POLLEN MORPHOLOGY AND DETAILED STRUCTURE OF FAMILY COMPOSITAE,TRIBE CICHORIEAE. I. SUBTRIBE STEPHANOMERIINAE

A survey of pollen morphology in 20 species representing the 11 genera of the North American subtribe Stephanomeriinae by light, scanning electron, and transmission electron microscopy revealed 10 of the 11 genera to have echinate, tricolporate pollen grains, Lygodesmia being the only genus with echinolophate pollen. Sectioned exines of most of the species examined are similar, being composed of ektexine and endexine. The ektexine surface is composed of spines which typically have globose perforate bases. A cavus occurs as a separation between the basis (foot layer) and the columellae in all of the genera examined except Chaetadelpha. Pollen of the two species of Glyptopleura were found to be strikingly different in exomorphology. Pollen of the putatively self-fertile G. marginata has much shorter spines than the closely related G. setulosa. Atrichoseris, Anisocoma, Calycoseris, Glyptopleura, Pinaropappus, Prenanthella, and most species of Malacothrix have pollen which lack paraporal ridges. The remaining genera, Chaetadelpha, Lygodesmia, Rafinesquia, and Stephanomeria have well-developed ridges of fused spine bases around the apertures. Pollen characters, particularly those of the aperture region, have been found to be systematically useful in the subtribe, therefore acetolyzed material gives more useful information than untreated pollen.     

CHARACTERIZATION OF POLLEN ANTIGENS FROM AMBROSIA L. (COMPOSITAE) AND RELATED TAXA BY IMMUNOELECTROPHORESIS AND RADIAL IMMUNODIFFUSION

The pollen antigens of various Ambrosia and related species were studied to learn whether substances closely related to antigen E (the major allergen of Ambrosia artemisiifolia) were present. After conventional immunoelectrophoresis, pollen extracts from six Ambrosia species each produced at least one pronounced precipitin line with antiserum for purified antigen E. Electrophoretic mobility was the same for several species (A. artemisiifolia, A. bidentata, A. psilostachya, and A. trifida) but was relatively lower for A. acanthicarpa and A. ambrosioides. Precipitin rings were also produced when pollen extracts of the various Ambrosia species were subjected to radial immunodiffusion in agarose which contained antiserum for purified antigen E. There was great variation among the Ambrosia species with respect to precipitin ring diameters. The variation may be due to differences among species in content of the antigen E-like substances or to altered interaction with the immobilized antibody. Crossed (2-dimensional) immunoelectrophoresis was shown to be useful for characterizing Ambrosia pollen antigens. Pollen extracts from A. artemisiifolia produced eight pronounced precipitin bands and at least eight faint, relatively fast-moving bands after crossed immunoelectrophoresis with antiserum against a whole pollen extract from the same species. One of the pronounced bands contained antigen E.     

COMPARATIVE POLLEN MORPHOLOGY AND TAXONOMIC AFFINITIES IN CYCADALES

Scanning and transmission electron microscopy of pollen grains of 29 species, representing the ten extant genera of Cycadales, has provided valuable insight into their relationships. Pollen grains of these taxa are boat-shaped, monosulcate, and bilaterally symmetrical. They range from narrowly to widely elliptical or subcircular when viewed distally, and have an exine surface of psilate, foveolate, or fossulate. Pollen wall ultrastructure of Cycadales is typically tectate with alveolate∗∗∗spongy exine. The nexine is laminated in all genera. Nexine 1 (footlayer) is present in most species as a thin and often discontinuous layer. There is consistent variation in thickness of the sporoderm layers among the genera but relative uniformity within them. Pollen characteristics are well correlated with macro- and micromorphological features, chromosome numbers, geographical distribution, and postulated pollination mode. A close affinity between Encephalartos, Lepidozamia, and Macrozamia is recognized. Pollen characteristics of the genus Bowenia show some similarity with those of the latter group. Except for two species of Macrozamia which are narrowly elliptic, all of the genera have widely elliptic pollen and share a psilate exine surface and the thinnest sexine with nearly identical arrangement of alveoli. Pollen grains of the species in the genus Dioon exhibit a unique morphology but are more similar to Stangeria than they are to those of taxa in Zamiaceae. The circular outline of the grains and the foveolate exine surface are characters shared by these two genera, but several morphological features distinguish Dioon from Stangeria. Ceratozamia and Zamia share a widely elliptic shape, foveolate exine surface and nearly identical sexine, as well as morphological features and chromosome numbers. They differ from Microcycas in sexine thickness, gross morphology and chromosome numbers. The pollen grains of Cycas circinalis and C. revoluta differ in size and structure of the sexine from all other genera and from each other, substantiating their distinct subgeneric delimitations.     

