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Jul 01,  · An overview of the study design is shown in Fig liehageludedownfumetheamegilern.coinfo natural season phase of the study was performed during the height of the natural ragweed season (September 27, , to October 11, ), and the PCC phase was 6 weeks later, when no pollen was detected in San Antonio, Texas ().Download: Download high-res image (KB) Download: Download full-size imageCited by: Pollen, a mass of microspores in a seed plant, usually appearing as a fine dust and varying greatly in shape and structure. Each pollen grain is formed in the male structures of seed-bearing plants and is transported by various means to the female structures to facilitate fertilization of the ovules. Aug 01,  · Methods. Two chambers, m 3 and m 3, seating 50 and 25 individuals, respectively, were constructed with clean room liehageludedownfumetheamegilern.coinfo computer-controlled air handler used powered diffusers and exhausts to maintain a laminar flow. Pollen was delivered by a feeder into a vortex created by an eductor through a series of stainless steel liehageludedownfumetheamegilern.coinfo by:

Every year around springtime, pollen spores come out and wreak havoc on thousands in the form of itchy watery eyes, runny noses, and uncontrollable sneezing. But how can these pesky spores help scientists learn about the past climate? Pollen grains are the sperm-carrying reproductive bodies of seed plants like conifers, cycads, and flowering plants. Each of these grains has its very own unique shape depending on what plant it comes from, and their walls are made of a substance known as sporopolleninwhich is very chemically stable and strong.

When pollen grains are washed or blown into bodies of water, their tough outer walls allow them to be preserved in sediment layers in the bottoms of ponds, lakes, or oceans.

Because of their unique shapes, scientists can then take a core sample of the sediment layers and determine what kinds of plants were growing at the time the sediment was deposited. Knowing what types of plants were growing in the area allows the scientists to make inferences about the climate at that time by using knowledge about modern and historical distributions of plants in relation to climate. Once they take a core sample, the scientists isolate the pollen and spores from the sediments and rocks using both chemical and physical means.

The grains are very small, typically between 10 and micrometers, which requires mounting them on microscope slides for examination. To give you an idea of how small that really is, there are 1, micrometers in 1 millimeter, and a millimeter is about equal to the width of a pinhead. The scientists then count and identify the grains using a compound microscope and generate diagrams of the type and abundance of pollen in their samples.

A kDa organelle-associated motor was identified as functionally, biochemically, and immunologically related to kinesin. This indicated that the movement of pollen tube organelles was not exclusively actin-based but also depended on microtubule-based motors. Further support for this finding came from evidence that isolated pollen tube mitochondria moved along microtubules and actin filaments in vitro Romagnoli et al.

Movement was slow and continuous along microtubules but very fast and irregular along actin filaments. Results also indicated that Movement Twenty Third - Various - In Chambers Of Pollen (Cassette) vesicles and mitochondria bound to identical myosins but specific kinesins, because the 90 kDa kinesin was found in association with mitochondria but not with Golgi vesicles.

The sum of these elements suggested that microtubules and kinesins contributed to the disposition of mitochondria in pollen tubes. Similar results were also found in cells of Arabidopsis thaliana Ni et al.

The presence of an additional kinesin-like protein associated with Golgi bodies of Nicotiana pollen tubes Wei et al. Golgi-associated kinesins are not peculiar to pollen tubes, also being found in Arabidopsis trichomes Lu et al. Although the contribution of microtubules and microtubule-based motors may be superfluous during pollen tube growth in vitroit is hypothesized that the role of microtubules in organelle motility may be more essential in vivowhen pollen tube growth is fastest Joos et al.

The presence of an additional microtubule-dependent transport system suggested that actin filaments and microtubules may co-operate in the motility of organelles and vesicles during pollen tube growth.

The information that the velocity of membranes along the two filamentous systems was drastically different indicated that the specific role of actin- and microtubule-motors was different. While the organization of actin filaments has been described in great detail and the cortical actin fringe is acknowledged as a typical feature of growing pollen tubes Lovy-Wheeler et al. Microtubules and actin filaments are organized differently in pollen tubes but also show some similarities.

