天仙子的花部特征及延迟自交机制

通过实验观察和野外控制授粉等方法,对天仙子的自交亲和能力和自交传粉机制进行了研究。结果显示:(1)天仙子的花不完全雌性先熟,开花进程中雄蕊伸长是维持其混合交配系统的重要花部特征。(2)野外控制授粉实验证明天仙子的自交亲和性高,具有主动自交能力,主动自交发生的时间集中在晚花期,与花药和柱头接触的时间吻合。(3)在花粉活力和柱头可授期内,花药与柱头的接触能够发生自花授粉,这种依赖花药与柱头接触发生的自花授粉机制属于典型的延迟自交类型。研究表明,天仙子不仅在花结构上首先选择了适于异交的特征,而且还利用雄蕊伸长成功实现自花授粉,通过异交与延迟自交混合的交配系统为该物种提供了灵活的遗传与繁殖保障。     

山姜属植物花柱卷曲性传粉机制的研究

暂性雌雄异株是一种在两性花或雌雄同株植物个体上表现出的雄蕊和雌蕊成熟时间不同而形成的暂时性雄性阶段和雌性阶段不重叠的现象。这种现象减少了自交亲和的雌雄同株和两性花种类发生自交的可能性。作系统研究了花柱郑曲性传粉机制在西双版纳姜科山姜属（Alpinia Roxb.）植物中的普遍性,这一机制使得植物通过完全的暂性异株达到了异交的目的。这类植物的种群中具有两种独特的表现型,其差异央开花行为的不同：柱头下垂型个体在刚开花时其柱头向上反卷。位于已开裂的花药上方,到中午开始向下运动,下午则位于花药下方;柱头上举型个体的柱头在开花初期向花冠内卷曲,位于未开裂的花药和唇瓣之间中午开始向上运动,当柱头上举到花药上方后,花药开裂,花偻开始散发。两种个体的开花行为是同步的,通过两种柱头反向运动授粉方式（不同时间的自花和异花授粉）具有相同的结实率,但套代的花序几科不结实,两种表型在自然种群中的比例为1：1。     

高山植物扁蕾的延迟自交机制

扁蕾(Gentianopsis barbata)具有鲜艳的花和显著的腺体,并且花开放的前5 d柱头和花药始终处于不同的位置(雌雄异位),这些花综合征表明该植物应为异花传粉。为检验这一假设,我们对青藏高原植物扁蕾的海北站种群进行了3年的传粉生物学研究实验。与花综合征所表明的繁育系统相反,两年的野外观察发现昆虫的访花频率十分低,不去雄并隔离昆虫处理也能产生大量种子,说明这一种群的繁殖主要是依赖于自花传粉。尽管利用种子结实评价的柱头可授性从花开放4 d后开始下降,但随着花的发育进程,雄蕊的伸长能使得花药与柱头完全接触。实验也证明,柱头可授性和花粉活力都超过5 d,说明花药和柱头的接触能够发生自花授粉。扁蕾的这种自花传粉机制应属于典型的延迟自交类型。自花授粉发生在单花花期快要结束前,自交之前仍然保持异交传粉机制,这种延迟自交避免了自交与异交竞争造成的花粉或者种子折损,并为扁蕾在青藏高原极端环境下由于访花昆虫缺乏造成的异交失败提供了繁殖保障。     

多叶斑叶兰繁育系统与传粉生物学研究

为探讨多叶斑叶兰(Goodyera folisa)的繁育系统与传粉生物学特征,对其开花物候、花粉活力与柱头可授性、人工授粉、花的挥发性成分以及昆虫传粉行为进行了研究。结果表明,多叶斑叶兰的唇瓣黄色,萼片白色或白色带红褐色;单花花期为(9.4±0.8)d;花粉在开花后第1天具备活力,柱头在开花后第2天具备可授性,花粉活力和柱头可授性都在开花后第5天达到峰值。去雄套袋和不去雄套袋都不能结实,人工自花授粉、同株异花授粉和异株异花授粉的结实率分别为93.3%、95.0%和96.7%,自然结实率为43.3%。花朵的主要挥发性成分为1-辛烯-3-醇、3-辛醇和N,N-二甲基甲酰胺。多叶斑叶兰传粉者为中华蜜蜂(Apis cerana)。多叶斑叶兰具有自交亲和能力,但在自然界不具有主动自交现象,必须依赖中华蜜蜂传粉,花色及花香气味为吸引传粉者的主要因素。     

