臭椿花器官分化的初步研究

利用扫描电镜(SEM)和光镜(LM)对臭椿花序及花器官的分化和发育进行了初步研究,表明:1)臭椿花器官分化于当年的4月初,为圆锥花序;2)分化顺序为花萼原基、花冠原基、雄蕊原基和雌蕊原基。5个萼片原基的发生不同步,并且呈螺旋状发生;5个花瓣原基几乎同步发生且其生长要比雄蕊原基缓慢;雄蕊10枚,两轮排列,每轮5个原基的分化基本是同步的;雌蕊5,其分化速度较快;3)在两性花植株中,5个心皮顶端粘合形成柱头和花柱,而在雄株中,5个心皮退化,只有雄蕊原基分化出花药和花丝。本研究着重观察了臭椿中雄花及两性花发育的过程中两性花向单性花的转变。结果表明,臭椿两性花及单性花的形成在花器官的各原基上是一致的(尽管时间上有差异),雌雄蕊原基同时出现在每一个花器官分化过程中,但是,可育性结构部分的形成取决于其原基是否分化成所应有的结构:雄蕊原基分化形成花药与花丝,雌蕊原基分化形成花柱、柱头和子房。臭椿单性花的形成是由于两性花中雌蕊原基的退化所造成,其机理有待于进一步研究。     

山鸡椒雄花花芽发育形态解剖特征观察

采用体视显微镜、扫描电镜和石蜡切片技术对山鸡椒（Litsea cubeba（Lour.） Pers.）雄花花芽分化发育的外部形态和内部解剖结构进行了观察研究。结果显示:（1）山鸡椒雄花花芽分化发生可分为5个时期,即未分化期、花序原基分化期、苞片原基分化期、花原基分化期和花器官分化期,其中花器官分化期又可细分为花被原基分化期、雄蕊原基分化期和雌蕊原基分化期;各相邻分化时期存在一定重叠现象;花期从翌年1月上旬至3月下旬。（2）雄花成熟结构中具有独特的雄蕊蜜腺,蜜腺绿色且形态不规则,着生于内轮雄蕊基部,分布于花丝两侧,夹在内外轮雄蕊的花丝之间,与内轮花丝紧密相连。（3）雄蕊花药四室,花药壁发育属于基本型;腺质绒毡层;小孢子母细胞减数分裂过程中胞质分裂属于连续型;成熟花粉为2-细胞花粉粒;成熟花粉粒外壁刺突较多,刺突基部膨大,外壁露出部分粗糙,无薄壁区,有少数小穿孔。（4）山鸡椒雄花中绝大多数雌蕊发育至腹缝线卷合形成子房室时停止,柱头发育不良或者败育,花柱缩短或缺失,不能受精,直到开花结束,即发生退化。本研究明确了山鸡椒雄花花芽发育发生各个阶段时间、形态变化特点及外部形态变化特征,山鸡椒小孢子发生、雄配子体发育至散粉期变化特点和规律以及雄花中退化雌蕊发育的进程,可为山鸡椒优良品种选育、调控花期和提高结实率提供一定的参考。     

太行花性器官发育的研究——两性花中雌雄性器官发育对温度的不同要求

用太行花（Ｔａｉｈａｎｇｉａ ｒｕｐｅｓｔｒｉｓ Ｙ汃ｅｔＬｉ）试管花进行雌雄蕊发育的温度试验表明：１． 雄蕊和雌蕊的发育对温度的要求是不同的,雄蕊发育的最适温度范围偏低,接近于１～６ ℃,高于１８ ℃雄蕊全部败育。雌蕊发育的最适温度范围偏高,约６～２６ ℃,低于３ ℃,大部分雌蕊在分化早期停止发育。２． 由高温引起的雄蕊败育过程始于雄蕊原基时期,这个过程一旦启动,雄蕊败育将不会因重新将它转入低温而逆转。通过控制实验温度获得了单性雄花（１～３ ℃）、单性雌花（６～２６ ℃）和两性花（６～１２ ℃）。实验结果将为性别控制和雄性不育研究开拓新思路     

