Male Cones Research Articles

Revision of the New World cycad weevils of the subtribe Allocorynina, with description of two new genera and three new subgenera(Coleoptera: Belidae: Oxycoryninae).

The taxonomy of the weevils inhabiting male cycad cones in the New World is reviewed. All species belong in a single subtribe, Allocorynina, of the family Belidae, subfamily Oxycoryninae and tribe Oxycorynini and are known to develop only in cones of the cycad genera Dioon and Zamia. Most species of Rhopalotria Chevrolat develop in male cones of Zamia ranging from Mexico, Belize, the Caribbean (Cuba, Isle of Youth, Cayman Islands, Jamaica and the Bahamas) to southern Florida, and one species in those of Dioon spinulosum in Mexico. Rhopalotria consists of three previously described species, two previously described genus-group names (treated herein as subgenera) and four new species described herein: subgenus Allocorynus Sharp with R. calonjei n.sp., R. furfuracea n.sp., R. mollis (Sharp) and R. vovidesi n.sp., and the nominate subgenus Rhopalotria with R. dimidiata Chevrolat, R. meerowi n.sp. and R. slossoni (Schaeffer). The species of Parallocorynus Voss develop only in cones of Dioon in Mexico, and the genus consists of one previously described species, the nominate subgenus and three new subgenera and 11 new species described herein: subgenus Dysicorynus n.subg. with P. andrewsi n.sp. and P. sonorensis n.sp., subgenus Eocorynus n.subg. with P. chemnicki n. sp. and P. schiblii n.sp., subgenus Neocorynus n.subg. with P. iglesiasi n.sp. and P. inexpectatus n.sp., and the nominate subgenus Parallocorynus with P. bicolor (Voss), P. gregoryi n.sp., P. jonesi n.sp., P. norstogi n.sp., P. perezfarrerai n.sp. and P. salasae n.sp. Two new genera are described, Protocorynus with one new species in Honduras, P. bontai, and Notorhopalotria with four new species ranging from Costa Rica to Colombia, N. montgomeryensis, N. panamensis, N. platysoma and N. taylori. Keys to genera, subgenera and species are provided. All of these weevils are believed to be involved in pollination of their host cycads.

Hormonal balance in apical meristems of Scots pine shoots as a very early symptom of flower sex differentiation

The investigations were conducted on the embryonic shoots which were taken at the stage just before the start of the elongation of the last year formed embryonic shoot; it means long time before male and female cone primordia initiation. The results point out to the existence of distinctive balance of auxins to gibberellins in apical meristems oi potentially female and male shoots for about a month before the initiation of new embryonic shoots. These results confirm our previous suggestions that femaleness and maleness in Scots pine is correlated with a high amount of auxins and gibberellins, respectively.

A new genus of male cones of voltzialean affinity, Uralostrobus voltzioides nov. gen., nov. sp., from the Lower Permian of the Urals (Russia)

A new genus and species of male cones of coniferophyte from the Lower Permian (Artinskian and Kungurian) deposits of the Urals, Russia is described: Uralostrobus voltzioides Naugolnykh nov. gen., nov. sp. The cone shows characters typical of some representatives of conifers belonging to the order Voltziales: more or less isometrical bracts of rhombic shape, prolonged sporangia with attenuate apices, and bisaccate pollen of Illinites-type. General information on the associated female seed scales and vegetative leafy shoots is given as well.

