Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pollination”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed1995

Pollen allergy in the Bilbao area (European Atlantic seaboard climate): pollination forecasting methods.

Forecasting pollination can help the allergist to establish the appropriate treatment and advice for patients. Based on previous studies, we have related the climate variables with the grass pollen counts in the search for pollination predictors. By relating the meteorological data of the temperature recorded every 6 h and of the rainfall in hourly periods, together with the daily pollen counts obtained by the Hirst volumetric system, over a period of 3 years, we have tried to predict the start, duration and severity of the grass pollination, as well as the days of peak pollination. We have established a relationship by means of a polynomic regression originating from the mean cumulated temperature higher than 9 degrees C [R2 = 0.927 (P = 0.0001)], with the pollination season starting from 300 degrees C and the maximum peak at 356 degrees C, in the 3 years of the study. During the days of pollination, peaks higher than 50 grains/m3 coincide with average daily temperatures of 18.7 +/- 3 and lower than 50 grains/m3 with temperatures of 16.8 +/- 3 (significant to 95%). The duration of the pollination is influenced by the cumulated average temperatures (from 800 to 900 degrees C) and especially by precipitation at the start of and during pollination. In order to forecast grass pollination, the cumulated average temperatures are useful, starting from a basal (9 degrees C), pollination begins when this sum is greater than 300 degrees C, whereas when 800 degrees C is reached and depending on the rainfall during the season, pollination will end.(ABSTRACT TRUNCATED AT 250 WORDS)

Climate↗
PubMed2003

Negative impacts of a vertebrate predator on insect pollinator visitation and seed output in Chuquiraga oppositifolia, a high Andean shrub.

Studies on plant-pollinator interactions have largely neglected the potential negative effects of the predators of pollinators on seed output, even though anti-predatory behaviour of pollinators may affect visitation patterns, pollen transfer, and therefore potentially, plant reproductive output. We tested the hypothesis that the presence of lizards and insectivorous birds, by reducing pollinator visitation, can have significant negative effects on seed output in the insect-pollinated, genetically self-incompatible lower alpine Andean shrub, Chuquiraga oppositifolia (Asteraceae). The lower alpine belt supports a high density of territorial Liolaemus (Tropiduridae) lizards and low shrubs interspersed among rocks of varying sizes, the latter inhabited by lizards and commonly used by flycatchers Muscisaxicola (Tyrannidae) as perching sites. In a 2x2 factorial predator-exclusion experiment, visitation rates of the most frequent pollinators of C. oppositifolia (the satyrid butterfly Cosmosatyrus chilensis and the syrphid fly Scaeva melanostoma), the duration of pollinator visits, and seed output, were 2-4 times greater when lizards were excluded, while birds had no effect. In a natural experiment, visits by S. melanostoma were 9 times shorter, and pollinator visitation rates of C. chilensis and S. melanostoma, and C. oppositifolia seed output were 2-3 times lower on shrubs growing adjacent to lizard-occupied rocks compared to those growing distant from rocks. Our results, verified for additional Andean sites, suggest that lizard predators can alter the behaviour of pollinators and elicit strong top-down indirect negative effects on seed output. Such effects may be especially important in high alpine plant communities, where pollinator activity can be low and erratic, and pollen limitation has been reported.

Altitude↗
PubMed2004

Limitations on reproductive success in endemic Aquilegia viscosa (Ranunculaceae) relative to its widespread congener Aquilegia vulgaris: the interplay of herbivory and pollination.

Plant reproduction can be strongly affected by herbivory and different features of pollination ecology, such as pollinator visitation rates and capacity for self-pollination. The purpose of this study is to compare the relative impact of herbivory and pollination on maternal reproductive success in endemic Aquilegia viscosa and its widespread congener Aquilegia vulgaris. We conducted herbivore exclusion experiments in two populations of each species in 2 different years and showed that the maternal fertility of A. viscosa was significantly more limited by floral predation and pre-dispersal seed predation than its widespread congener. In the absence of herbivory, A. viscosa retained significantly lower maternal fertility than A. vulgaris. Experimental pollinations in an insect-free glasshouse showed that the two species have an equal seed/ovule ratio both in the absence of pollinators and in the presence of non-limiting outcross pollination. Pollinator visitation rates were significantly higher in populations of A. vulgaris than in populations of A. viscosa. In addition, path analyses showed that spur length, an important trait for pollinator attraction in Aquilegia, and, indirectly sepal and petal width, contribute positively to the seed/ovule ratio in A. vulgaris, but not in A. viscosa. These results indicate that maternal fertility of endemic A. viscosa is strongly reduced by flower and seed predation despite low rates of pollinator visitation, and that pollen or resource limitation in the wild may further reduce maternal fertility. Finally, floral trait variation appears to be decoupled from fertility variation in endemic A. viscosa, which possibly constrains the evolution of reproductive traits in this species.