花柱卷曲性异交机制及其进化生态学意义

 有花植物具有纷繁复杂的繁育系统,以避免或促进自交或异交。花柱卷曲性异交机制(Flexistyly)是最近在热带山姜属(Alpinia)植物中发现的一种促进异交的行为机制。具有这一机制的种类其自然种群中的个体根据开花行为的不同分为两种表型：一种上午散发花粉而其柱头向上反卷,远离昆虫拜访的通道;另一种其柱头上午垂向唇瓣,能够接受拜访昆虫的传粉,但自身的花药却不打开。到中午时分,两种表型花通过互为相反的柱头卷曲运动转换性别——前者柱头向下卷曲,后者柱头向上卷曲且花药打开。每朵花的花期为12 h,两种表型在自然种     

山莨菪(茄科)的传粉生物学

茄科的多数种类具有自交不亲和的特点, 主要通过异花传粉结实; 但是, 一些物种或者物种内的部分种群或者个体却高度自交亲合, 转变为自交的繁育系统。该科植物山莨菪(Anisodus tanguticus)主要分布在青藏高原, 开花较早, 比其他晚开花的植物种类更加缺少有效的异花传粉昆虫。我们选择了位于不同海拔高度的2个种群进行比较研究, 主要目的是检验该物种的繁育系统是否在极端环境下由于传粉者的缺乏而发生了部分改变。研究发现,山莨菪的花不完全雌性先熟, 柱头和花药间的平均距离随着花开放时间的延长而不断缩小, 但两者在多数花的单花花期结束时并没有发生接触。因此, 山莨菪花主要表现为适应异花传粉的雌雄异位特征。然而, 少数花 (4.9％)的柱头和花药发生接触, 为“自动自交”的传粉解除了空间隔离。2个种群的多数个体存在自交不亲和机制, 应具有异花传粉的繁育系统; 但是部分个体具有明显的自交亲和能力, 为自交提供了生理基础。高海拔种群的传粉昆虫主要是厕蝇(Fannia sp.), 它们在不同植株间的活动能够保证异花传粉结实; 同时该种群的部分个体存在“自动自交”。低海拔种群的主要访花昆虫是蚂蚁, 它们在花内的活动导致花粉在同一朵花内传递, 而引起“协助自交”; 而异花传粉昆虫厕蝇的访花频率则较高海拔种群低。两个种群的结实均由于异花传粉者不足而受到传粉限制。因此两种不同类型的自交机制为该早期开花植物异花访花昆虫的不足提供了一定程度上的繁殖补偿。     

山羊臭虎耳草的延迟自动自花授粉机制

通过对山羊臭虎耳草6个花形态及其发育阶段、授粉过程的连续观察和对花粉活性、柱头可授性的连续检测,报道了一种新的延迟自动自花授粉机制,即山羊臭虎耳草花丝运动引导的延迟自动自花授粉。利用电子显微镜研究了花粉囊的破裂方式和柱头结构,同时利用苏丹Ⅲ研究了花粉的组织化学性质。结果显示:(1)第四生长阶段,当花丝引导大部分花粉囊运动至柱头上方时,花粉和柱头的可授性才均达到峰值[可授性分别为(94±6)%和(96±13)%],这种运动消除了第三生长阶段花粉活性较高[(90±8)%]而柱头可授性较低[(6±17)%]的异花授粉特征,即消除了花粉与柱头的时空隔离;自动自花授粉发生于异花授粉特征消除之后,因此山羊臭虎耳草具有典型的延迟自动自交行为。(2)第四发育阶段柱头空腔的大量柱状突起和花粉鞘的油脂性特征,增加了花粉和柱头的接触表面,并且使花粉更好地互相堆积粘附在柱头上,提高授粉效率。(3)对山羊臭虎耳草的繁育系统研究表明,强制自花授粉和人工自花授粉产种量无明显差异,2007年和2008年的自交系数高达0.92和0.91,说明山羊臭虎耳草具有很好的自交能力并且不存在花粉数量限制;人工异花授粉的产种率显著高于人工自花授粉,说明自花花粉的质量显著低于异花花粉,虎耳草延迟自动自花授粉存在生殖衰退,生殖保障系数2007年为0.92,2008年为0.91,表明在极端环境下自动自花授粉为该植物提供了繁殖保障,但极端环境下,没有观察到有效的授粉昆虫。研究表明,作为高山冰缘植物的山羊臭虎耳草,保留了开花植物异花授粉的特征,在极端环境下利用延迟自动自花授粉机制完成授粉,保障生殖。     

