Air current Pollination

As a outcome, air current pollination (anemophily) is well-nigh effective when a species grows in high densities, as demonstrated by the authorization of this strategy in grasses and their relatives, and in tree species that grow in depression diversity temperate forests.

From: Encyclopedia of Applied Plant Sciences (2d Edition) , 2017

Ecology | Reproductive Ecology of Wood Trees

J. Ghazoul , in Encyclopedia of Forest Sciences, 2004

Wind Pollination

Other angiosperms have reverted to current of air pollination and consequently have much reduced flowers, as visually attractive flowers are no longer necessary for pollinator attraction. While wind is e'er-present, it is not a selective pollinator and is consequently inefficient over large distances. Wind pollination is therefore favored in species-poor forests where conspecifics are closely spaced. Wind-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 air current, and stigmas are usually well exposed and have large surface areas.

Wind pollination is associated with temperate forests and dry, or seasonally dry, habitats where fauna 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, wind pollination is again common, despite the wet climate. Open forests and savannas are specially well represented by wind-pollinated copse. In the dumbo vegetation of a rainforest wind pollination is usually restricted to emergent coniferous trees (e.grand., Araucaria and Agathis) and to copse occurring on ridge tops (Balanops australiana, Nothofagus). Wind pollination does, very rarely, occur in the rainforest understory amidst more specialized angiosperm groups, including Euphorbiaceae, Pandanaceae, and Palmaceae.

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Breeding Genetics and Biotechnology

D.E. Pattemore , in Encyclopedia of Practical Plant Sciences (Second Edition), 2017

Modes of Pollination

Angiosperm pollination evolved from earlier reproduction strategies that initially involved aquatic ship of gametes and so current of air pollination post-obit the development of the pollen capsule, which prevented desiccation during this process. One of the main distinctive features of angiosperms has been the conscription of animals as pollen vectors (pollinators), but a number of significant angiosperm groups take secondarily evolved abiotic vectors.

Abiotic pollination typically requires the production of large 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 equally nectar to maximize effective pollination by animals.

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

Insect pollination (entomophily) in the angiosperm lineage most probably evolved about 130   million years agone when the introduction of a hermaphroditic flower caused pollen-eating insects (such equally beetles) to pollinate ovules every bit a by-product of their presence on the early flower. This highly successful approach to reproduction has been modified extensively since then, depending on the diverse selection factors acting on flower morphology and function. Bees are the well-nigh of import group of pollinators globally because of their specialization on pollen and nectar as food resources. The major radiation of bee taxa occurred 120–130   1000000 years ago at the same time as the major angiosperm radiation. Later on, other insect groups, birds, mammals, and lizards have also been conscripted into pollination.

Animal pollinators are attracted to flowers through flower colors and patterns, floral scents, nectar rewards, or through deception by the blossom'southward mimicry of oviposition sites or the fauna'due south sexual partners. Because of the diversity 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 particular group of pollinators based on floral traits. The underlying hypothesis is that it is virtually efficient for a plant to adapt to a detail group of pollinators to ensure their visitation and constancy, thereby reducing the wasteful deposition of pollen from other plant species. While recent testify instead points to generalization as the ascendant theme in pollination, this concept of plant specialization on particular taxonomic groups is at least useful in that pollination syndromes can function as readily disprovable hypotheses.

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

Animal-pollinated flowers are typically divided into syndromes based on features perceived past and bonny to different groups. For example, bee-pollinated flowers are often said to be blue, yellow, or white, with patterns that emphasize the location of pollen and nectar. Ultraviolet color patterns are visible to bees, so that flowers that appear to humans to exist a single color tin can exhibit distinct patterns to bees. Some flowers have features that require specific behaviors to access the floral rewards that appear to favor bees, such as flag-blossoms which require the weight of a large bee to open, buzz-pollinated flowers like those of tomatoes, or flowers with nectar secreted in tubes that require a long insect tongue to access (up to near 15   mm).

In contrast, green or white flowers of a dish or bowl shape with readily accessible rewards are frequently described as adapted for fly or protrude pollination. Information technology is worth noting, however, that these flowers do not preclude access by other pollinator groups and insects do not perceive color in the same way every bit humans. There are a few flowers that accept specialized in the attraction of long-tongued flies and accept long thin tubular perianths and nectar spurs similar to flowers pollinated past long-tongued bees and Lepidoptera. Some floral trails do appear to be specializations for fly pollination, including the presence of strong, pungent odour that concenter flies that lay eggs in rotting carrion.