Field evidence from Namibia does not support the designation of Angolan and Namibian subspecies of Welwitschia mirabilis Hook

Welwitschia mirabilis is an ancient, endemic gymnosperm found in numerous disjunct populations in western Namibia north of the Namib Sand Sea to the Bentiaba River in southwestern Angola. Based on six plants grown in the Berlin-Dahlem Botanical Garden, Leuenberger [2001, Welwitschia mirabilis (Welwitschiaceae), male cone characters and a new subspecies. Willdenowia 31: 357–381] differentiated two groups of plants using eight male inflorescence characters. He concluded that the two groups represented geographical subspecies: W. mirabilis subsp. mirabilis in Angola and W. mirabilis subsp. namibiana in Namibia, based on putative location data of the seed sources for the plants. Leuenberger called for field data collection, especially in northern Namibia, to verify his results. However despite this lack of data, numerous authors have cited his work as definitive in scientific papers and online plant descriptions and keys. We analysed five distinguishing male cone characters from 13 Namibian plant populations and found significant variation that encompasses both descriptions of the Namibian and Angolan subspecies. Data collected from plants grown from Angolan and Namibian seed in the Kirstenbosch Botanical Garden also fell within the range of the Namibian field populations. We found significant evidence of latitudinal gradients in cone and peduncle length, but cone colour, secondary branch length and bract shape were highly variable within and between the Namibian populations sampled. Our data do not support the designation of an Angolan and Namibian subspecies. W. mirabilis has probably been evolving in this landscape for more than 100 million years with unknown metapopulation dynamics predetermining current geographical populations. Our study calls for molecular characterisation in conjunction with a thorough investigation of both male and female plant characteristics throughout the current range of the plant to further clarify the phylogenetic relevance of the variation observed in male cone characters.

<i>Abies sibirica</i> Male Reproductive Cones Developmental Shift at Introduction

A strong effect of climate on phenological events in conifers has been documented by several studies. To study adaptation of reproductive processes in Abies sibirica Ledeb. to changing environment, the phenology of the development of the species male reproductive cones at introduction was studied. Phenological shift in Abies sibirica meiosis and pollination was observed. An earlier start of male bud reproductive development is founded in V.N. Sukachev Institute of Forest Arboretum resulted in increasing meiosis and pollen irregularities. Insufficient high quality pollen in the species at its pollination stage may be a major factor responsible for the incapability to produce the viable seeds in quantities sufficient for pollination in seed gardens. Responses of the fir male cone development to the current environmental conditions at the Arboretum may be considered as a model of adaptation of the species to climatic changes.

Reproductive biology of the endangered cypress Calocedrus macrolepis

We studied the reproductive biology of the endangered species Calocedrus macrolepis. We examined flower phenology and morphology, spatial distribution of male and female cones, pollen viability, variation in pollen density around the crown, and the pollination process. Calocedrus macrolepis is monoecious with unisexual flowers on the same branches. Pollen‐shed from male cones occurred from early September to mid‐February, whereas the female cones were receptive from mid‐September to mid‐March. The inconsistency of flowering periods between male and female cones within populations and among individuals extended the pollination period. There was a layered distribution pattern of male and female cones in the crown, with more male cones in the lower layer and more female cones in the upper layer. This resulted in different selfing and outcrossing rates at various locations. The pollen of C. macrolepis lack airbags, and consequently, it was dispersed within only 10 m of the mother tree. The short pollen dispersal distance could restrict gene flow among different geographical populations. Calocedrus macrolepis is endangered because of its high degree of selfing and inbreeding resulting from its monoecious characteristics and the short distance of pollen spread. These factors may result in a population decline.

Pollen cones and associated leaves from the Lower Cretaceous of China and a re-evaluation of Mesozoic male cycad cones

