Wind Pollination

As a consequence, wind pollination (anemophily) is most effective when a species grows in loftier densities, as demonstrated by the dominance of this strategy in grasses and their relatives, and in tree species that grow in low variety temperate forests.

From: Encyclopedia of Applied Plant Sciences (Second Edition) , 2017

ECOLOGY | Reproductive Ecology of Forest Trees

J. Ghazoul , in Encyclopedia of Forest Sciences, 2004

Current of air Pollination

Other angiosperms take reverted to wind pollination and consequently have much reduced flowers, equally visually attractive flowers are no longer necessary for pollinator attraction. While air current is always-nowadays, it is non a selective pollinator and is consequently inefficient over large distances. Wind pollination is therefore favored in species-poor forests where conspecifics are closely spaced. Current of air-pollinated plants are associated with abundant pollen production and synchronous mass flowering events to ensure successful pollen transfer. To maximize the probability of catching randomly globe-trotting airborne pollen, flowers are placed at the outermost edges of the crown or in pendant catkins to maximize exposure to wind, and stigmas are usually well exposed and have big surface areas.

Air current pollination is associated with temperate forests and dry, or seasonally dry, habitats where animal pollination vectors are comparatively rare and where rainfall rarely hinders pollen dispersal. The temperate forests of northern mid-high latitudes are dominated by species such as oak, beech, and birch, that rely on wind pollination. In the temperate rainforests of Chile, New Zealand, and the Pacific Northwest of America, air current pollination is once again common, despite the moisture climate. Open up forests and savannas are particularly well represented by wind-pollinated trees. In the dense vegetation of a rainforest wind pollination is usually restricted to emergent coniferous trees (e.one thousand., Araucaria and Agathis) and to trees occurring on ridge tops (Balanops australiana, Nothofagus). Current of air pollination does, very rarely, occur in the rainforest understory among more specialized angiosperm groups, including Euphorbiaceae, Pandanaceae, and Palmaceae.

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Convenance Genetics and Biotechnology

D.East. Pattemore , in Encyclopedia of Applied Institute Sciences (2d Edition), 2017

Modes of Pollination

Angiosperm pollination evolved from earlier reproduction strategies that initially involved aquatic ship of gametes and and then wind pollination following the development of the pollen capsule, which prevented desiccation during this process. Ane of the chief distinctive features of angiosperms has been the conscription of animals as pollen vectors (pollinators), just a number of significant angiosperm groups take secondarily evolved abiotic vectors.

Abiotic pollination typically requires the production of big numbers of pollen grains to ensure that enough are deposited on stigmas through the untargeted action of air current or water. In contrast, biotic pollination modes that are highly specialized require much less pollen to be produced, with energy instead expended on structures and rewards such as nectar to maximize effective pollination by animals.

Current of air-dispersed pollen is by and large deposited within a pocket-size distance around the source plant, with only very small quantities transported vast distances on air currents. As a consequence, wind pollination (anemophily) is most effective when a species grows in high densities, equally demonstrated past the authority of this strategy in grasses and their relatives, and in tree species that grow in low multifariousness temperate forests.

Insect pollination (entomophily) in the flowering plant lineage most probably evolved about 130   million years ago when the introduction of a hermaphroditic flower caused pollen-eating insects (such every bit beetles) to pollinate ovules as a by-product of their presence on the early bloom. This highly successful approach to reproduction has been modified extensively since and so, depending on the various selection factors acting on bloom morphology and function. Bees are the almost of import group of pollinators globally considering of their specialization on pollen and nectar as food resources. The major radiation of bee taxa occurred 120–130   million years ago at the same time as the major angiosperm radiation. Subsequently, other insect groups, birds, mammals, and lizards have likewise been conscripted into pollination.

Animal pollinators are attracted to flowers through flower colors and patterns, floral scents, nectar rewards, or through charade by the bloom's mimicry of oviposition sites or the animal's sexual partners. Because of the multifariousness of strategies to attract and control a diverse range of pollinator species, animal-pollinated plants exhibit a bewildering range of floral forms.

Pollination syndromes have been used historically to assign flowers to a item group of pollinators based on floral traits. The underlying hypothesis is that it is virtually efficient for a plant to adapt to a particular grouping of pollinators to ensure their visitation and constancy, thereby reducing the wasteful deposition of pollen from other found species. While recent evidence instead points to generalization as the dominant theme in pollination, this concept of plant specialization on particular taxonomic groups is at least useful in that pollination syndromes tin function as readily disprovable hypotheses.

