锦鸡儿(Caragana sinica(Buchoz) Rehd)传粉生物学研究

对唐家河国家自然保护区内锦鸡儿(Caragana sinica(Buchoz)Rehd)的花期、访问者、有效传粉者种类及行为、花蜜分泌节律和繁育系统等进行定点观察和实验处理。结果表明:锦鸡儿单花花期约5d,种群花期约20d。拥有以吸蜜为主的条蜂属(Anthophora)、熊蜂属(Bombus)和太阳鸟属(Aethopyga)3种传粉者功能群。综合访花频率和花粉落置数,茜条蜂(Pyganthophora rubricus Dours)和蓝喉太阳鸟(Aethopyga gouldiae)为主要有效传粉者,熊蜂(Bombus)为次要有效传粉者;蚂蚁(formicidae)和西方蜜蜂(Apis mellifera Linnaeus)为主要盗蜜者。套袋处理结果表明,花蜜分泌日变化中,最大花蜜量发生在16:00左右;花蜜随单花花期变化中,花蜜体积最大发生于单花第5天;分泌均呈递增趋势。花蜜分泌节律与访花频率呈正相关。繁育系统检测显示,花粉胚珠比为3779±320.92,柱头最适可授期在开花第2—3天;结合不同授粉处理表明:锦鸡儿自交不亲和,需要传粉者,为蜂媒兼鸟媒植物。     

青藏高原东缘同域分布的2种橐吾属杂草的合子前生殖隔离

生殖隔离是阻止种间杂交、保持物种完整性和独立性的关键,对生物多样性的产生和维持有重要意义.不同物种间的生殖隔离形成阶段、方式和强度不完全相同,因而对物种间隔离机制的研究有助于揭示物种形成和维持机制.对青藏高原东缘同域分布的2种橐吾属杂草黄帚橐吾和箭叶橐吾的花期物候观察、访花昆虫观察及花粉-柱头亲和性进行研究,分析了2种橐吾多种合子前生殖隔离机制的特点及其在生殖隔离中的作用.结果表明: 黄帚橐吾种群花期比箭叶橐吾早20 d左右,虽然盛花期存在差异,但是2种群花期存在10 d左右的重叠期,并且在重叠期内2种橐吾花粉和柱头均具有活性.2种橐吾共享传粉昆虫,为泛化传粉模式,并且传粉者对2种植物的访花行为相似,存在2种植物间交叉访问.尽管2种橐吾花期不存在完全的时间隔离,也不存在完全的传粉者隔离,但2种橐吾柱头对异源花粉的亲和性差,表现为柱头对异源花粉有明显的排斥反应,异源花粉管在柱头上的生长过程明显受阻.这种花粉-柱头排异形式很有可能是2种橐吾属植物重要的合子前隔离机制,从而避免了种间的自然杂交,更好地维持了自然种群的多样性和遗传结构的稳定性.     

同域分布共享传粉者的鼠尾草属植物的生殖隔离

生殖隔离是生物多样性产生的重要原因之一,不同物种间的生殖隔离形成阶段、方式和强度不完全相同。为了揭示生殖隔离在鼠尾草属(Salvia)物种多样性产生和维持过程中的作用和特点,本文研究了浙江天目山同域分布的舌瓣鼠尾草(S.liguliloba)和南丹参(S.bowleyana)的开花、传粉和生殖隔离,利用人工授粉和杂交实验检测它们的种间遗传相容程度。结果表明,在花的形态结构、花及花序的生长、着生方式与数量特征上,2种鼠尾草属植物均差异显著(P0.05)。2种鼠尾草属植物共享同一种有效传粉昆虫——三条熊蜂(Bombus trifasciatus),但通过访花行为的显著差异和明显不同的花粉落置部位,有效避免了异源花粉干扰。人工杂交授粉的结果表明2个物种间遗传相容性较高,互为亲本的杂交结实率分别达到77.8±10.7%和78.7±11.2%。我们的研究表明,同域分布、花期重叠且共享唯一传粉者的2种鼠尾草属植物,以花部的传粉结构和传粉部位的差异,产生了较高程度的传粉前生殖隔离,避免了物种间的异源花粉干扰和自然杂交,保障各自较高的繁殖成效,以维持自然种群的多样性和遗传结构的稳定。     

