Staminate Catkins Research Articles

Transcriptomic landscape of staminate catkins development during overwintering process in Betula platyphylla.

Betula platyphylla, belonging to the cold-specialized lineage Betulaceae, exhibits a unique reproductive strategy where staminate catkins emerge in the first summer and undergo an overwintering process, culminating in flowering in the following year. However, the underlying regulatory mechanism remains unclear. In this study, we investigated the male germline development of B. platyphylla in four distinct stages: microsporocytes in Oct. (S1), uninuclear microspores from Dec. (S2) to Mar. of the following year (S3), and bicellular microspores in Apr. (S4). We performed RNA sequencing on mature pollen and the four stages of staminate catkins. Using weighted gene co-expression network analysis (WGCNA), we identified five highly correlated gene modules with distinct expression profiles. These modules exhibited strong correlations with sugar metabolism, cell cycle, flowering, and cell wall dynamics, highlighting their dynamic roles during male germline developmental stages. During the overwintering process, we observed that the expression of transcription factors such as BpDUO1 and BpAMS at the appropriate developmental stages, suggests their significant roles in male germline development. The expression patterns of BpFLC and BpFT suggest their potential involvement in temperature perception during male reproductive development. These findings offer valuable insights into the reproductive success of plants adapting to cold environments.

The chemical composition of pollen, staminate catkins, and honey of Castanea sativa Mill.

The chemical composition of pollen and honey primarily depends on the botanical and geographical origin of the species, as well as other factors – climatic conditions, soil type, plant species, etc. The present study was to knowledge the biochemical profile of pollen, staminate catkins, and honey samples of Castanea sativa Mill. which were examined under conditions of Ukraine. Proteins are the major components of pollen and staminate catkins (169.0 ±1.60 g.kg-1 and 69.8 ±1.67 g.kg-1, respectively), while saccharides are predominant in honey samples (38.0 ±1.32 g.kg-1 fructose, 32.5 ±0.68 glucose g.kg−1 and 6.1 ±0.06 g.kg-1 sucrose). Glutamic acid (13.30 g.kg-1), aspartic acid (13.05 g.kg-1), and proline (12.45 g.kg-1) were predominant nonessential amino acids in the chestnut pollen. The content of macro and microelements was found in the pollen and staminate catkins much higher than in the honey. All Castanea sativa samples are a very valuable source of potassium as the main mineral element contained in pollen (7400 mg.kg-1), staminate catkins (7760 mg.kg-1), and honey (981 mg.kg-1). Microelements such as manganese and iron prevailed in pollen (478 mg.kg-1 Mn and 461 mg.kg-1 Fe), and staminate catkins (247 mg.kg-1 Mn and 109 mg.kg-1 Fe), and heavy metals (Hg, Sr, Sn, Sb, Li) are present only in the pollen samples with the most abundant Sr (12.8 mg.kg-1) and Sn (1.9 mg.kg-1) content and can be used as indicator suggesting the environmental pollution status in the region. Regarding the vitamin content, vitamin C was the most represented in all samples. Obtained results indicate that chestnut is species with important constituents such as amino acids and vitamins, with low content of heavy metals and high content of biogenic elements that may be used in phytotherapy and phytopharmacology.

Floral characterization and pollen germination protocol for Castanea crenata Siebold & Zucc

Chestnuts have staminate (male) and androgynous (hermaphrodite) flowers in the same individual. The male flowers are grouped into unisexual catkins, while the female flowers are located at the base of male inflorescences. There is divergence in the functionality of pollen grains among chestnut species. As this species requires cross-pollination, germination tests are essential in breeding programs. The objective of this study was to comparatively evaluate pollen viability as a function of the type of flower using colorimetric assays, to develop a culture medium protocol for in vitro pollen germination and characterize the floral morphology of the Japanese chestnut (C. crenata). Eleven Japanese chestnut cultivars were evaluated for characterization and description of the floral morphology, pollen viability by staining, and in vitro germination with determination of the percentage of viability regarding the type of inflorescence (staminate x androgynous). In addition, a culture medium was established to induce germination of chestnut pollen and determination of the percentage of in vitro pollen germination, as well as quantification of the number of anthers per flower and pollen grains per anther and per flower for all cultivars. There was no difference in pollen viability between androgynous and staminate catkins. The culture medium containing 6 g L−1 of agar, 46.5 g L−1 of sucrose, and 460.23 mg L−1 of boric acid in the absence of calcium nitrate, pH 5.25, promoted the best conditions for in vitro pollen germination. Cultivars with the highest percentage of viability recorded the lowest amounts of pollen per anther and per flower. This characteristic may influence the number of flowers necessary for extraction of anthers in crosses and the success of hybridization in the field.

