焕镛木花部数量变异和腋生花现象

对广西环江木论的焕镛木Woonyoungia septentrionalis(Dandy)Law]自然居群花朵着生方式和性别比例作了随机抽样调查，首次发现其花的着生方式除多数为顶生花外，还有少量的腋生花，自然居群中雄株与雌株的性别比例为1.21:1，对中国科学院华南植物园栽培居群和广西环江木论自然居群20株600朵花进行的解剖统计揭示，雌、雄花各部分的数量是变化的，雄花的花被片一轮或两轮，2－6片，雄蕊81－152枚，雌花的花被片两轮，外轮2－4片，内轮4－13片，心皮3－8枚，只有雄花花药2室及雌花每心皮具2个胚珠是稳定的。花部表型性状的大幅度变异表明焕镛木具有较丰富的遗传多样性。讨论了生花与顶生花在木兰科系统发育中的意义、表型性状的异步进化现象以及建立焕镛木属Woonyoungia Law的依据。

NUMERICAL VARIATION OF FLOWER PARTS AND THE AXILLARY FLOWERS IN WOONYOUN GIA SEPTENTRIONALIS (DANDY) LAW

Flowerlocation,sex ratioand numericalvariationof the flowerpartsof Woonyoungia septen trionalis(Dandy)Law,an endemicspeciesin China,wereinvestigatedby randomsamplingtrees fromnaturalpopulationof Woonyoungia septentrionalis inMulunVillage,HuanjiangCounty(Guangxi Province).Althoughmostof theflowers(90%)wereterminalas previouslydescribed,a smallfraction(10%)werefoundto be axillary,whichwas not recordedpreviously.The ratioof maleto female individualswas1.21:1.Statisticresultsfrom600flowersin20individualsfrom introducedtreesin SouthChinaBotanicalGardenandfromnaturalpopulationin Mulunshowthatthenumberof flower parts,exceptthenumberof thecaeperstamenandthenumberof ovulespercarpel,is variable.The variationsare:2-6tepalsin oneor two whorls,81-152stamensin maleflowers,two whorlsof tepals,2-4intheouterwhorl,5-13intheinner,and3-8carpelsinfemalflowers.Two thecaeineachstamen,andtwoovulesineachcarpelaretheonlystablecharacters.Greatvariationinfloralcharactersindicates thatthisspeciespossesseshighgeneticdiversity.The phylogeneticsignificanceof co-occurrenceof axillaryand terminalflowers,the heterobathmyof floralcharacters,and the tenabilityof the genus Woonyoungia arediscussed.