yuǎn)軸端初級(jí)共同原基隨后分化成對(duì)萼雄蕊原基和2枚次級(jí)共同原基(圖版Ⅱ,4),側(cè)面的2個(gè)初級(jí)共同原基分別分化成對(duì)萼雄蕊原基和1枚次級(jí)共同原基,近軸端的初級(jí)共同原基也開始產(chǎn)生(圖版Ⅱ,5)。此后,近軸端的初級(jí)共同原基分化成2枚對(duì)萼雄蕊原基和1枚次級(jí)共同原基(圖版Ⅱ,6、7),次級(jí)共同原基由遠(yuǎn)軸端向近軸端又分化成向心的對(duì)瓣雄蕊原基和離心的花瓣原基(圖版Ⅱ,7～9),而且近軸端的花瓣原基在發(fā)生時(shí)已經(jīng)大于其它花瓣原基(圖版Ⅱ,9)。心皮原基在近軸端初級(jí)共同原基產(chǎn)生后發(fā)生,為半球形的凸起(圖版Ⅱ,5),隨后近軸端的一面變得扁平(圖版Ⅱ,6～8),當(dāng)所有花器官分化完成時(shí),心皮的腹縫線形成(圖版Ⅱ,9)。

2.3花器官發(fā)育過(guò)程

在萼片原基形成后,其基部開始聯(lián)合生長(zhǎng),形成花萼筒和萼齒(圖版Ⅲ,1),花萼筒通過(guò)居間生長(zhǎng)向上延長(zhǎng)生長(zhǎng),包住內(nèi)輪器官。發(fā)育過(guò)程中,花萼上逐漸產(chǎn)生毛狀體?；ò暝诎l(fā)育的初始階段生長(zhǎng)得相對(duì)較慢,而其他幾輪器官生長(zhǎng)較快,在大小上超過(guò)了花瓣原基的生長(zhǎng)速度(圖版Ⅲ,2)。隨后,花瓣原基發(fā)育成薄片狀,旗瓣明顯大于其他花瓣并且這種生長(zhǎng)優(yōu)勢(shì)保持到花期(圖版Ⅲ,3～8)。當(dāng)所有雄蕊都分化出花藥和花絲時(shí),花瓣邊緣開始發(fā)生重疊(圖版Ⅲ,5),而后形成下降的覆瓦狀排列方式(圖版Ⅲ,6),這也是蝶形花亞科普遍的排列方式。隨后,龍骨瓣邊緣逐漸粘合生長(zhǎng)(圖版Ⅲ,6)。在花期前,花瓣之間緊密排列,旗瓣幾乎包住整朵花(圖版Ⅲ,8)。外輪雄蕊從始至終要高于內(nèi)輪雄蕊(圖版Ⅲ,1～5),而且從遠(yuǎn)軸端到近軸端依次降低(圖版Ⅲ,7)。當(dāng)外輪雄蕊開始分化時(shí),雄蕊原基基部變窄形成花絲,上部擴(kuò)大形成花藥(圖版Ⅲ,2、3)。分化初期是基部著藥(圖版Ⅲ,2、3),隨著生長(zhǎng)發(fā)育最終形成背著藥(圖版Ⅲ,9)。內(nèi)輪雄蕊的發(fā)育過(guò)程和外輪雄蕊相似。在花藥分化完成后,2輪雄蕊排成1輪,10枚雄蕊一開始各自分離,后花絲從基部向上逐漸融合形成近軸端斷開的雄蕊管,而近軸端的對(duì)旗瓣雄蕊保持獨(dú)立(圖版Ⅲ,9),在它們之間形成2個(gè)開口(圖版Ⅲ,10、11)。隨著繼續(xù)生長(zhǎng),雄蕊管基部向內(nèi)彎曲近90度緊貼子房再向上生長(zhǎng)形成一種特殊結(jié)構(gòu)(圖版Ⅲ,12)。在發(fā)育過(guò)程中,心皮的腹縫線逐漸愈合,愈合后不久分化出柱頭,花柱和子房。柱頭發(fā)育成乳突狀,花柱彎成鉤狀,子房密被毛(圖版Ⅲ,10)。