Male cones of Ixostrobus hailarensis from Lower Cretaceous strata of the Hailar region of north-east China were re-examined for features of their cuticle and in situ pollen. The cones are loosely aggregated and possess helically arranged peltate microsporophylls containing resin bodies. Microsporophyll cuticle is thick, papillate and has elliptical stomata with 6–9 subsidiary and ∼10 encircling cells. Adaxial sporangia contain monosulcate pollen assignable to the dispersed taxon Cycadopites minimus. Both the cuticle and pollen are distinct from Ixostrobus but are consistent with the cycad genera Androstrobus, Aegianthus, Loricanthus and the putative angiosperm Solaranthus. Reanalysis of the type species of Androstrobus, A. zamioides, provides new information on its structure and allows an accurate delimitation of the genus and improved comparison with other genera. A new genus, Schimperstrobus, is erected for species now excluded from Androstrobus. Comparisons indicate that Solaranthus represents a male cycad cone and that Aegianthus, Loricanthus and Solaranthus are synonyms; Aegianthus has nomenclatural priority. We emend the combined generic and specific diagnoses for Aegianthus sibiricus to allow additional species to be placed in the genus, and erect the new combinations Aegianthus resinifera for specimens previously assigned to Loricanthus, and Aegianthus daohugouensis for specimens previously placed within Solaranthus. The Hailar cone conforms to the generic circumscription of Aegianthus and represents a new species that we name A. hailarensis comb. nov. Androstrobus phialophora also conforms with Aegianthus and is transferred to Aegianthus phialophora comb. nov. Co-occurring with A. hailarensis are cuticles of the ginkgophyte leaf Sphenobaiera longifolia that are similar to microsporophyll cuticles of A. hailarensis. However, we discount that they belong to a single plant species and conclude that the cuticles of some Mesozoic ginkgoalean and cycadalean taxa may be virtually indistinguishable. We consider that Aegianthus was widespread across China, Mongolia and southern Russia during the Upper Jurassic to Lower Cretaceous.

Patterns of odour emission, thermogenesis and pollinator activity in cones of an African cycad: what mechanisms apply?

Ontogenetic patterns of odour emissions and heating associated with plant reproductive structures may have profound effects on insect behaviour, and consequently on pollination. In some cycads, notably Macrozamia, temporal changes in emission of specific odour compounds and temperature have been interpreted as a 'push-pull' interaction in which pollinators are either attracted or repelled according to the concentration of the emitted volatiles. To establish which mechanisms occur in the large Encephalartos cycad clade, the temporal patterns of volatile emissions, heating and pollinator activity of cones of Encephalartos villosus in the Eastern Cape (EC) and KwaZulu Natal (KZN) of South Africa were investigated. Gas chromatography-mass spectrometry (GC-MS) analyses of Encephalartos villosus cone volatiles showed that emissions, dominated by eucalyptol and 2-isopropyl-3-methoxypyrazine in EC populations and (3E)-1,3-octadiene and (3E,5Z)-1,3,5-octatriene in the KZN populations, varied across developmental stages but did not vary significantly on a daily cycle. Heating in male cones was higher at dehiscence than during pre- and post-dehiscence, and reached a maximum at about 1830 h when temperatures were between 7·0 and 12·0 °C above ambient. Daily heating of female cones was less pronounced and reached a maximum at about 1345 h when it was on average between 0·9 and 3·0 °C above ambient. Insect abundance on male cones was higher at dehiscence than at the other stages and significantly higher in the afternoon than in the morning and evening. There are pronounced developmental changes in volatile emissions and heating in E. villosus cones, as well as strong daily changes in thermogenesis. Daily patterns of volatile emissions and pollinator abundance in E. villosus are different from those observed in some Macrozamia cycads and not consistent with the push-pull pattern as periods of peak odour emission do not coincide with mass exodus of insects from male cones.

Two Global Conformation States of a Novel NAD(P) Reductase Like Protein of the Thermogenic Appendix of the Sauromatum guttatum Inflorescence

