Pollination of the southwestern Opuntias

This paper presents an overview of pollination systems inOpuntia sens. lat. in the southwestern United States. The floral syndrome of large, colorful, bowl-shaped, diurnal flowers is present in all of the prickly-pear species and most of the cholla (Cylindropuntia) species in this area. Pollination by medium-sized and large bees is established for some of the species with this floral syndrome and is predicted for the others. The same floral syndrome is widespread inOpuntia in other geographical areas.—Deviations from this floral syndrome occur in certain species of southwestern chollas, one of which has nocturnal disc-shaped flowers, and in several tropical American species groups or segregate genera with red hummingbird flowers. But such cases are relatively infrequent. Divergence between species with respect to floral syndrome and pollination system is not a common feature in the evolutionary pattern ofOpuntia. Pollination of North American Cacti, IV.—Previons parts of this series:Grant & Grant 1979a,Grant & al. 1979,Grant & Grant 1979b.     

Pollination: the price of attraction

Nectar is the major currency bringing together plants and pollinators; yet the costs and benefits of nectar production remain poorly understood. A low nectar line developed in Petunia offers an innovative approach to this problem and may offer clues to why some plants cheat and secure pollination via deception.     

中国鹅掌楸传粉生物学研究

对中国鹅掌楸(Liriodendron chinense)的不育现象已有了许多的研究。与自然传粉和杂交控制传粉相比,自花传粉常常导致较低的结实率。经过传粉以后,仅落在柱头上的花粉才有可能得到正常发育,并对植物的结实率产生影响。研究结果表明：中国鹅掌楸不同花期开放的各个花朵,所接收到的花粉量是不—致的,在中期开放的花朵接收花粉量较多。在多数情况下,花的下部位柱头接收了较多的花粉,中部位的柱头次之,而上部位接收的花粉较少。通过比较分析,认为有必要对落在柱头上的花粉来源和花粉纯度及这些指标与结实率之间的关系做进一步研究。     

Pollination in conifers

Our understanding of pollination in conifers has advanced rapidly in recent years, but it still lags behind our knowledge of this process in angiosperms. In part this is because conifers are not considered to be high priority crops and, unlike many cultivated flowers, conifer seed cones are generally neither large nor colorful. The use of genetics to improve tree growth has primarily been through selection and asexual propagation rather than breeding, and because incompatibility is not thought to occur in conifer pollination systems, concern about pollination has primarily been with regard to seed production. Here we examine the ancestral wind-pollination mechanism in conifers and discuss how the process may have evolved to improve pollination success.     

Pollination of the edelweiss, Leontopodium alpinum

This paper describes the pollinators, scent and nectar composition of the edelweiss ( Leontopodium alpinum). In contrast to former statements in the literature, the flowers of this famous plant are frequently visited by various insects in 29 familieS. However, in the two populations of L. Alpinum investigated here, flies (Muscidae) were the most frequent visitorS. Although the investigated insects carried pollen grains all over their bodies and qualify as mess and soil pollinators, pollen grains were not randomly distributed on the bodies of the insects but were most concentrated on their legs. Their loads of L. Alpinum pollen varied greatly, but more than 60% of all Leontopodium pollen grains found on the insects were carried by only 12% of the specimens collected, suggesting that a small fraction of the visitors is responsible for most of the pollen transfer. The number of pollen grains found on the insects also increased significantly with increasing body size of the insects. The scent of the flowers is sweet and honey-like (phenylethyl alcohol and phenylacetic acid) but also contains disagreeably smelling, sweat-like components (3-methyl-2-pentenoic acids, butyric acid and other fatty acids).Nectar is secreted in minute amounts in the tiny florets of the flower heads. The sugar composition of the nectar is dominated by the hexoses fructose and glucose. It also contains a high amino acid concentration with many different amino acidS. Nectar, scent and the shape of the flowers of L. Alpinum all fit the syndrome of fly pollination.     