Pollination syndromes have also been described for moth and butterfly pollination, bird pollination, bat pollination, and even cadger 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 particular groups, or on 'secret' signals (visual or scent) only detectible by particular groups of pollinators. For all these approaches to classifying flowers, it is important to go along in mind that even if these features are useful for developing hypotheses about evolutionary relationships, they may non necessarily reflect what species currently visit the flowers and act as effective pollinators. Human being commerce and trade has resulted in plants and pollinators existence transported well beyond their natural ranges, and still these new interactions betwixt flowers and pollinators that have not evolved together still lead to effective pollination that is integral to crop production.

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Grapevine Structure and Office

Ronald S. Jackson PhD , in Wine Science (3rd Edition), 2008

POLLINATION AND FERTILIZATION

Cocky-pollination appears to exist the dominion for most grapevine cultivars. Nether vineyard weather condition, wind and insect pollination appear to be of little significance. Fifty-fifty in areas where grapes are the ascendant agricultural crop, pollen levels in the air are generally low during flowering – in dissimilarity to the relatively high levels associated with cross-pollinated wild grapevines (see Stevenson, 1985). Yields of about ane.iv × 104 pollen grains/m2/day, sedimenting out of the air during July, take been recorded in Montpellier, French republic (Cour et al., 1972–1973). In Portugal, pinnacle pollen counts were recorded at 24 pollen grains per m3 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 most simultaneous blooming of innumerable vines over wide areas. Nevertheless, syrphid flies, long-horned and tumbling flower beetles, besides as bees occasionally visit grape flowers. The master attractant appears to be the olfactory property produced by nectaries. Sesqiterpenes and monoterpenes appear to be the primary effluvious compounds produced (Buchbauer et al., 1995). Nectaries are located between the stamens and pistil (Fig. 3.20C) and are particularly prominent in male person flowers on wild V. vinifera vines. Nectaries are modified for scent, rather than nectar production every bit the name might propose. Visiting insects feed on pollen, non nectar. Pollen fertility has no influence on bloom bewitchery, but the presence or absence of anthers does affect the duration of visits to female person flowers (Branties, 1978).

Shortly 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 prevent osmotic lysis of the germ tube. The stigmatic fluid also occurs in the intercellular spaces of the style. This may explain why pelting does not significantly inhibit or filibuster pollen germination, 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), even though viability is less afflicted. In contrast, ovules show obvious signs of degeneration within near a week at temperatures below 10 °C. Absurd temperatures, merely before flowering at favorably warm temperatures, can filibuster pollen germinability and germ-tube growth. Similar conditions tin can equally reduce fertility by disrupting aspects of ovule development (Ebadi et al., 1995).

Figure 3.21. Charge per unit of pollen germ-tube growth in relation to temperature.

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

As the pollen tube penetrates the style, the germinative nucleus divides into two 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 also 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 unremarkably complete within ii–3 days of pollination.

In sure 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 production to prevent abscission of the fruit (shatter), it is inadequate to permit normal berry enlargement. 'Black Corinth,' the primary commercial source of dried currants, is the most important parthenocarpic diverseness. Although parthenocarpic varieties produce no seed, other seedless varieties such as 'Thompson seedless' incorporate seeds. Equally these usually arrest a few weeks after fertilization, the seeds are empty, small and soft. Because of fractional seed evolution, greater auxin product induces medium-size fruit development. This situation is called stenospermocarpy. If ballgame occurs even later, as in the cultivar 'Chaouch,' normal-size fruit develop containing hard empty seeds. In dissimilarity 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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TREE Convenance, PRACTICES | Convenance and Genetic Resources of Scots Pino

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

Breeding System

Some other of import trait of Scots pine is its convenance system. There is no self-incompatibility organization, and wind pollination results in considerable proportions of cocky-pollination and self-fertilized zygotes. Straight measurements at the zygote stage have not been made, but information technology tin can be inferred that the primary selfing charge per unit must be frequently at least 20%. In the mature seed, withal, in that location are ordinarily merely a low percentage of selfs. There seems to be niggling occurrence of other kinds of inbreeding. Several studies accept shown that adult Scots pine populations do not accept any selfs. Thus, between the zygote phase and the adult tree stage the selfs are preferentially eliminated past usually astringent inbreeding depression. Much of the elimination takes place very early, during seed development. At the age of a few years natural populations evidence little evidence of inbreeding. When selfs survive in experimental conditions, they show a cumulative decline in relative survival with lowered fettle over several decades due to poorer growth, which results in size-specific elimination of selfs by competition. The inbreeding depression is presumably due to a large number of deleterious recessive genes in the Scots pine genome. The average tree is heterozygous for 8–10 so-called embryo lethals, which means that Scots pine 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 become fully reproductively mature before the historic period of twenty. Not only is there no asexual reproduction in the natural populations, but Scots pine has also proved a very recalcitrant species for diverse modes of vegetative propagation.