栝楼不同性别花芽分化形态解剖特征观察

采用体视显微镜、石蜡切片和树脂切片技术对栝楼(Trichosanthes kirilowii Maxim.)不同性别花芽分化发育时期的外部形态和内部解剖结构进行了观察。结果显示,栝楼花为雌雄异株,仅有雌花、雄花两种性别分化,且雄花的发育速度明显快于雌花的发育速度。栝楼雌雄花芽长0.2 mm左右已完成性别分化;栝楼雄花为单性花,分化过程可分为6个时期,整个发育过程仅见雄蕊原基的分化及生长。栝楼雌花为"两性花",分化过程可分为7个时期,存在雌蕊和雄蕊共同发育阶段,后期雄蕊发育败退。本研究明确了不同性别栝楼花芽发育发生的各个阶段、形态变化特点、外部形态变化特征以及雌雄花芽的分化差异,建立了雌雄花芽内部结构分化与外部形态之间相关性,为栝楼早期幼苗鉴定及性别分化研究提供了一定的参考。     

敦煌‘李光杏’花芽发育过程中雌蕊败育观察及生物学特性调查

为克服杏生产中雌蕊败育现象、提高坐果率,该研究以甘肃省敦煌市的‘李光杏’盛果期不同树势(强势树、中庸树和弱势树)和不同类型结果枝(花束状果枝、短果枝、中果枝、长果枝)的花芽为试材,对其开花物候期及生物学特性进行调查,采用石蜡切片观察易发生败育时期(花芽分化初期、雌蕊分化期、花粉细胞期和花蕾膨大期)的花芽内部组织结构形态,同时测定各主要败育时期叶片可溶性糖、淀粉含量及矿质元素的变化。结果表明:(1)弱树花芽的平均败育率最高(91.26%),中庸树最低(71.08%);不同类型结果枝中,花束状果枝花芽的败育率最低,长果枝的败育率最高。(2)不同结果枝类型的花粉生活力表现为花束状果枝>短果枝>中果枝>长果枝,花粉发芽率表现为短果枝>花束状果枝>中果枝>长果枝。各花型花粉生活力表现为雌蕊高于雄蕊>雌雄等长>雌蕊低于雄蕊>无雌蕊,发芽率的表现为雌雄等长>雌蕊高于雄蕊>雌蕊低于雄蕊>无雌蕊。(3)各树势花芽雌蕊分化期叶片可溶性糖与淀粉含量显著低于其他时期;叶片P、K、Ca含量在分化前期较高,但是雌蕊、雄蕊分化期显著下降。(4)与正常花相比,败育花主要表现为子房发育异常,多数生长点不均匀,子房萎缩,胚珠原基发育停滞;雌蕊的花柱低于花丝,且花粉粒急剧减少。研究发现,‘李光杏’树势的强弱会造成败育花比例和坐果率的差异,并以中庸树果实坐果率最高,且花败育率最低;雌蕊发育是否正常直接关系到‘李光杏’正常开花,雌蕊的发育受阻,最终成为整个花芽退化的主要形式;叶片碳水化合物和矿质元素等营养物质参与并保证了花器官的正常发育。     

罗汉果花芽分化过程中形态及其激素水平变化特征

采用石蜡切片和酶联免疫法(ELISA)对罗汉果雄性、雌性、两性花芽分化过程的形态和激素水平变化进行观测,为罗汉果开花调控和品种选育提供科学依据。结果表明:(1)罗汉果雄性、雌性、两性花的花芽分化过程均可分为花芽未分化期、花芽分化初期、花序分化期、萼片原基分化期、花瓣原基分化期、雄蕊原基分化期和雌蕊原基分化期7个阶段。雄蕊原基分化期前,3种花芽分化过程无明显差异,各时期形态特征均依次为:茎端呈圆锥状(花芽未分化期)→茎端经半球形变成扁平状(花芽分化初期)→距茎端5~7节位处分化出穗状花序(花序分化期)→小花原基周围形成5个萼片原基(萼片原基分化期)→萼片原基内侧形成5个花瓣原基(花瓣原基分化期)。雄蕊和雌蕊原基分化期,3种花芽分化过程存在明显差异,雄蕊原基内侧出现雌蕊原基后,雄花芽雄蕊原基继续发育成雄蕊,雌蕊原基停滞生长,退为一个小突起;雌花芽雌蕊原基继续发育成雌蕊,雄蕊原基生长缓慢,退化为小花丝;两性花芽雌蕊和雄蕊原基均继续发育,形成外观正常的雌蕊和雄蕊。(2)内源激素脱落酸(ABA)、赤霉素(GAs)和玉米素核苷(ZR)含量在3种花芽分化过程中变化规律相似,即ABA含量在花芽生理分化期降低,花芽形态分化期升高,而GAs和ZR含量则基本保持不变;吲哚乙酸(IAA)含量在3种花芽分化过程中变化存在明显差异,雌花芽IAA含量在花芽生理分化期升高,花芽形态分化期逐渐降低,而雄性和两性花芽的IAA含量则基本保持不变。ABA/GAs、ABA/IAA、ZR/IAA和ZR/GAs激素含量比值在3种花芽分化过程中变化规律相似,ABA/GAs在花芽生理分化期降低,花芽形态分化期升高,而BA/IAA、ZR/IAA和ZR/GAs则基本保持不变。研究认为,罗汉果花芽分化过程经历一个"两性期",高ABA含量和ABA/GAs比值有利于罗汉果花芽分化,IAA可能对罗汉果花性分化具有重要作用。     