Analysis of Variance↗
PubMed1996

Pollination induces mRNA poly(A) tail-shortening and cell deterioration in flower transmitting tissue.

Pollination induces many physiological responses in the flower, including deterioration and death in specific pistil cell types. It is shown here that within the style of tobacco, pollination-induced cell deterioration was restricted to the transmitting tissue while the surrounding cortical tissue was not affected. It was distinct from general senescence since exogenously applying the senescence-inducing hormone ethylene, or its precursor aminocyclopropane-1-carboxylic acid (ACC), to the flower or the pistil induced overall deterioration in the entire flower. Furthermore, both pollen tube growth and ethylene action were needed for the entire spectrum of cellular changes associated with this pollination-induced transmitting tissue deterioration process. It is also shown that pollination-induced mRNA poly(A) tail-shortening for at least three major classes of transmitting tissue-specific mRNAs. As is commonly observed for poly(A) tail-shortened mRNAs, the levels of two of these three mRNA classes decline after pollination. On the other hand, the third class of mRNAs, transmitting tissue-specific (TTS) mRNAs, was maintained at a very high level subsequent to pollination, even after substantial poly(A)-tail shortening. TTS mRNAs encode a pollen tube growth-promoting and -attracting protein needed for optimal in vivo pollen tube growth. The specific preservation of TTS mRNAs in the deteriorating transmitting tissue cells suggests that these cells can distinguish molecules needed in the pollinated styles from those that are dispensable, and protect them from degradation. It is suggested that the pollination-induced mRNA poly(A) tail-shortening and cell death are programmed processes suited to the post-pollination transmitting tissue environment. Results showing that ACC is a candidate signal molecule for the pollination-induced mRNA-shortening which is accentuated by ethylene and mediated via a protein phosphorylation-dependent signal transduction pathway are also presented.

Amino Acids↗
PubMed2004

Tolerance of pollination networks to species extinctions.

Mutually beneficial interactions between flowering plants and animal pollinators represent a critical 'ecosystem service' under threat of anthropogenic extinction. We explored probable patterns of extinction in two large networks of plants and flower visitors by simulating the removal of pollinators and consequent loss of the plants that depend upon them for reproduction. For each network, we removed pollinators at random, systematically from least-linked (most specialized) to most-linked (most generalized), and systematically from most- to least-linked. Plant species diversity declined most rapidly with preferential removal of the most-linked pollinators, but declines were no worse than linear. This relative tolerance to extinction derives from redundancy in pollinators per plant and from nested topology of the networks. Tolerance in pollination networks contrasts with catastrophic declines reported from standard food webs. The discrepancy may be a result of the method used: previous studies removed species from multiple trophic levels based only on their linkage, whereas our preferential removal of pollinators reflects their greater risk of extinction relative to that of plants. In both pollination networks, the most-linked pollinators were bumble-bees and some solitary bees. These animals should receive special attention in efforts to conserve temperate pollination systems.

Animals↗
PubMed2005

Evidence for pollinator sharing in Mediterranean nectar-mimic orchids: absence of premating barriers?

Pollinator specificity has traditionally been considered the main reproductive isolation mechanism in orchids. Among Mediterranean orchids, however, many species attract and deceive pollinators by mimicking nectar-rewarding plants. To test the extent to which deceptive orchid species share pollinators, we collected and identified hemipollinaria-carrying insects, and used ribosomal sequences to identify the orchid species from which hemipollinaria were removed. We found that social and solitary bees, and also flies, carried hemipollinaria belonging to nine orchid species with different degrees of specialization. In particular, Anacamptis morio, Dactylorhiza romana and Orchis mascula used a large set of pollinator species, whereas others such as Orchis quadripunctata seemed to be pollinated by one pollinator species only. Out of the insects with hemipollinaria, 19% were found to carry hemipollinaria from more than one orchid species, indicating that sympatric food-deceptive orchids can share pollinators. This sharing was apparent even among orchid sister-species, thus revealing an effective overlap in pollinator sets among closely related species. These results suggest varying degrees of pollinator specificity in these orchids, and indicate that pollinator specificity cannot always act as the main isolation mechanism in food-deceptive temperate orchids.