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Grapevine structure and function

Ronald S. Jackson PhD , in Wine Scientific discipline (5th Edition), 2020

Pollination and fertilization

Self-pollination is typical for well-nigh grapevine cultivars, occurring prior to cap fall (Staudt, 1999) or shortly thereafter (Heazlewood and Wilson, 2004). Correspondingly, wind and insect pollination are of footling significance. Even 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 nigh 1.4   ×   104 pollen grains/m2/solar day have been recorded in Montpellier, France (Cour et al., 1972–1973). In Portugal, peak pollen counts were recorded at 24 pollen grains/m3 air (Cunha et al., 2003); also recorded was 90 grains/m3 air for Cabernet Sauvignon in Espana (Muñoz-Rodríguez et al., 2011). Despite airborne pollen often beingness unnecessary for successful fertilization in domesticated grapevines, information technology may raise seed gear up (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 conditions that favor pollen release and air dispersal are the same equally those favoring self-pollination and fertilization.

The relative insignificance of insect pollination in vineyards may exist accounted for by the nearly simultaneous blooming of tens of thousands of vines over vast areas. It is of greater significance in feral vines. Insects visiting grapevine flowers include bees and syrphid flies as well every bit long-horned and tumbling flower beetles. The principal attractant appears to be 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 name, nectaries are modified for odour, not nectar production. Visiting insects feed on the pollen, non nectar. Pollen fertility has no influence on insect visitation, just the presence or absence of anthers does affect the duration of visits to female flowers (Branties, 1978).

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

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 preclude osmotic lysis of the germ tube. The appropriate residuum of macro- and micronutrients is as well required. The stigmatic fluid also occurs in the intercellular spaces of the style. This may explain why pelting does not significantly inhibit or filibuster pollen germination or delay the penetration of the germ tube down the manner. Even so, absurd temperatures, which normally accompany rainy spells, markedly affect pollen germination and germ-tube growth (Fig. 3.25) fifty-fifty though viability is less influenced. In contrast, ovules show obvious signs of harm at cool temperatures. Degeneration may occur within a week at temperatures beneath 10   °C. In add-on, cool temperatures, simply before flowering at warm temperatures, can filibuster pollen germinability and germ-tube growth. Like atmospheric condition can reduce fertility by disrupting aspects of ovule development (Ebadi et al., 1995).

Figure 3.25. Rate of pollen-germ tube growth in relation to temperature.

 From Staudt, G., 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 downward the way, the generative nucleus divides into ii sperm nuclei, if this has not already occurred. This initiates changes in gene expression in the pistil, preparing it for fertilization and fruit evolution (Kühn and Arce-Johnson, 2012). On reaching the opening of the ovule (micropyle), one 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 also inaugurates a series of events that transform the ovules into seeds and the ovary wall into the peel and flesh of the berry. Fertilization is usually complete within 2–3 days of pollination.

In certain varieties, abnormalities result in viable seed not forming. Even in fertile, seeded cultivars, but twenty%–thirty% of the flowers successfully develop fully mature fruit; greater than l% fruit fix is considered "normal." Seed maturation is typically necessary for total berry development, notably the cell segmentation growth component of fruit development (Friend et al., 2009). Fractional drupe development may occur if the seed aborts after initiation, with drupe growth limited to prison cell enlargement. Shot berries (small green fruit that may or may not abscise) (Plate 3.vii) are probably the result of pollination without fertilization. Details on the productivity of important Australian cultivars is provided by Dry et al. (2010).

Plate iii.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 incorporate normal seeds only volition ripen; alive greenish ovaries, which bear witness limited development.

