POLLINATION BIOLOGY OF LISTERA CORDATA (ORCHIDACEAE)

Pollination biology of northern California populations of Listera cordata (L.) R. Br. is presented. The flowers are allogamous, self-compatible, and protandrous. At anthesis, access to the stigma is blocked by the flap-like rostellum. When an insect contacts the touch-sensitive trigger hairs of the rostellum, the pollinia are suddenly released and become cemented to the insect's body. One to two days after the pollinia are removed, the rostellum rises and exposes the receptive stigma. Visitors are attracted to the flowers by their foul odor and minute quantities of nectar presented on the surface of the labellum. Pollination efficiency is high with 61–78% of flowers from several localities setting fruit. The most important and abundant pollinators of L. cordata at our study sites are fungus gnats (Sciaridae and Mycetophylidae). Other less frequently encountered pollinators are members of these families: Braconidae, Ichneumonidae, and Tipulidae. At present, there is no compelling evidence that the floral characteristics of L. cordata have evolved as a result of an evolutionary interaction with any specific group of insects. Nor is there any indication that the flowers are sapromyophilous, despite their putrid odor.     

POLLINATION BIOLOGY AND CHEMOTAXONOMY OF THE ECHINOCEREUS VIRIDIFLORUS COMPLEX (CACTACEAE)

The Echinocereus viridiflorus complex is morphologically distinct from other members of the genus. Temporal differences in flowering preclude natural interspecific hybridization between taxa of the E. viridiflorus complex and sympatric congeners. All taxa within the complex are xenogamous and self-incompatible. Considerable taxonomic disagreement exists among herbarium and field botanists with regard to species boundaries and infraspecific classification of the taxa constituting the E. viridiflorus complex. One author views the complex as consisting of a single species, E. viridiflorus while other authors additionally recognize E. chloranthus, E. russanthus, and E. davisii. Pollination in E. viridiflorus is by solitary halictid bees. Photographs taken with a filter transmitting long-wave ultraviolet (UV) light revealed two floral patterns among entities of the complex: entirely UV-absorbing tepals and tepals with UV-reflective outer segments and UV-absorbing centers (target-type blossoms). We suggest that UV-floral patterning increases pollinator visitation and efficiency. Six flavonol-O-glycosides and two dihydroflavonol-7-O-glycosides were localized in tepal tissue. No qualitative differences were seen either between differentially UV-patterned flowers or among E. viridiflorus, E. chloranthus, E. davisii, and E. russanthus. Flavonoid evidence indicates that these taxa are conspecific.     

POLLINATION AND SEED PRODUCTION IN IPOMOPSIS AGGREGATA: DIFFERENCES AMONG AND WITHIN FLOWER COLOR MORPHS

The pollination of red, pink, and white color morphs of Ipomopsis aggregata was evaluated to assess whether ethological isolation based on pollinator color discrimination may occur. We observed animal visitors, assessed pollen delivery, seed set per fruit, percentage of flowers setting fruit, nectar production, and timing of flower opening for different color morphs in the Front Range of Colorado. Based on traditional zoophilous flower classifications, we expected hummingbirds to pollinate red-flowered I. aggregata subsp. collina and hawkmoths to pollinate white-flowered I. aggregata subsp. Candida. However, ethological isolation does not appear to occur among color morphs of I. aggregata in the Front Range. Hummingbirds visited red-flowered plants in excess overall, and, to a lesser extent, so did hawkmoths. Both hummingbirds and hawkmoths visited all color morphs and probably transferred pollen among them. Pollen delivery data and a day-night bagging experiment also suggest that pollinators do not necessarily behave as predicted by flower classifications. In addition, there is little evidence for major differences between red, white, and pink flowers in any aspects of reproductive biology. Indeed, most variation occurs within a given color morph.     