The most well-supported pollination syndrome is that of wind pollination. Air current-pollinated flowers tend to have numerous pendulous anthers that produce copious pollen and multiple stigmas with a large full receptive surface area. Petals tend to exist significantly reduced or inconspicuous and floral rewards are normally absent. Unisexual flowers are common in air current-pollinated plants as a mechanism to reduce self-pollination, including the farthermost of dioecy. Examples of wind-pollinated plants include monocotyledons, such every bit grasses, and members of the Fagaceae family such as oak and beech.

Animal-pollinated flowers are typically divided into syndromes based on features perceived by and attractive to different groups. For example, bee-pollinated flowers are oftentimes said to be blue, xanthous, or white, with patterns that emphasize the location of pollen and nectar. Ultraviolet colour patterns are visible to bees, and then that flowers that announced to humans to be a single color tin exhibit singled-out patterns to bees. Some flowers have features that require specific behaviors to access the floral rewards that announced to favor bees, such as flag-blossoms which require the weight of a big bee to open up, buzz-pollinated flowers like those of tomatoes, or flowers with nectar secreted in tubes that crave a long insect tongue to access (up to about xv   mm).

In contrast, dark-green or white flowers of a dish or bowl shape with readily attainable rewards are often described as adapted for fly or beetle pollination. It is worth noting, however, that these flowers do non prevent access past other pollinator groups and insects do non perceive color in the aforementioned way as humans. There are a few flowers that have specialized in the allure of long-tongued flies and take long thin tubular perianths and nectar spurs similar to flowers pollinated by long-tongued bees and Lepidoptera. Some floral trails do appear to be specializations for wing pollination, including the presence of strong, pungent smell that attract flies that lay eggs in rotting carrion.

Pollination syndromes have also been described for moth and butterfly pollination, bird pollination, bat pollination, and even lizard pollination. However, field studies often overturn the predictions of traditional pollination syndromes, leading many to question their utility. Alternative approaches have been proposed, including classifying flowers based on features that excluded item groups, or on 'underground' signals (visual or olfactory property) only detectible by particular groups of pollinators. For all these approaches to classifying flowers, it is important to keep in mind that even if these features are useful for developing hypotheses about evolutionary relationships, they may not necessarily reflect what species currently visit the flowers and act as effective pollinators. Human being commerce and trade has resulted in plants and pollinators being transported well beyond their natural ranges, and yet these new interactions between flowers and pollinators that have not evolved together even so pb to effective pollination that is integral to crop product.

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Grapevine Structure and Function

Ronald South. Jackson PhD , in Wine Science (Third Edition), 2008

POLLINATION AND FERTILIZATION

Self-pollination appears to be the rule for most grapevine cultivars. Under vineyard conditions, wind and insect pollination appear to be of petty significance. Even in areas where grapes are the dominant agricultural crop, pollen levels in the air are by and large low during flowering – in contrast to the relatively high levels associated with cantankerous-pollinated wild grapevines (see Stevenson, 1985). Yields of near ane.4 × ten4 pollen grains/m2/day, sedimenting out of the air during July, have been recorded in Montpellier, France (Cour et al., 1972–1973). In Portugal, peak pollen counts were recorded at 24 pollen grains per one thousandiii air (Cunha et al., 2003). Despite the apparent insignificance of airborne pollen to successful pollination, they were able to predict vino production from pollen counts in dryer climatic regions of Portugal.

The minimal importance of insect pollination to vine fertilization may accrue from the nearly simultaneous blooming of innumerable vines over wide areas. Nevertheless, syrphid flies, long-horned and tumbling blossom beetles, as well as bees occasionally visit grape flowers. The main attractant appears to be the scent produced by nectaries. Sesqiterpenes and monoterpenes appear to exist the primary aromatic compounds produced (Buchbauer et al., 1995). Nectaries are located betwixt the stamens and pistil (Fig. 3.20C) and are peculiarly prominent in male flowers on wild V. vinifera vines. Nectaries are modified for olfactory property, rather than nectar production equally the name might suggest. Visiting insects feed on pollen, not nectar. Pollen fertility has no influence on flower attractiveness, but the presence or absence of anthers does affect the duration of visits to female flowers (Branties, 1978).

Shortly after landing on the stigma, the pollen begins to keen. The sugary solution produced by the stigma is required both for pollen growth and to prevent osmotic lysis of the germ tube. The stigmatic fluid also occurs in the intercellular spaces of the manner. This may explicate why rain does non significantly inhibit or filibuster pollen formation, or filibuster the penetration of the germ tube into the style. However, pollen germination and germ-tube growth are markedly afflicted past temperature (Fig. 3.21), fifty-fifty though viability is less affected. In contrast, ovules show obvious signs of degeneration within about a week at temperatures below 10 °C. Cool temperatures, just earlier flowering at favorably warm temperatures, can filibuster pollen germinability and germ-tube growth. Similar weather condition can equally reduce fertility by disrupting aspects of ovule development (Ebadi et al., 1995).