Adaptation, Biological↗
PubMed2005

Farming practices influence wild pollinator populations on squash and pumpkin.

Recent declines in managed honey bee, Apis mellifera L., colonies have increased interest in the current and potential contribution of wild bee populations to the pollination of agricultural crops. Because wild bees often live in agricultural fields, their population density and contribution to crop pollination may be influenced by farming practices, especially those used to reduce the populations of other insects. We took a census of pollinators of squash and pumpkin at 25 farms in Virginia, West Virginia, and Maryland to see whether pollinator abundance was related to farming practices. The main pollinators were Peponapis pruinosa Say; honey bees, and bumble bees (Bombus spp.). The squash bee was the most abundant pollinator on squash and pumpkin, occurring at 23 of 25 farms in population densities that were commonly several times higher than that of other pollinators. Squash bee density was related to tillage practices: no-tillage farms hosted three times as great a density of squash bees as tilled farms. Pollinator density was not related to pesticide use. Honey bee density on squash and pumpkin was not related to the presence of managed honey bee colonies on farms. Farms with colonies did not have more honey bees per flower than farms that did not keep honey bees, probably reflecting the lack of affinity of honey bees for these crops. Future research should examine the economic impacts of managing farms in ways that promote pollinators, particularly pollinators of crops that are not well served by managed honey bee colonies.

Agriculture↗
PubMed2001

Pollen limitation of reproductive success in two sympatric alpine willows (Salicaceae) with contrasting pollination strategies.

We compared the extent of pollen limitation on female reproductive success of Salix lanata L., an entirely insect-pollinated willow, and S. lapponum L., which is 50 : 50% insect : wind pollinated (ambophilous). Supplemental hand-pollination significantly increased seed number per fruit by nearly 50% in the insect-pollinated willow, but had no significant impact on seed number in the dually pollinated species. Fruit set was not affected by the treatment in either of the species. These results demonstrate that pollen limitation on reproductive success is most pronounced in the species that depends entirely on insects for pollination. In general, pollinator visitation was highest to S. lapponum, but bumble bees were only observed on S. lanata, suggesting that the quantity and quality of pollinator visitation differed between the species. Our results empirically support the hypothesis that a dual pollination strategy is most effective in alpine environments with low and infrequent pollinator activity and high wind speeds.

Journal Article↗
PubMed2005

Evaluation of the neotropical stingless bee Melipona quadrifasciata (Hymenoptera: Apidae) as pollinator of greenhouse tomatoes.

The Neotropical stingless bee Melipona quadrifasciata Lepeletier was evaluated for pollinating tomatoes (variety Rodas; long-life hybrid) in greenhouses under plastic and with a hydroponic system and "organic concepts" in Minas Gerais State, Brazil. Flowers not pollinated did not set any fruit. Pollination by bees plus manual pollination did not differ from either bee or manual pollination. Maximum fruit diameter, fruit height, and roundness (quotient between maximum fruit diameter and fruit height) were not significantly different between treatments, but fruit visited by M. quadrifasciata had 10.8% less seeds (dry mass) than manual pollination. This apparently low efficiency of M. quadrifasciata pollination was attributed to the overlap of only 30 min between highest bee foraging activity and highest flower stigma receptivity. Thus, it was concluded that M. quadrifasciata is a feasible pollinator of greenhouse tomatoes because of 1) the observed increase in fruit quality with lower mechanical injury than traditional manual pollination, 2) no significant decrease in fruit size, and 3) high price of such product in the market. Some considerations for sustainable use of M. quadrifasciata as greenhouse pollinator are presented. Although techniques for keeping captive colonies of M. quadrifasciata are currently available, the sole current method for acquiring new colonies is removing them from the forest, and if demand was created for large numbers of colonies for commercial use, techniques for captive rearing must be developed to prevent serious declines in wild populations.

Agriculture↗
PubMed2001

Phylogeographic structure in the bogus yucca moth Prodoxus quinquepunctellus (Prodoxidae): comparisons with coexisting pollinator yucca moths.