凤仙花属3种植物的开花性状和繁育系统研究

通过形态、扫描电镜观察及人工控制授粉等方法对温室环境中的睫毛萼凤仙花(Impatiens blepharosepala Pritz. ex Diels)、绿萼凤仙花(I.chlorosepala Hand.-Mazz.)、菱叶凤仙花(I.rhombifolia Y. Q. Lu et Y. L. Chen)等凤仙花属3种植物的开花物候、花部性状以及繁育系统进行探究。结果显示：3种植物的开花物候依据花部形态变化可分为6个时期,各植物花期存在部分重叠;花部性状、部分繁育指标、花粉粒和子房微形态等方面均存在部分差异;3个物种的花粉生活力与柱头可授性变化趋势在整体上呈单峰型;3种植物的繁育系统均为兼性异交,其具体特征为自交亲和、需要传粉者;花蜜报酬满足小体型昆虫的传粉需要;3个物种的6种控制授粉处理中对照处理结实率低于3种人工授粉处理结实率,且不存在自花授粉和无融合生殖的现象;3种处理中人工异株异花授粉处理结实率最高,人工同株异花授粉处理结实率最低。     

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。     

稀有植物小丛红景天花部综合特征与繁育系统

对稀有物种生物学特征及繁育系统的研究将有利于我们对稀有物种的保育。该文通过野外定位观测稀有植物小丛红景天(Rhodiola dumulosa)的花部综合特征,并运用杂交指数、花粉-胚珠比的方法首次对其繁育系统进行初步测定。结果表明:该物种单花花期一般为5~6 d,开花过程中花柱逐渐伸长并向外弯曲,子房开裂并逐渐伸长,花药散粉具有先后顺序,一般外轮对萼花药先散粉,其后1 d左右对瓣花药开始散粉。单花花期依照其形态和散粉时间可分为6个阶段:花蕾期、内轮散粉期、内轮散粉末期、外轮散粉期、外轮散粉末期和凋谢期。而种群花期一般可持续30 d以上,不同海拔观测地点有所不同,海拔2 202 m处的观测地点B开花物候最为滞后。由于其杂交指数不小于4,花粉-胚珠比在700~1 000之间, 根据Dafni(1992)和Cruden(1977)的标准,初步判定该物种的繁育系统属于异交为主,部分自交亲和,传粉过程需要传粉者。     

同域分布的紫堇属三种植物的繁育系统和传粉差异

为研究近缘物种之间繁育系统分化对传粉环境的适应性意义,本文针对湖北地区的3种紫堇属植物（紫堇Corydalis edulis Maxim.、尖距紫堇C.shearer S.Moore.和小花黄堇C.racemosa（Thunb.） Pers.）进行了传粉生态学研究,对比分析了它们在花部特征、分布模式、花期、交配系统、传粉系统等方面的差异。3种紫堇属植物常见伴生现象,花期有一定重叠;花色、距长、花蜜量等方面均有显著差异;尖距紫堇交配系统为自交不亲和、依靠传粉者异花授粉;而紫堇和小花黄堇交配系统为自交亲和,兼有自交和异交的混合交配系统。3个物种均由蜂类传粉,且花部性器官与传粉者的接触部位一致,但访花频率差异较大。在混合群落中,传粉者访花具有较高的忠实性,花部特征差异可能是传粉者选择性访花的原因。对于紫堇属3个物种,花部特征和交配系统的分化有助于其避免传粉过程的相互干扰,交配系统与传粉环境具有一定相关性,混合交配系统可能有利于提高植物对不同生境和气候的适应性。     