杭州石荠苎和石香薷（唇形科）的传粉生物学比较研究

杭州石荠苎（ＭｏｓｌａｈａｎｇｃｈｏｕｅｎｓｉｓＭａｔｓｕｄａｓ）和石香薷（Ｍ．ｃｈｉｎｅｎｓｉｓＭａｘｉｍ．）是一对种对,前零星分布于浙江,后广布于长江流域以南地区。杭州石荠苎以异花传粉为主,花粉／胚珠（Ｐ／Ｏ）为７５６＝－６１６３;石香薷以自花传粉为主,Ｐ／Ｏ＝１１０。     

THE POLLINATION BIOLOGY OF TILIA

An anthecological study of Tilia in the Great Plains and New England was undertaken for both native and introduced species. The floral bracts are postulated as being at least as important in pollinator attraction as they are in fruit dispersal. A characteristic sweet odor is always present, but becomes stronger at dusk. Flowers are protandrous with anthers opening for the first time late in the afternoon and releasing pollen abundantly for about 24 hr. Initial nectar production coincides with stigma receptivity which begins late in the afternoon, but on the second day a flower is open. Sixty-six species of insects in 29 families were collected. Bees and flies are the most common diurnal visitors and moths are the primary nocturnal visitors. Samples of pollen taken from the insects indicate a relatively high constancy. Experimental tests show that Tilia is not apomictic or self compatible. Anemophily plays a secondary role to entomophily in pollination. Nocturnal pollinators are slighly less effective than diurnal pollinators in effecting fruit set. Although nocturnal pollinators are favored by the syndrome of floral characteristics, it is concluded that Tilia is a generalist in regard to pollination. It is proposed that the lack of clear morphological differences between Tilia species leads to pollinator inconstancy and thus hybridization.     

THE POLLINATION BIOLOGY OF TUCKAHOE,PELTANDRA VIRGINICA (ARACEAE)

This study describes the specialized brood-site-based pollination system of Peltandra virginica Kunth (Araceae) with the chloropid fly Elachiptera formosa Loew and provides experimental evidence that gender-related changes in floral odor composition synchronize pollinator behavior with the blooming sequence. P. virginica is protogynous and does not self-pollinate because of a strong temporal separation in sexual function, and it is dependent upon insects for pollination because the spathe completely surrounds the spadix during the pistillate stage. Field observations conducted in central New Jersey and southeastern Pennsylvania showed that E. formosa is closely associated with P. virginica inflorescences. Within the floral chamber, E. formosa adults feed on pollen, mate, and find oviposition sites while the larvae complete their development. Although drosophilid and syrphid flies were collected and reared from inflorescences of both sexual stages, only E. formosa emerged from pistillate-stage inflorescences and adult E. formosa rapidly transferred fluorescent dye particles between inflorescences of both sexual stages in laboratory enclosures. These findings indicate that this fly species is the primary pollinator at our study locations. Field censuses demonstrated that although E. formosa visited P. virginica inflorescences of both sexual stages with equal frequency, the female flies preferentially oviposited within pistillate-stage inflorescences. Analysis of floral volatiles with gas chromatography-mass spectrometry showed that only the spathes emit the floral fragrance and that the composition of the floral volatiles changed during the transition from pistillate to staminate stage. A particularly noticeable change occurred in the emission ratio of the two primary floral odor components, 4,5,7-trimethyl-6,8-dioxabicyclo[3.2.1.]octane and an unidentified chemical analog with molecular weight of 142. The relationship between floral volatile composition and fly oviposition behavior was evaluated using sham inflorescences placed in the P. virginica study population. The sham inflorescences were constructed by covering spadices dissected from mature inflorescence buds with spathes excised from different-age inflorescences. After a 2-hr-long exposure period, sham inflorescences fitted with pistillate-stage spathes contained more E. formosa eggs than the sham inflorescences with staminate-stage spathes. However, the highest number of ovipositions occurred in sham inflorescences fitted with spathes excised from mature inflorescence buds. The fragrance emitted by these spathes was composed almost entirely of the two principal odor components. The decline in ovipositions observed in both real and sham inflorescences corresponded to an increase in the emission ratio of 4,5,7-trimethyl-6,8-dioxabicyclo[3.2.1.]octane to the molecular weight 142 analog. This suggests that gravid flies searching for oviposition sites used the ratio of the two primary floral volatile components as an inflorescence gender or age recognition cue.     