2.4胚珠發(fā)生發(fā)育

胚珠原基發(fā)生于心皮邊緣,為邊緣胎座。胚珠發(fā)生時(shí)成圓柱形,排成單列,有多數(shù)胚珠(圖版Ⅳ,1)。具雙珠被,其中內(nèi)珠被在胚珠原基中上部發(fā)生(圖版Ⅳ,2),很快外珠被在內(nèi)珠被的下面發(fā)生(圖版Ⅳ,3、4)。隨后胚珠開始向外彎曲生長(zhǎng)(圖版Ⅳ,5～7),外觀上內(nèi)珠被呈圓形,外珠被半圓形(圖版Ⅳ,8)。之后,外珠被逐漸覆蓋內(nèi)珠被,最終包住珠心,彎向胎座繼續(xù)生長(zhǎng)發(fā)育出珠孔(圖版Ⅳ,9～12),形成倒生胚珠。

3討論

3.1器官重疊及共同原基

太原黃耆花器官的發(fā)生方式同伊朗學(xué)者研究過(guò)的本屬3個(gè)種相似,同樣存在器官重疊發(fā)生的現(xiàn)象,即后一輪花器官在前一輪所有花器官都發(fā)生之前就已發(fā)生[7-9]。這種發(fā)生模式在蝶形花亞科其他類群也有出現(xiàn)[11-16],表現(xiàn)在花萼原基和初級(jí)共同原基,對(duì)萼雄蕊原基、次級(jí)共同原基和心皮原基,以及花瓣原基和對(duì)瓣雄蕊原基三個(gè)層次。這種特殊的發(fā)生方式被認(rèn)為是心皮和對(duì)萼雄蕊輪早熟的結(jié)果?；ㄆ鞴僭缡飕F(xiàn)象在較為特化的蝶形花亞科中比較盛行,被認(rèn)為是一種高級(jí)的演化特征[14-17]。在太原黃耆花器官發(fā)生過(guò)程中,共同原基發(fā)生在萼片和心皮之間的區(qū)域,與前人研究結(jié)果一致[7-9]。據(jù)認(rèn)為這代表了一種進(jìn)化上的特化形式,可縮短不同輪花器官發(fā)生的時(shí)間間隔[17-18],本文支持這一結(jié)論。

3.2雄蕊管基部開口

對(duì)旗瓣雄蕊保持獨(dú)立,與雄蕊管保持分離的狀態(tài),從而在雄蕊管近軸端基部產(chǎn)生2個(gè)開口,這在蝶形花亞科是比較普遍的現(xiàn)象,比如Erythrinacaffra、Pisumsativum和Psoraleapinnata都存在這種現(xiàn)象[15,19,20]。在云實(shí)亞科的Cercis也有發(fā)現(xiàn)[21]。Tucker研究了蝶形花亞科中的32族,大部分也存在這種現(xiàn)象[19]。這些開口是為了傳粉者從此進(jìn)入采蜜而特化的結(jié)構(gòu),是一種適應(yīng)機(jī)制[22],也被認(rèn)為是在進(jìn)化過(guò)程中產(chǎn)生的有利結(jié)構(gòu)[23]。

3.3胚珠發(fā)育

太原黃耆的胚珠為倒生胚珠,而在海人樹科(Surianaceae)和豆科的許多類群中為彎生胚珠[24-25]。在現(xiàn)存被子植物中,倒生胚珠最有可能是祖先性狀[26-27]。雙珠被在豆科植物較為常見,但在Lupinus中發(fā)現(xiàn)只有1層珠被[28],而在Acaciacelastrifolia中,作者也觀察到只有外珠被可見,內(nèi)珠被延遲發(fā)育而不可見[29]。在太原黃耆的胚珠發(fā)生發(fā)育過(guò)程中,內(nèi)外珠被都是可見的,內(nèi)珠被先發(fā)生,而后外珠被發(fā)生。研究認(rèn)為被子植物胚珠的祖先狀態(tài)很可能具有2層珠被[27,30]。胚珠發(fā)生彎曲是被子植物的一個(gè)主要特征,這區(qū)別于通常為直生胚珠的裸子植物(羅漢松科Podocarpaceae除外)[31],而且胚珠發(fā)生彎曲使珠孔彎向胚珠著生的地方,接近胎座從而利于接觸花粉管進(jìn)行受精作用[22]。Tucker認(rèn)為內(nèi)外2層珠被的發(fā)生是胚珠最終發(fā)育成倒生胚珠的主要原因[31],太原黃耆倒生胚珠的發(fā)育符合這一規(guī)律。顯然,在花的發(fā)生和發(fā)育以及胚珠的發(fā)育過(guò)程中,太原黃耆顯示出進(jìn)化不同步的現(xiàn)象。