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

Where inadequate fruit set is frequent, shoot pinching at flowering can be beneficial. This reduces contest for photosynthate between shoot growth and early stages of fruit development. Application of CCC just before flowering (to restrict vegetative growth) may too better fruit prepare (Collins and Dry, 2006). Alternatively, foliar application with abscisic acid appears to redirect photosynthate to developing fruit (Quiroga et al., 2009). With Merlot, tardily pruning (after bud burst) appears to ameliorate fruit prepare. In this instance, delaying bud burst and flowering until climatic conditions are more favorable to fertilization and reproductive development seems to be the mechanism of action (Friend and Trought, 2007; Keller et al., 2010).

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

In contrast to wine grapes, about table and raisin cultivars are seedless. In parthenocarpic cultivars, pollination stimulates sufficient auxin production to forestall fruit abscission (shatter) but is inadequate to allow normal berry enlargement. Black Corinth, the primary source of currants, is the most of import parthenocarpic variety. Although parthenocarpic varieties produce no seed, other seedless varieties initiate seed development—a state of affairs termed stenospermocarpy. As seed development ceases a few weeks subsequently fertilization, the seeds are empty, small, and soft. Because of fractional seed development, greater auxin production induces medium-sized fruit development. An instance is Thompson Seedless (referred to every bit Sultana when used to brand raisins). If abortion occurs even after, as in the cultivar Chaouch, normal-sized fruit develop, containing hard empty seeds. In contrast 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 Research, 2015

i.2 Traits Modulating Wild Plant Response to Habitat Fragmentation

To produce seeds sexually, flowering plants range from complete dependence on animal pollination up 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 cocky-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 constitute species may exist considered facultative outbreeders that partially depended on fauna pollination. Although animate being pollinators are needed to transport pollen, a single visit of a pollinator to each individual flower may allow seed production. Moreover, some self-uniform species may have the ability to reproduce sexually via democratic self-pollination, without the intervention of pollinators (Richards, 1997). As expected, results from a meta-analysis on the furnishings of habitat fragmentation on plant pollination and reproduction testify that the reproductive success of found species with higher dependence on fauna pollination (i.e. self-incompatible plants) was more negatively and strongly affected than that of less dependent ones (i.e. cocky-compatible species; Aguilar et al., 2006). Moreover, habitat fragmentation tin subtract the incidence of species highly dependent on brute pollination, as reported for tropical trees of a fragmented landscape of the Brazilian Atlantic Wood (Girão et al., 2007).

The sensitivity of plants to habitat fragmentation may also exist determined past their degree of pollination generalization (Bond, 1994; Johnson and Steiner, 2000; Renner, 1998). Plant species range from "super-generalists" that interact with hundreds of pollinator species to "extreme specialists" interacting with just 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 than probable than losing all the pollinators associated with a generalist plant species. This prediction was grounded in the thought that whatever change imposed by fragmentation in pollinator assemblages is more likely to cause reproductive failure in plants interacting with pollinator assemblages of lower richness (Aizen et al., 2002; Bond, 1994; Waser et al., 1996). Conversely, generalist plants are expected to be more resilient to the changes imposed by fragmentation on their pollinator assemblages because of the functional back-up among their pollinators (Fægri and van der Pijl, 1979; Morris, 2003). For both self-compatible and cocky-incompatible species, however, the negative effect of habitat fragmentation on found reproductive success seems to be independent of plant pollination generalization (Aguilar et al., 2006).

The number of seeds produced by plants and their dispersal mode are the primary traits determining species dispersal success (Willson and Traveset, 2000). Habitat fragmentation may modify seed dispersal success past affecting seed size and quantity (east.one thousand. Aguilar et al., 2006; Fakheran et al., 2010; Galetti et al., 2013), establish and inflorescence meridian (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 exist favoured in fragmented landscapes (Hagen et al., 2012; but see Cheptou et al., 2008). It has been reported, for instance, that habitat fragmentation affects more negatively the proportion of seeds of plant species with larger seeds and of animal-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 multifariousness of creature-dispersed plant species in woods fragments (Tabarelli et al., 1999) also 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 production may be positively related to the probability of plant species occurrence in isolated habitat fragments (Evju et al., 2015), more fecund institute species will have higher probabilities of persistence in fragmented landscapes (McEuen and Curran, 2004). Finally, information technology has been recently suggested that when a landscape becomes more fragmented over evolutionary relevant time scales, increased (mean and long-distance) dispersal rates will exist selected (Aparicio et al., 2008; Koh et al., 2015; but see Cheptou et al., 2008). This prediction seems to be supported by empirical evidence showing that increased isolation among patches leads to increased richness of species with long-distance 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 Found Virus Diseases