珍稀濒危植物陕西羽叶报春的开花及传粉生物学研究

陕西羽叶报春为中国珍稀濒危植物,研究其开花物候、传粉者及访花行为、花粉活力、柱头可授性、繁育系统,以明确陕西羽叶报春的传粉特性及制濒机制。以勉县陕西羽叶报春野生居群为研究对象,通过野外观察和人工授粉实验首次对陕西羽叶报春的传粉生物学进行研究。结果表明:(1)陕西羽叶报春种群花期为2-4月中旬,单花花期一般为14~17 d;单花开花进程中花部形态有6个明显发育变化:全部被萼片包裹、花苞伸出并为深粉色、花朵打开为淡粉色、花冠为白色、花朵枯萎、花冠脱落花萼宿存。(2)陕西羽叶报春为异花授粉植物,蜜蜂属为其主要传粉者。(3)柱头在花粉未开裂前就具有可授性,可授性逐渐增强;花药在花瓣打开后的第3天才开始开裂、散粉,在第4天活力最高,为98.18%,此后逐渐减弱。(4)繁育系统检测显示,长、短柱型花的花粉/胚珠比分别为902.26和831.48,杂交指数为4;套袋实验显示,陕西羽叶报春异型交配可育,同型交配不可育。由此表明,陕西羽叶报春的繁育系统为异交型,自交不亲和,需要传粉者。综上所述,陕西羽叶报春传粉者种类少、自交不亲和、胚珠败育现象可能是导致陕西羽叶报春濒危的重要原因。     

草豆蔻传粉生物学的研究

比较研究了花柱卷曲性植物草豆蔻 Alpinia hainanensis两种表型(上举型和下垂型)的传粉生物学特性。结果表明:草豆蔻的花柱卷曲运动节律与其他已报道的山姜属Alpinia植物基本一致,而下垂型花的花柱卷曲运动明显滞后于上举型花约2 h。草豆蔻的花柱卷曲运动中存在一些不同步的现象,甚至在同一花序上的两朵花的花柱运动节律亦会表现出不一致的现象,但上举型花的花药开裂时间却严格同步,都发生在同类型个体的柱头全部位于花药上方之后进行。草豆蔻上举型花的花蜜分泌量、单花花粉量、花粉/胚珠比率(P/O)均明显比下垂型花多,而两种表型的胚珠数、花蜜糖含量、氨基酸含量无显著差异。在草豆蔻的单花期内不同时间段进行人工授粉,上举型花在其柱头位于花药下方时进行人工授粉,其结实率明显比柱头位于花药上方时人工授粉的处理高,下垂型花则没有显著差异。在自然居群中,草豆蔻的主要传粉者是无垫蜂Ameglla sp.和两种木蜂Xylocopa sp.,但存在传粉者不足而影响结实率的现象。完全套袋、去雄和去雌(去柱头)处理的均不结实,表明草豆蔻中不存在无融合生殖、主动自花授粉和滞后自交的生殖保障现象。而人工自交和异交均具有较高的结实率,表明草豆蔻为自交亲和植物。草豆蔻的繁育系统是具花柱卷曲性运动的异花授粉的交配系统。     