參考文獻(xiàn):

[1]PODLECH D.Phylogeny and Progression of Characters in Old World Astragali (Legominoseae)[M]//ZANG A,WU S.Floristic Characteristic and Diversity of East Asian Plants.Beijing:China Higher Education Press,1998:405-407.

[2]POLHILL R M.Papilionoideae[M]//POLHILL R M,RAVEN P H.Advances in Legume Systematics.Royal Botanic Gardens:Kew,1981,1:191-208.

[3]傅坤俊,等.中國(guó)植物志[M].北京:科學(xué)出版社,1993,42(1):78-82.

[4]PODLECH D.The genusAstragalusL.(Fabaceae) in Europe with exclusion of the former Soviet Union[J].FeddesRepertorium,2008,119:310-387.

[5]ZARRE S,PODLECH D.Taxonomic revision ofAstragalusL.sect.AcanthophaceBunge (Fabaceae)[J].Sendtnera,2001,7:233-251.

[6]KANTZ K E,TUCKER S C.Developmental Basis of Floral Characters in the Caesalpinieae[M]//FERGUSON I K,TUCKER S C.Advances in Legume Systematic,Structural botany.Royal Botanic Gardens:Kew,1994,6:33-40.

[7]MOVAFEGHI A,NAGHILOO S,etal.Inflorescence and floral development inAstragaluslagopoidesLam.(Leguminosae:Papilionoideae:Galegeae)[J].Flora,2011,206:219-226.

[8]NAGHILOO S,DADPOUR M R,MOVAFEGHI A.Floral ontogeny inAstragaluscompactus(Leguminosae:Papilionoideae:Galegeae):variable occurrence of bracteoles and variable patterns of sepal initiation[J].Planta,2012,235:793-805.

[9]MOVAFEGHI A,DADPOUR M R,NAGHILOO S,etal.Floral development inAstragaluscaspicusBieb.(Leguminosae:Papilionoideae:Galegeae)[J].Flora,2010,205:251-258.

[10]何善寶.中國(guó)植物志黃芪屬預(yù)報(bào)(六)[J].植物研究,1983,3(4):58-65.

HO S B.Prascursores floraeAstragalorumsinensium(Ⅵ)[J].BulletinofBotanicalResearch,1983,3(4):58-65.

[11]BENLLOCH R,NAVARRO C,BELTRN J P,etal.Floral development of the model legumeMedicagotruncatula:ontogeny studies as a tool to better characterize homeotic mutations[J].SexualPlantReproduction,2003,15:231-241.

[12]MANSANO VF,TUCKER SC,TOZZI AMGA.Floral ontogeny ofLecointea,Zollernia,ExostylesandHarleyodendron(Leguminosae:Papilionoideae:Swartzieae s.l.)[J].AmericanJournalofBotany,2002,89:1 553-1 569.

[13]PRENNER G.Floral ontogeny inLespedezathunbergii(Leguminosae:Papilionoideae:Desmodieae):variations from the unidirectional mode of organ formation[J].JournalofPlantResearch,2004,117:297-302.

[14]TUCKER S C.Unidirectional organ initiation in leguminous flowers[J].AmericanJournalofBotany,1984,71:1 139-1 148.

[15]TUCKER S C.Overlapping organ initation and common primordia in flowers ofPisumsativum(Leguminosae:Papilionoideae)[J].AmericanJournalofBotany,1989,76:714-729.

[16]TUCKER S C.Floral ontogeny in Sophoreae (Leguminosae:Papilionoideae).Ⅲ.Radial symmetry and random petal aestivation inCadiapurpurea[J].AmericanJournalofBotany,2002,89:748-757.