Both are disposed in bundles along the main axis, with actin filaments also being present in the cytoplasm while microtubules are mostly found in the cell cortex. In the cortex, single actin filaments are usually observed to be aligned with microtubules and elements of the endoplasmic reticulum; microtubules appear to be cross-linked to actin filaments and to the plasma membrane Lancelle et al.

Close association of microtubules with actin filaments has also been shown by immunogold labelling, indicating that microtubules may act as guide elements for actin filaments or vice versa Lancelle and Hepler, Co-localization of microtubules and actin filaments in the pollen tube cortex has also been revealed by double labelling with fluorescent probes, suggesting functional relationships with organelle movement and the organization of the cell cortex Pierson et al.

A schematic drawing of actin filaments and microtubules based on visualization with GFP-fluorescent probes and their hypothetical relationships in pollen tubes is shown in Fig. A Schematic distribution of actin filaments and microtubules in a pollen tube as shown by GFP-tagged proteins.

Actin filaments are found in the cortical and central regions of the tube. Microtubules exist prevalently in bundles formed by uncharacterized proteins in the cortical cytoplasm and their organization in the subapex is still unclear; presence of a microtubule fringe has been proposed Lovy-Wheeler et al. Microtubules probably associate with the plasma membrane through p Cai et al. Sites of origin and polarity of microtubules are not known.

Monomers of actin and tubulin are probably present in the apical region. Objects are not drawn to scale. B Regulation of cytoplasmic streaming. This picture is derived from A but is essentially focused on the relationships between the signal transduction pathway and the pollen tube cytoskeleton. It enters the pollen tube in the tip region 1 and generates a local increase in concentration 2which also depends on the concerted activity of phospholipase C PLCphosphoinositol biphosphate PIP 2inositol triphosphate IP 3 3and of Rop GTPases activity 4.

Regulation of actin filaments and inactivation of myosin prevent large-sized organelles from entering the apical domain 8. Vesicles enter and accumulate in the apical domain 10 and fuse with the plasma membrane 11 or turn back toward the grain Nothing is known about the regulation of microtubules, but they could be regulated by phospholipase D not shown. The polymerization state of actin filaments may also regulate microtubule dynamics Although a kind of interplay between microtubules and actin filaments probably exists, its implications are enigmatic and controversial.

Microtubules are probably not involved in the capacity of pollen tubes to overcome mechanical obstacles, whereas actin filaments seem very important. Conversely, maintenance of the direction of growth in vitro was susceptible to microtubule degradation whereas actin filaments were less or non critical Gossot and Geitmann, In addition, the organization of microtubules probably depended on actin filaments, while actin filaments seemed to be independent of microtubules.

These findings suggested that microtubules and actin filaments were physically connected in some way. In this context, a microtubule-associated protein, SB, was identified in the pollen of Solanum berthaultii and shown to bind to actin filaments Huang et al. Inadequate data on microtubule-associated proteins MAPs in pollen tubes makes any type of realistic hypothesis even more difficult, although a search of the literature and BLAST comparison of proteins brought forth several MAP-homologous proteins expressed in Arabidopsis thaliana and putatively involved in different functions Gardiner and Marc, MAPs have still to be demonstrated in pollen tubes and it is not clear whether they are required for organelle movement.

Results of in vitro motility assays indicated that pollen tube organelles move constantly along single microtubules, suggesting that microtubule bundles may not be necessary Romagnoli et al. The same ambiguity also concerns post-translational modification of tubulin. The effects of MAP-mediated differential density of microtubules on organelle movement is an open question. The final fate of Golgi-derived secretory vesicles in pollen tubes is fusion with the apical plasma membrane.

Relationships between endoplasmic reticulum, Golgi bodies, and vesicles have been studied using Brefeldin A, which induced subapical membrane accumulation derived from the backflow of apical vesicles and from Golgi-derived membranes. This evidence suggests that the Golgi system is a central element in the production and recycling of vesicular materials; these activities depend on the actin cytoskeleton Parton et al.