Effigy three.21. Rate of pollen germ-tube growth in relation to temperature.

 (From Staudt, 1982, reproduced past permission) Copyright © 1982

As the pollen tube penetrates the style, the germinative nucleus divides into 2 sperm nuclei, if this has not occurred previously. On reaching the opening of the ovule (micropyle), one sperm nucleus fuses with the egg nucleus, whereas the other fuses with the ii polar nuclei. The fertilization of the egg nucleus initiates embryo development, whereas fusion with polar nuclei induces endosperm differentiation. Fertilization too inaugurates a series of events that transforms the ovules into seeds and the ovary wall into the skin and flesh of the berry. Fertilization is usually complete within 2–3 days of pollination.

In certain varieties, abnormalities result in the absence of feasible seed following pollination. Even in fully fertile cultivars, only 20–30% of the flowers successfully develop fruit. In parthenocarpic cultivars, ovules fail to develop in the flower. Although pollination stimulates sufficient auxin product to prevent abscission of the fruit (shatter), it is inadequate to permit normal drupe enlargement. 'Blackness Corinth,' the primary commercial source of stale currants, is the most important parthenocarpic diverseness. Although parthenocarpic varieties produce no seed, other seedless varieties such as 'Thompson seedless' contain seeds. As these usually abort a few weeks later fertilization, the seeds are empty, small and soft. Considering of partial seed development, greater auxin product induces medium-size fruit development. This situation is called stenospermocarpy. If abortion occurs even later, as in the cultivar 'Chaouch,' normal-size fruit develop containing hard empty seeds. In contrast to the well-known examples of parthenocarpy and stenospermocarpy, the evolution of fruit and viable seeds in the absence of fertilization (apomixis) is unconfirmed in grapevines.

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TREE Breeding, PRACTICES | Breeding and Genetic Resources of Scots Pine

O. Savolainen , Thou. Kärkkäinen , in Encyclopedia of Forest Sciences, 2004

Breeding System

Another important trait of Scots pine is its breeding organisation. There is no self-incompatibility system, and air current pollination results in considerable proportions of self-pollination and self-fertilized zygotes. Directly measurements at the zygote stage have not been made, but it can be inferred that the primary selfing rate must be ofttimes at least 20%. In the mature seed, however, at that place are usually only a low percentage of selfs. In that location seems to exist little occurrence of other kinds of inbreeding. Several studies take shown that adult Scots pino populations do not have any selfs. Thus, between the zygote stage and the adult tree phase the selfs are preferentially eliminated by usually astringent inbreeding depression. Much of the elimination takes place very early, during seed evolution. At the historic period of a few years natural populations show little evidence of inbreeding. When selfs survive in experimental weather, they evidence a cumulative reject in relative survival with lowered fettle over several decades due to poorer growth, which results in size-specific elimination of selfs by contest. The inbreeding depression is presumably due to a large number of deleterious recessive genes in the Scots pino genome. The average tree is heterozygous for 8–10 so-called embryo lethals, which means that Scots pino is among the species with the very highest genetic loads. Scots pine reproduction is exclusively sexual. Note that the generation time is very long; the trees do non go fully reproductively mature earlier the historic period of 20. Non only is in that location no asexual reproduction in the natural populations, but Scots pine has also proved a very recalcitrant species for various modes of vegetative propagation.

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Grapevine structure and function

Ronald S. Jackson PhD , in Vino Science (Fifth Edition), 2020

Pollination and fertilization

Self-pollination is typical for about grapevine cultivars, occurring prior to cap fall (Staudt, 1999) or shortly thereafter (Heazlewood and Wilson, 2004). Correspondingly, air current and insect pollination are of little significance. Even in areas where grapes are the ascendant agricultural ingather, pollen levels in the air are low during flowering in comparing with levels associated with cross-pollinated wild grapevines (run across Stevenson, 1985). Yields of almost 1.4   ×   ten4 pollen grains/m2/twenty-four hours have been recorded in Montpellier, France (Cour et al., 1972–1973). In Portugal, acme pollen counts were recorded at 24 pollen grains/giii air (Cunha et al., 2003); too recorded was xc grains/thousand3 air for Cabernet Sauvignon in Kingdom of spain (Muñoz-Rodríguez et al., 2011). Despite airborne pollen often beingness unnecessary for successful fertilization in domesticated grapevines, information technology may enhance seed set (Chkhartishvili et al., 2006). This may explain why pollen counts predict yield in some areas (Cunha et al., 2003). An alternative explanation may be that the dry sunny weather condition that favor pollen release and air dispersal are the same every bit those favoring self-pollination and fertilization.