Pollination by brood-site deception

Pollination is often regarded as a mutualistic relationship between flowering plants and insects. In such a relationship, both partners gain a fitness benefit as a result of their interaction. The flower gets pollinated and the insect typically gets a food-related reward. However, flower-insect communication is not always a mutualistic system, as some flowers emit deceitful signals. Insects are thus fooled by irresistible stimuli and pollination is accomplished. Such deception requires very fine tuning, as insects in their typically short life span, try to find mating/feeding breeding sites as efficiently as possible, and following deceitful signals thus is both costly and time-consuming. Deceptive flowers have thus evolved the ability to emit signals that trigger obligate innate or learned responses in the targeted insects. The behavior, and thus the signals, exploited are typically involved in reproduction, from attracting pheromones to brood/food-site cues. Chemical mimicry is one of the main modalities through which flowers trick their pollen vectors, as olfaction plays a pivotal role in insect-insect and insect-plant interactions. Here we focus on floral odors that specifically mimic an oviposition substrate, i.e., brood-site mimicry. The phenomenon is wide spread across unrelated plant lineages of Angiosperm, Splachnaceae and Phallaceae. Targeted insects are mainly beetles and flies, and flowers accordingly often emit, to the human nose, highly powerful and fetid smells that are conversely extremely attractive to the duped insects. Brood-site deceptive plants often display highly elaborate flowers and have evolved a trap-release mechanism. Chemical cues often act in unison with other sensory cues to refine the imitation.     

Pollination of Habenaria tridactylites on the Canary Islands

We investigated the pollination of Habenaria tridactylites, an endemic orchid of the Canary Islands. The entirely green, widely open flowers have a long spur containing nectar. We carried out fieldwork, a molecular clock analysis, herbarium surveys, identified pollinators by both morphology and DNA barcoding, and measured the length of floral spurs and insect tongues using a combination of traditional and innovative micro‐CT scanning methods to 1) determine the pollinator of this orchid and 2) investigate correlations between local mean spur length and age, altitude and longitude of the island. Habenaria tridactylites was found to be pollinated on Tenerife by both small and intermediate sized moth species with variable tongue lengths and mostly belonging to Geometridae and to a lesser extent Crambidae, Erebidae, Noctuidae and Tortricidae. Of the sixteen moth species identified, nine are endemic to the Canary Islands or Macaronesia. The different local populations of H. tridactylites on the islands of Gran Canaria, El Hierro, La Gomera, La Palma and Tenerife with different ages and distances from mainland Africa, did not show a significant correlation of mean spur length and altitude, but did show a significant and positive linear correlation with longitude and the geological age of the island. The latter is congruent with the evolutionary arms race theory first proposed by Darwin, suggesting that flowers gradually evolve longer spurs and pollinators longer tongues.     

Pollination ecology of Yucca elata

The pollination biology of a population of 250 Yucca elata (Liliaceae) plants was studied in southern New Mexico. Yucca elata and the prodoxid yucca moth Tegeticula yuccasella have a mutualistic association that is essential for the successful sexual reproduction of both species. However, a wide range of other invertebrate species visit flowers during the day and at night. Our aim was to quantify the role of yucca moths and other invertebrate visitors in pollination and fruit set, using manipulative field experiments. Inflorescences were bagged during the day or night (N=12 inflorescences) to restrict flower visitors to either nocturnal or diurnal groups. Yucca moths were active exclusively nocturnally during the flowering period and thus did not visit inflorescences that were unbagged during the day. None of the 4022 flowers exposed only to diurnal visitors set fruit, whereas 4.6% of the 4974 flowers exposed only to nocturnal visitors (including yucca moths) produced mature fruit. The proportion of flowers producing fruit in the latter treatment was not significantly different from unbagged control inflorescences. In a series of experimental manipulations we also determined that: (1) flowers opened at dusk and were open for two days on average, but were only receptive to pollen on the first night of opening; (2) pollen must be pushed down the stigmatic tube to affect pollination; and (3) most plants require out-cross pollination to produce fruit. The combination of these results strongly suggests that yucca moths are the only species affecting pollination in Y. elata, and that if another species was to affect pollination, it would be a rare event.     