PROTANDRY,INCOMPATIBILITY, AND SECONDARY POLLEN PRESENTATION IN CEPHALANTHUS OCCIDENTALS (RUBIACEAE)

Cephalanthus occidentalis L. is protandrous and presents pollen secondarily on the stigma surface. Because self-pollen is present on the stigma, the degree of selling vs. outcrossing in this species will depend on 1) the phenology of pollen presentation and stigma receptivity; 2) whether the species is self-incompatible; and 3) the rates of self vs. crossed pollen tube growth. This study describes floral morphology and phenology, self-incompatibility, and pollen tube growth rates in self- and crosspollinations of C. occidentalis. Light and scanning electron microscopy were used to study stigma morphology after flower opening, while controlled pollinations tested for incompatibility. Stigmas were unreceptive initially but became receptive by the second day after flower opening. Ninety-two percent of cross-pollinated flowers set fruit, compared to 12% fruit set in self-pollinations. Pollen tubes from selfed and out-crossed pollen initially had similar growth rates. Out-crossed pollen tubes began to grow rapidly ca. 5 hr after pollination of a receptive stigma, whereas selfed pollen tubes ceased growth or grew slowly after this time. Pollen tubes from out-crossed pollen grew the length of the style within 24 hr after pollination, while selfed pollen tubes were inhibited at the stigma-style junction. Our results indicate that C. occidentalis has selfincompatibility, in addition to protandry and secondary pollen presentation. Protandry allows removal of self-pollen from the unreceptive stigma, while self-incompatibility prevents fertilization by unremoved self-pollen.     

POLLEN MORPHOLOGY AND PLANT TAXONOMY OF WHITE OAKS IN EASTERN NORTH AMERICA

An evaluation of possible approaches to fossil oak pollen identification utilized scanning electron microscopy to examine exine-surface features of 171 collections, representing 16 Quercus subgenus Lepidobalanus species and varieties of eastern North America. Twenty qualitative pollen morphological characters were defined and tabulated for each of 217 pollen grains. The data were subjected to cluster analysis and cluster diagrams were compared with published white oak taxonomy. Pollen morphology and plant taxonomy compared well in series of the subgenus Lepidobalanus due primarily to consistency of character presence and absence within species and varieties. Pollen morphology of white oaks appears to reflect plant systematics above the species level. Use of routine SEM analysis to identify series of white oaks among fossil pollen grains likely will yield valid results.     

POLLEN MORPHOLOGY OF THE CHLORAEINAE (ORCHIDACEAE: DIURIDEAE) AND RELATED SUBTRIBES

Pollen organization and morphology of the South American Chloraeinae (Orchidaceae) was examined by scanning electron microscopy and compared with that of the remainder of the otherwise Australasian Diurideae. All five genera of the Chloraeinae, Bipinnula, Chloraea, Codonorchis, Gavilea, and Geoblasta, and at least one genus from each of the other subtribes were sampled. The Australasian Diurideae are diverse in pollen organization and morphology. The two genera of the Acianthinae, Corybas and Acianthus, have very different pollen and their classification is questioned. Monad pollen organization of Pterostylis (Pterostylidinae) is reinterpreted as primitive and not secondarily derived. Pollen of the Chloraeinae is uniform in exine morphology and organization. Most species sampled have reticulate pollen which tends to be foveolate distally. The basic pollen unit of all Chloraeinae is the tetrad, except Codonorchis which possesses monads. Pollen morphology and organization of the Chloraeinae is most similar to the Caladeniinae, which supports the contention that the Chloraeinae including Codonorchis should be retained in the Diurideae.     