The relative insignificance of insect pollination in vineyards may exist accounted for by the nigh simultaneous blooming of tens of thousands of vines over vast areas. Information technology is of greater significance in feral vines. Insects visiting grapevine flowers include bees and syrphid flies likewise as long-horned and tumbling blossom beetles. The principal attractant appears to exist the scent from nectaries and pollen. Nectaries are located between the stamens and pistil (Fig. 3.24C). They occur prominently in male flowers on feral vines. Despite the proper name, nectaries are modified for aroma, not nectar product. Visiting insects feed on the pollen, not nectar. Pollen fertility has no influence on insect visitation, but the presence or absenteeism of anthers does bear upon the duration of visits to female flowers (Branties, 1978).

In dissimilarity, insect pollination is essential for optimal fruit production in Vitis rotundifolia. This is true even for mod, bisexual, self-fertile cultivars (Sampson et al., 2001). Their flowers produce both nectar (a bee attractant) and pollen. Both act as food sources.

After landing on the stigma, the pollen begins to cracking. The sugary solution produced by the stigma is required both for pollen growth and to prevent osmotic lysis of the germ tube. The appropriate balance of macro- and micronutrients is besides required. The stigmatic fluid also occurs in the intercellular spaces of the way. This may explain why pelting does not significantly inhibit or filibuster pollen formation or delay the penetration of the germ tube down the style. Notwithstanding, cool temperatures, which usually back-trail rainy spells, markedly affect pollen germination and germ-tube growth (Fig. three.25) fifty-fifty though viability is less influenced. In contrast, ovules show obvious signs of damage at cool temperatures. Degeneration may occur inside a calendar week at temperatures below 10   °C. In addition, cool temperatures, but before flowering at warm temperatures, can delay pollen germinability and germ-tube growth. Similar conditions can reduce fertility by disrupting aspects of ovule development (Ebadi et al., 1995).

Figure iii.25. Rate of pollen-germ tube growth in relation to temperature.

 From Staudt, M., 1982. Pollenkeimung und Pollenschlauchwachstum in vivo bei Vitis und die Abhähgigkeit von der Temperatur. Vitis 21, 205–216, reproduced by permission.

As the pollen tube penetrates and grows down the style, the generative nucleus divides into two sperm nuclei, if this has non already occurred. This initiates changes in gene expression in the pistil, preparing it for fertilization and fruit development (Kühn and Arce-Johnson, 2012). On reaching the opening of the ovule (micropyle), 1 sperm nucleus fuses with the egg nucleus, whereas the other fuses with the two polar nuclei. Fertilization of the egg nucleus initiates embryo development, whereas fusion with the polar nuclei induces endosperm differentiation. Fertilization besides inaugurates a serial of events that transform the ovules into seeds and the ovary wall into the pare and mankind of the berry. Fertilization is usually complete within 2–3 days of pollination.

In certain varieties, abnormalities result in feasible seed not forming. Fifty-fifty in fertile, seeded cultivars, simply xx%–30% of the flowers successfully develop fully mature fruit; greater than 50% fruit set is considered "normal." Seed maturation is typically necessary for total berry evolution, notably the cell partition growth component of fruit development (Friend et al., 2009). Partial berry development may occur if the seed aborts after initiation, with berry growth limited to cell enlargement. Shot berries (pocket-size green fruit that may or may not abscise) (Plate 3.7) are probably the result of pollination without fertilization. Details on the productivity of important Australian cultivars is provided by Dry out et al. (2010).

Plate 3.7. Examples of the dissimilar berry types used when assessing bunch yield components: "seeded" berries of "normal" size, which incorporate seeds and ripen; smaller "seedless" berries, which do not comprise normal seeds only will ripen; live green ovaries, which show express development.

 From Friend, A.P., Trought, M.C.T., 2007. Delayed winter spur-pruning in New Zealand tin alter yield components of Merlot grapevines. Aust. J. Grape Wine Res. 13, 157–164; reproduced by permission.

Where inadequate fruit set up is frequent, shoot pinching at flowering can be beneficial. This reduces competition for photosynthate between shoot growth and early on stages of fruit development. Application of CCC just earlier flowering (to restrict vegetative growth) may also improve fruit set (Collins and Dry, 2006). Alternatively, foliar application with abscisic acrid appears to redirect photosynthate to developing fruit (Quiroga et al., 2009). With Merlot, late pruning (after bud burst) appears to improve fruit set. In this instance, delaying bud outburst and flowering until climatic conditions are more favorable to fertilization and reproductive development seems to exist the mechanism of activeness (Friend and Trought, 2007; Keller et al., 2010).

Depending on the cultivar, cool conditions suppress fruit gear up and subsequent berry development. This is especially marked if the climate is favorable for flowering but the soil is still absurd (∼10 ̊C) (Tabing et al., 2013). Information technology slows mobilization of carbohydrates in the root, retarding shoot and reproductive development (Rogiers et al., 2014).