Alnus subgenus Alnus in the Eocene of western North America based on leaves, associated catkins, pollen, and fruits.

The fossil record of alder (Alnus) is well known in the Cenozoic deposits throughout the northern hemisphere, based on numerous reports of the distinctive pollen, cone-like infructescences, staminate inflorescences, and leaves. However, our understanding of the systematic position of these fossils relative to the modern phylogeny of the genus has been limited because most fossils were described from only one organ. We examined well-preserved leaves and associated fruiting and staminate catkins from the middle Eocene, Clarno Formation, Oregon, USA by stereomicroscopy. In situ and dispersed pollen were cleaned with HF and acetolized for light and scanning electron microscopy. We reconstructed a new extinct species based on multiple organs and discuss significant phytogeographic and phylogenetic implications for Alnus. Alnus clarnoensis sp. nov. is described based on serrate leaves with 1-4 small teeth between each primary tooth, associated cone-like fruiting catkins with fruits in situ, and associated slender pollen catkins bearing in situ 3- to 6-pored pollen with arci between the pores. Combined investigations of each organ indicate that they probably derive from the same species and can be confidently attributed to subgenus Alnus Furlow based on leaf architecture and pollen pore number frequency. The Clarno fossils are most similar to the extant North American species of subgenus Alnus rather than to those from Asia and Europe, indicating that this modern subgenus was already distinct by the middle Eocene and that the intercontinental migration likely occurred earlier.

CmRT1, a Ty3-gypsy-like retrotransposon in Castanea mollissima,is associated with a short-catkin mutation

SummaryRetrotransposons are major components of the genomes of most eukaryotic organisms and have resulted in the introduction of desirable traits in many crops, including fruit trees. Here, we describe a Ty3-gypsy-like retrotransposon associated with a short-catkin mutant in Chinese chestnut (Castanea mollissima), resulting in catkins that are < 20% the length of normal staminate catkins. A partial sequence of the retrotransposon, named CmRT1, detected by amplified fragment length polymorphism (AFLP) analysis, and its complete sequence were determined from the genome of Chinese chestnut (Castanea mollissima) using improved Tail-PCR. CmRT1 was 10,067 bp in length and shared high homology in its predicted amino acid sequence and motifs with other Ty3/gypsy-like retrotransposons. The 5’ long terminal repeat (LTR) of CmRT1 contained a TATA box and several cis-elements that were predicted to be important for processes involving abscisic acid, gibberellic acid, and auxins and in stress-mediated responses. Further characterisation of the transposition event that led to the short-catkin phenotype was performed using two pairs of primers that aligned with the flanking region of the LTRs. The expected PCR bands were observed only in genomic DNA from plants that showed the mutation. Finally, cloning and real-time qPCR analysis of an NADP-dependent alkenal double-bond reductase (CmADBR) target gene that was adjacent to CmRT1, revealed that CmADBR expression was significantly down-regulated in the short-catkin mutant. Taken together, these results suggest that the CmRT1 retrotransposon is responsible for the short-catkin phenotype.

Fagaceae from the early Oligocene of Central Europe: Persisting new world and emerging old world biogeographic links

Dispersed pollen from phosphoritic nodules of early Oligocene age from Cospuden (Rupelian, Saxony, Central Europe) comprises six distinct types of Fagaceae belonging to four to five genera, three of which belong to extinct lineages. Eotrigonobalanus and Trigonobalanopsis have stratigraphic ranges from the Eocene to the Miocene and the Pliocene, respectively, and an unassigned fagaceous pollen type might belong to a lineage related to the middle to late Oligocene Amentoplexipollenites from North America. Also pollen of Eotrigonobalanus from Cospuden is strikingly similar to pollen attached to staminate catkins in middle to late Oligocene sediments from the North American Gulf Coastal Plain. Both types of pollen co-occur with foliage of the Eotrigonobalanus type ( Dryophyllum, Berryophyllum). Furthermore, cupules and fruits from the middle Eocene to lower Miocene in Europe ( Trigonobalanus andreanszkyi Mai) and the Oligocene of the Gulf Coastal Plain are structurally similar. This suggests an intercontinental distribution of this extinct lineage of Fagaceae with migration across the North Atlantic. Trigonobalanopsis is endemic during the Cenozoic in Europe. Although present in late Miocene sediments of Iceland it has not been reported from North America. The extant genera Fagus and Quercus are not known prior to the Eocene. The unequivocal presence of Fagus in Rupelian sediments of Central Europe is the oldest record of the genus in western Eurasia. Fagus migrated to Europe from the east (Central and East Asia) after the closure of the Turgai Seaway. Pollen belonging to Quercus Group Ilex also marks the oldest record for Europe. Today, this group of oaks is endemic to Eurasia with isolated occurrences in the Mediterranean, the Himalayas, and East Asia. It is unclear, whether the group originated in Europe or East Asia. Pollen belonging to either Quercus Group Quercus or Group Lobatae (white and red oaks) dates back at least to the Eocene in Europe (Baltic Amber). Based on systematic affinities of leaves from late Oligocene sediments in Saxony, pollen from Cospuden with the distinctive features of these infrageneric groups may represent Group Lobatae (red oaks). This group is at present confined to North America, but appears to be represented in the fossil record of East Asia and Europe.