POLLEN MORPHOLOGY AND SYSTEMATICS OF SIPHONOGLOSSA SENSU LATO (ACANTHACEAE)

Pollen morphology of 15 species of Siphonoglossa and of two closely related groups was investigated. Two tribal-specific pollen types are found within Siphonoglossa sensu lato suggesting that the genus is artificial, composed of taxa belonging in several genera among two tribes (subtribes sensu Bremekamp) of Acanthaceae. Five taxa currently included in an informal subgeneric category of Siphonoglossa have tricolporate, prolate pollen (termed Type I) that is characteristic of Odontonemeae (= Odontoneminae, Justicieae). Pollen of the remaining taxa, belonging in two formal sections of the genus, are mostly 2-porate, bilateral (Type II) with a sexine sculpturing characteristic of Justicieae (= Justiciinae). Pollen of section Siphonoglossa is rather uniform, 2-porate, bilateral with lolongate pores, and seem to delimit a natural group. Taxa of section Pentaloba have a more heterogeneous pollen morphology, mostly 2-porate, bilateral with lalongate pores. Controversial aspects of the interpretation of pollen morphology in Justiciinae are presented and their relevance to this study are examined. Hypothetical trends in the evolution of pollen of Justiciinae are discussed and the application of pollen morphology to taxonomy of the genus is presented, including a recommendation for narrowing the generic concept of Siphonoglossa to the taxa of the type section.     

POLLEN TUBE GROWTH AND INCOMPATIBILITY FOLLOWING INTRA- AND INTER-SPECIFIC POLLINATIONS IN LILIUM LONGIFLORUM

The growth of pollen tubes of a sampling of Lilium species in styles of L. longiflorum incubated at 24 C for 48 hr after pollination indicated two types of interspecific incompatibility. Pollen tubes of two self-compatible species of section Leucolirion, the section including L. longiflorum, stopped growth abruptly upon reaching the stylar canal, were of abnormal morphology, and were incapable of continued growth with longer incubation. Pollen tubes of self-compatible or self-incompatible species of sections Sinomartagon, Pseudolirium, Liriotypus, and Daurolirion approached but did not exceed the length of intraspecific incompatible pollen tubes in styles of L. longiflorum. Pollen tube morphology was normal and tubes were capable of continued growth with additional incubation. Unilateral interspecific incompatibility occurred in reciprocal crosses between self-incompatible L. longiflorum and self-compatible L. regale and L. formosanum, but exceptions occurred in Aurelian hybrids. Incubation of interspecifically pollinated L. longiflorum styles at 39 C, which removes the self-incompatibility reaction, had no effect on interspecific incompatibility.     

FINE STRUCTURE OF MISTLETOE POLLEN. III. LARGE-FLOWERED NEOTROPICAL LORANTHACEAE AND THEIR AUSTRALIAN RELATIVES

Pollen of all large-flowered neotropical loranthaceous genera and related Australian taxa (Nuytsia, Atkinsonia) were examined in the light, scanning, and transmission electron microscopes. Trilobate, deeply concave, peroblate or oblate pollen shapes are basic within the complex; triangular, slight convex, suboblate shapes are more derived features. The non-fixiform pollen of Atkinsonia is unique within the family. Most of the large-flowered genera possess exclusively syncolpate aperture types. However, among Psittacanthus species tricolpate, diplosynrugate and diplorugate apertures are also present, representing derived types for the complex. The inaperturate pollen of Atkinsonia appears to have developed independently within the family. Pollen sculpturing is typically non-uniform, i.e., there are pronounced sculpturing differences in polar and equatorial regions. Uniformly sculptured pollen is restricted to Atkinsonia, Ligaria and some species of Psittacanthus. Ultrastructurally, most exine modifications have occurred in the equatoral ektexine. Here the basic organization ranges from essentially columellaless to columellate, the latter the more derived condition. Endexine is typically thick and stratified in polar areas, thin and lamellate in peripheral and apertural regions. Similar pollen morphologies of Nuytsia and Gaiadendron support the idea of a transoceanic evolutionary connection between the Old and New Worlds. Pollen characters show Gaiadendron to be the most primitive and Psittacanthus the most advanced among the large-flowered neotropical genera.     

