In this species, paraphyses are senesced, but retain functional membranes. Spores grey are mature. Once the walls of the spores are formed, the nuclei are no longer in contact with the epiplasm and are unlikely to direct development. Therefore, all gene expression related to ascus formation probably occurs before the formation of spore walls. Ion channels are in place small rectangles on left side of the ascus.
Pore is present at tip. Paraphyses are fully expanded. Forcible discharge of ascospores is an important part of basic fungal biology, but the mechanism is poorly understood. Ascospores initiate the disease cycle for a great many plant pathogens. Thus, in practical terms, understanding ascospore dispersal will contribute to understanding of disease.
Interestingly, despite the fact that several known human pathogens fall into the Pezizomycotina, there are no known human pathogens that rely on ascospore discharge as an epidemiological component.
There is no obvious reason for this disparity. It may be artificial due to the very small number of known fungal human pathogens about in total when compared with fungal plant pathogens [more than species; Agrios, ].
In addition, a trend toward suppression of the sexual cycle may exist in human pathogens, which may suppress dependence on sexual propagules Heitman, However, sexual cycles may be present and not yet appreciated epidemiologically. For instance, the recent discovery in pigeon droppings of a sexual stage of Cryptococcus neoformans , although not an ascomycete, has strong implications for the epidemiology of that disease Nielsen et al. The most effective controls for any disease are those that interrupt the life cycle.
Elimination of ascospore distribution would be a very effective control for ascomycetous plant pathogens, but most effective on those that use ascospores as their primary inoculum e.
Venturia inaequalis , the apple scab pathogen; Sclerotinia sclerotiorum , white mold of beans and other vegetables; G. More knowledge of the basic mechanism and the variations throughout the Kingdom Fungi should facilitate the design of controls targeting this life cycle stage. Steven Vogel is thanked for sharing his insights on the biomechanics of ascospore discharge and Wayne Trail for discussions on the physics of springs.
Marlene Cameron rendered Figs. Agrios G. Google Scholar. Google Preview. Aylor D. Anagnostakis S. Phytopathology 81 : — Beckett A. Ascomycete Systematics. The Luttrellian Concept Reynolds D. Springer-Verlag , New York. Bellemere A. Revue Mycologie 41 : — Berbee M. Taylor J. Molec Phylogenet Evol 1 : 59 — Longmans, Green and Co , London. Czymmek K. Klomparens K. Deacon J. Blackwell , Oxford. DeBary A. Clarendon Press , Oxford. Fischer M. Cox J. Davis D.
Wagner A. Taylor R. Huerta A. Money N. Fungal Genet Biol 41 : — Funk A. Shoemaker R. Can J Bot 45 : Hallen H. Huebner M. Gueldener U. Shiu S. Trail F. Fungal Genet Biol , in press. Heitman J. Curr Biol 16 : R — R Hung C. Can J Bot 55 : — Ingold C. University Press , Oxford.
The Fungus Spore. Colston Papers , Vol. University of Bristol , London. James T. Kauff F. Schoch C. Nature : — Lachance M. Miranda M. Miller M.
Phaff H. Can J Microbiol 22 : — Landvik S. Schumacher T. Eriksson O. Moss S. Mycol Res : — Minter D. Cannon P.
Points indicate projectile positions at 10 ms intervals. The truncated trajectories of A. Inertia is more significant for the flight of the larger sporangia of P. To enrich our picture of the discharge processes in these fungi, we used quantitative spectroscopic methods to determine the chemical composition of the ascus sap in A.
The minuscule quantity of fluid ejected with the discharged spores of B. In the three species examined, hydrostatic pressure was generated by the combined osmolality of sugar alcohols and inorganic ions. The dominant sugars were mannitol, glycerol, erythritol, and pinitol, but the relative concentrations varied between species.
In the ascus sap of A. The combined osmolality of these compounds will generate a turgor pressure of 0. The most abundant sugars in P. The corresponding turgor pressure estimate from the spectroscopic data was 0. Finally, published pressure measurements and estimates from spectroscopic data for A.
In this paper we have documented a series of remarkable feats of natural engineering, based on universal aspects of fungal structure and metabolism. Unusual features of these mechanisms include the controlled and rapid rupture of the pressurized squirt guns that allow the nearly instantaneous release of energy and discharge of the spores and sporangia.