Palaeocarpinus dakotensissp.n. (Betulaceae: Coryloideae) and Associated Staminate Catkins, Pollen, and Leaves from the Paleocene of North Dakota

Palaeocarpinus dakotensis Manchester, Pigg, et Crane sp.n. (Coryloideae, Betulaceae) is described from the Late Paleocene Almont and Beicegel Creek floras of North Dakota based on infructescences with associated staminate catkins, pollen, and leaves. The well‐preserved, silica‐permineralized specimens provide both anatomical and morphological data for this widely distributed genus of the Northern Hemisphere Paleogene. Characters that were previously unknown for the genus are described from anatomically preserved specimens, supporting earlier suggestions that Palaeocarpinus combines features found separately in the extant Coryleae and Carpineae. Features of Coryleae include infructescences composed of cymes with paired nuts, each enclosed within two highly dissected bracts of equal size quite similar to those of some species of modern Corylus, and staminate catkins with four to six bifurcate stamens per bract. Similarly, there are four bifurcate stamens per bract in extant Corylus and four to six in Ostryopsis, whereas more numerous stamens are found in Carpinus and Ostrya. Other features, however, are characteristic of the Carpineae, including external longitudinal ribs on bracts, many fruits per infructescence, and small, ribbed nuts with vascular bundles lying outside the endocarp. Pollen from the stamens of associated catkins is triporate with a scabrate exine and apparently lacks opercula on the apertures, as in Corylus. Simple, cordate‐based elliptical leaves with pinnate, craspedodromous secondary veins and serrate margins referred to Corylites sp. are also found in association and are thought to represent the same coryloid plant. The appearance of Palaeocarpinus in the fossil record apparently predates that of extant genera in the Coryloideae, and it is likely that Palaeocarpinus‐like plants were the forerunners of both Coryleae and Carpineae.

Corylus, Carpinus, and Palaeocarpinus (Betulaceae) from the Middle Eocene Klondike Mountain and Allenby Formations of Northwestern North America

Coryloid reproductive remains (Betulaceae, subfamily Coryloideae) are documented from the middle Eocene Republic flora of northeastern Washington State and the Princeton flora of southern British Columbia. The oldest confirmed examples of two modern genera, Corylus johnsonii Pigg, Manchester & Wehr sp. nov., and Carpinus perryae Pigg, Manchester & Wehr sp. nov., are reported from the Republic flora, and three new species of the extinct genus Palaeocarpinus, Palaeocarpinus barksdaleae Pigg, Manchester & Wehr sp. nov., Palaeocarpinus stonebergae Pigg, Manchester & Wehr sp. nov., and Palaeocarpinus dentatus (Penhallow) Pigg, Manchester & Wehr comb. nov., are described from Republic, Washington; Princeton, British Columbia; and Stump Lake, British Columbia, respectively. Corylus johnsonii resembles three extant Asian species: Corylus wangii, Corylus ferox, and Corylus heterophylla. Involucres of this fossil species vary from being highly dissected and spiny like C. wangii and C. ferox to more laminar like C. heterophylla. This similarity is interesting because C. ferox and perhaps also C. wangii are members of section Acanthochlamys, thought to be basal within the genus. Carpinus perryae has asymmetric leaflike bracts that partly enclose an ovate nutlet and, thus, fits within the extant Carpinus subgenus Carpinus, a group with Asian, European, and North American affinities today. Palaeocarpinus, thought to be basal within the Coryloideae, is reported from several Eocene localities in the Okanogan Highlands. These occurrences demonstrate that this primarily Paleocene, extinct genus extended into the Eocene in western North America as it did in Asia. Associated staminate catkins containing coryloid pollen and Corylus‐like leaves also occur at Republic along with P. barksdaleae. The presence in the Okanogan Highlands floras of a suite of coryloid plants including both extinct and extant genera demonstrates that, like the birch subfamily Betuloideae, the subfamily Coryloideae was also a significant and diverse group in western North America during the middle Eocene.