FLORAL BIOLOGY,HUMMINGBIRD POLLINATION AND FRUIT PRODUCTION OF TRUMPET CREEPER (CAMPSIS RADICANS,BIGNONIACEAE)

Trumpet creeper is self-incompatible and bears long, tubular, orange flowers from June to September. Flowering peaks rapidly, then declines and continues at low levels for several weeks. The initial burst of flowering may attract pollinators that return even during subsequent reduced flowering. Most flowers open before noon and nectar production totals 110 μl of 26% sucrose equivalents per flower, an exceptionally high production for a temperate zone plant. Production ceases within 20–30 hr of flower opening, but corollas persist for several days and may serve to attract pollinators. Effective pollination reduces the period of stigma receptivity and speeds closing of stigma lobes. Only 1–9% of flowers produced mature fruits at four sites in Illinois and Missouri. Roughly 400 pollen grains had to be deposited on a receptive stigma to cause fruit development beyond an initial period of high abortion. At two sites, 17% and 89% of stigmas received over 400 pollen grains. Assuming 50% of deposited grains were from the same plant, fruit production at one site was clearly pollinator limited, that at the second site may have been. Ruby-throated Hummingbirds (Archilochus colubris) deposited ten times as much pollen per stigma per visit as honeybees (Apis mellifera) and bumblebees (Bombus spp.). Fruit set was highest where rubythroat visitation was most frequent. Trumpet creeper appears primarily adapted for hummingbird pollination, but can also be adequately pollinated by honeybees and bumblebees. This is one of the first attempts to relate pollen-depositing capabilities of pollinators of any plant to pollen requirements for fruit production. Several characteristics suggest that trumpet creeper may be adapted to pollination at low densities (often called traplining) in its presumed original, woodland, habitat.     

CHANGES IN MEGAGAMETOPHYTE STRUCTURE IN PAPAVER NUDICAULE L. (PAPAVERACEAE) FOLLOWING IN VITRO PLACENTAL POLLINATION

Papaver nudicaule placentae with attached ovules were dissected out of unpollinated gynoecia 1–3 days after anthesis, dusted with pollen, and cultured on modified Nitsch's growth medium at 23 C. Ovules were removed from expiants at 15, 24, 31, and 48 hr postpollination, fixed in GA-OsO₄, embedded in Spurr's resin and sectioned (1.0 μm) for light microscopy. Placentae, 15 hr after pollination, were fixed and processed for scanning electron microscopy. Pollen germinates within 1 hr. Although most pollen tube growth appears random, there is directional growth toward the micropyle. The crassinucellate ovule contains an embryo sac consisting of three antipodals, two polar nuclei, and an egg apparatus composed of two synergids and a polarized egg having a large chalazal vacuole and micropylar nucleus. Pollen tube access into the megagametophyte is through a degenerate synergid, with fertilization occurring between 24 and 31 hr after pollination. Zygote establishment is accompanied by polarity reversal in which the nucleus assumes the chalazal position subtended by a large micropylar vacuole. Fertilized ovules normally develop into germinable seeds.     