A novel NAD(P) reductase like protein (RL) belonging to a class of reductases involved in phenylpropanoid synthesis was previously purified to homogeneity from the Sauromatum guttatum appendix. The Sauromatum appendix raises its temperature above ambient temperature to ~30 °C on the day of inflorescence opening (D-day). Changes in the charge state distribution of the protein in electrospray ionization-mass spectrometry spectra were observed during the development of the appendix. RL adopted two conformations, state A (an extended state) that appeared before heat-production (D - 4 to D - 2), and state B (a compact state) that began appearing on D - 1 and reached a maximum on D-day. RL in healthy leaves of Arabidopsis is present in state A, whereas in thermogenic sporophylls of male cones of Encephalartos ferox is present in state B. These conformational changes strongly suggest an involvement of RL in heat-production. The biophysical properties of this protein are remarkable. It is self-assembled in aqueous solutions into micrometer sizes of organized morphologies. The assembly produces a broad range of cyclic and linear morphologies that resemble micelles, rods, lamellar micelles, as well as vesicles. The assemblies could also form network structures. RL molecules entangle with each other and formed branched, interconnected networks. These unusual assemblies suggest that RL is an oligomer, and its oligomerization can provide additional information needed for thermoregulation. We hypothesize that state A controls the plant basal temperature and state B allows a shift in the temperature set point to above ambient temperature.

Study on allergenicity of Thuja orientalis pollen grains in rat

Cupressaceae pollen allergy is an important cause of pollen allergy throughout the world. Prevalence of allergy to Cupressaceae pollen has increased significantly during the winter over the past 3 decades because of extensive planting of cypress trees for different purposes. Thuja orientalis (Cupressaceae) is a naturally grown plant in Iran and is widely cultivated as a common ornamental plant in this country and other ones. Allergenicity of its pollen has been established, but to this day no allergenic component has been detected. The aim of this research is to study allergenicity and evaluate the immunoglobulin E reactivity to T. orientalis pollen extracts. Pollen grains were directly collected from mature male cones of trees. Pollen proteins were extracted and were analyzed by SDS-PAGE. Total protein content of pollen extracts was measured by Bradford assay. Immunoblotting using the serum of sensitized rats showed a single immunogenic band at about 44KD in pollen extracts. Result of this research proved that pollen grains of T. orientalis are allergenic.

Composition, Mosquito Larvicidal, Biting Deterrent and Antifungal Activity of Essential Oils of Different Plant Parts of Cupressus arizonica var. glabra (‘Carolina Sapphire’)

Essential oils obtained by hydrodistillation of female cones (FC), male cones (MC), needle-twigs (NT) and wood-bark (WB) of 'Carolina Sapphire' [Cupressus arizonica var glabra (Sudw.) Little] were analyzed simultaneously by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). The main constituents of the investigated essential oils were as follows: FC: alpha-pinene 68.5% and myrcene 11.9%; MC: alpha-pinene 22.5%, epi-zonarene 9.9%, zonarene 6.9%, limonene 6.8% and cadina-3,5-diene 6.1%; NT: alpha-pinene 20.7%, epi-zonarene 10.4%, zonarene 7.6%, limonene 5.9% umbellulone 5.8% and cadina-3,5-diene 5.8%; WB: alpha-pinene 40.7%, limonene 3.2% and umbellulone 2.9%. Essential oils were evaluated for antifungal activity against the strawberry anthracnose causing fungal plant pathogens Colletotrichum acutatum, C. fragariae and C. gloeosporioides. Only WB essential oil showed moderate activity when compared with the commercial antifungal standards. Carolina Sapphire essential oils exhibited biting deterrent activity at 10 microg/cm2 with Biting Deterrence Index (BDI) values of 0.64, 0.59, 0.65 and 0.72, for FC, MC, NT and WB, respectively, and were significantly lower (P < or = 0.05) than the synthetic insect repellent, DEET (N,N-diethyl-meta-toluamide), at 25 nmol/cm2 against Aedes aegypti. The biting deterrence of NT and WB oils at 100 microg/cm2 with BDI values of 1.04 and 1.01, respectively, were similar, whereas the activity of MC (BDI = 0.88) and FC (BDI = 0.62) essential oils was lower than DEET at 25 nmol/cm2. Essential oil from FC with LD50 of 33.7 ppm was most toxic against 1-day-old Ae. aegypti larvae at 24-h post treatment. Female cone essential oil was significantly more toxic than MC (LD50 = 53.6 ppm), NT (LD50 = 55.5 ppm) and WB (LD50 = 44.6 ppm) essential oils.