峨眉拟单性木兰雄性不育的细胞形态学及生理生化特性研究

峨眉拟单性木兰(Parakmeria omeiensis)是木兰科(Magnoliaceae)拟单性木兰属(Parakmeria)的常绿乔木,属于国家Ⅰ级保护的极度濒危植物。为探究峨眉拟单性木兰两性花中雄性败育发生的时期及花药不同发育时期的生理生化特性,以两性花中的不育雄蕊和雄花中的可育雄蕊为材料,利用石蜡切片观察2种雄蕊的花药发育过程,并测定不同发育时期的可溶性糖、可溶性蛋白、脯氨酸的含量,分析过氧化氢酶(CAT)、过氧化物酶(POD)的活性。结果表明：(1)不育雄蕊与可育雄蕊在减速分裂时期出现明显差异,不育雄蕊的绒毡层致密、没有发育,四分体未形成,随后解体,花粉囊中无花粉;可育雄蕊的绒毡层和小孢子母细胞发育正常,成熟时花粉囊开裂,花粉粒溢出。(2)不育雄蕊的可溶性糖含量、可溶性蛋白含量、脯氨酸含量,在减数分裂时期、单核期和花粉成熟期都显著低于可育雄蕊。(3)不育雄蕊POD活性整体呈上升趋势,在减数分裂时期、单核期和花粉成熟期都显著高于可育雄蕊;不育雄蕊CAT活性整体呈下降趋势,显著低于同时期的可育雄蕊。综上认为,两性花中雄性败育发生在减速分裂时期,其败育的主要原因是物质能量代谢降低...     

刺山柑雄全同株性系统的适应意义

对分布于新疆北部干旱荒漠区的刺山柑Capparisspinosa性系统进行了研究.结果表明:(1)该物种具有典型的雄全同株性系统.雄花和两性花的雄蕊均正常发育,且有长短之分;两性花的雌蕊发育正常,而雄花的雌蕊败育,只行使雄性功能.(2)居群间每天开放的雄花和两性花比率、两性花的长短雄蕊数及雄花短雄蕊的花丝与花药长等存在极显著差异(P<0.01),但花器官生物量没有显著差异(P>0.05).(3)单花花期为15-16 h,每天18:00时左右开始开放,有强烈的气味和花蜜产生.植株每天产生的雄花和两性花数是随机的,可形成短时的雄花与两性花异株,但居群内雄花数比两性花数多.(4)三个居群两性花的P/O值分别为1.57×104、1.65×104和1.71×104.居群内雄花和两性花的花粉数及长、短雄蕊花药的花粉数均无显著差异(P>0.05),居群间雄花和两性花的花粉数、两性花的胚珠数及P/O值差异也不显著(P>0.05).(5)各居群雄花和两性花长短雄蕊的花粉活力动态变化曲线相似,花粉寿命为18-20 h,两性花雌蕊柱头的可授期为16-18h.(6)访花昆虫为膜翅目Hymenoptera和鳞翅目Lepidoptera昆虫,3个居群共有7种访花昆虫,其活动受天气影响很大.(7)两性花不存在无融合生殖现象,授自花花粉、同株异花花粉和异株异花花粉后均可结实,属于混合交配系统.刺山柑的雄全同株性系统可能是在长期与荒漠环境相适应的过程中由遗传和环境共同作用的结果.雄花的出现不仅增加了花粉数和P/O值,提高了植株的雄性适合度,同时增加了花的数量、对传粉昆虫的吸引力以及两性花柱头接受异花花粉的机会,提高了异交率和雌性适合度,保障其在荒漠极端环境中繁殖成功.     