In contrast to wine grapes, most table and raisin cultivars are seedless. In parthenocarpic cultivars, pollination stimulates sufficient auxin production to prevent fruit abscission (shatter) but is inadequate to permit normal berry enlargement. Black Corinth, the chief source of currants, is the most important parthenocarpic variety. Although parthenocarpic varieties produce no seed, other seedless varieties initiate seed development—a situation termed stenospermocarpy. As seed evolution ceases a few weeks afterwards fertilization, the seeds are empty, small, and soft. Because of fractional seed evolution, greater auxin product induces medium-sized fruit development. An instance is Thompson Seedless (referred to as Sultana when used to make raisins). If abortion occurs even afterward, as in the cultivar Chaouch, normal-sized fruit develop, containing hard empty seeds. In dissimilarity to parthenocarpy and stenospermocarpy, apomixis, the development of fruit and viable seeds in the absence of fertilization, is unconfirmed in grapevines.

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Ecosystem Services

Julia Astegiano , ... François Massol , in Advances in Ecological Enquiry, 2015

1.ii Traits Modulating Wild Plant Response to Habitat Fragmentation

To produce seeds sexually, flowering plants range from consummate dependence on animal pollination upwardly to complete autonomy from pollinators either via spontaneous self-pollination (Lloyd, 1992; Richards, 1997; Vogler and Kalisz, 2001 ) or via wind pollination ( Fægri and van der Pijl, 1979; Mulder et al., 2005). Dioecious, monoecious and hermaphrodite self-incompatible found species are obligate outbreeders that completely depend on pollinator agents to exchange pollen among plants and to sexually reproduce with success. Conversely, self-compatible plant species may be considered facultative outbreeders that partially depended on animal pollination. Although creature pollinators are needed to transport pollen, a single visit of a pollinator to each individual flower may permit seed product. Moreover, some cocky-uniform species may accept the ability to reproduce sexually via autonomous self-pollination, without the intervention of pollinators (Richards, 1997). Equally expected, results from a meta-analysis on the furnishings of habitat fragmentation on constitute pollination and reproduction show that the reproductive success of establish species with higher dependence on animal pollination (i.e. self-incompatible plants) was more negatively and strongly affected than that of less dependent ones (i.due east. self-compatible species; Aguilar et al., 2006). Moreover, habitat fragmentation can subtract the incidence of species highly dependent on animal pollination, as reported for tropical trees of a fragmented landscape of the Brazilian Atlantic Forest (Girão et al., 2007).

The sensitivity of plants to habitat fragmentation may besides be determined by their degree of pollination generalization (Bond, 1994; Johnson and Steiner, 2000; Renner, 1998). Plant species range from "super-generalists" that collaborate with hundreds of pollinator species to "extreme specialists" interacting with simply a single pollinator species (Fægri and van der Pijl, 1979; Waser et al., 1996). Conventionally, the expectation has been that the sexual reproduction of specialist plants should be more affected by habitat fragmentation than that of generalists because losing a few pollinator species locally is more likely than losing all the pollinators associated with a generalist found species. This prediction was grounded in the thought that any change imposed by fragmentation in pollinator assemblages is more probable to cause reproductive failure in plants interacting with pollinator assemblages of lower richness (Aizen et al., 2002; Bail, 1994; Waser et al., 1996). Conversely, generalist plants are expected to exist more resilient to the changes imposed by fragmentation on their pollinator assemblages because of the functional redundancy among their pollinators (Fægri and van der Pijl, 1979; Morris, 2003). For both cocky-uniform and self-incompatible species, however, the negative effect of habitat fragmentation on found reproductive success seems to exist independent of plant pollination generalization (Aguilar et al., 2006).