THE POLLINATION ECOLOGY OF ASTRAGALUS CIBARIUS AND ASTRAGALUS UTAHENSIS (LEGUMINOSAE)

Astragalus cibarius and A. utahensis are common perennial species of a widespread legume genus. The pollination of Astragalus has been briefly discussed in the literature, but little work has been done on species in the intermountain West. This study was conducted from 1970–1973 in Utah with mixed and single species populations. The flowers of both species were homogamous and papilionaceous, but the species were different as to color, size, and ultraviolet reflectance. Astragalus cibarius usually flowered 10 days ahead of A. utahensis, but both species flowered earlier than most other plants in the community. Bagging experiments indicated both species were strongly allogamous. Exclosure studies indicated both species relied on insects as pollen vectors. Of the 44 insect species which were observed visiting flowers, only 14 carried Astragalus pollen, and the pollinator fauna varied between study sites. Pollen quantities and distributions on Diptera and Coleoptera indicated a poor potential for pollination. Floral structure, pollen distribution and quantity, and behavior implied that large bees of the families Apidae and Anthophoridae were the primary pollinators. These bees visited only one species of Astragalus when the plants occurred in mixed populations; this constancy may have been related to relative flower abundance. Non-pollinating floral foragers affect other phases of Astragalus life history.     

STAMINATE BLOOM DATE AND TEMPERATURE RESPONSES OF POLLEN GERMINATION AND TUBE GROWTH IN TWO WALNUT (JUGLANS) SPECIES

Pollen was collected from ten cultivars of Juglans regia and three cultivars of the later-blooming species, J. nigra. Extensive phenological data were available for these cultivars. Cultivars were chosen on the basis of staminate bloom date to include the earliest and latest blooming individuals available and a representative range throughout the bloom season. Mean staminate bloom dates for the cultivars examined covered a period of 46 days over which time mean daily temperatures rose 6 C. In order to determine if adaptations to temperature were expressed by the gametophyte generation, pollen was subjected to controlled temperatures from 5 to 40 C in 2 to 4 C increments and analyzed for germination percentages and pollen tube elongation. A positive relationship was found for pollen germination percentage and mean staminate bloom date such that earlier blooming individuals showed lower minimum temperature thresholds for germination, and optimum temperature for pollen germination was positively correlated with mean staminate bloom date. Differences in pollen tube growth, determined separately from hydration and germination responses, were less clear. Most J. regia clones had lower minium temperature thresholds for growth than the J. nigra clones, but there was no clear relationship to earliness of bloom within the species. No differences were discerned in optimum temperatures for pollen tube growth either between the two species or within species.     

INTERFERENCE THROUGH IMPROPER POLLEN TRANSFER IN MIXED STANDS OF IMPATIENS CAPENSIS AND I. PALLIDA (BALSAMINACEAE)

Mechanisms of interference through improper pollen transfer are described for sympatric populations of the simultaneously flowering annuals Impatiens capensis and I. pallida. Stigmas of both Impatiens species are receptive to conspecific pollen from the time of androecium disarticulation until after perianth drop. Pollen of I. pallida adheres to, and germinates on, the stigmas of I. capensis. The pollen tubes reach the ovules but do not fertilize them. In contrast, pollen of I. capensis adheres poorly to I. pallida stigmas and fails to germinate. Pollen mixtures of the two Impatiens species cause a much greater reduction in fruit set in I. capensis than in I. pallida. Despite the interference of I. pallida pollen, I. capensis persists in mixed populations with I. pallida by: 1) possessing stigmas receptive to pollen throughout the female phase; 2) having the ability to produce a full seed complement via one pollination event; and 3) possessing cleistogamous flowers to ensure sexual reproduction.     

Pollen as a marker for migration of Helicoverpa armigera and H. punctigera (Lepidoptera: Noctuidae) from western Queensland

Abstract Pollen carried on the probosces of Helicoverpa punctigera (Wallengren) and H. armigera (Hübner) trapped in western Queensland and in cropping areas of eastern Australia in September 1989 and 1990 was identified by scanning electron microscopy. Ninety-five per cent of moths carried pollen. A total of 19 morphological pollen species’, representing 14 plant families, was found. Up to six pollen species were found on individual moths, and 61% carried more than one. Pollen from plants unsuitable for larval survival was common. Pollen loads generally reflected the abundance of locally flowering plants, but there were exceptions which suggested migration. Pollen of Ptilotus (Amaranthaceae), Velleia (Goodeniaceae) and Eremophila (Myoporaceae), and the Asteraceae (Tubuliflorae) were found on moths trapped in the east. These plants either did not occur in the areas where the moths were caught, or did not flower there at the time the moths were caught. However, they were abundant in possible source areas such as western Queensland. Among moths caught in eastern regions, 30% of H. punctigera and 18% of H. armigera carried pollen from such plants. The value and limitations of moth-borne pollen as a marker for migration are discussed.     