花叶芋(天南星科)的花器官发生

利用扫描电镜首次观察了天南星科花叶芋(Colocasia bicolor) 的花器官发生过程。花叶芋的肉穗花序由无花被的单性花构成, 雌花发生于花序基部, 雄花发生于花序上部, 中性花位于花序中间部位。雄花: 3 或4 个初生雄蕊原基轮状发生, 随后每个初生原基一分为二, 形成6或8个次生原基; 一部分次生原基在其后的发育过程中融合, 形成5 或7 枚雄蕊; 雄花发育过程中未见雌性结构的分化; 花药的分化先于花丝; 雄蕊合生成雄蕊柱。雌花: 合生心皮, 3或4个心皮原基轮状发生, 未见雄性结构的分化。中性花来源于雌雄花序过渡带上, 属于雄蕊原基的滞后发育以及发育成熟过程中的退化; 与彩叶芋属(Caladium)不同, 此过渡区未见畸形两性花。初生雄蕊原基二裂产生次生原基的次生现象在目前天南星科花器官发生中显得比较特殊, 同时初步探讨了次生原基的融合方式。     

大叶铁线莲大小孢子发生及雌雄配子体发育

铁线莲属植物在花部形态和结构方面存在较大差异, 遗传背景相对复杂。因此, 在杂交育种前对其进行胚胎学研究具有重要意义。利用石蜡切片技术对大叶铁线莲(Clematis heracleifolia)大小孢子发生及雌雄配子体发育过程进行研究, 结果显示, 大叶铁线莲具雄株和两性花植株。雄花中, 雄配子体发育偶见败育现象; 而两性花中多数花粉发育异常, 形成功能性雌花。正常发育的两性花中, 雄蕊较雌蕊先发育完全。花药4室, 具腺质绒毡层, 偶见变形绒毡层。胞质分裂为同时型, 以四面体型四分体为主, 偶见左右对称型。成熟花药中, 花药壁由纤维状加厚的表皮及药室内壁构成, 花粉粒为2-细胞型, 近球状, 散沟型。子房1室, 内含少量退化胚珠及1个发育正常的胚珠, 倒生, 单珠被, 薄珠心, 蓼型胚囊, 具线形大孢子四分体及双核反足细胞。大叶铁线莲可能处于相对进化的过渡地位。在杂交育种中, 建议以雄花植株作为父本, 两性花植株仅用作母本; 在两性花花芽大小为0.5-0.8 cm时进行去雄处理。     

Correlation between development of female flower buds and expression of the CS-ACS2 gene in cucumber plants

Ethylene plays a key role in sex determination of cucumber flowers. Gynoecious cucumber shoots produce more ethylene than monoecious shoots. Because monoecious cucumbers produce both male and female flower buds in the shoot apex and because the relative proportions of male and female flowers vary due to growing conditions, the question arises as to whether the regulation of ethylene biosynthesis in each flower bud determines the sex of the flower. Therefore, the expression of a 1-aminocyclopropane-1-carboxylic acid synthase gene, CS-ACS2, was examined in cucumber flower buds at different stages of development. The results revealed that CS-ACS2 mRNA began to accumulate just beneath the pistil primordia of flower buds at the bisexual stage, but was not detected prior to the formation of the pistil primordia. In buds determined to develop as female flowers, CS-ACS2 mRNA continued to accumulate in the central region of the developing ovary where ovules and placenta form. In gynoecious cucumber plants that produce only female flowers, accumulation of CS-ACS2 mRNA was detected in all flower buds at the bisexual stage and at later developmental stages. In monoecious cucumber, flower buds situated on some nodes accumulated CS-ACS2 mRNA, but others did not. The proportion of male and female flowers in monoecious cucumbers varied depending on the growth conditions, but was correlated with changes in accumulation of CS-ACS2 mRNA in flower buds. These results demonstrate that CS-ACS2-mediated biosynthesis of ethylene in individual flower buds is associated with the differentiation and development of female flowers.     