华凤仙花部特征和传粉系统研究

研究了华凤仙（Impatiens chinensis L.）的花部特征和传粉系统,结果表明华凤仙单花期为2.3 d,雄性期是雌性期的6.8倍。花蜜量和花蜜可溶性糖含量分别为0.56 μL和28.2%。开花当天柱头即具有可授性,花粉活力在花朵刚开放时最高（95%）,至花朵凋谢之前仍保持较高的活力（55%）。花粉胚珠比（5 730.3±2 941.1）和套袋实验的结果表明华凤仙属于自交亲和但以异交为主的繁育系统,传粉过程需要传粉者。蜜蜂、熊蜂、蝶类和几种芦蜂是华凤仙的主要访花者,最有效的传粉者为三条熊蜂。考氏无垫蜂作为盗蜜者,可能是除正常访花者之外,对华凤仙的有性繁殖影响最大的生物因素。     

海南三七（姜科）的食源性欺骗传粉

有花植物为繁殖成功,进化出各种各样的花部特征来吸引传粉者,如为传粉者提供花蜜、花粉、栖息地等,然而在33科146属的被子植物中也存在着不提供任何报酬而欺骗昆虫为其传粉的现象。这种欺骗性传粉模式主要出现在高度进化的具有多样化传粉模式的兰科植物中。报道了在姜科植物中首次发现的食源性欺骗传粉模式。对姜科山柰属海南三七进行连续2年的传粉生物学观察和研究发现,海南三七的花在早上5:30～6:00之间开放,下午17:00～18:00左右闭合萎蔫,持续大约11～12h。开花过程中花粉活性与柱头可受性均保持较高水平(>90%)。花粉/胚珠比率(P/O)为82.20±47.89(n=20)。木蜂是其主要的访花和传粉昆虫,访花目的是吸取花蜜。海南三七虽有细长线形的蜜腺,但并不分泌花蜜作为传粉昆虫访花的报酬,采用食源性欺骗的方式欺骗木蜂为其传粉。繁育系统的研究表明广西弄化的海南三七居群主要是通过根茎进行无性繁殖。     

新疆党参的花部综合征与次级花粉呈现

次级花粉呈现是植物提高花粉输出和接受的效率与准确性以及促进异交的一种繁殖策略.新疆党参(Codonopsis clematidea)具有典型的次级花粉呈现特性.本文采用野外观测、授粉实验与室内显微观测等方法,对该物种的花部综合征及其次级花粉呈现过程进行了详细观测,并对这些特征的适应意义进行了探讨.结果表明:新疆党参钟状下垂的蓝色花冠及黑黄色蜜腺,不仅避免了雨水冲刷雌雄蕊、稀释花蜜以及风移出花粉等不利影响,还增加了对传粉者的吸引,延长了花粉活力及柱头可授性持续时间.次级花粉呈现属于亚顶端花柱呈现者,呈现机制为沉积机制.该特性限制了单个传粉者带走的花粉量,延长了花粉呈现时间,使更多传粉者参与传粉过程,增加了雄性适合度.其雄性先熟及雌雄蕊空间位置变化,避免了雌雄功能干扰,为传粉者取食花蜜、输出花粉以及柱头接受异源花粉提供了通道和机会.其泛化传粉系统的主要传粉昆虫为林野熊蜂(Bombus silvarum)、草地熊蜂(B.paradoxus)和树长黄胡蜂(Dolichovespula sylvestris),其较长的单花花期(6 d左右),昆虫访花高峰期与花粉活力最高时期及柱头最佳授粉期相吻合,以及较大的泌蜜量、较高的花蜜糖浓度和较长的泌蜜时间等特征,可提高传粉者的访花频率,增加成功传粉的机会和传粉效率.在气候多变的天山山区,该物种特殊的花部综合征和次级花粉呈现机制对提高其传粉效率并促进异交繁殖成功具有重要意义.     