贯叶连翘的开花动态与繁育系统研究

野外观察贯叶连翘的开花进程和花部形态特征,运用花粉萌发、杂交指数、花粉-胚珠比等方法测定其繁育系统。结果显示:贯叶连翘雌雄异熟,柱头先花药成熟,雌雄蕊无明显异位。单花花期4～5d。仅在开花当日有昆虫传粉,蜜蜂为主要传粉者。花粉在花药开裂1h后活力最大,萌发率达40.10%,花粉在柱头萌发3h后接近子房。根据杂交指数(OCI)推测其繁育系统属于异交,部分自交亲和,有时需要传粉者。花粉-胚珠比(P/O)则表明贯叶连翘的繁育系统为兼性异交。贯叶连翘结实率低,可能与花粉活力,花粉管的生长速度及花粉在柱头的竞争有关。     

Corolla wilting facilitates delayed autonomous self-pollination in Pedicularis dunniana (Orobanchaceae)

Structural changes associated with corolla wilting may serve as a mechanism for effecting self-pollination. Low pollinator visitation, high seed production and a corolla that persists after anthesis indicates that Pedicularis dunniana is autogamous. Delayed autonomous self-pollination is facilitated by corolla wilting. Wilting of the upper lip (galea) brought the pollen laden anthers into contact with the stigma resulting in the deposition of self pollen on the stigma. The seed set of flowers either emasculated, or with restrained galeae thus preventing anthers brushing against the stigma, was significantly lower than that of open-pollinated flowers. This demonstrates that autogamy occurs in this species through corolla wilting. Germination experiments indicated that outcross seedlings were more vigorous than selfed seedlings as a result of inbreeding depression. It is likely that autogamy provides reproductive assurance for P. dunniana under conditions of pollinator scarcity.     

Reproductive biology ofPolyalthia littoralis (Annonaceae)

Flowering phenology of some annonaceous trees and reproductive biology ofPolyalthia littoralis (Annonaceae) were studied. The trees showed various types of flowering phenology within the family. Among them,P. littoralis had hermaphroditic and protogynous flowers, and exhibited continuous flowering throughout the year. Bagged flowers set fruits and seeds comparable to the control. The observations of meiotic stages and the results of castrated tests indicated no possibility of apomictic reproduction. The abscised anthers attached to torus by the extended spiral thickenings, and accomplished self-pollination. Outbreeding possibly occurs, but the following self-pollination guarantees seed set.     

Experimental dissection of inbreeding and its adaptive significance in a flowering plant, Aquilegia canadensis (Ranunculaceae)

Inbreeding is a major component of the mating system in populations of many plants and animals, particularly hermaphroditic species. In flowering plants, inbreeding can occur through self-pollination within flowers (autogamy), self-pollination between flowers on the same plant (geitonogamy), or cross-pollination between closely related individuals (biparental inbreeding). We performed a floral emasculation experiment in 10 populations of Aquilegia canadensis (Ranunculaceae) and used allozyme markers to estimate the relative contribution of each mode of inbreeding to the mating system. We also examined how these modes of inbreeding were influenced by aspects of population structure and floral morphology and display predicted to affect the mating system. All populations engaged in substantial inbreeding. On average, only 25% of seed was produced by outcrossing (range among populations = 9-37%), which correlated positively with both population size (r = +0.61) and density (r = +0.64). Inbreeding occurred through autogamy and biparental inbreeding, and the relative contribution of each was highly variable among populations. Estimates of geitonogamy were not significantly greater than zero in any population. We detected substantial biparental inbreeding (mean = 14% of seeds, range = 4-24%) by estimating apparent selfing in emasculated plants with no opportunity for true selfing. This mode of inbreeding correlated negatively with population size (r = -0.87) and positively with canopy cover (r = +0.90), suggesting that population characteristics that increase outcross pollen transfer reduce biparental inbreeding. Autogamy was the largest component of the mating system in all populations (mean = 58%, range = 37-84%) and, as expected, was lowest in populations with the most herkogamous flowers (r = -0.59). Although autogamy provides reproductive assurance in natural populations of A. canadensis, it discounts ovules from making superior outcrossed seed. Hence, high autogamy in these populations seems disadvantageous, and therefore it is difficult to explain the extensive variation in herkogamy observed both among and especially within populations.     