POLLEN MORPHOLOGY IN THE GENUS ERYTHRONIUM (LILIACEAE) AND ITS SYSTEMATIC IMPLICATIONS

Pollen morphology was examined in 40 samples from 19 species in the genus Erythronium (Liliaceae) using scanning (SEM) and transmission electron microscopy (TEM). Pollen grains are monosulcate monads, except for a plant of E. oregonum which has dyad grains. North American and European species are characterized by reticulate exine sculpture composed of various degrees of wavy muri and variably-sized lumina. The most distinctive feature of exine sculpture in the genus is exhibited by the Asian species E. japonicum, which has a unique reticulate pattern composed of striate muri and a distinctive exine structure without columellae. The distinctness of E. japonicum pollen suggests that it has specialized in isolation from species in North America and Europe.     

Exposure to water increased pollen longevity of pondweed (Potamogeton spp.) indicates different mechanisms ensuring pollination success of angiosperms in aquatic habitat

Pollen longevity in seven Potamogeton species representing different pollination systems (anemophily, epihydrophily and hydroautogamy) was assessed both under aerial condition and in contact with water to investigate how water impacts the sexual reproduction in these aquatic taxa. Stainability of pollen with MTT was considered as an indicator of pollen viability. The half-life of pollen longevity was calculated using exponential decay regression. Overall, pollen viability decreased relatively rapidly with time. Pollen grains of obligate anemophilic species had lower initial viability and shorter half-lives than those of facultative anemophilic species. Pollen in these latter species may take more time to reach the stigma. The pollen of Potamogeton may be categorized as partially hydrated pollen owing to its generally spherical shape and lack of furrows, rapid loss of viability, and fast pollen tube initiation. The half-life is positively correlated with pollen size. Smaller-sized grains are at greater risk of desiccation than larger grains. In contrast with the situation observed in most terrestrial angiosperms, contact with water increases pollen longevity in Potamogeton species. In our present study the half-lives of pollen longevity of Potamogeton species in which the pollen had come into contact with water (mean of 10.65 h) were markedly higher than those under aerial conditions (mean of 5.79 h, t = 2.622, P = 0.039). The results of our study contradict a widely held belief that water is detrimental to pollen viability in angiosperms and furthermore indicate that close proximity to water results in selection for wettability. The transition to a hydrated status together with its morphology, make Potamogeton pollen more adapted to the aquatic environment and thus serves to ensure reproductive process. Results of our present study may have direct implications for understanding the evolution of the sexual reproductive system in aquatic angiosperms.     

Pollen morphology and localization of Ni in some Ni-hyperaccumulator taxa of Alyssum L. (Brassicaceae)

Pollen morphology of seven Alyssum L. taxa growing on serpentine soils in different places in the European Mediterranean macrobioclimate territory were studied, described and compared. Cluster analysis was performed to show similarity between species and their populations. The shape of the pollen grains varies among the species and among the grains within the same anther. The pollen grains are 3-colpate, prolate, with long and narrow colpi reaching the poles. The ornamentation of the exine varies from micro-reticulate to reticulate between the species. Pollen sterility/fertility was also calculated. The highest percentage of sterile pollen (73.76%) was calculated for Alyssum murale subsp. murale and the lowest (9.54%) for A. bertolonii subsp. bertolonii. All species are representatives of sect. Odontarrhena (C.A. Meyer) Koch well known as Ni-hyperaccumulators. Nickel and other elements present in pollen and stamen were studied by inductively coupled plasma-mass spectrometry. The stamen parts of all species were micromorphologically analyzed by scanning electron microscopy coupled to an energy-dispersive X-ray probe. Accumulation of Ni was detected in the stamens of all studied species and rarely in the pollen grains. The distribution patterns of Ni were similar among the species examined.     