Thus, the growth of pollen tubes is essentially based on focusing Golgi-derived vesicles that accumulate through the motor activity of the actin—myosin complex and fuse in specific sites of the pollen tube apex polarized exocytosis. From the early work of Steer and Steerit emerged that the number of secretory vesicles in the pollen tube apex largely exceeded the number effectively required for growth, suggesting that excess plasma membrane must be recovered by other mechanisms endocytosis.

Vesicle streaming and tube growth can be unplugged by Latrunculin B Cardenas et al. Thus, current discussion about vesicle motility which is based on cytoskeleton-membrane interactions also needs to consider the subsequent phase of vesicle fusion which includes regulation and the dynamics of this process.

This model of subapex-delimited vesicular secretion has also been suggested by other authors using spatiotemporal correlation spectroscopy and fluorescence recovery after photobleaching; secretory vesicles were shown to move towards the apex in the pollen tube cortex and accumulate close to the tip, returning through the tube centre Bove et al.

The velocity of secretory vesicles matched the speed of Golgi vesicles as measured in vitro along actin filaments and microtubules Romagnoli et al. These findings imply relationships between the zone of active secretion and the actin cytoskeleton, Movement Twenty Third - Various - In Chambers Of Pollen (Cassette). Vesicles are known to move along the actin filaments, but the precise role of actin in the secretion mechanism is still unclear.

Identification of the actin fringe in pollen tubes Lovy-Wheeler et al. Speculatively, exocytic vesicles may traffic directly to the site of exocytosis through the actin fringe or the actin fringe may somehow label or delimit the site of exocytosis. A putative model may therefore be that accumulation of secretory vesicles in the tube apex depends on longitudinal actin filaments Cardenas et al. The apex and subapex of pollen tubes may also possibly be the region of actin assembly.

New actin filaments probably arise from membrane-associated protein complexes containing formin. Overexpression of formin in pollen tubes induces the formation of actin filaments, arising from the plasma membrane, in the cytoplasm. Formin-dependent actin polymerization is therefore important for polar growth of pollen tubes Cheung and Wu, The actin fringe may also act as a functional domain to delimit the region of growth.

Little is known about the organization of microtubules in the pollen tube apex. Despite evidences that microtubules are absent from the apical domain, GFP-labelled EB1 indicated that microtubules may lie closer to the pollen tube tip than previously thought Cheung et al.

The presence of microtubules in close proximity to the tip may also depend on the bending features of pollen tubes Foissner et al. The presence of a microtubule fringe in the subapex of pollen tubes was suggested by microtubule labelling with fluorescent taxol Lovy-Wheeler et al.

The exocytotic event is closely related to the opposite process of endocytosis, which most likely occurs in two distinct regions of the pollen tube, along the apex, and in the distal region Zonia and Munnik, ; Moscatelli et al.

In this context, hydrodynamic flux was assumed to regulate exocytosis and endocytosis because hypotonic treatment and thus cell swelling stimulated exocytosis and reduced endocytosis, while hypertonic treatment and cell shrinking stimulated endocytosis but decreased exocytosis. The growth rate of pollen tubes is, consequently, the result of fine-tuning of the apical volume of pollen tubes, which influences the activity of endocytosis at the apex and along the distal tube and exocytosis in the subapical region and thus defines the boundary of the growth zone.

Visualization of endocytosis by fluorescent phospholipids Lisboa et al. Depolymerization of actin filaments abolished plasma membrane retrieval, whereas oryzalin had no effect, suggesting that actin filaments but not microtubules may be responsible for the endocytotic process.

The latter presumably mediate the effects of growth regulators by affecting the rate of vesicle fusion and the delivery of vesicles to the apical domain through modulation of the actin cytoskeleton. Specifically, it was found that RIC4 overexpression of which promoted actin assembly determined the accumulation of secretory vesicles but inhibited exocytosis; on the other hand, disassembly of actin by RIC3 was required for exocytosis Lee et al.