A New Genus of Coryloideae (Betulaceae) from the Paleocene of North America

A new genus of Betulaceae, Cranea, is recognized from the Paleocene of central and northern Wyoming based on infructescences with associated leaves, staminate inflorescences, and in situ pollen The elongate infructescences bear numerous closely spaced sessile, persistent, obconical involucres that each envelope an elliptical nut with an epigynous perianth. Although some aspects of the infructescence morphology remain unknown, the involucres and nuts are similar to those of extant Ostryopsis of eastern Asia. The fossil infructescences are more elongate than those of Ostryopsis, and the involucres at the apical and basal ends of the infructescence are small and apparently infertile. Staminate catkins found in association with Cranea bear triporate pollen resembling that of Coryloideae. Associated leaves have compound teeth, closely spaced parallel secondary veins, and closely spaced, percurrent tertiary veins and are similar to the leaves of extant Carpinus and Ostrya. The reconstructed plant conforms to th...

Reproductive and vegetative morphology of Polyptera (Juglandaceae) from the Paleocene of Wyoming and Montana

The morphology, systematics, and ecology of the extinct juglandaceous genus Polyptera are interpreted on the basis of infructescences, fruits, staminate catkins, pollen, and compound leaves from the Paleocene of Wyoming and Montana. The elongate infructescences of Polyptera manningii bear numerous helically arranged sessile fruits. The fruit is a pyramidal nut with a vascularized husk and a multilobed disk-like wing adaptive for wind dispersal. Associated staminate catkins bear numerous helically arranged florets, each with six or more stamens. Pollen from the anthers is triporate and isopolar, with ultrastructure diagnostic of Juglandaceae, but with a pattern of exinous thinning characteristic of the extinct dispersed pollen type Maceopolipollenites anellus (Nichols et Ott) comb. nov. The correlated leaves, Juglandiphyllites glabra (Brown ex Watt) comb. nov., are deciduous, pinnately compound, and have five to seven petiolulate finely serrate leaflets. Systematically, Polyptera shows relationships both with the Hicorieae and the Juglandeae. Occurrences in the Torrejonian and Tiffanian stages of the Paleocene place Polyptera as the oldest unequivocal record of Juglandaceae. Polyptera manningii typically occurs in low-diversity assemblages of 8-15 species, and usually is a dominant or subdominant constituent of floodplain assemblages. It may have been an early-successional colonizer.

Palaeocarpinus aspinosa Sp. Nov. (Betulaceae) from the Paleocene of Wyoming, U. S. A.

A new species of Palaeocarpinus Crane (Betulaceae) is recognized from the Paleocene of southwestern Wyoming that extends the concept of the genus to include fruits with nonspiny bracts. Fruits of P. aspinosa sp. nov. are borne in pairs on an elongate infructescence, each fruit enclosed by two equal bracts that are entire-margined to serrate but not dissected or spiny. Associated staminate catkins contain well-preserved pollen that is not only triporate, but commonly tetra- to pentaporate. The pollen exine is tectate-granular, with spinulate ornamentation. Co-occurring betulaceous leaves are similar to those of P. joffrensis Sun et Stockey from Canada and P. orientalis from China and to leaves of extant Corylus. The associated infructescences, leaves, and staminate inflorescences with in situ pollen facilitate detailed reconstruction of this extinct species and provide a clearer understanding of the genus and its relation to extant genera. Palaeocarpinus aspinosa, with its nonspiny fruit bracts and multiporate pollen, adds to our understanding of the morphological diversity present in this widespread early Tertiary genus. The nondissected bracts may have been effective for wind and water dispersal whereas other species with spiny burrlike bracts may have been dispersed by furry animals.

Palaeocarpinus (Extinct Betulaceae) from Northwestern China: New Evidence for Paleocene Floristic Continuity between Asia, North America, and Europe

Spiny-bracted fruits of Palaeocarpinus Crane, a genus of Betulaceae previously known only from Europe and North America, have been discovered in the Paleocene of Altai, northwestern China. The fruits are found in association with abundant Corylus-like foliage and staminate catkins containing Corylus-like pollen. Because of problems distinguishing leaves of Corylus from those of extinct betulaceous genera, we place these leaves in the genus Corylites Gardner ex Seward & Holttum. The fruits, staminate catkins, pollen, and leaves from Altai were probably all produced by a single species. Palaeocarpinus orientalis is nearly identical in its morphology to Palaeocarpinus joffrensis from the Paleocene of North America except in the more rounded primary bracts of the associated staminate catkins. The species is less similar to Palaeocarpinus laciniata from the Paleocene of southern England.