A preliminary study on pollination biology of Omphalogramma souliei Franch. (Primulaceae), a species endemic to China

The pollination biology of Omphalogramma souliei Franch., a species endemic to southwestern China, was investigated. Floral phenology, flower visitors, pollen/ovule ratio, attractants and rewards to the visitors were observed, measured, and recorded. Bagging experiments to exclude pollinators were carried out in the wild for two years. Our results revealed five important aspects of the reproductive biology of Omphalogramma souliei. 1) The pollen-ovule ratio was 1748±233. The breeding system was self-compatible, with facultative xenogamy. 2) The pollination syndrome is entomophily, and this species could not be pollinated by wind if the pollinators were unavailable. 3) Six insect species were observed visiting the flowers of Omphalogramma souliei in the wild, of them, three species of hymenoptera, Lasioglossum sp., Heriades parvula Cockerell and Micrapis florae Fabricius, are the principal floral visitors and effective pollinators. 4) The visual attractants to the visitors are floral color and shape, the large yellow anthers, and the rewards for visitors are pollen and nectar. 5) Cleistogamy may also occur, since the anthers of some flowers dehisced before opening of the corolla. The results of floral biology and pollination characters suggest that xenogamy predominated and autogamy played an assistant role in the evolution of reproduction and breeding system of O. souliei.     

FLORAL PARAMETERS,BREEDING SYSTEM AND POLLINATOR TYPE IN TRICHOSTEMA (LABIATAE)

Diversity in flower size and degree of exsertion of anthers and stigma from the corolla in the California species of Trichostema appear to be correlated with breeding system and pollinator type (bee vs. bird). Autogamous (self-pollinating) species unlike xenogamous (cross-pollinating) species lack spatially separate anthers and stigma and nototribic pollination. The outcrossing species have significantly larger flowers, significantly larger nectar volumes and significantly higher pollen-ovule ratios than do selfing species. Because autogamous species are less reliant on flower visitors to facilitate pollination, there may be relaxed selection for large nectar producing flowers. Pollen-ovule ratios are correlated with breeding system and reflect the efficiency of pollen transport. Data on floral parameters suggest xenogamous species expend more energy per floral unit and are less efficient seed producers than closely related autogamous species.     

Pollination by hummingbirds and bees in eight syntopic species and a putative hybrid of Ericaceae in Southeastern Brazil

We report on flowering phenology, floral morphology, pollinators, and nectar for eight species and a putative natural hybrid belonging to Agarista, Gaultheria and Gaylussacia that occur syntopically in a montane area. The campanulate to tubular flowers of eight out of nine Ericaceae taxa are primarily pollinated by either hummingbirds or bees. Flowering overlaps in all species but slight differences of floral shape, colour, and nectar characterize pollination by each pollinator group. Differences in floral traits are not large enough to exclude secondary pollinators. Thus, either the main pollinators of a species belonging to its syndrome, or secondary pollinators of a species belonging to different syndromes, may allow for inter-specific crosses.     

Divergence on floral traits and vertebrate pollinators of two endemic Encholirium bromeliads

Shifts in pollen vectors favour diversification of floral traits, and differences in pollination strategies between congeneric sympatric species can contribute to reproductive isolation. Divergence in flowering phenology and selfing could also reduce interspecific crossing between self‐compatible species. We investigated floral traits and visitation rates of pollinators of two sympatric Encholirium species on rocky outcrops to evaluate whether prior knowledge of floral characters could indicate actual pollinators. Data on flowering phenology, visitation rates and breeding system were used to evaluate reproductive isolation. Flowering phenology overlapped between species, but there were differences in floral characters, nectar volume and concentration. Several hummingbird species visited flowers of both Encholirium spp., but the endemic bat Lonchophylla bokermanni and an unidentified sphingid only visited E. vogelii. Pollination treatments demonstrated that E. heloisae and E. vogelii were partially self‐compatible, with weak pollen limitation to seed set. Herbivores feeding on inflorescences decreased reproductive output of both species, but for E. vogelii the damage was higher. Our results indicate that actual pollinators can be known beforehand through floral traits, in agreement with pollination syndromes stating that a set of floral traits can be associated with the attraction of specific groups of pollinators. Divergence on floral traits and pollinator assemblage indicate that shifts in pollination strategies contribute to reproductive isolation between these Encholirium species, not divergence on flowering phenology or selfing. We suggest that hummingbird pollination might be the ancestral condition in Encholirium and that evolution of bat pollination made a substantial contribution to the diversification of this clade.     