Temporal and spatial characteristics of male cone development in Metasequoia glyptostroboides Hu et Cheng

Metasequoia glyptostroboides, a famous relic species of conifer that survived in China, has been successfully planted in large numbers across the world. However, limited information on male cone development in the species is available. In this study, we observed the morphological and anatomical changes that occur during male cone development in M. glyptostroboides using semi-thin sections and scanning electron microscopy. The male cones were borne oppositely on one-year-old twigs that were mainly located around the outer and sunlit parts of crown. Male cones were initiated from early September and shed pollen in the following February. Each cone consisted of spirally arranged microsporophylls subtended by decussate sterile scales, and each microsporophyll commonly consisted of three microsporangia and a phylloclade. The microsporangial wall was composed of an epidermis, endothecium, and tapetum. In mid-February, the endothecium and tapetum layers disintegrated, and in the epidermal layer the cell walls were thickened with inner protrusions. Subsequently, dehiscence of the microsporangia occurred through rupturing of the microsporangial wall along the dehiscence line. These results suggest that the structure, morphology, architecture and arrangement of male cones of M. glyptostroboides are mainly associated with the production, protection and dispersal of pollen for optimization of wind pollination.

Pseudofrenelopsis cf. parceramosa and its reproductive organs from the Lower Cretaceous Youngdong Group of Korea

A large number of cheirolepidiaceous shoots and some associated male and female cones collected from the Lower Cretaceous Youngdong Group in the Youngdong area of Chungcheongbug-do, Korea, are described as Pseudofrenelopsis cf. parceramosa (Fontaine) Watson, its male cone of Classostrobus comptonensis Alvin et al. and female cone based on their external morphology respectively. The abundant presence of Pseudofrenelopsis shoots in the Youngdong Group indicates that it was a dominat group flourished during the Early Cretaceous in Korea.

Zamia grijalvensis sp. nov. (Zamiaceae, Cycadales) from Chiapas, Mexico with notes on hybridization and karyology

Zamia grijalvensis, a new cycad species from Chiapas, México, is described and illustrated. This species is similar to Z. lacandona with respect to leaves, but differs in habit, morphology and colour of the female and male cones. The female cone of Z. grijalvensis is reddish brown to orange brown, whereas that of Z. lacandona is dark brown with lighter beige tomentum. The male cone of Z. grijalvensis is erect, whereas that of Z. lacandona is decumbent. The new species may be of natural hybrid origin and is discussed in the light of other findings among cycads. Preliminary diploid chromosome counts for Z. grijalvensis 2n = 19, 20 and karyotypes appear variable, as previously found in its congeners with wide distribution, such as Z. paucijuga and Z. prasina, both of which are characterised by high diploid numbers with a high number of telocentric and few metacentric chromosomes. These changes in chromosome number are probably the result of stressful environmental factors.

Analysis of Phytohormone Profiles during Male and Female Cone Initiation and Early Differentiation in Long-shoot Buds of Lodgepole Pine

In lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm), cone initiation and gender differentiation are site-specific in long-shoot buds, with female cones in the distal portion and male cones in the proximal portion. By using high-performance liquid chromatography–electrospray ionization tandem mass spectrometry (HPLC–ESI–MS/MS) in multiple-reaction monitoring (MRM) mode, cytokinins, indole-3-acetic acid (IAA), abscisic acid (ABA), and their selected metabolites were investigated in developing long-shoot buds from multiple genotypes. Spatially, higher concentrations of trans-zeatin riboside (t-ZR) and dihydrozeatin riboside (dhZR) existed in the distal parts of long-shoot buds, whereas concentrations of isopentenyl adenosine (iPA), IAA, ABA glucose ester (ABA-GE), and phaseic acid (PA) were higher in the proximal parts in all investigated genotypes. In long-shoot buds of genotypes with a history of high female cone yield, concentrations of t-ZR and the ratio of zeatin-type to isopentenyl-type cytokinins were higher in the entire buds, whereas dhZR or IAA was higher in either the distal or the proximal part, respectively. In low female cone yielding genotypes, concentrations of c-ZR, iPA, ABA-GE, and PA were higher in both of the parts. Temporally, concentrations of several hormone-related compounds showed obvious changes in late June and late July, prior to male and female cone bud differentiation. This study reveals that the local hormonal status in a long-shoot bud at specific developmental stages may play an important role in gender determination and cone yield.