传粉对杭州石荠苎（唇形科）结实的影响

杭州石荠苎（ＭｏｓｌａｈａｎｇｃｈｏｕｅｎｓｉｓＭａｔｓｕｄａ）自交亲和,人工自花授粉,同株异花授粉和异花授粉的结实没有明显差异。杭州自然居中新开花朵的调查没有发现闭花传粉现象。原因是花药和柱头之间存在空间隔离和发育上的时间隔离。这些隔离使昆虫花粉传播的必要媒介,结实从而取决于传粉昆虫的活动。     

杜鹃红山茶的传粉生物学

杜鹃红山茶(Camellia changii)为中国特有的濒危植物,仅见于广东省阳春市鹅凰嶂自然保护区内。对该保护区杜鹃红山茶自然种群进行了杂交指数(OCI)、花粉-胚珠比(P/O)和控制授粉试验研究,探讨其致濒原因。结果表明:杜鹃红山茶的繁育系统为专性异交型,自交不亲和,为典型的虫媒传粉型植物;在自然条件下,其子房败育率高达64%;杜鹃红山茶种群的花柱呈长度分化:20%为长花柱型(L型),76%为短花柱型(S型);杜鹃红山茶的有效传粉昆虫主要为蝶类和蜂类,但昆虫的访花频率较低。综合以上结果,杜鹃红山茶的濒危原因可能包括2个方面,一是自交不亲和性和花柱异长现象导致子房败育率高,二是传粉昆虫访花频率低导致自然结实率低。     

越南篦齿苏铁传粉媒介的研究

利用排除法和引入昆虫的方法相结合,研究越南篦齿苏铁(Cycas elongata)的传粉媒介.结果表明,越南篦齿苏铁靠风媒传粉和虫媒传粉的雌株结实率分别55.3%和57.2%,自然传粉的结实率为63.5%,说明风和象鼻虫都是越南篦齿苏铁的有效传粉媒介.越南篦齿苏铁散粉高峰在白天,夜间散粉很少,在3.0 m以内风传花粉的密度较高,3.0 m之外的密度急剧下降.可见,风媒和虫媒都是越南篦齿苏铁的有效传粉途径,与泽米铁类植物为专一寄主性昆虫传粉的结论不一致.     

Pollination characteristics of the ephemeroid plant Eremurus anisopterus

This study was conducted to examine the pol-lination characteristics of Eremurus anisopterus,an ephe-meroid plant in the Gurbantunggut Desert in Xinjiang,China.An integrative approach combining field studies with lab analysis was adopted.Pollen traps were used to measure air-borne pollen loads and artificial isolation experiments were applied to test the potentiality of cross-pollination or apomixes.Results show that the duration of the flowering of Eremurus anisopterus varied from late April to mid-May.Anthesis of a single flower often lasted for 1 d.However,if the daily maximum air temperature was under 20℃,the anthesis of a single flower could be prolonged up to 2 d.The pollen disper-sion period of the single flower could last for 4 to 5 h,from 10:30 to 15:00 local time,with the duration of pollen dispersion for a single anther lasting approximately 40 rain.The heterotypical maturation of the stigma could significantly prolong the pollen dispersion period of the single flower suggesting an adaptation to the habitat of E.anisopterus in the desert where the pollinators were not reliable.The timing of the blossoms of the ephemeroid plant show close correlations with the wind velocity and the habit and characteristics of the pollinators in the desert.Plant pollens may be spread to over 70 m by wind with approximately 60% of the pollens falling within 20 m away from the plant.Insects,especially bees,hover flies,flesh flies,mason bees and Halictus sp.were very import-ant pollinators.Bees and hover flies usually landed on the yellowish green spot on the tepal and then entered the flower along the purple vein on the pink tepals.The yel-lowish green spot might be a mimetic structure of nectar that could attract insects to visit.This was also an adapta-tion of the plant to the sandy desert environment.A higher visiting frequency was reached between 10:30 and 13:30.The pollen-ovule ratio (P/O) of E.anisopterus (6164) suggested that the species was from cross-pollina-tion according to Cruden's criterion.However,the arti-ficial isolation experiment shows that E.anisopterus is self-compatible which might act as a compensation mech-anism for the inadequate opportunities for breeding in the desert environment.Since there was no seed set in the bagged emasculated flowers,apomixes did not occur.In conclusion,E.anisopterus might adapt to the unreliable pollinator habits by self-pollination and by lengthening the pollen dispersion period of a single flower.     