Many to flower, few to fruit: the reproductive biology of Hamamelis virginiana (Hamamelidaceae)

Hamamelis virginiana flowers from late September to late November. In 1977, we began studying the reproductive biology of this eastern North American arborescent shrub by examining floral phenology and rewards, pollen-ovule ratios, breeding system, pollination, pollinator and resource limitation, and seed dispersal. The homogamous, self-incompatible flowers emit a faint odor, bear nectar with sucrose ratios typical of bee- and fly-pollinated flowers, and produce abundant sticky pollen. Flowers were visited infrequently by insects representing six orders. Flies were the most common floral visitors, specifically members of the genus Bradysia, but small bees also carried high percentages of Hamamelis pollen. Despite high pollen/ovule ratios (11?445 grains/ovule), bees and flies are likely pollinators, as experiments indicate wind pollination is less likely. Pollen quantity and resource availability did not appear to limit reproductive output, but pollen quality did. Tests of >40?000 flowers showed natural fruit set to be <1%. The flowering time, breeding system, and clumped distribution of plants, likely due in part to limited seed dispersal, combine to yield this remarkably low fruit set. Because all other species of Hamamelis flower from late winter to early summer, it may be that H. virginiana evolved a fall flowering phenology to avoid competition for pollinators with the closely related H. vernalis.     

峨眉拟单性木兰的开花生物学特性与繁育系统

为阐明峨眉拟单性木兰(Parakmeria omeiensis)在自然条件结实率低的原因和确定最佳人工授粉时期,该文通过观察峨眉拟单性木兰的开花动态,采用杂交指数估算、花粉胚珠比、花粉活力及柱头活性检测、人工授粉试验等方法对其繁育系统进行了研究。结果表明:(1)植物园保育的峨眉拟单性木兰花期在4月底到5月中下旬,持续17～23 d,雄株始花期比雌株早3～4 d,但两者花期可遇。(2)两性花经检测雄蕊败育,实为功能上的雌性,部分雄株个体的雄花上残留1～2个心皮,其性别分化是通过雌、雄蕊选择性败育形成的,为隐性雌雄异株(cryptic dioecy)。(3)雄花、两性花开放经历佛焰苞开裂、花被片开裂、展开、闭合、二次开放、凋落6个阶段,历时4 d。(4)雄花初次展开时花粉活力最高,达92.8%,开花2 d后活力显著下降;两性花柱头在花被片展开期可授性最强,盛开后柱头部分可授。(5)杂交指数为5,P/O比为2.14×10~4。(6)套袋试验表明,峨眉拟单性木兰不能进行自花传粉,人工异花授粉的结实率和出种数显著高于自然授粉,且不存在无融合生殖。这说明峨眉拟单性木兰繁育系统为专性异交,传粉过程需要传粉媒介,自然条件下结实率低,主要是受传粉昆虫和柱头可授期短的限制。     

广西特有属——异裂菊属开花生物学及繁育系统特征

以异裂菊属5个种的实生苗为试验材料,通过田间观察,采用TTC法、联苯胺-过氧化氢法、杂交指数、花粉-胚珠比等方法,对异裂菊属的开花物候、花部特征、繁育系统及访花昆虫行为进行了研究。结果表明:(1)绢叶异裂菊的花期最早,为6~7月份;小花异裂菊和柳州异裂菊花期为6~8月份;凹脉异裂菊和异裂菊的花期为8~12月份,整个花期持续约5个多月,单花花期约为3d,单个花序花期约为5d。(2)异裂菊属的花粉在开花后1~18h具有活力,柱头的可授性持续约48h;杂交指数OCI为4,花粉/胚珠比(P/O)为1 450~2 250,繁育系统属于异交、部分自交亲和,需要传粉者。(3)传粉昆虫主要是食蚜蝇科灰带管食蚜蝇和胡蜂科黑尾胡蜂,昆虫访花高峰期在上午10:00~12:00,每次可连续访问多朵花,每朵花访问时间约为2~10s。     