This again showed that the process of vesicle transport in the tube tip and exocytosis depend on distinct mechanisms and that fine-tuning of the equilibrium between F- and G-actin is Movement Twenty Third - Various - In Chambers Of Pollen (Cassette) for tube growth.

The activity of Rop-GTPases is probably mediated by protein kinase activity. The presence of type 2A protein phosphatase inhibitors had dramatic effects on the cytoskeleton randomly oriented actin filaments and microtubules, alteration of actin bundle alignment, and disassembly of microtubules Foissner et al.

This finding suggested that PLC hydrolysed phosphatidylinositol 4,5-bisphosphate to the signalling molecules inositol 1,4,5-trisphosphate and diacyl glycerol DAG. The negative effects of expression of PLC were reversed by treatment with low concentrations of the actin drug Latrunculin B, suggesting that PLC alters actin structure in growing tube tips and restricts growth to the very tip of pollen tubes.

Overexpressed PLC also inhibited tube growth and accumulated laterally at the pollen tube tip plasma membrane mimicking the distribution of phosphatidylinositol 4,5-bisphosphate. Diacylglycerol DAG also showed a localization similar to that of phosphatidylinositol 4,5-bisphosphate Helling et al. Phospholipase D PLD and its product phosphatidic acid PA also play a role in the polarization of pollen tubes and their activity can be blocked by primary alcohols, like 1-butanol. When inhibited by 1-butanol, pollen tube growth can be restored by taxol treatment, indicating that microtubules may be one target of PLD activity.

This hypothesis is supported by the finding that PLD is linked to microtubule dynamics Dhonukshe et al. The role of microtubules if any in vesicle targeting and fusion is unclear. Although kinesin-related proteins have been localized in apical vesicles Tiezzi et al. Nevertheless, the evidence that oryzalin treatment affected pulsatory growth Geitmann et al.

In addition, the finding that plant phospholipase D associates with membranes and microtubules Gardiner et al. Regulated elongation of actin filaments along with the inactivation of myosin probably prevents large-sized organelles from entering the apical domain 8 but allows them to turn back.

Secretory vesicles also move along actin filaments using the motor activity of myosin 9. Vesicles that do not fuse may return to the subapical region, together with endocytic vesicles 12 ; this tip-to-subapex movement may rely on actin and myosin.

Nothing is known about the regulation of microtubule activities; speculatively, they may be regulated by phospholipase D not shownor the polymerization state of actin filaments may regulate microtubule dynamics 13 Gossot and Geitmann, ; Poulter et al.

Advances in the last 20 years of research have offered important new insights into the functions of actin filaments and microtubules in organelle transport inside pollen tubes. A great amount of data indicates that actin filaments are the main tracks of organelle and vesicle transport; actin filaments support cytoplasmic streaming in the basal domain and accumulation of vesicles in the tip domain.

External signals appear to be critical for redirecting tip growth when the pollen tube has to follow signals from female tissues; external signals presumably modulate the activity of motor proteins and organization of actin filaments. The role of microtubules is still unclear, although their function could be more prominent for the growth of pollen tubes in vivo.

Whether actin and the microtubule cytoskeleton co-operate in motor activity is still unclear and there are major challenges to be solved in the near future. Some of these questions are listed below. The motility pattern of mitochondria, Golgi bodies, endoplasmic reticulum, and vesicles needs to be clarified. We do not know whether single organelles move Movement Twenty Third - Various - In Chambers Of Pollen (Cassette) of the others or ignore whether or not the trafficking of each organelle class depends on that of other classes.

Do specific motor receptors exist? Does this imply involvement of multiple myosins? It is current opinion that organelle transport in eukaryotic cells is achieved by regulating the activities of motor proteins of different families Goode et al. This model has been the subject of relatively little study in plant cells, although there is evidences that myosin and kinesin may ultimately be required for organelle trafficking Wei et al.