The match between predicted and measured flights also suggest that very little of this energy is lost to friction during the earliest phases of spore release.
The launch speeds of the species in this study are likely to be among the fastest among any fungi because their coprophilous ecology has demanded much longer ranges than those necessary for the dispersal of species that need only escape boundary layers. Hamann University of Frankfurt , were treated in the same way. Analysis of digital images was performed with VideoPoint v.
Wet paper towels were placed in the box to maintain high humidity. Numbered microscope slides were placed in straight paths beneath the culture plates to catch spores after horizontal discharge from their phototropic asci [11].
Spores on each slide were counted to produce spore density versus distance plots. Sap expelled from asci and sporangiophores was collected on the underside of Petri dish lids above sporulating cultures. The lids were air dried and the number of spores captured on each lid was counted under a dissecting microscope.
Measurements of the mean sap volume shot from the asci or sporangiophores of each species were made from light microscopic images of mature asci; these values were multiplied by the number of spore clusters Water soluble ions and organic compounds in the sap were harvested by swirling 1 mL of sterile distilled water in the inverted lids.
Aqueous extracts were then transferred to microfuge tubes. Most of the spores remained attached to the lids, but spores that were transferred with the aqueous extracts were removed by centrifuging at 10, g for 5 min. Samples were derivatized to produce alditol acetates of the sugar alcohols [21].
The concentrations of the major osmolytes were determined from standard curves produced by plotting the log of the concentration of standards versus the log of the ion intensity of a characteristic ion fragment for each osmolyte for glycerol, and for mannitol. Samples harvested from Petri dish lids were diluted to 10 mL and ion concentrations were determined from standard curves produced from dilutions of ion standards in nitric acid Inorganic Ventures, Inc.
Spore flight trajectories were modeled in two ways. This vector force, combined with Newton's second law, can be analytically integrated to yield expressions for the x - and y -positions of the spore as functions of time which can be plotted parametrically to determine the spore trajectory.
An analytical expression for the range of the projectile can also be derived. Spore trajectories were also calculated using a more complicated, quasi-empirical model for the drag which has been proposed for particles moving through fluids at the onset of turbulence, a regime characterized by Reynolds numbers between 1 and 1, [16].
This expression can be combined with Newton's second law but cannot be integrated analytically. Instead, it must be numerically integrated using any standard numerical integration algorithm. In some cases, acceleration was computed from the position of the projectiles in multiple video frames, but in others, the accelerations were accomplished so swiftly that we estimated acceleration from the observed change in velocity during the time interval between two successive frames.
Once again, we'll start with a common mushroom growing in the middle of a field. When a spore is mature it is forcibly shot from the basidium, into the air space between the gills.
While the spore is ejected horizontally with considerable force up to 25, times the force of gravity , air resistance stops the spore in a fraction of a millimetre. The air in the space between two gills is still, so after coming to a stop the only influence on the spore is gravity and the spore falls downward.
Once the spore has fallen below the bottom edge of the mushroom cap, and is clear of the gills, it strikes air that is not still. Even on what looks like a windless day, there are always slight breezes. While a human may not feel them, they are usually strong enough to be felt by a spore that is only about a hundredth of a millimetre long. These micro-breezes may pick up the spore and carry it higher into the air and away from the parent mushroom.
The spore may come to rest a metre or a kilometre or even further away from the mushroom. It may come to rest on a grass blade, be eaten by a kangaroo that then moves away a few more kilometres and deposits it in a dropping. Basidiomycetes with similar mechanisms are the boletes , polypores , paint fungi , stereoid fungi , coral fungi and jelly fungi.
A basidiomycete with a very different active method of spore dispersal is the Cannonball Fungus Sphaerobolus stellatus. The "egg" inside the two millimetre diameter cup contains a mass of spores and is forcible flicked out of the cup.
In a cup fungus the surface of the cup is lined with the spore-producing asci. As the spores in an ascus are maturing, fluid pressure builds up in the ascus. At maturity, the pressure is sufficient to force the spores out through the top of the ascus. In some species of cup fungi there is a little lid at the top of the ascus which is forced open to allow the spores out. The mechanism has long been thought to be driven by turgor pressure within the extending ascus; however, relatively little genetic and physiological work has been carried out on the mechanism.
Recent studies have measured the pressures within the ascus and quantified the components of the ascus epiplasmic fluid that contribute to the osmotic potential.
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