The pollination mutualism between yucca moths and yuccas highlights the potential importance of host plant specificity in insect diversification. Historically, one pollinator moth species, Tegeticula yuccasella, was believed to pollinate most yuccas. Recent phylogenetic studies have revealed that it is a complex of at least 13 distinct species, eight of which are specific to one yucca species. Moths in the closely related genus Prodoxus also specialize on yuccas, but they do not pollinate and their larvae feed on different plant parts. Previous research demonstrated that the geographically widespread Prodoxus quinquepunctellus can rapidly specialize to its host plants and may harbor hidden species diversity. We examined the phylogeographic structure of P. quinquepunctellus across its range to compare patterns of diversification with six coexisting pollinator yucca moth species. Morphometric and mtDNA cytochrome oxidase I sequence data indicated that P. quinquepunctellus as currently described contains two species. There was a deep division between moth populations in the eastern and the western United States, with limited sympatry in central Texas; these clades are considered separate species and are redescribed as P. decipiens and P. quinquepunctellus (sensu stricto), respectively. Sequence data also showed a lesser division within P. quinquepunctellus s.s. between the western populations on the Colorado Plateau and those elsewhere. The divergence among the three emerging lineages corresponded with major biogeographic provinces, whereas AMOVA indicated that host plant specialization has been relatively unimportant in diversification. In comparison, the six pollinator species comprise three lineages, one eastern and two western. A pollinator species endemic to the Colorado Plateau has evolved in both of the western lineages. The east-west division and the separate evolution of two Colorado Plateau pollinator species suggest that similar biogeographic factors have influenced diversification in both Tegeticula and Prodoxus. For the pollinators, however, each lineage has produced a monophagous species, a pattern not seen in P. quinquepunctellus.

Analysis of Variance↗
PubMed2003

The effectiveness of insect-pollination test to evaluate the level of self-incompatibility and their genetic analysis in radish (Raphanus sativus L.).

We have tried an insect-pollination self-incompatibility (SI) test to strictly evaluate the level of SI as a model for the actual F(1) seed production field using radish as experimental material. Twelve inbred lines, homozygous for the S-alleles, were used in the artificial self-pollination and the insect-pollination SI test. There was a positive correlation ( r = 0.606) between the results by these two methods. Some lines showed a low level of SI in the insect-pollination test despite showing a high level of SI in the artificial self-pollination test. On the other hand, no lines showing a low level of SI in artificial self-pollination had a high level of SI in insect-pollination. These results show that the insect-pollination SI test can be considered to be a more reliable and stricter method than the artificial self-pollination test with respect to an evaluation of SI levels. We have raised and analyzed an F(2) population and F(3) lines derived from an F(1) cross between a line showing a high level of SI (R00-04) and one showing a low level. The rate of self-seed settings of the F(2) population showed a binomial distribution. There were 39 high-level SI plants to 15 low-level SI plants. This result and F(3) progeny tests suggested that the high level of SI which R00-04 showed is controlled by a dominant gene.

Animals↗
PubMed2005

Non-additive effects of herbivores and pollinators on Erysimum mediohispanicum (Cruciferae) fitness.

In this study, the non-additivity of effects of herbivores and pollinator on fitness of the plant Erysimum mediohispanicum (Cruciferae) has been experimentally tested. The abundance and diversity of the pollinator assemblage of plants excluded from and exposed to mammalian herbivores, and the combined effect of pollinators and herbivores on plant reproduction were determined over a period of 2 years. Pollinator abundance was higher and diversity was lower on plants excluded from herbivores. Furthermore, the experimental exclusions demonstrated that both pollinators and herbivores affected plant fitness, but their effects were not independent. Herbivores only had a detrimental effect on plant fitness when pollinators were present. Similarly, pollinators enhanced fitness only when herbivores were excluded. This outcome demonstrates that the importance of pollinators for plant fitness depends on the occurrence of herbivores, and suggests that herbivores may hamper pollinator-mediated adaptation in plants.

Analysis of Variance↗
PubMed2002

Developing and establishing bee species as crop pollinators: the example of Osmia spp. (Hymenoptera: Megachilidae) and fruit trees.

The development of a bee species as a new crop pollinator starts with the identification of a pollination-limited crop production deficit and the selection of one or more candidate pollinator species. The process continues with a series of studies on the developmental biology, pollinating efficacy, nesting behaviour, preference for different nesting substrates, and population dynamics of the candidate pollinator. Parallel studies investigate the biology of parasites, predators and pathogens. The information gained in these studies is combined with information on the reproductive biology of the crop to design a management system. Complete management systems should provide guidelines on rearing and releasing methods, bee densities required for adequate pollination, nesting materials, and control against parasites, predators and pathogens. Management systems should also provide methods to ensure a reliable pollinator supply. Pilot tests on a commercial scale are then conducted to test and eventually refine the management system. The process culminates with the delivery of a viable system to manage and sustain the new pollinator on a commercial scale. The process is illustrated by the development of three mason bees, Osmia cornifrons (Radoszkowski), O. lignaria Say and O. cornuta (Latreille) as orchard pollinators in Japan, the USA and Europe, respectively.