Since organelles interact dynamically with actin filaments and microtubules, the pollen tube may be an excellent model for studying this process; unfortunately, we do not know how many myosins and kinesins are present in pollen tubes, and how motor proteins co-operate in organelle and vesicle movement. A speculative basic model is reported in Fig. Delivery of vesicles to the apical region supports pollen tube growth, which is under the control of external signals from female tissues Herrero, Does control of motor activity simply rely on the regulation of cytoskeletal filaments?

There Movement Twenty Third - Various - In Chambers Of Pollen (Cassette) evidences that pollen tube organelles and vesicles move along microtubules Romagnoli et al. Gene sequences of kinesins and inhibition of expression by iRNA may provide some answers. In order to appreciate the contribution of the cytoskeleton to the pollen tube shaping process, it is essential to determine the secretion pattern of cell wall-synthesizing enzymes, their activation scheme, and dependence on exocytosis and actin filaments or microtubules.

Is proper organization of the cytoskeleton required for pollen tube cell wall construction? How do these activities depend on molecular motors? This feature merits considerable attention because the actin fringe presumably under the control of the alkaline band is a key element in vesicle secretion. Does the actin fringe define the secretion zone or does it drive secretory vesicles to the secretion site? What is the role if any of the actin fringe during endocytosis?

Where does the responsibility of myosins end in the transport of secretory vesicles? Hypothetical interactions of pollen tube organelles with both actin filaments and microtubules. Speculatively, organelles move rapidly along actin filaments using myosin as motor protein; organelles may be stopped in specific sites of the pollen tube for finer positioning through dynamic interaction of kinesin with microtubules.

Microtubule-actin interacting proteins are hypothetical; they may help organize cytoskeletal architecture but their role in organelle transport is hard to decipher. The different sized arrows indicate the approximate intensity of motility along actin and microtubules. Google Scholar. Google Preview. Oxford University Press is a department of the University of Oxford.

It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Sign In.

Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Article Contents Abstract. Introduction: the importance of actin filaments. The indecipherable role of microtubules. Multiple myosins? Fast progress on actin Movement Twenty Third - Various - In Chambers Of Pollen (Cassette) through gene cloning and GFP technology.

Dynamics of specific organelle classes. Organelles and vesicles also move along microtubules. Actin-microtubule and related proteins. Conclusions and future prospects. Oxford Academic. Mauro Cresti. Select Format Select format. Permissions Icon Permissions. Abstract Organelle movement is an evident feature of pollen tubes and is essential for the process of tube growth because it enables the proper distribution of organelles and the accumulation of secretory vesicles in the tube apex.

Actin filamentscell growthcytoplasmic movementkinesinmicrotubulesmyosinorganellespollen tube. Open in new tab Download slide. Google Scholar Crossref. Search ADS. Role of microtubules in the movement of the vegetative nucleus and generative cell in tobacco pollen tubes. Magnitude and direction of vesicle dynamics in growing pollen tubes using spatiotemporal image correlation spectroscopy and fluorescence recovery after photobleaching.

The kinesin-immunoreactive homologue from Nicotiana tabacum pollen tube: biochemical properties and subcellular localization. Identification and characterization of plasma membrane proteins that bind to microtubules in pollen tubes and generative cells of tobacco.

Identification and characterization of a novel microtubule-based motor associated with membranous organelles in tobacco pollen tubes.

Pollen tube growth oscillations and intracellular calcium levels are reversibly modulated by actin polymerization. Actin polymerization promotes the reversal of streaming in the apex of pollen tubes. The regulation of actin organization by actin-depolymerizing factor in elongating pollen tubes. Overexpression of an Arabidopsis formin stimulates supernumerary actin cable formation from pollen tube cell membrane.