Effects of stem girdling on cone yield and endogenous phytohormones and metabolites in developing long shoots of Douglas-fir (Pseudotsuga menziesii)

Stem-girdling treatments were applied in early spring to stimulate cone formation in two genotypes of interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco). After girdling treatments, male cone yield increased significantly in the next growing season. The increase was 14-fold in genotype 9137. In genotype 9550, more than 8,700 male cones were induced from each tree whereas no male cones were found in controls. Female cone yield was zero in controls and low for girdled trees in both genotypes. Multiple phytohormone-related compounds, including gibberellins (GAs), cytokinins, indole-3-acetic acid (IAA), abscisic acid (ABA) and their selected metabolites, were analyzed in developing long shoots after girdling treatments by high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC–ESI–MS/MS) in multiple reaction monitoring mode. Concentrations of GA4 were slightly higher at week 2 following girdling treatment, whereas at week 8 lower GA4 concentrations were found in girdled samples. Stem girdling did not affect concentrations of IAA and major cytokinins, such as zeatin riboside and isopentenyl adenosine. Concentrations of ABA differed two-fold between the genotypes. Although girdling treatment did not cause differences in ABA concentrations, it generally resulted in higher concentrations of ABA glucose ester. Concentration increase of 7′-hydroxy ABA by girdling was only found in genotype 9550 at week 8. Girdling caused little change in concentrations of phaseic acid in both genotypes.

Male cone morphogenesis, pollen development and pollen dispersal mechanism in Ginkgo biloba L.

Lu, Y., Wang, L., Wang, D., Wang, Y., Zhang, M., Jin, B. and Chen, P. 2011. Male cone morphogenesis, pollen development and pollen dispersal mechanism inGinkgo bilobaL. Can. J. Plant Sci. 91: 971-981. Ginkgo biloba L. is one of the oldest gymnosperms. Male cone morphogenesis, pollen development and dispersal are important for successful pollination and reproduction. In this study, we investigated the development of male cone, pollen and the sporangial wall in detail. The results indicate that: (1) The primordia of male cones and leaves begin to differentiate in early June and remain open until the following March. The male cones then mature and release pollen in mid-April. The male cones are drooped and approximately perpendicular to the leaves during pollination. (2) The microsporocytes develop from the sporogenous cell and form a tetrahedral tetrad after two simultaneous asymmetrically meioses, then produce a matured four-cell pollen after three polar mitotic divisions. The matured pollen is hemispheric in shape with a large aperture area and three pollen wall layers; once released from the microsporangia, the pollen becomes boat-like in shape. (3) The sporangial walls are eusporangiate and consist of epidermis, endothecium and tapetum. The differentiation of the tapetum occurs separately from that of the epidermis and endothecium, and originates from the outermost layer of sporogenous cells. The sporangial walls exhibit shrinkage of the epidermis, fibrous thickening of the endothecium, and enzymic dissolution of the tapetum during pollen dispersal, which contributes to microsporangia opening. Based on these results, we conclude that there many unique and primitive characteristics of the development of the male cones, pollen and sporangial wall of G. biloba. In addition, we also found that the male cones, pollen and sporangial walls have evolved efficient structural and morphological adaptations to anemophily.

Male cone morphogenesis, pollen development and pollen dispersal mechanism in Ginkgo biloba L.