[17]KLITGAARD B B.Floral ontogeny in tribe Dalbergieae (Leguminosae:Papilionoideae):Dalbergiabrasiliensis,Machaeriumvillosums.l.,PlatymisciumfloribundumandPterocarpusrotundifolius[J].PlantSystematicsandEvolution,1999,219:1-25.

[18]TUCKER S C.Floral development in legumes[J].PlantPhysiology,2003,131:911-926.

[19]TUCKER S C.Floral Initiation and Development in Legumes[M]//STIRTON C H.Advances in Legume Systematics.Royal Botanic Gardens,Kew,1987,3:183-239.

[20]TUCKER S C,STIRTON CH.Development of the cymose inflorescence,cupulum and flower ofPsoraleapinnata(Leguminosae:Papilionoideae)[J].BotanicalJournaloftheLinneanSociety,1991,106:209-227.

[21]TUCKER S C.Floral ontogeny ofCercis(Leguminosae:Caesalpinioideae:Cercideae):does it show convergence with papilionoids?[J].InternationalJournalofPlantSciences,2002,163:75-87.

[22]ENDRESS P K.Diversity and Evolutionary Biology of Tropical Flowers[M].Cambridge University Press,Cambridge,1994.

[23]POLHILL R M,RAVEN P H,STIRTON C H.Evolution and Systematics of the Leguminosae[M]//POLHILL R M,RAVEN P H.Advances in Legume Systematics.Royal Botanic Gardens:Kew,1981,1:1-26.

[24]HEO K,TOBE H.Embryology and relationships ofSurianamaritimaL.(Surianaceae)[J].JournalofPlantResearch,1994,107:29-37.

[25]PRAKASH N.Embryology of the Leguminosae[M]//STIRTON C H.Advances in Legume Systematics.Royal Botanic Gardens:Kew,1987,3:241-278.

[26]DOYLE JA.Integrating molecular phylogenetic and paleobotanical evidence on origin of the flower[J].InternationalJournalofPlantSciences,2008,169:816-843.

[27]ENDRESS PK,DOYLE JA.Reconstructing the ancestral flower and its initial specializations[J].AmericanJournalofBotany,2009,96:22-66.

[28]ATABEKOVA AI.Comparative embryological studies inLupinus(Tourn.) L.[J].Izvest.Timir.Sel'sk.Jaistv.Akad,1963,2(51):219-221.

[29]PRENNER G.Floral Ontogeny ofAcaciacelastrifolia:An Enigmatic Mimosoid Legume with Pronounced Polyandry and Multiple Carpels[M]//WANNTORP L,RONSE D C LP.Flower on The Tree of Life[M].Cambridge University Press,Cambridge.2011:256-278.

[30]DOYLE J A,ENDRESS P K.Morphological phylogenetic analysis of basal angiosperms:comparison and combination with molecular data[J].InternationalJournalofPlantSciences,2000,161:S121-S153.

圖版 Ⅰ太原黃耆成熟花解剖圖

1.花序;2.花萼片;3.旗瓣;4.翼瓣;5.龍骨瓣;6.雄蕊;7.雌蕊。

Plate ⅠPhotographs of inflorescence and all the floral organs ofA.taiyuanensis

Fig.1.Mature inflorescence;Fig.2.Five fused sepals;Fig.3.Vexillum or standard petal;Fig.4.Wing petal;Fig.5.Keel petal;Fig.6.Androecium;Fig.7.Gynoecium.

[31]ENDRESS P K.Angiosperm ovules:diversity,development,evolution[J].AnnalsofBotany,2011,107:1 465-1 489.