POLLEN MORPHOLOGY AND ULTRASTRUCTURE OF THE CABOMBACEAE: CORRELATIONS WITH POLLINATION BIOLOGY

Of all species comprising the two genera of the Cabombaceae, only Brasenia schreberi J. F. Gmel. and Cabomba caroliniana Gray have been critically investigated with regard to their pollination biology. Brasenia schreberi has been shown to be anemophilous, while C. caroliniana has an entomophilous (myophilous) pollination syndrome. In the present paper, a number of pollen and pollen-related characters, including pollen size, shape, quantity, terminal settling velocity, pollen-ovule ratios, and overall exine architecture of B. schreberi and C. caroliniana are evaluated. Pollen from both species is elliptic, monosulcate, and has a tectate-columellate sporoderm with supratectal surface ornamentation. Grains of B. schreberi are small, produced in copious amounts, and settle relatively slowly. Flowers of this species have large pollen-ovule ratios. The exine of B. schreberi pollen is scabrate, relatively thin, has a uniformly thick sexine composed of a two-zoned (homogeneous/granular) tectum and distinct columellae, and a homogeneous nexine. Pollen of C. caroliniana is relatively large, produced in small quantities, and has a rapid terminal settling velocity. Flowers exhibit small pollen-ovule ratios. Exine organization of C. caroliniana pollen is typically two times thicker than that of B. schreberi; ornamentation is striate. Nonapertural sexine regions have a thick tectum and well-defined columellae, with both sexine components traversed by a dense system of channels. The nexine is relatively thin. All of the palynological characters examined correlate well with the anemophilous and entomophilous syndromes of B. schreberi and C. caroliniana, respectively. Moreover, several other parameters of exine ultrastructure from each species exhibit positive correlations with the respective pollination mechanisms, including: tectum thickness, columellae diameter, tectum-nexine ratios, and the consistency, distribution, and total amount of pollenkitt present. Overall exine ultrastructure is also discussed from a historical perspective as well as with respect to its phylogenetic significance.     

POLLINATION BIOLOGY OF PLATANTHERA STRICTA (ORCHIDACEAE) IN OLYMPIC NATIONAL PARK,WASHINGTON

Platanthera striata Lindley is entomophilous and can produce seed via facultative self-pollination and intraracemic and interracemic pollination. Capsule production is pollinator-limited and seed set may be pollen-limited. In experimental plants capsules produced via self- and intraracemic pollination contained fewer seeds with normally developed embryos than did capsules produced via interracemic pollination. The inflorescence of Platanthera stricta is fragrant and is attractive to a wide array of anthophilous insects. It is pollinated by a diverse assemblage of short-tongued insects. The primary pollinators are Eustroma fasciata B. and McD. (Lepidoptera: Geometridae), Bombus flavifrons Cresson and B. melanopygus Nylander (Hymenoptera: Apidae), an undescribed species of Greya (Lepidoptera: Prodixidae), and several species of Empis, Rhamphomyia, and Anthepiscopus longipalpis Melander (Diptera: Empididae). Small amounts of glucose are present on the raceme. The extrafloral glucose may retain small pollinators on the inflorescence until they locate the floral spur aperture.     

东北地区野豌豆属植物花生物学和繁育系统研究

对东北地区野豌豆属植物花生物学研究表明文中类群均为自花授粉植物,ＡＴＰ酶活性与柱头间的可授性有关。花粉－胚珠比高于Ｃｒｕｄｅｎ标准,开花物候期分化成早春－春季和夏季两种开花类型,表现出在物种形成时地理条件的差异。     

滇西北马先蒿属传粉生物学的初步研究

对云南西北部的中甸和德钦高山地区４种马先蒿属（ＰｅｄｉｃｕｌａｒｉｓＬ．）植物的传粉生物学进行了观察。晚夏开花的马先蒿与传粉熊蜂（ＢｏｍｂｕｓＬａｔｒ．）的出现在物候上有一定的相关性。其中短管、无喙、无蜜腺的肉根马先蒿（Ｐ．ｒｏｙｌｅｉＭａｘｉｍ．）和茨口马先蒿（Ｐ．ｔｓｅｋｏｕｅｎｓｉｓＢｏｎａｔｉ）是由熊蜂工蜂震动花粉、背触式传粉,这与其花冠类型的较原始性有关;长管、具喙、无蜜腺的斑唇马先蒿（Ｐ．ｌｏｎｇｉｆｌｏｒａｖａｒ．ｔｕｂｉｆｏｒｍｉｓ（Ｋｌｏｔｚ．）Ｔｓｏｏｎｇ）和云南长管马先蒿（Ｐ．ｓｉｐｈｏｎａｎｔｈａＤｏｎ．ｖａｒ．ｄｅｌａｖａｙｉ（Ｆｒａｎｃｈ．）Ｔｓｏｏｎｇ）通过熊蜂工蜂震动花粉、腹触式传粉。长管类马先蒿在植株相对矮小的情况下,通过较长的花冠管具喙向外伸出以实现授粉,这可能是与其传粉熊蜂协同进化的结果。     