蝶形花植物猪屎豆自花传粉机制研究

猪屎豆( Crotalaria pallida)为典型的蝶形花植物,分布极广,是路边或遭破坏生境中最常见的先锋种之一,野外观察未发现其有营养生殖的现象,主要为种子繁殖。该研究通过对自然生境中猪屎豆开花物候、访花昆虫及繁育系统的研究,旨在从繁殖的角度阐述其快速扩张的能力。结果表明：尽管猪屎豆的主要访花昆虫是蜜蜂,但蜜蜂的访花频率极低[(1.73±1.30)次/花序·h-1],且在整个花期内花药和柱头均被龙骨瓣包裹,蜜蜂访花时未成功接触柱头和花粉,不能实现传粉,因此蜜蜂不是猪屎豆有效的传粉昆虫,这与假说“蝶形花普遍是对膜翅目昆虫,尤其是对蜜蜂传粉的适应”不一致。人工授粉结果显示,猪屎豆为自交亲和种,不存在无融合生殖现象,其繁殖主要通过主动自交生产种子来实现,且在自交过程中长短花药都参与主动自交。这种自交方式不同于其他蝶形花植物的主动自交仅由短花药实现。对猪屎豆而言,长短花药均参与自交能够增加柱头的授粉几率,保证其在不利的生境中成功结籽,是其成功扩张的关键因素之一。     

Phenology and pollination biology of eight Peperomia species (Piperaceae) in semideciduous forests in southeastern Brazil

Data on flowering phenology and pollination of Peperomia species are virtually non-existent. This study presents data on the pollination biology of eight Peperomia species from south-eastern Brazil, including the flowering phenology, pollination system, and reproductive success. Data on flowering phenology were recorded weekly and exclusion experiments on inflorescences provided data on autonomous self- and wind pollination. Direct visual observations were made and insect visits were recorded. Four Peperomia species showed continuous flowering, while the others were seasonal and flowered in the wet season. Pollination by wind and Syrphidae was confirmed for two self-incompatible Peperomia species. The remaining species are self-compatible and their high fruit set may be accounted for by autonomous self-pollination and perhaps agamospermy. Although the floral morphology of Peperomia species suggests wind- and/or insect pollination, most of the species studied exhibit autogamy and perhaps agamospermy as the main method of reproduction.     

Movement herkogamy in Kosteletzkya virginica: Effect on reproductive success and contribution to pollen receipt and reproductive assurance

Herkogamy may act as a mechanism to reduce interference between the reproductive functions of female and male organs, but too great a distance between stigmas and anthers may also decrease the outcross pollen transfer and male and female fitness. Our goal was to quantify the effect of movement herkogamy in Kosteletzkya virginica on reproductive success and its contribution to pollen receipt and reproductive assurance. Field investigations and hand-pollination experiments were performed to test: (1) the relationship between herkogamy before curvature of un-pollinated lobes and reproductive success under pollinator exclusion; (2) the contribution of movement herkogamy to pollen receipt; and (3) the relationship between pollen load and seed set. We noted that variation in herkogamy before curvature of un-pollinated lobes did not affect the outcome of autogamous self-pollination measured by fruit set and mean number of seeds per fruit. Under natural conditions, 39% of pollen grains deposited per flower were from autogamous self-pollination via movement herkogamy resulting in contact between anthers and stigmas. The relationship between the amount of pollen grains and the number of seeds per capsule was highly significant. Flowers producing four or five seeds received more pollen grains than those producing only one seed. Our data provides experimental evidence that movement herkogamy, which decreases the separation between anthers and stigmas and results in delayed self-pollination, contributes to pollen receipt and further enhances seed set when pollinators are scarce or absent.     