圖版 Ⅱ太原黃耆花器官發(fā)生發(fā)育掃描電鏡照片

器官發(fā)生順序用數(shù)字表示;A.外輪雄蕊原基;a.內(nèi)輪雄蕊原基;rB.去除的苞片;C.心皮原基;CP1.初級(jí)共同原基;CP2.次級(jí)共同原基;P.花瓣原基;S.萼片原基

1.第一枚和第二枚萼片原基發(fā)生;2.第三枚萼片發(fā)生,遠(yuǎn)軸端一枚初級(jí)共同原基和側(cè)面的兩枚初級(jí)共同原基發(fā)生;3.近軸端兩枚萼片發(fā)生;4.遠(yuǎn)軸端初級(jí)共同原基分化出對(duì)萼雄蕊原基和次級(jí)共同原基;5.側(cè)面兩枚初級(jí)共同原基分化出對(duì)萼雄蕊原基和次級(jí)共同原基,近軸端初級(jí)共同原基發(fā)生,心皮原基也在中央發(fā)生;6.近軸端初級(jí)共同原基分化出對(duì)萼雄蕊原基和次級(jí)共同原基;7.遠(yuǎn)軸端次級(jí)共同原基分化出花瓣原基和對(duì)瓣雄蕊原基;8.側(cè)面次級(jí)共同原基分化出花瓣原基和對(duì)瓣雄蕊原基;9.近軸面次級(jí)共同原基分化出花瓣原基和對(duì)瓣雄蕊原基,心皮腹縫線開始形成(箭頭所指)。

Plate ⅡSEM photographs of floral organogenesis ofA.taiyuanensis

Adaxial side is at base in all.Initiation order is numbered.A.Outer whorl stamen;a.Inner whorl stamen;rB.Removed bract;C.Carpel;CP1.Primary common primordia;CP2.Secondary common primordia;P.Petal primordia;S.Sepal primordia

Fig.1.The first two sepal primordia initiates;Fig.2.The third sepal primordia and three common primordia initiates;Fig.3 The adaxial two sepals initiates;Fig.4.The abaxial primary common primordia begins to develop into two second common primordia and one antesepalous stamen primordia;Fig.5.The adaxial primary common primordia and the middle carpel primordia initiates and the lateral two primary common primordia begins to develop into one second common primordia and one antesepalous stamen primordia respectively;Fig.6.The adaxial primary common primordia begins to develop into one second common primordia and one antesepalous stamen primordia;Fig.7.The two abaxial second common primordia begin to develop into one petal primordia and one antepetalous primordia,respectively;Fig.8.The two lateral second common primordia begin to develop into one petal primordia and one antepetalous primordia,respectively and the adaxial antesepalous stamen initiates.The carpel begins to form;Fig.9.The adaxial second common primordia develops into one petal primordia and one antepetalous primordia.The carpel cleft becomes apparent(at arrow).

圖版 Ⅲ太原黃耆花器官發(fā)生發(fā)育掃描電鏡照片

器官發(fā)生順序用數(shù)字表示;A.外輪雄蕊;a.內(nèi)輪雄蕊;C.心皮;K.龍骨瓣;P.花瓣原基;S.萼片原基;St.柱頭;V.旗瓣;W.翼瓣

1.萼片開始長(zhǎng)毛;2.外輪雄蕊開始分化出花藥和花絲;3.心皮腹縫線開始愈合;4.心皮頂端開始彎曲生長(zhǎng)形成柱頭,內(nèi)輪雄蕊開始分化出花藥和花絲;5.旗瓣、翼瓣和龍骨瓣邊緣開始重疊;6.花瓣形成覆瓦狀排列方式,龍骨瓣邊緣開始粘合生長(zhǎng)(箭頭所指);7.去除旗瓣示接近成熟的柱頭;8.花瓣緊密重疊;9.去除花瓣示二體雄蕊;10.子房密被毛,雄蕊管基部具兩個(gè)開口(箭頭所指);11.示基部開口放大;12.成熟花的雄蕊管在基部彎曲近90度。

Plate ⅢSEM photographs of floral organogenesis ofA.taiyuanensis

A.Outer whorl stamen;a.Inner whorl stamen;C.Carpel;K.Keel petal;P.Petal;S.Sepal;St.Stigma;V.Vexillum;W.Wing petal

Fig.1.The hairs on the sepals begin to initiate;Fig.2.Outer stamens develop into anthers and filaments;Fig.3.The carpel cleft begins to appress.Fig.4;The carpel begins to curve to form the stigma and the inner stamens begin to develop into anthers and filaments;Fig.5.The vexillum petal,the wing petal and the keel petal begin to overlap;Fig.6.The descending imbricate corolla forms and the two keel petals begin to apress at the margin (at arrow);Fig.7.The nearly mature stigma;Fig.8.The five petals overlap tightly;Fig.9.Diadelphus stamens;Fig.10.The ovary is fulled of hairs at the surface and there are two holes at the base of the filament tube (at arrow);Fig.11.The details of base of the filament tube;Fig.12.The filaments curve for almost 90 degrees at maturity