Animals↗
PubMed2002

Early ovule development following self- and cross-pollinations in Eucalyptus globulus Labill. ssp. globulus.

The study was conducted to identify the self-incompatibility mechanism in Eucalyptus globulus ssp. globulus. Controlled self- and cross-pollinations were conducted on individual flowers from three mature trees that had self-incompatibility levels of 76, 99.6 and 100%. Flowers were harvested at 4, 6 and 8 weeks after pollination. Embryology was investigated by bright field microscopy on material harvested at 4 and 6 weeks after pollination. Fertilization had taken place at 4 weeks after pollination with zygotes and free nuclear endosperm visible. There was a greater proportion of healthy, fertilized ovules in the cross- compared with the self-pollination treatment, and approx. half the ovules examined from both pollen treatments were not fertilized or were degenerating. By 6 weeks after pollination a few zygotes were starting to divide. The number of healthy, fertilized ovules was still greater in the cross-pollination treatment, but the number of healthy fertilized ovules was lower in both treatments compared with 4 weeks after pollination, and many ovules were degenerating. Fertilized ovules were significantly larger than non-fertilized or degenerating ovules and this difference was detectable by eye at 6 and 8 weeks after pollination. The mechanism of self-incompatibility appears to have both late pre- and post-zygotic components.

Algorithms↗
PubMed2003

Early blooming's challenges: extended flowering season, diverse pollinator assemblage and the reproductive success of Gynodioecious Daphne laureola.

BACKGROUND AND AIMS: The scarcity and unpredictability of active pollinators during late winter in temperate areas tends to favour extended flowering seasons and increased floral longevity in early blooming species, which are usually pollinated by diverse sets of insects. Daphne laureola is a gynodioecious woody perennial that flowers from January to April in southern Spain, a period characterized by cold temperatures, frequent rains and irregular snowfalls. METHODS: Pollinators were excluded at four different times during the flowering season in order to determine the effect of decreased exposure to pollinators on fruit set in female and hermaphrodite individuals. The role of nocturnal and diurnal pollination on reproductive success in each gender was simultaneously evaluated by selective exclusion. KEY RESULTS: A 50 % reduction in the flowering period decreased fruit set of females by 50 %, whereas the corresponding decrease in self-compatible hermaphrodites was only approx. 25 %. Day-active hymenopterans and lepidopterans were infrequent visitors, and nocturnal pollinators were inefficient, suggesting that pollen beetles, Meligethes elongatus, were the main pollinators of D. laureola in the study region. CONCLUSIONS: Beetles were less abundant in pollenless females, although discrimination did not apparently result in pollination limitation of female reproduction. A preference of beetles for sunny locations emphasized the relevance of abiotic conditions for pollination of this early blooming shrub.

Animals↗
PubMed2005

Chiropterophily in Sinningieae (Gesneriaceae): Sinningia brasiliensis and Paliavana prasinata are bat-pollinated, but P. sericiflora is not. Not yet?

BACKGROUND AND AIMS: Based on the bell shape and greenish colour of the flowers, bat-pollination was suggested for some Sinningieae species (Gesneriaceae). Actually, there are no reports on pollination biology and visitors for these species. This paper reports on pollination biology of Sinningia brasiliensis, Paliavana prasinata and P. sericiflora in south-eastern Brazil. METHODS: Flowers were observed in situ to determine phases of anthesis, colour patterns and scent intensity. Corolla measures were taken from fresh flowers. Nectar production and concentration were measured in flowers bagged at the pre-anthesis phases. Direct visual observations of visitors were made during the day and night, and photographs were taken to analyse their visiting behaviour. KEY RESULTS: Some floral features of the three species fit the bat-pollination syndrome: large, robust and gullet-shaped corollas, colour patterns and large amount of nectar. However, other floral features-such as onset of anthesis, nectar attributes and odour intensity-differ among the species. Nectar volume and total sugar production increased significantly at midnight in S. brasiliensis and P. prasinata, but in P. sericiflora there were no significant differences in the total nectar and sugar production during anthesis. Scent intensity is much higher in S. brasiliensis and P. prasinata than P. sericiflora. Flowers of S. brasiliensis and P. prasinata, whose features fit the chiropterophilous syndrome, are pollinated by glossophagine bat species. Paliavana sericiflora, on the other hand, presents floral features intermediate between bat and hummingbird syndromes, but is visited and pollinated only by hummingbirds. CONCLUSIONS: These data strengthen the statement that the bat syndrome in Sinningieae originated independently in Sinningia brasiliensis and in Paliavana species. Paliavana sericiflora may be another example of a plant 'in transition' from the hummingbird to the bat pollination, but a reversion in the direction of bat to hummingbird might not be excluded. It is also possible that this is a case of speciation on both bat and hummingbird pollination. Studies on Paliavana sister species may provide insights about origins and the evolutionary directions of the pollination systems of these species.