Pollination biology of the deceptive orchid Changnienia amoena

The pollination biology of Changnienia amoena , an endangered terrestrial orchid, was investigated at two sites in the Shennongjia Mountains, Hubei, central China. The results show that the orchid is exclusively pollinated by bumblebees. In Longmenhe, Bombus ( Diversobombus ) trifasciatus is the primary effective pollinator, whereas B.  ( Tricornibombus ) imitator is the only pollinator in Guanmenshan. These two bumblebees can be treated as a functional group because they carry pollinaria on the same position on their bodies and have similar pollinating behaviours. The morphological traits of the flower adapt precisely to the pollinators. Visitation by bumblebees is mainly in the first half of the flowering period of C. amoena . Pollinarium removal and pollinia deposition take place when bumblebees withdraw from the flower. Crossing experiments show that C. amoena is a self-compatible and outcrossing species. Fruit set in this species is low and may result from limited pollinators because 87.5% of individuals set fruits under hand-pollination, but only 6–12% of individuals set fruits under natural conditions. These results imply that it is important to conserve the pollinator community together with the plants when conservation management for this endangered species is undertaken. Artificial pollination would also be a useful measure to facilitate restoration of the small populations.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 165–175.     

入侵植物美洲商陆的传粉生态学特性

从开花物候、花朵数量性状、花粉活力、花粉组织化学、柱头可授性、花粉在柱头上的萌发状况、杂交指数、花粉胚珠比、传粉媒介以及繁育系统等方面,研究了外来入侵植物美洲商陆(Phytolacca americana)的传粉生态学特性,为揭示该物种成功入侵的机理提供依据.结果表明:美洲商陆种群花期可达45~70 d,单花花期为2~3d,可进一步分为杯状花期、花瓣平展期、花瓣下垂期、花瓣反卷期;花冠直径在下垂期最大且不超过1 cm,花药与柱头间距离在1 ~2.5 mm,有利于自交的发生;花瓣平展期与花瓣下垂期花粉活力差异显著(P<0.05),杯状花期与花瓣平展期花粉活力差异不显著(P>0.05),花瓣平展期花粉活力可达85%;雌蕊柱头可授性在花瓣平展期最强;杯状花期合生柱头开裂,花瓣平展期柱头9~ 10裂,接受花粉的表面积增大;花药散粉时间与合生柱头开裂时间相吻合,有助于柱头接受花粉;扫描电镜下观察到花粉在花瓣平展期的柱头上已萌发;每朵花可提供1667~3222粒花粉,胚珠9~10个,花粉胚珠比(P/O)为340.88±34.99,表现为兼性自交;美洲商陆杂交指数(OCI)为3,花粉粒属于含脂型,主要传粉昆虫有蜜蜂、胡蜂、食蚜蝇、细腰蜂.综上所述,美洲商陆自交亲和,花粉活力高、柱头可授性强,且高花粉活力与强柱头可授性出现在相同的时期,增加了花粉落置柱头及在柱头上萌发的几率;虫媒花,访花者行为与花朵相适应,有利于提高坐果率,这样的繁殖机制与传粉特点是美洲商陆成功入侵的主要因素之一.     

三角梅开花习性与人工授粉方法初探

本文研究三角梅开花时花器的变化规律及三角梅的杂交授粉技术。通过对不同时期花器的观察对比,发现三角梅的最佳花粉采集时间为花被片微开裂1～2 mm,最佳授粉时间为花初开2 d内;通过人工杂交授粉试验,摸索出三角梅杂交授粉技术。杂交试验表明,伊娃夫人与帝国喜悦的杂交结实率最高,可达8.3%。     

苏铁类植物传粉生物学研究进展(综述)

苏铁类植物是现存最古老的种子植物,研究其传粉特点,对于研究种子植物的起源与演化、植物与动物的协同进化以及苏铁类植物的繁殖机制、濒危机制有重要意义。本文从苏铁雌雄株开花物候学、传粉媒介及传粉机制等方面,对苏铁类植物传粉生物学相关研究进行综述,并提出今后该类植物传粉生物学研究的建议：对更多苏铁属种类未知的传粉机制进行研究;更广泛地应用排除法研究苏铁类特别是苏铁属植物的传粉媒介,进一步探讨传粉昆虫与苏铁类的共生关系问题。