ONTOGENY AND CYTOCHEMISTRY OF ALKALOIDAL VESICLES IN LATICIFERS OF PAPAVER SOMNIFERUM L. (PAPAVERACEAE)

Development of alkaloidal vesicles in laticifers of opium poppy, Papaver somniferum L., was investigated at the ultrastructural level. Laticifer initials possessed abundant endoplasmic reticulum throughout their dense cytoplasm. During differentiation the endoplasmic reticulum organized into long, folded sheets that were parallel to the longitudinal walls along the periphery of the cell. Vesicles appeared to be derived from dilation of endoplasmic reticulum. This relationship was confirmed through cytochemical data obtained with zinc iodide-osmium tetroxide and osmium tetroxide impregnation. Alkaloidal vesicles had electron-dense regions or caps that occurred early in laticifer differentiation, but these caps became less conspicuous in mature cells. Caps appeared to be derived from small particles which condensed along the inner surface of the vesicle membrane and subsequently accumulated at one or two positions along the membrane of the vesicle.     

RELATION OF FLOWER COLOR TO OPTICAL-DENSITY SPECTRA OF INTACT TISSUE AND OF ANTHOCYANIN EXTRACTS

Data from measurements of optical density of intact tissue and of anthocyanins in extracts resolved on cellulose thin layer plates were compared with visual evaluations of color quality and intensity in poinsettia, rose, and snapdragon. Visual evaluation was in good agreement with both instrumental and chemical determinations. However, the number or kinds of anthocyanins present could not be predicted from the visual evaluation or from the spectra of the fresh tissue. Data from the resolved extracts did not provide a basis for predicting the optical-density spectrum or the color of the intact tissue. In addition to the genetic factors which have been shown to control (1) the type of anthocyanin, (2) the amount of anthocyanin, and (3) the distribution of anthocyanins within the flower, we suggest another group of genes which apparently affect color through control of structural modification of individual anthocyanins in the living cell through shift in pH, metal chelation, and/or copigmentation. Such genes are apparently responsible for the modification of red color within the Wh Wh genotype of poinsettias containing both pelargonidin and cyanidin glycosides and for a very similar pink color in a snapdragon and a rose, each containing a single anthocyanin, a pelargonidin glycoside, and a cyanidin glycoside, respectively.     

STOMATA ON THE FRUITS AND SEEDS OF ESCHSCHOLZIA (PAPAVERACEAE)

Stomata are present on the outer and inner fruit walls and seed coats of Eschscholzia californica, E. covillei, E. glyptosperma, E. lemmonii and E. minutiflora. The stomata on the inner fruit wall and seed coat remain constantly open, even under plasmolyzing conditions, whereas those of the outer fruit wall are able to open and close. This allows for gas exchange in these chlorophyllous structures. Fibrous bundle caps in the costal regions of the fruit act as windows allowing light transmission to the photosynthetic seeds within. Preliminary results show that the total photosynthesis by the fruits and seeds of Eschscholzia californica together appears to at least balance respiratory losses, and under favorable conditions might significantly contribute to seed and fruit development.     

REPRODUCTIVE BIOLOGY OF TROPICAL LOWLAND RAIN FOREST TREES. II. POLLINATION SYSTEMS

The reproductive biology of tree species of a tropical rain forest was investigated to determine the relative frequency and spatial distribution of different types of pollination mechanisms. Species pollinated by medium-sized to large bees were most frequent, followed by those pollinated by moths, small diverse insects and small bees, in that order. Almost one half the total species were found to have pollinators with wide foraging ranges. Species pollinated by various groups of pollinators were distributed non-randomly. The greatest diversity of pollination systems was found in the subcanopy. As compared to the subcanopy, pollination mechanisms in the canopy were monotonous, consisting primarily of species pollinated by bees and small diverse insects. The hummingbird- and sphingid moth-pollinated species were found mainly in the subcanopy. The factors underlying the non-random distribution of pollinators are discussed and the potential implications of such distribution on the forest structure are explored.