The gynoecium of male Anchietea pyrifolia (Violaceae): Preserved structure with a new function

Structure of inflorescences and flowers and flowering behaviour are reported for the woody liana Anchietea pyrifolia (Violaceae) from Brazil. The specimen studied is grown for some decades now in the greenhouses of Halle Botanical Garden and turned out unisexually male, which adds a further example of dioecism to the family Violaceae, in which this type of sex distribution is rarely encountered. The flowers are exceptional also for the strongly asymmetric anterior petal, which represents a rare case of a species with enantiomorphic flowers pollinated by Lepidoptera. They have a fully developed gynoecium with a complicated architecture comparable to the pistil of bisexual Violaceae flowers, though without ovules. The style head is capable to release viscose liquid on tactile stimulation or pressure, which is known to act as pollen-gathering mechanism in bisexual Violaceae species with usually dry pollen and buzz-pollination. This function has switched in male A. pyrifolia to a mechanism for efficient pollen release mediated by insect pollinators from its short-lived flowers.     

濒危植物羊角槭小孢子发生与雄配子体发育研究

利用常规石蜡切片法对羊角槭的小孢子发生及配子体发育进行了研究,结果表明：羊角槭花分两性花与雄花,两性花花药不散粉,雄花散粉;花药具四个花粉囊,其发育类型为基本型;药室内壁呈纤维状加厚;绒毡层为腺质型;孢质分裂为同时型;小孢子四分体呈四面体形排列;成熟花粉粒为二细胞型。羊角槭花药发育过程中出现严重败育现象,表现为四分体胼胝质提早溶解、单核小孢子彼此粘连、花粉液泡化等,形成干瘪、内陷的花粉,一定程度上影响花粉质量;另初步测得羊角槭的花粉生活力在36.98%~60.54%之间,平均生活力为45.97%。本文将为羊角槭花药发育、小孢子发生和雄配子体发育过程及出现的异常现象提供解剖学资料。     

Characterization of ethylene effects on sex determination in cucumber plants

Sex differentiation in cucumber plants (Cucumis sativus L.) appears to be determined by the selective arrest of the stamen or pistil primordia. We investigated the influence of an ethylene-releasing agent (ethephon) or an inhibitor of ethylene biosynthesis (aminoethoxyvinyl glycine) on sex differentiation in different developmental stages of flower buds. These treatments influence sex determination only at the stamen primordia differentiation stage in both monoecious and gynoecious cucumbers. To clarify the relationships between the ethylene-producing tissues and the ethylene-perceiving tissues in inducing female flowers in the cucumber, we examined the localization of mRNA accumulation of both the ACC synthase gene (CS-ACS2) and the ethylene-receptor-related genes (CS-ETR1, CS-ETR2, and CS-ERS) in flower buds by in situ hybridization analysis. CS-ACS2 mRNA was detected in the pistil primordia of gynoecious cucumbers, whereas it was located in the tissues just below the pistil primordia and at the adaxial side of the petals in monoecious cucumbers. In flower buds of andromonoecious cucumbers, only CS-ETR1 mRNA was detected, and was located in the pistil primordia. The localization of the mRNAs of the three ethylene-receptor-related genes in the flower buds of monoecious and gynoecious cucumbers overlap but are not identical. We discuss the relationship between the mRNA accumulation patterns and sex expression in cucumber plants.     

桂味荔枝花器官的发生和发育过程研究

利用SV11立体显微镜和JSM-6360LV型扫描电镜观察‘桂味’荔枝花器官的发生和发育过程。结果表明:花序原基最先发生,然后形成数个大小不等的单花原基;4个萼片原基的发生不同步,其中一侧对位先发生;6～10枚雄蕊原基以轮状方式几乎同时发生;心皮原基最后发生,2～3枚(稀4枚)心皮原基同时出现,随后进行侧向生长,逐渐合拢形成子房。雌花中,花柱、柱头分化明显,雄蕊退化。雄花中,花丝细长,花药饱满,雌蕊退化或发育不完全。两性花中,雌雄蕊发育完全。花粉粒近球形,具3孔沟,表面为条纹状纹饰。     

The arrest of development of abortive reproductive organs in the unisexual flower of<Emphasis Type="Italic"> Vitis vinifera</Emphasis> ssp.<Emphasis Type="Italic"> silvestris</Emphasis>