Animals↗
PubMed2006

Bird pollination in an angraecoid orchid on Reunion Island (Mascarene Archipelago, Indian Ocean).

BACKGROUND AND AIMS: Although numerous angraecoid orchids in Madagascar display typical sphingophilous syndrome (i.e. white, nectariferous, long-spurred flowers, producing a strong scent at the crepuscule that is attractive to moths), three species of Angraecum in Reunion, belonging to the endemic section Hadrangis, have atypical unscented and short-spurred flowers. The aim of the study was to investigate the implication of plant-pollinator interaction on the evolution of floral morphology of these peculiar island floral forms. METHODS: The flower morphology of A. striatum (one of the three section Hadrangis species) was investigated by performing a set of floral measures, and the reproductive biology was investigated by a set of hand pollination experiments. Natural pollinators were observed by means of a digital video camera. Pollinator efficiency (pollen removal and deposition) and reproductive success (fruit set) were quantified once a week in natural field conditions during the 2005 flowering season (i.e. from January to March). KEY RESULTS: The orchid is self-compatible but requires a pollinator to achieve fruit set. Only one pollinator was observed, the endemic white-eye Zosterops borbonicus (Zosteropidae). These birds perched on inflorescences, and probed most fresh-looking flowers on each plant for nectar. Nectar was both abundant (averaging 7.7 microL) and dilute (averaging 9.7 % sugar in sucrose equivalents). Birds were mostly active between 0830 and 0930 h. Visits to plants were extremely short, lasting from 9 to 27 s. At the study site, 60.9 % of flowers had pollen removed, and 46.4 % had pollinia deposited on stigmas. The proportion of flowers that initiated a fruit averaged 20.6 % in natural conditions. CONCLUSIONS: For the first time, a bird-pollinated orchid is described from a sub-tribe that is mainly specialized for moth pollination. This study documents a morphological shift in flowers in response to pollinator adaptations in the insular context of the Mascarene Archipelago.

Animals↗
PubMed2004

Ethylene synthesis and auxin augmentation in pistil tissues are important for egg cell differentiation after pollination in maize.

The role of ethylene and auxin in stigma-to-ovule signalling was investigated in maize (Zea mays L.). Maturation of the egg cells in an ear was stimulated before actual fertilization by the application of fresh pollen grains or quartz sand to fully receptive stigmas. Ethylene emission by maize ears increased in response to those treatments. Silks and ovaries were involved in ethylene synthesis after pollen or sand was shed over the silks. The content of ethylene precursor [1-aminocyclopropane-1-carboxylic acid (ACC)] increased in both pistil parts soon after pollination. ACC rise was delayed by 4 h in the ovaries, and by 8 h in the silks after mock-pollination with sand. The auxin level increased rapidly in the silks and ovaries after pollination, and it was very high in the pollinated silks due to the high indole-3-acetic acid (IAA) content of pollen grains. IAA rise also appeared in the silks and ovaries after treatment with sand but it was delayed by 8 h. Application of ACC (10 microM) or IAA (6 microM) solutions to non-pollinated silks stimulated maturation of the egg cells. Moreover, the response of the egg cells to pollination was cancelled by l-alpha-(2-aminoethoxyvinyl)-glycine, alpha-aminoisobutyric acid or 2,3,5-triiodobenzoic acid applied to the silks before pollination. Thus ethylene synthesis and polar auxin transport in the silks pollinated with fresh pollen were necessary to evoke accelerated differentiation of the egg cells in maize ovules. Differences in pistil responses found between true- and mock-pollination suggest that signalling pathways are at least partially different for the reception of pollen grains and sand crystals on maize stigma.

Amino Acids, Cyclic↗