Lu, Y., Wang, L., Wang, D., Wang, Y., Zhang, M., Jin, B. and Chen, P. 2011. Male cone morphogenesis, pollen development and pollen dispersal mechanism in Ginkgo biloba L. Can. J. Plant Sci. 91: 971–981. Ginkgo biloba L. is one of the oldest gymnosperms. Male cone morphogenesis, pollen development and dispersal are important for successful pollination and reproduction. In this study, we investigated the development of male cone, pollen and the sporangial wall in detail. The results indicate that: (1) The primordia of male cones and leaves begin to differentiate in early June and remain open until the following March. The male cones then mature and release pollen in mid-April. The male cones are drooped and approximately perpendicular to the leaves during pollination. (2) The microsporocytes develop from the sporogenous cell and form a tetrahedral tetrad after two simultaneous asymmetrically meioses, then produce a matured four-cell pollen after three polar mitotic divisions. The matured pollen is hemispheric in shape with a large aperture area and three pollen wall layers; once released from the microsporangia, the pollen becomes boat-like in shape. (3) The sporangial walls are eusporangiate and consist of epidermis, endothecium and tapetum. The differentiation of the tapetum occurs separately from that of the epidermis and endothecium, and originates from the outermost layer of sporogenous cells. The sporangial walls exhibit shrinkage of the epidermis, fibrous thickening of the endothecium, and enzymic dissolution of the tapetum during pollen dispersal, which contributes to microsporangia opening. Based on these results, we conclude that there many unique and primitive characteristics of the development of the male cones, pollen and sporangial wall of G. biloba. In addition, we also found that the male cones, pollen and sporangial walls have evolved efficient structural and morphological adaptations to anemophily.

Adaptation of male reproductive structures to wind pollination in gymnosperms: Cones and pollen grains

Lu, Y., Jin, B., Wang, L., Wang, Y., Wang, D., Jiang, X.-X. and Chen, P. 2011. Adaptation of male reproductive structures to wind pollination in gymnosperms: Cones and pollen grains. Can. J. Plant Sci. 91: 897-906. Wind pollination (anemophily) in gymnosperms is thought to be an ancestral state. Previous studies considered wind pollination to be a largely random phenomenon, but recent evidence suggests that wind-pollinated species have evolved different complex reproductive adaptations for controlling and maximizing the success of wind pollination. However, compared with angiosperms, wind pollination in gymnosperms is poorly understood. We investigated the male reproductive structures of 13 representative gymnosperm species using a scanning electron microscope and digital camera, and analyzed how the morphological characteristics of male cones and pollen facilitate pollination. These characteristics showed a surprising variation between different gymnosperm species in improving pollination success. For ex...

Adaptation of male reproductive structures to wind pollination in gymnosperms: Cones and pollen grains

Lu, Y., Jin, B., Wang, L., Wang, Y., Wang, D., Jiang, X.-X. and Chen, P. 2011. Adaptation of male reproductive structures to wind pollination in gymnosperms: Cones and pollen grains. Can. J. Plant Sci. 91: 897–906. Wind pollination (anemophily) in gymnosperms is thought to be an ancestral state. Previous studies considered wind pollination to be a largely random phenomenon, but recent evidence suggests that wind-pollinated species have evolved different complex reproductive adaptations for controlling and maximizing the success of wind pollination. However, compared with angiosperms, wind pollination in gymnosperms is poorly understood. We investigated the male reproductive structures of 13 representative gymnosperm species using a scanning electron microscope and digital camera, and analyzed how the morphological characteristics of male cones and pollen facilitate pollination. These characteristics showed a surprising variation between different gymnosperm species in improving pollination success. For example, the relationship between the position of the male cone and the surrounding vegetative structures is adjusted to optimize pollen release. The pollen grains have sacs and papilla and exhibit particular shapes after release from microsporangia, including boat-like, saccate, papilla-like and spheroid shapes, which facilitate pollen dispersal in the air. Taken together, our results suggest that the extensive diversity of male reproductive structures within gymnosperms represents an evolutionary response to long-term selection and results in solutions to the physical restraints of anemophily.