圖版 Ⅳ太原黃耆胚珠發(fā)生發(fā)育掃描電鏡照片

F.珠柄;Ⅱ.內(nèi)珠被;N.珠心;O.胚珠原基;OI.外珠被

1.胚珠原基;2.內(nèi)珠被發(fā)生;3.外珠被發(fā)生;4.稍大一些的胚珠,胚珠開始彎曲生長(zhǎng);5.珠柄明顯,胚珠彎曲近90度;6.胚珠繼續(xù)彎曲;7.胚珠彎向胎座,約180度;8.示內(nèi)珠被圓形,外珠被半圓形;9.示外珠被的生長(zhǎng)超越內(nèi)珠被;10.示珠孔形成前;11.珠孔形成(箭頭所指);12.花期時(shí)的胚珠,珠孔依然可見(箭頭所指)。

Plate ⅣSEM photographs of ovular organogenesis ofA.taiyuanensis

F.Funicle;Ⅱ.Inner integument;N.Nucellus;O.Ovule primordia;OI.Outer integument

Fig.1.Ovule primordia initiates;Fig.2.The inner integument initiates;Fig.3.The outer integument initiates;Fig.4.The ovule begins to curve and a little older than that of Fig 3;Fig.5.The ovule curves for almost 90 degrees and the funicle is apparent;Fig.6.The ovule goes on curving;Fig.7.The ovule curves to placenta for nearly 180 degrees;Fig.8.The inner integument is ciruelar and the outer integument is semi-circular;Fig.9.Outer integument covers the inner integument;Fig.10.Will form the exostomial micropyle;Fig.11.The exostomial micropyle forms (at arrow);Fig.12.Ovule at flowering stage and the exostomial micropyle is still visible (at arrow).

(編輯:潘新社)

Floral and Ovular Development inAstragalustaiyuanensisS.B.Ho

ZHOU Jing,ZHAO Liang,JIANG Dandan,CHANG Zhaoyang*

(Life college of Sciences,Northwest A&F University,Yangling,Shaanxi 712100,China)

Abstract:Astragalus taiyuanensis was newly found,which was only located in Shanxi and Shaanxi Province of China.Floral organogenesis and development in A.taiyuanensis were studied by means of scanning electron microscopy.Results were as followed:(1)sepals,petals,outer stamens,and inner stamens were formed unidirectionally in each whorl from the abaxial to the adaxial sides of the flower.Overlap in starting time between members of adjacent whorls occured.(2)The existence of two forms of common primordia,categorized as primary and secondary,was observed.Primary common primordia develop into antesepalous stamens and secondary common primordia.In comparison,the five secondary common primordia subdivide into a petal and an antepetalous stamen primordia respectively.(3)Filament tube had two adaxial fenestrations at base,which was adaptation to the pollinators and in favor of pollination activities.(4)Ovules were anatropous and bitegmic in A.taiyuanensis.Anatropous ovules was a result of the appearance of both inner and outer integuments.

Key words:Astragalus;floral development;common primordia;ovular development

中圖分類號(hào):Q248;Q944.58

文獻(xiàn)標(biāo)志碼:A

*通信作者:常朝陽(yáng),教授,博士生導(dǎo)師,主要從事植物系統(tǒng)分類學(xué)研究。E-mai:czybbg@nwsuaf.edu.cn

作者簡(jiǎn)介:周晶(1990-),男,碩士研究生,主要從事植物系統(tǒng)分類學(xué)研究。E-mail:nfu080705133@126.com

基金項(xiàng)目:國(guó)家自然科學(xué)基金(30270106,30870155)

收稿日期:2015-11-08;修改稿收到日期:2016-01-11

文章編號(hào):1000-4025(2016)02-0296-07

doi:10.7606/j.issn.1000-4025.2016.02.0296