The number of seeds produced past plants and their dispersal way are the main traits determining species dispersal success (Willson and Traveset, 2000). Habitat fragmentation may change seed dispersal success by affecting seed size and quantity (e.g. Aguilar et al., 2006; Fakheran et al., 2010; Galetti et al., 2013), plant and inflorescence tiptop (Fakheran et al., 2010; Lobo et al., 2011) and the diversity and behaviour of dispersal vectors (Cordeiro et al., 2009; Galetti et al., 2013). Overall, increased dispersal ability would appear to be favoured in fragmented landscapes (Hagen et al., 2012; but see Cheptou et al., 2008). Information technology has been reported, for instance, that habitat fragmentation affects more negatively the proportion of seeds of institute species with larger seeds and of beast-dispersed plants arriving in habitat fragments (Magrach et al., 2014; McEuen and Curran, 2004). The negative human relationship between seed size and fragment occupancy (Ehrlén and Eriksson, 2000) and the lower diversity of animate being-dispersed found species in woods fragments (Tabarelli et al., 1999) as well suggest that fragmentation may select for smaller seed size and abiotically dispersed species (Fakheran et al., 2010; Galetti et al., 2013; Lobo et al., 2011; Magrach et al., 2014; Melo et al., 2010). Moreover, as seed product may be positively related to the probability of institute species occurrence in isolated habitat fragments (Evju et al., 2015), more fecund institute species volition have higher probabilities of persistence in fragmented landscapes (McEuen and Curran, 2004). Finally, it has been recently suggested that when a landscape becomes more fragmented over evolutionary relevant time scales, increased (mean and long-altitude) dispersal rates will be selected (Aparicio et al., 2008; Koh et al., 2015; but see Cheptou et al., 2008). This prediction seems to exist supported by empirical prove showing that increased isolation among patches leads to increased richness of species with long-altitude dispersal and to decreased richness of species with brusque-distance dispersal (Aparicio et al., 2008; Koh et al., 2015).

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Control of Plant Virus Diseases

Yehezkel Antignus , in Advances in Virus Research, 2014

3.five Effect of UV filtration on pollinators

Pollination improves the yield and increases the quantity of nigh crop species, thus contributing to 1-third of global ingather production. More than 75% of the 115 leading ingather species worldwide are dependent on or at least benefit from animal pollination, whereas wind and self-pollination are sufficient for only 28 ingather species (Klatt et al., 2014).

UV-poor environments might have an influence on pollinator behavior in two ways: first, the overall flying activeness may be diminished due to scarce low-cal conditions, and second, the light weather might change the color perception of the ingather flowers by the pollinators then that they will have difficulty in localizing the flowers among the foliage mass (van der Blom, 2010).

Bumblebees [Bombus terrestris (Linnaeus)] are important pollinators of angiosperms. The pollination of tomato flowers requires the agitation of flower anther cones to enable an efficient pollination, and bumblebees are widely used in love apple greenhouses (Kevan, Straver, Offering, & Laverty, 1991). Studies carried out nether laboratory conditions take shown that bumblebees perceive when ultraviolet radiation is either removed or added to an illumination source, and are capable of using their visual arrangement to forage efficiently in a UV-deficient surround. Thus, their forage efficiency is non affected past the type of greenhouse covering (Dyer & Chittka, 2004). A delay in the hive kickoff up of the bumblebee B. terrestris (Bio-Bee, Ltd., State of israel) was observed in experimental mini greenhouses covered with UV-blocking films (Steinberg et al., 1997; van der Blom, 2010). Later, this trouble was solved by placing the hives near the greenhouse walls, where they were exposed to unfiltered light (Y. Antignus, unpublished). In a field report, no significant differences were found in bumblebee activity or in the numbers of flowers visited, nether standard or UV-blocking films (Fig. 1.7) (Antignus & Ben-Yakir, 2004). Studies in commercial tomato greenhouses have demonstrated that biomass and size of hives were not significantly affected, whether the greenhouses were covered with standard or UV-blocking films (Antignus & Ben-Yakir, 2004; Hefez, Izikovitch, & Dag, 1999; Seker, 1999). No differences were found in the numbers of workers that foraged nor in the terminal harvest in field trials where the pollination activity of bumblebees, under UV-absorbing and -ordinary films, was compared in both tomato and watermelon crops (van der Blom, 2010). Contrary to the bumblebees, honeybees did show significant behavioral changes nether the UV-blocking plastic. Two trials were carried out in watermelon, and one in melon using honey bees for pollination. In all iii cases, a reduced foraging activeness was observed under the UV-blocking material, resulting in a significantly lower fruit yield. This reduction was seen in the number of workers leaving and entering the hive, and so information technology seems to be the issue of deficient general lite conditions, more than of the difficulty to localize the flowers in one case foraging (van der Blom, 2010).

Figure 1.seven. Bumblebee (Bombus terrestris) pollination activity in tomatoes grown in a greenhouse with ordinary cladding materials (polyethylene film   + 50 mesh screen) versus a greenhouse covered with UV-absorbing cladding materials (polyethylene motion-picture show   +   l mesh "Bionet" screen). Pollination action is expressed every bit per centum of visited flowers identified past typical brown ring on the bloom stamens cone.