The dynamic pollen tube cytoskeleton: live cell studies using actin-binding and microtubule-binding reporter proteins. The identification of F actin of the pollen tube and protoplast of Amaryllis belladonna. Germination and early tube development in vitro of Lycopersicum peruvianum pollen: ultrastrucutral features. Fibrous masses and cell and nucleus movement in the pollen tube of Petunia hybrida. Rab11 GTPase-regulated membrane trafficking is crucial for tip-focused pollen tube growth in tobacco.

Interactive computer-assisted position acquisition procedure designed for the analysis of organelle movement in pollen tubes. Del Casino.

Phospholipase D activation correlates with microtubule reorganization in living plant cells. Differential trafficking of Kif5c on tyrosinated and detyrosinated microtubules in live cells. Growing pollen tubes possess a constitutive alkaline band in the clear zone and a growth-dependent acidic tip. Reversible protein phosphorylation regulates the dynamic organization of the pollen tube cytoskeleton: effects of calyculin A and okadaic acid.

Rop GTPase-dependent dynamics of tip-localized F-actin controls tip growth in pollen tubes. A 90 kDa phospholipase D from tobacco binds to microtubules and the plasma membrane.

Putative microtubule-associated proteins from the Arabidopsis genome. The role of cytoskeleton and dictyosome activity in the pulsatory growth of Nicotiana tabacum and Petunia hybrida pollen tubes. Pollen tube growth: coping with mechanical obstacles involves the cytoskeleton.

Pollen tube tip growth depends on plasma membrane polarization mediated by tobacco PLC3 activity and endocytic membrane recycling. Organelle movement and fibrillar elements of the cytoskeleton in the angiosperm pollen tube. Cytochalasin effects on structure and movement in the pollen tube of Iris. Myosin associated with the surface of organelles, vegetative nuclei and generative cells in angiosperm pollen grains and tubes.

Cytoskeletal elements, cell shaping and movement in the angiosperm pollen tube. A gelsolin-like protein from Papaver rhoeas pollen PrABP80 stimulates calcium-regulated severing and depolymerization of actin filaments. SB, a pollen-specific protein from Solanum berthaultiibinds to and bundles microtubules and F-actin. Identification and molecular characterization of myosin gene family in Oryza sativa genome.

The anti-microtubule drug carbetamide stops Nicotiana sylvestris pollen tube growth in the style. Characterization of the translocator associated with pollen tube organelles. Partial purification of myosin from lily pollen tubes by monitoring with in vitro motility assay. Ultrastructure of cytoskeleton in freeze-substituded pollen tubes of Nicotiana tabacum.

Association of actin with cortical microtubules revealed by immunogold localization in Nicotiana pollen tubes. Rho-GTPase-dependent filamentous actin dynamics coordinate vesicle targeting and exocytosis during tip growth. Cytoskeletal motors in Arabidopsis. Sixty-one kinesins and seventeen myosins. Organelle targeting of myosin XI is mediated by two globular tail subdomains with separate cargo binding sites.

Circular F-actin bundles and a G-actin gradient in pollen and pollen tubes of Lilium davidii.

In simple terms, pollen chamber refers to the cavity just above the nucleus in gymnosperms which is the site where pollen accumulates and germinate during ovulation. Jun 01,  · The pollen–stigma interface can differ from species to species as a result of the wide variability in the morphology and content of stigma exudates, exine layers, and pollen coats. Several different methods have been devised to investigate and measure pollen–stigma adhesion (Stead et al., ; Luu et al., a, b; Zinkl et al., Cited by: unique pollen, and until now the analysis methods were different every time. Methods commonly used to determine the quality of pollen are: Staining and counting by microscopy to determine develop-mental stage or viability In vitro or in situ germination of pollen These methods have multiple constraints. Pollen .

pollen levels. Also effective are various types of air-filtering devices. Avoiding Irritants. During periods of high pollen levels, people with pollen allergy should try to avoid unnecessary exposure to irritants such as dust, insect sprays, tobacco smoke, air pollution, and fresh tar or paint. Any of these can aggravate the symptoms of pollen.