During the first stages of development, flowers of most dioecious species are hermaphroditic, with their transition to unisexual flowers being the result of the developmental arrest of one set of reproductive organs. In this work, we describe the development of male and female flowers of the dioecious wild grape species Vitis vinifera ssp. silvestris through scanning electron microscopy analysis and cytological observations, focusing our attention on the transition from bisexual to unisexual development. We divide floral development of the wild grape into eight stages. Differences between male and female flowers appear first at stage 6, when the style and stigma start to differentiate in female but not in male flowers. Cytological analysis of the slowly growing abortive pistil of male flowers shows that megagametophyte formation is, surprisingly, not inhibited. Instead of pistil abortion in the male flower, sexual determination is accomplished through programmed death of external nucellus cells and some layers of integumentary cells. Sterility of male structures in female flowers follows a different pattern, with microspore abnormalities evident from the time of their release from the tetrad. Sterile microspores and pollen grains in female flowers display an abnormal round shape, lacking colpi and possessing uniformly thickened cell walls that impede germination.     

The Control of Sex Expression in Cucurbits by Ethephon

Application of ethephon to field-grown plants of both bush andtrailing forms of Cucurbita maxima and C. pepo caused leaf epinasty,suppression of male flowers and earlier production and increasein numbers of female flowers. This gave rise to an increasein the ratio of female to male flowers per plant and a decreasein the total number of flowers. Observations of C. pepo showed that even at the two true leafstage there are several nodes present in the unexpanded shoot.Each node has one main and several secondary buds. The sex ofthe main bud at the first five to six nodes is usually determinedat this stage but the secondary buds still have bisexual potential.The change in sex expression was brought about by all male flowerbuds that had formed by the spraying time aborting, and allbuds that developed (both main and secondary) for at least 7days after spraying became female flowers. Thus, nodes fiveand six had male flowers in the controls, whereas in ethephon-sprayedplants the presumptive male flowers aborted at the bud stageat these nodes and secondary primordia developed into functionalfemale flowers. Cucurbita maxima, Cucurbita pepo, sex expression, ethephon, ethylene, flower abortion, flower differentiation     

Pollen-pistil Interaction in a Non-pseudogamous Apomict,Commiphora wightii

Structural and cytochemical details of the pistil and the interactionof pollen and pistil were studied in a non-pseudogamous apomict,Commiphorawightii.The anthers in the male and bisexual flowers producefunctional pollen grains. The stigma is of the wet and papillatetype. The style is typically solid with two strands of transmittingtissue that traverse the entire length of the style. There isa marked reduction in the area occupied by the transmittingtissue from the stigma to the base of the style. The cells ofthe transmitting tissue are isodiametric in transverse as wellas longitudinal section and do not form longitudinal files ofelongated cells as reported for other taxa. Proteins could notbe localized in the intercellular matrix. Although pollen grainsgerminate on the stigma, pollen tubes do not grow beyond theproximal one third of the style. Changed orientation of thecells of the transmitting tissue and absence of proteins inthe intercellular matrix could account for the failure of thepistil to support pollen growth.Copyright 1998 Annals of BotanyCompany Guggul, pollen-pistil interaction, non-pseudogamous apomict,Commiphora wightii, transmitting tissue     

Floral morphology and anatomy of Pittosporum tobira (Pittosporaceae)

Comparative studies are made on floral morphology and anatomy of female and male flowers of Pittosporum tobira. The two types of flower differ little from each other in structure at the early stage of floral development, but appear dimorphic towards anthesis. The male flower becomes cryptically bisexual, although its pistil is slender compared to that of the female flower. The stigmas of the male flower are receptive and can induce pollen germination. The structure of the style in the male flower is identical to that in the female flower. Ovules are produced on the protruded parietal placenta in the male flower, but their development is arrested at the stage of the 4–nucleate embryo sac. The female flower is clearly unisexual, with obviously aborted and sagittate anthers. Its pistil is rather plump and can produce darkish red seeds immersed in sticky pulp. The male and female flowers are similar in vascular anatomy. A conspicuous difference between the two types of flower lies in the stamens. Variation of sexual organs in the genus Pittosporum is reviewed. We assume that the flowers of Pittosporum are derived from the hermaphrodite-flowered ancestor and the female flower has become unisexual through partial reduction of sexual organs at a faster rate than the male flower.