Yehezkel Antignus , in Advances in Virus Inquiry, 2014

iii.v Effect of UV filtration on pollinators

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

UV-poor environments might have an influence on pollinator behavior in two ways: first, the overall flight activity may be macerated due to scarce calorie-free conditions, and second, the light weather condition might modify the color perception of the ingather flowers past the pollinators so that they will have difficulty in localizing the flowers among the leaf 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 tomato plant greenhouses (Kevan, Straver, Offering, & Laverty, 1991). Studies carried out nether laboratory weather have shown that bumblebees perceive when ultraviolet radiation is either removed or added to an illumination source, and are capable of using their visual organization to forage efficiently in a UV-deficient surround. Thus, their forage efficiency is not afflicted by the type of greenhouse covering (Dyer & Chittka, 2004). A delay in the hive start upwardly of the bumblebee B. terrestris (Bio-Bee, Ltd., Israel) was observed in experimental mini greenhouses covered with UV-blocking films (Steinberg et al., 1997; van der Blom, 2010). Afterwards, this problem was solved by placing the hives near the greenhouse walls, where they were exposed to unfiltered low-cal (Y. Antignus, unpublished). In a field study, no significant differences were establish in bumblebee action or in the numbers of flowers visited, under standard or UV-blocking films (Fig. 1.vii) (Antignus & Ben-Yakir, 2004). Studies in commercial tomato greenhouses have demonstrated that biomass and size of hives were non 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 plant in the numbers of workers that foraged nor in the concluding harvest in field trials where the pollination activity of bumblebees, under UV-absorbing and -ordinary films, was compared in both lycopersicon esculentum and watermelon crops (van der Blom, 2010). Contrary to the bumblebees, honeybees did show significant behavioral changes under the UV-blocking plastic. Two trials were carried out in watermelon, and one in melon using honey bees for pollination. In all three cases, a reduced foraging activity 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 inbound the hive, so information technology seems to be the consequence of deficient full general calorie-free atmospheric condition, more than than of the difficulty to localize the flowers one time foraging (van der Blom, 2010).

Figure 1.seven. Bumblebee (Bombus terrestris) pollination activeness in tomatoes grown in a greenhouse with ordinary cladding materials (polyethylene film   + l mesh screen) versus a greenhouse covered with UV-absorbing cladding materials (polyethylene moving picture   +   fifty mesh "Bionet" screen). Pollination activity is expressed equally pct of visited flowers identified by typical dark-brown band on the flower stamens cone.

In Canada, bumblebees' activity 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 Israel may be explained past the differences in dominicus light intensities and temperatures between these two locations. A positive correlation exists between the rate of bumblebees' action and temperature. Higher temperatures (in the range 5–25   °C) may compensate for the inhibitory effect of reduced UV radiation (Morandin et al., 2001; Morandin, Laverty, Kevan, Khosla, & Shipp, 2002). Areas inside the greenhouse that have relatively high levels of UV radiation (normally the southern wall side) were found equally optimal sites for placing bumblebees' hives in greenhouses covered with UV-blocking films (Y. Antignus, unpublished).

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Grapevine Structure and Function

Ronald S. Jackson PhD , in Wine Science (4th Edition), 2014

Pollination and Fertilization

Self-pollination appears to be the rule for about grapevine cultivars, occurring prior to cap fall (Staudt, 1999). Pollen germination may, still, occur only after cap fall (Heazlewood and Wilson, 2004).

For most cultivars, current of air and insect pollination is of little significance. Fifty-fifty in areas where grapes are the dominant agricultural crop, pollen levels in the air are depression during flowering, in comparing with levels associated with cross-pollinated wild grapevines (run into Stevenson, 1985). Yields of nigh i.iv×10iv pollen grains/grand2/day have been recorded in Montpellier, France (Cour et al., 1972–1973). In Portugal, peak pollen counts were recorded at 24 pollen grains/grand3 air (Cunha et al., 2003), and 90 grains/chiliadthree air for Cabernet Sauvignon in Spain (Muñoz-Rodríguez et al., 2011). Despite airborne pollen ofttimes being unnecessary for the successful fertilization of domesticated grapevines, information technology may enhance seed set (Chkhartishvili et al., 2006). This may explain 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 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 be deemed for by the almost simultaneous blooming of tens of thousands of vines over vast areas. It is presumably of greater importance to wild grapevines. Insects visiting grapevine flowers include bees and syrphid flies, besides as long-horned and tumbling flower beetles. The principal attractant appears to be the scent 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 name, nectaries are modified for odour, non 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 affect the elapsing of visits to female flowers (Branties, 1978).