For example if 10 each of three smooth pollen grains of 14, 20, and 26 microns diameter were found on a square centimeter in twenty-four hours their concentrations would differ by (Table I) n - x 10 = per cubic yard n - x 70 - 73 per cubic yard n- x - 4: per cubic yard a difference of nearly per cent. ctical office use. Jan 01,  · Furthermore, the pollen of some species (e.g., Populus) may begin to disintegrate even before reaching a deposition site (Davis, ). Pollen Productivity and Dispersal: the Pollen Rain All plants that participate in sexual reproduction produce pollen grains, dispersing them by various mechanisms in an endeavor to reach and fertilize the.

- The air is heavy with pollen and spores. Vision into testing chamber is difficult. - Movement is heard within the chamber. Several different small insect-like creatures are observed. Creatures are seemingly made of plant matter.

a plant with naked seeds that are not enclosed in a protective chamber, such as an evergreen. the female reproductive part of a flower where eggs are produced. pollen fingerprint. the number and type of pollen grains found in a geographic area at a particular time of year. pollen grain. a reproductive structure that contains the male. Jun 06,  · The pressure chambers P1, P2, P3 and P4 are respectively supplied with a pressurized fluid such as pressurized air or evacuated via fluid channels , , and The pressure chamber P1 in the center is circular and the pressure chambers P2, P3 and P4 are annular. The pressure chambers P1, P2, P3 and P4 are concentrically arranged.

a plant with naked seeds that are not enclosed in a protective chamber, such as an evergreen. the female reproductive part of a flower where eggs are produced. pollen fingerprint. the number and type of pollen grains found in a geographic area at a particular time of year. pollen grain. a reproductive structure that contains the male.


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  1. Jan 01,  · Furthermore, the pollen of some species (e.g., Populus) may begin to disintegrate even before reaching a deposition site (Davis, ). Pollen Productivity and Dispersal: the Pollen Rain All plants that participate in sexual reproduction produce pollen grains, dispersing them by various mechanisms in an endeavor to reach and fertilize the.
  2. Bihler H, Eing C, Hebeisen S, Roller A, Czempinski K, Bertl A () TPK1 is a vacuolar ion channel different from the slow-vacuolar cation channel. Plant Physiol – [PMC free article] Blatt MR () Cellular signaling and volume control in stomatal movements in .
  3. B () Twenty-Eight Report of the State Entomologist of Connecticut Britton, W.E. B () Soil Reaction and Liming As Factors in Tobacco Production in Connecticut. Morgan, M.F. B () The Thirty-Third Report on Food Products and the Twenty-First Report on .
  4. Jan 22,  · Pollen-mediated gene flow at a distance could allow the spread of rare herbicide-resistant alleles and favor the evolution of multiple herbicide-resistant biotypes through the accumulation of different resistant genes in an individual weed or weed population. From the Nebraska Crop Management Conference Proceedings.
  5. Ragweed 3pollen in grains/m was counted daily. Twenty-six of these subjects were challenged to short ragweed pollen in a chamber outside the natural season for 3 hours/day for up to 4 days. Symptoms and pollen counts were recorded at 30 minute intervals. Symptomatology in the chamber and natural season.
  6. - The air is heavy with pollen and spores. Vision into a testing chamber is difficult. - Movement is heard within the chamber. Several different small insect-like creatures are observed. Creatures are seemingly made of plant matter.
  7. Jun 01,  · The pollen–stigma interface can differ from species to species as a result of the wide variability in the morphology and content of stigma exudates, exine layers, and pollen coats. Several different methods have been devised to investigate and measure pollen–stigma adhesion (Stead et al., ; Luu et al., a, b; Zinkl et al., Cited by:
  8. Jun 06,  · The pressure chambers P1, P2, P3 and P4 are respectively supplied with a pressurized fluid such as pressurized air or evacuated via fluid channels , , and The pressure chamber P1 in the center is circular and the pressure chambers P2, P3 and P4 are annular. The pressure chambers P1, P2, P3 and P4 are concentrically arranged.