Movement herkogamy in Kosteletzkya virginica: Effect on reproductive success and contribution to pollen receipt and reproductive assurance

Herkogamy may act as a mechanism to reduce interference between the reproductive functions of female and male organs, but too great a distance between stigmas and anthers may also decrease the outcross pollen transfer and male and female fitness. Our goal was to quantify the effect of movement herkogamy in Kosteletzkya virginica on reproductive success and its contribution to pollen receipt and reproductive assurance. Field investigations and hand-pollination experiments were performed to test: (1) the relationship between herkogamy before curvature of un-pollinated lobes and reproductive success under pollinator exclusion; (2) the contribution of movement herkogamy to pollen receipt; and (3) the relationship between pollen load and seed set. We noted that variation in herkogamy before curvature of un-pollinated lobes did not affect the outcome of autogamous self-pollination measured by fruit set and mean number of seeds per fruit. Under natural conditions, 39% of pollen grains deposited per flower were from autogamous self-pollination via movement herkogamy resulting in contact between anthers and stigmas. The relationship between the amount of pollen grains and the number of seeds per capsule was highly significant. Flowers producing four or five seeds received more pollen grains than those producing only one seed. Our data provides experimental evidence that movement herkogamy, which decreases the separation between anthers and stigmas and results in delayed self-pollination, contributes to pollen receipt and further enhances seed set when pollinators are scarce or absent.     

The effectiveness of some mechanisms of reproductive isolation in Arum maculatum and A. italicum (Araceae)

Mechanisms of reproductive isolation were studied in two species of Arum , A. italicum and A. maculatum , growing in England and the south of France. The study focused on three potential mechanisms for reproductive isolation: the effectiveness of dichogamy as a barrier to autogamy; the ability of self and outcrossed pollen to germinate on stigmas at different stages of anthesis and to effect pollination; and postzygotic barriers to selfing. Dichogamy was found to provide a very effective barrier to within-inflorescence selfing in these species, as no seeds were produced by spontaneous self-pollination (i.e. autogamy) in any population of either species. However, the study found that geitonogamy (cross-pollination between inflorescences of a same individual or clone) was possible, as genotypes frequently produced several inflorescences and stigmas were found to be receptive to pollen from before anthesis until their contraction at the end of the female phase of flowering. Hand pollination with self pollen from clone inflorescences produced as numerous and heavy seeds as outcross pollination. In addition, the germination and growth of geitonogamously produced seed was similar to that of outcrossed seed, suggesting that this potential postzygotic barrier is absent or weak. These findings suggest that geitonogamous seed production may be unrestricted by significant pre- or postzygotic barriers. The possible advantages of geitonogamy in Arum are discussed.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 323–328.     

The breeding system of Fumana ericifolia: first evidence of autogamy in woody Cistaceae

Fumana ericifolia belongs to the family Cistaceae, in which all perennial species previously studied have been reported to be self-incompatible and xenogamous. Here we show that F. ericifolia is self-compatible and autogamous. Its flowers last only four to eight hours and produce a small amount of pollen and ovules. Self-pollination depends on changes in the relative position of the stigma and the anthers, triggered by the abscission of the petals; this in turn causes closing of the sepals, which push the anthers onto the stigma. Pollen remains highly viable and germinable, and the stigma keeps its receptivity several hours after the loss of the petals. Hand pollination treatments revealed that fruits are produced both in selfed and crossed flowers. The germination of pollen grains on the stigma, the rate of pollen tube growth along the style, and the penetration into the ovules were similar in self-and cross-pollinations; also, there were no significant differences in fruit set, seed set and weight of seeds. Thus, we report the first evidence of autogamy in a woody Cistaceae and suggest that selfing may ensure reproductive success when pollinators are limited.     

海滨蝇子草功能性雌全同株性系统的初步研究

雌全同株是指植株同时具有两性花和雌花性系统,目前国内外相关研究多集中于菊科（Asteraceae）植物。海滨蝇子草（Silene uniflora Roth.）单株具有2种花朵类型,分别是可育两性花和功能上为雌花的雄性不育两性花,属于功能性雌全同株植物。可育两性花具有雄性先熟和雌雄异位的性别分离特征;其繁育系统主要为异交,部分自交,花内自交坐果率为31.71%。功能性雌花的雄蕊和花粉畸形,花粉量少。在初花期和末花期,功能性雌花较可育两性花所占比例更大。海滨蝇子草的功能性雌全同株性系统,在进化上可能具有降低自交、增加异交率,避免雌雄功能干扰和提高雌雄功能资源分配等适应性机制。