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

After landing on the stigma, the pollen begins to swell. The sugary solution produced past 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 style. This may explicate why rain does not significantly inhibit or filibuster pollen germination, or delay the penetration of the germ tube down the fashion. Nonetheless, cool temperatures, which usually accompany rainy spells, markedly impact 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 x °C. In add-on, absurd temperatures, just before flowering at warm temperatures, can filibuster pollen germinability and germ-tube growth. Similar conditions can reduce fertility by disrupting aspects of ovule evolution (Ebadi et al., 1995).

Effigy 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 two sperm nuclei, if this has not already occurred. On reaching the opening of the ovule (micropyle), one sperm nucleus fuses with the egg nucleus, whereas the other fuses with the two polar nuclei. The fertilization of the egg nucleus initiates embryo development, whereas fusion with the polar nuclei induces endosperm differentiation. Fertilization also inaugurates a serial of events that transform the ovules into seeds, and the ovary wall into the pare and flesh of the drupe. Fertilization is usually complete within 2–3 days of pollination.

In certain varieties, abnormalities result in viable seed not forming. Even in fertile, seeded cultivars, only 20–30% of the flowers successfully develop fully mature fruit; greater than 50% fruit prepare is considered 'normal' and desirable. Seed maturation is essential for full berry development, notably the jail cell sectionalisation growth component of fruit development (Friend et al., 2009). Partial development may occur if the seed aborts after initiation, with berry growth express to jail cell enlargement. Shot berries (small green fruit that may or may not abscise) (Plate iii.8) 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 prepare is oftentimes a problem, shoot pinching at flowering is often beneficial. This reduces contest for photosynthate between growth of the shoot tip and early on stages of fruit development. Application of chlormequat chloride (CCC) just earlier flowering (to restrict vegetative growth) may also ameliorate fruit fix (Collins and Dry out, 2006). Alternatively, foliar application with abscisic acid appears to redirect photosynthate to developing fruit (Quiroga et al., 2009). With Merlot, tardily pruning (after bud burst) appears to ameliorate fruit set. In this instance, delaying bud burst and flowering until climatic conditions are more than favorable to fertilization and reproductive development seems to be the mechanism of action (Friend and Trought, 2007; Keller et al., 2010).

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

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FLOWERING AND REPRODUCTION | Pollination

J.Fifty. Osborne , J.B. Free , in Encyclopedia of Applied Plant Sciences, 2003

Wind Pollination

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

The rate of fall of pollen grains in at-home air varies considerably from about 2   cm   s−i for small-scale buoyant pollen grains (e.g., hazel (Corylus avellana), birch (Betula spp.)) to fifty   cm   southward−1 for heavy windborne pollen (e.g., corn (Zea mays; maize)). The distribution and dynamics of pollen flow away from the source will depend non only on the institute and atmospheric conditions, including turbulence, but also on the vegetation and surrounding mural. In temperate deciduous copse, the flowers are borne and pollination is effected earlier the leaves unfurl and obstruct air movement around the trees. Airborne pollen dispersal often shows a leptokurtic distribution (Effigy four). This means that pollen deposition close to the source is greater than expected from a normal distribution. In that location is often a long thin tail to the distribution: tiny quantities of pollen are distributed very long distances. Since wind pollination is nigh effective at curt distances, it is well-nigh often found in establish species growing at high density, for case grasses and temperate woods copse.

Effigy 4. Simulation of a leptokurtic distribution of airborne pollen grains at unlike distances from a air current-pollinated plant source. This is the typical course 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.M. Kevan , in Reference Module in Life Sciences, 2017

Abstract

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

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

A pollinator is the agent that causes that transfer. Pollinators range from physical agents, especially the wind (current of air pollination is called anemophily), or biotic agents such as insects, birds, bats and other animals (pollination by insects is called entomophily, by birds ornithophily, by bats chiropterophily). When one thinks about insects as visitors to flowers, one thinks of pollinators, nectar and pollen feeders, and sometimes virtually feeding damage to flowers. All are office of the anthecology (floral ecology) of roses. The form of the flowers is crucial to understanding how pollination takes place.

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