In Canada, bumblebees' action was 94% greater under standard films than under UV-blocking films (expressed as the number of entrances and exits to and from the hive). No relationship was found in that location between bumblebees' activity and the amount of solar radiation or the humidity in the greenhouse (Morandin, Laverty, Kevan, Khosla, & Shipp, 2001). The differences between the results from Canada and State of israel may exist explained past the differences in sunday low-cal intensities and temperatures betwixt these two locations. A positive correlation exists between the charge per unit of bumblebees' activity and temperature. College temperatures (in the range 5–25   °C) may compensate for the inhibitory effect of reduced UV radiations (Morandin et al., 2001; Morandin, Laverty, Kevan, Khosla, & Shipp, 2002). Areas within the greenhouse that have relatively high levels of UV radiations (normally the southern wall side) were institute as optimal sites for placing bumblebees' hives in greenhouses covered with UV-blocking films (Y. Antignus, unpublished).

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Grapevine Construction and Office

Ronald S. Jackson PhD , in Vino Science (Fourth Edition), 2014

Pollination and Fertilization

Cocky-pollination appears to be the rule for most grapevine cultivars, occurring prior to cap autumn (Staudt, 1999). Pollen formation may, however, occur merely after cap autumn (Heazlewood and Wilson, 2004).

For most cultivars, wind and insect pollination is of little significance. Fifty-fifty in areas where grapes are the ascendant agricultural ingather, pollen levels in the air are low during flowering, in comparison with levels associated with cantankerous-pollinated wild grapevines (see Stevenson, 1985). Yields of most ane.4×x4 pollen grains/m2/day take been recorded in Montpellier, France (Cour et al., 1972–1973). In Portugal, tiptop pollen counts were recorded at 24 pollen grains/m3 air (Cunha et al., 2003), and 90 grains/one thousand3 air for Cabernet Sauvignon in Espana (Muñoz-Rodríguez et al., 2011). Despite airborne pollen oft beingness unnecessary for the successful fertilization of domesticated grapevines, it may heighten seed set (Chkhartishvili et al., 2006). This may explicate why pollen counts tin can predict yield in some areas (Cunha et al., 2003). An alternative explanation for this correlation may be that the dry out sunny atmospheric condition that favor pollen release and air dispersal are the same as those favoring self-pollination and fertilization.

The relative insignificance of insect pollination in vineyards may exist deemed for past the nearly simultaneous blooming of tens of thousands of vines over vast areas. Information technology is presumably of greater importance to wild grapevines. Insects visiting grapevine flowers include bees and syrphid flies, equally well as long-horned and tumbling blossom beetles. The principal attractant appears to be the aroma from nectaries and pollen. Nectaries are located between the stamens and pistil (Fig. 3.25C). They occur prominently in male person flowers on feral vines. Despite the proper name, nectaries are modified for odor, not nectar production, and visiting insects feed on the pollen, not nectar. Pollen fertility has no influence on insect visitation, but the presence or absence of anthers does bear upon the duration of visits to female flowers (Branties, 1978).

In contrast, for V. rotundifolia insect pollination is essential for optimal fruit production. This is true even for modern, bisexual, self-fertile cultivars (Sampson et al., 2001). Their flowers produce both nectar (a bee attractant) and pollen. Both act every bit a food source.

After landing on the stigma, the pollen begins to swell. The sugary solution produced by the stigma is required both for pollen growth and to foreclose osmotic lysis of the germ tube. The stigmatic fluid also occurs in the intercellular spaces of the manner. This may explain why rain does not significantly inhibit or delay pollen germination, or filibuster the penetration of the germ tube down the fashion. Nevertheless, cool temperatures, which usually accompany rainy spells, markedly bear upon pollen germination and germ-tube growth (Fig. 3.26), even though viability is less affected. In contrast, ovules show obvious signs of damage at cool temperatures. Degeneration may occur within a week at temperatures below ten °C. In addition, cool temperatures, just earlier flowering at warm temperatures, can filibuster pollen germinability and germ-tube growth. Similar atmospheric condition tin can reduce fertility past disrupting aspects of ovule development (Ebadi et al., 1995).

Figure 3.26. Rate of pollen-germ tube growth in relation to temperature.

 (From Staudt, 1982, reproduced by permission.)

As the pollen tube penetrates the mode, the generative nucleus divides into ii sperm nuclei, if this has non already occurred. On reaching the opening of the ovule (micropyle), i sperm nucleus fuses with the egg nucleus, whereas the other fuses with the two polar nuclei. The fertilization of the egg nucleus initiates embryo evolution, whereas fusion with the polar nuclei induces endosperm differentiation. Fertilization also inaugurates a series of events that transform the ovules into seeds, and the ovary wall into the skin and flesh of the berry. Fertilization is usually complete within 2–iii days of pollination.

In certain varieties, abnormalities effect in viable seed not forming. Even in fertile, seeded cultivars, only 20–30% of the flowers successfully develop fully mature fruit; greater than fifty% fruit set is considered 'normal' and desirable. Seed maturation is essential for total berry evolution, notably the cell division growth component of fruit development (Friend et al., 2009). Fractional development may occur if the seed aborts after initiation, with drupe growth limited to prison cell enlargement. Shot berries (modest green fruit that may or may not abscise) (Plate 3.eight) are probably the result of pollination without fertilization. Details on productivity of important Australian cultivars is provided past Dry et al. (2010).