TRACKING POLLEN FLOW OF SOLANUM ROSTRATUM (SOLANACEAE) USING BACKSCATTER SCANNING ELECTRON MICROSCOPY AND X-RAY MICROANALYSIS

A technique using micronized metal powders was developed for both general labeling of pollen and marking of individual pollen grains. After labeling, pollen flow is analyzed by the use of backscatter scanning electron microscopy and X-ray microanalysis. To test the efficiency and efficacy of the technique, we assessed differences in pollen distribution in Solanum rostratum, an enantiostylous species with dimorphic anthers which are putatively feeding and pollinating anthers. Pollen from each set of anthers was labeled using different micronized metal powders. We could not confirm the differentiation of functional anthers in S. rostratum. This technique provides an efficient and convenient method for tracking pollen movement within and between flowers, and anthers within a single blossom can be differentially marked.     

POLLEN TRANSFER BY NATURAL HYBRIDS AND PARENTAL SPECIES IN AN IPOMOPSIS HYBRID ZONE

Models of hybrid zones differ in their assumptions about the relative fitnesses of hybrids and the parental species. These fitness relationships determine the form of selection across the hybrid zone and, along with gene flow, the evolutionary dynamics and eventual outcome of natural hybridization. We measured a component of fitness, export and receipt of pollen in single pollinator visits, for hybrids between the herbaceous plants Ipomopsis aggregata and I. tenuituba and for both parental species. In aviary experiments with captive hummingbirds, hybrid flowers outperformed flowers of both parental species by receiving more pollen on the stigma. Although hummingbirds were more effective at removing pollen from anthers of I. aggregata, hybrid flowers matched both parental species in the amount of pollen exported to stigmas of other flowers. These patterns of pollen transfer led to phenotypic stabilizing selection, during that stage of the life cycle, for a stigma position intermediate between that of the two species and to directional selection for exserted anthers. Pollen transfer between the species was high, with flowers of I. aggregata exporting pollen equally successfully to conspecific and I. tenuituba flowers. Although this study showed that natural hybrids enjoy the highest quality of pollinator visits, a previous study found that I. aggregata receives the highest quantity of pollinator visits. Thus, the relative fitness of hybrids changes over the life cycle. By combining the results of both studies, pollinator-mediated selection in this hybrid zone is predicted to be strong and directional, with hybrid fitness intermediate between that of the parental species.     

Pollen competition and environmental effects on hybridization dynamics between Phlox drummondii and Phlox cuspidata

Pollen competition between species strongly influences hybridization dynamics in plants. By performing single- and mixed-donor pollinations, we show that soil Ca alters the outcome of interspecific pollen competition in the annual Phlox hybrid system of Phlox cuspidata and P. drummondii. In the absence of interspecific pollen competition, heterospecific pollen siring success of both species was influenced most strongly by the maternal growth environment, such that hybridization was facilitated when heterospecific pollen was deposited on stigmas of maternal plants growing in high Ca soils. When heterospecific pollen was forced to compete against conspecific pollen, however, the maternal growth environment did not influence hybridization, but the environmental origin of heterospecific pollen did, and this effect depended on the maternal species. Pollen of P. drummondii was more effective at outcompeting P. cuspidata pollen and preventing hybridization in P. drummondii dams when P. cuspidata pollen was derived from low Ca. Pollen competition within pistils of P. cuspidata was unaffected by pollen Ca environment. In situations in which P. cuspidata grows in lower soil Ca than P. drummondii, as has been documented in one population, these results suggest that the competitive ability of heterospecific pollen will be diminished by environmental effects of soil Ca. Thus, the environment in which pollen develops can influence interspecific pollen competition and hybridization frequency.     

Pollen morphology and its relation with meiotic irregularities in ten species of Campuloclinium (Eupatorieae,Asteraceae)

Pollen grains of ten species of Campuloclinium (Eupatorieae, Asteraceae) are described and illustrated using light and scanning electron microscopy. The species included in this study are C. burchelli, C. campuloclinioides, C. chlorolepis, C. hirsutum, C. irwinii, C. macrocephalum, C. megacephalum, C. parvulum, C. purpurascens and C. riedelli. Pollen grains of Campuloclinium are typically radially symmetric, echinate, tectate, oblate-spheroidal to prolate-spheroidal (P/E ratio: 0.94–1.10). Pollen is mostly triaperturate, but tetraaperturate or biaperturate pollen also occurs in some species. The pollen diameter was highly variable ranging from 10.54 µm to 36.18 μm. The significance of the variation in type and size of pollen is discussed in relation to diverse meiotic abnormalities and possible reproductive apomictic processes within the polyploid species.