Primary nectar robbing by Apis mellifera (Apidae) on Pyrostegia venusta (Bignoniaceae): behavior,pillaging rate,and its consequences

The interactions between plants and their pollinators are the result of convergent evolution of floral attributes reflecting pressure exerted by pollinators. Nonetheless, the strategies employed by floral visitors to collect floral resources are extremely complex, and commonly involve theft or robbery in addition to pollination. We describe here the behavioral repertory of Apis mellifera during the collection of the floral resources, and evaluated the robbing rates of A. mellifera on the buds and flowers of Pyrostegia venusta during periods of intense and sparse flowering. We recorded the behaviors exhibited by foraging bees while collecting floral resources, quantified the numbers of floral buds and flowers with perforations in their corolla tissues, and determined whether that damage reduced nectar production. The evaluations were conducted during two distinct periods: during the period of intense flowering of P. venusta, and during the period of sparse flowering. Nectar robbing was observed during 93.4% of the visits of foraging A. mellifera bees, while nectar theft was observed during only 0.7% of the visits, and pollen theft during 5.9%. The robbing of floral buds and flowers was most intense during the period of heavy flowering. Flowers that had been intensely robbed secreted significantly less nectar than those non-robbed. The unusual nectar robbing activities of A. mellifera, especially during the period of intense flowering indicates an optimization of access to larger volumes of food resources. Our results therefore point to a major limitation of nectar per floral unit during the intense flowering period of P. venusta due to the high activity of nectar robbing by A. mellifera bees.

     

Contrasting breeding systems in twoEriotheca (Bombacaceae) species of the Brazilian cerrados

The pollination biology and breeding systems ofEriotheca pubescens andE. gracilipes have been studied. These two species occur as trees in cerrado vegetation, the neotropical savannas of Central Brazil, with partially sympatric distributions. They have similar phenology and floral structure, although the flowers ofE. pubescens are larger. Both species have nectar flowers pollinated by largeAnthophoridae bees but the main pollinators of each species differ in size. The species have markedly different breeding systems: late-acting self-incompatibility inE. gracilipes and apomixis stimulated by pollination inE. pubescens.     

Pollination Ecology and Effect of Nectar Removal in Macleania bullata (Ericaceae)1

The floral syndrome of Macleania bullataYeo (Ericaceae) reflects its adaptation to hummingbird pollination. Its flowers, however, are subject to high levels of nectar robbing. I examined the floral visitor assemblage of M. bullata in a tropical montane wet forest in southwestern Colombia, focusing on the behavior of the visitors. I also tested for the presence of nocturnal pollination and the effects of nectar removal on new nectar production. The principal floral visitors were the nectar robbing hummingbirds Ocreatus underwoodii (19.1% of visits) and Chlorostilbon mellisugus (18.9%). Only two species of long–billed hummingbirds visited the flowers of M. bullata as “legitimate” pollinators: Coeligena torquata (14.7% of visits) and Doryfera ludoviciae (14.3%). The remaining visits constituted nectar robbing by bees, butterflies, and other species of hummingbirds. Nocturnal pollination took place, although fruit set levels were 2.4 times higher when only diurnal pollination was allowed as opposed to exclusively nocturnal pollination. Nectar robbers removed floral nectar without pollinating the flower. Treatments of experimental nectar removal were carried out to examine if flowers synthesize more nectar after nectar removal. Nectar removal increased the total volume of nectar produced by each flower without affecting sugar concentration. Thus, nectar robbing can impose a high cost to the plants by forcing them to replace lost nectar.