Where inadequate fruit set is frequently a trouble, shoot pinching at flowering is often beneficial. This reduces competition for photosynthate between growth of the shoot tip and early on stages of fruit development. Application of chlormequat chloride (CCC) only before flowering (to restrict vegetative growth) may also better fruit set (Collins and Dry, 2006). Alternatively, foliar application with abscisic acid appears to redirect photosynthate to developing fruit (Quiroga et al., 2009). With Merlot, late pruning (after bud burst) appears to improve fruit set. In this instance, delaying bud flare-up and flowering until climatic conditions are more favorable to fertilization and reproductive development seems to be the mechanism of activity (Friend and Trought, 2007; Keller et al., 2010).

Seedless cultivars are classified relative to their method of fruit development. In parthenocarpic cultivars, pollination stimulates sufficient auxin production to prevent fruit abscission (shatter), but is inadequate to permit normal berry enlargement. Black Corinth, the primary commercial source of dried currants, is the nearly important parthenocarpic variety. Although parthenocarpic varieties produce no seed, other seedless varieties, such every bit Thompson seedless, initiate seed development. Equally seed development ceases a few weeks after fertilization, the seeds are empty, small, and soft. Because of partial seed evolution, greater auxin production induces medium-size fruit development. This state of affairs is termed stenospermocarpy. If abortion occurs even later, every bit in the cultivar Chaouch, normal-size fruit develop, containing hard empty seeds. In contrast to the well-known examples of parthenocarpy and stenospermocarpy, the development of fruit and viable seeds in the absence of fertilization (apomixis) is unconfirmed in grapevines.

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FLOWERING AND REPRODUCTION | Pollination

J.L. Osborne , J.B. Gratuitous , in Encyclopedia of Applied Establish Sciences, 2003

Air current Pollination

Almost all the grasses, sedges, and rushes are wind-pollinated, as are the majority of forest trees in temperate climates, including conifers. Airborne pollen cannot be targeted to stigmas of compatible plants as specifically as insect-borne pollen. The success of wind pollination therefore relies on huge quantities of light, dry out pollen being produced and transported into air currents so that at least a small proportion lands on the exposed stigmas of other plants. Millions of grains of pollen fill the air when trees or grasses are in flower, and it is this pollen which is largely responsible for hay fever, an allergic reaction to a multifariousness of pollens. Wind pollination has the advantage that it does non rely on the presence and seasonality of insects.

The rate of fall of pollen grains in calm air varies considerably from about 2   cm   s−1 for small buoyant pollen grains (e.g., hazel (Corylus avellana), birch (Betula spp.)) to 50   cm   s−1 for heavy windborne pollen (e.one thousand., corn (Zea mays; maize)). The distribution and dynamics of pollen flow away from the source volition depend not merely on the plant and atmospheric conditions, including turbulence, but also on the vegetation and surrounding landscape. In temperate deciduous trees, the flowers are borne and pollination is effected before the leaves unfurl and obstruct air movement around the copse. Airborne pollen dispersal often shows a leptokurtic distribution (Figure iv). This ways that pollen degradation shut to the source is greater than expected from a normal distribution. There is oft a long thin tail to the distribution: tiny quantities of pollen are distributed very long distances. Since wind pollination is about effective at short distances, it is most often found in found species growing at high density, for example grasses and temperate wood trees.

Figure 4. Simulation of a leptokurtic distribution of airborne pollen grains at different distances from a air current-pollinated plant source. This is the typical form of the dispersal curve when pollen is sampled using traps. Dotted line shows a normal distribution for comparing.

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Pollination in Roses☆

P.G. Kevan , in Reference Module in Life Sciences, 2017

Abstract

Roses attract many insects. Why is this, and what do the insects proceeds? What do the plants gain? Merely what is known about roses and their pollination?

Pollination does non necessarily result in fertilization of the ovules within the flower׳south ovary. Self-compatibility is required if cocky-pollination is to be fruitful.

A pollinator is the agent that causes that transfer. Pollinators range from physical agents, especially the wind (wind pollination is chosen anemophily), or biotic agents such every bit insects, birds, bats and other animals (pollination past insects is called entomophily, past birds ornithophily, by bats chiropterophily). When i thinks nearly insects equally visitors to flowers, one thinks of pollinators, nectar and pollen feeders, and sometimes nearly feeding harm to flowers. All are function of the anthecology (floral environmental) of roses. The class of the flowers is crucial to understanding how pollination takes identify.

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