Pollination dynamics of arctic dwarf birch (Betula glandulosa; Betulaceae) and its role in the loss of seed production

At the northern limit of its distribution, arctic dwarf birch, Betula glandulosa, shows nearly complete absence of sexual reproduction (i.e., &lt;;0.5% viable samaras) and maintains its populations vegetatively. To investigate the possible role of pollination dynamics in the loss of sexual reproduction, pollination biology of arctic dwarf birch was compared at two locations: Tarr Inlet on Baffin Island, Northwest Territories near the northern limit of the species, and Kuujjuaq, Quebec in the center of its distribution where sexual reproduction is the primary mode of reproduction. Relative production of staminate and pistillate flowers, pollen rain, pollen viability, and stigmatic pollen loads throughout pollen dispersal were compared. Plants at Tarr Inlet produced 15%–30% of pollen produced at Kuujjuaq, both as a result of a lower density of staminate catkins and less pollen per catkin. Potential seed productivity is limited at the northern limit because pistillate catkins produce 50% fewer flowers in the north than in the south. While stigmatic pollen loads were similar at both sites, lower pollen viability (68% vs. 93%) and a higher probability of geitonogamous pollen due to clonal growth pattern reduced fertilization success at the northern site. These data suggest that lack of sexual reproduction in B. glandulosa at its northern limit is in part due to pollen limitation.

Pollination Dynamics of Arctic Dwarf Birch (Betula glandulosa; Betulaceae) and Its Role in the Loss of Seed Production

At the northern limit of its distribution, arctic dwarf birch, Betula glandulosa, shows nearly complete absence of sexual reproduction (i.e., <;0.5% viable samaras) and maintains its populations vegetatively. To investigate the possible role of pollination dynamics in the loss of sexual reproduction, pollination biology of arctic dwarf birch was compared at two locations: Tarr Inlet on Baffin Island, Northwest Territories near the northern limit of the species, and Kuujjuaq, Quebec in the center of its distribution where sexual reproduction is the primary mode of reproduction. Relative production of staminate and pistillate flowers, pollen rain, pollen viability, and stigmatic pollen loads throughout pollen dispersal were compared. Plants at Tarr Inlet produced 15%–30% of pollen produced at Kuujjuaq, both as a result of a lower density of staminate catkins and less pollen per catkin. Potential seed productivity is limited at the northern limit because pistillate catkins produce 50% fewer flowers in the north than in the south. While stigmatic pollen loads were similar at both sites, lower pollen viability (68% vs. 93%) and a higher probability of geitonogamous pollen due to clonal growth pattern reduced fertilization success at the northern site. These data suggest that lack of sexual reproduction in B. glandulosa at its northern limit is in part due to pollen limitation.

EXTINCT TRANSITIONAL FAGACEAE FROM THE OLIGOCENE AND THEIR PHYLOGENETIC IMPLICATIONS

Fruits, catkins, and associated leaves of at least two extinct trigonobalanoid taxa have been discovered at an Oligocene fossil plant locality rich in fagaceous remains. These fossils exhibit a mosaic of fruit and pollen characters found in the two extant subfamilies Castaneoideae and Fagoideae of Fagaceae. Comparison with cladograms based on modern taxa suggests that these extinct taxa were similar to the ancestors of subfamily Fagoideae and may have been intermediate between Fagus and the modern trigonobalanoid genera. Pollen types isolated from the fossil staminate catkins provide unique character states that are transitional between modern pollen types in Fagaceae and are important in understanding the evolution of exine micromorphology within the family. This analysis provides a striking example of the use of character data from fossils to determine character‐state adjacency prior to polarization of characters using outgroup comparison. Because of the mosaic nature of their character complexes, these fossils support monophyly in both the family Fagaceae and the subfamily Fagoideae. In addition, the occurrence of trigonobalanoid fossils in the Oligocene of North America has interesting biogeographic implications and provides insights into the nature of North American Fagaceae during the Tertiary.

Extinct Transitional Fagaceae from the Oligocene and their Phylogenetic Implications

Fruits, catkins, and associated leaves of at least two extinct trigonobalanoid taxa have been discovered at an Oligocene fossil plant locality rich in fagaceous remains. These fossils exhibit a mosaic of fruit and pollen characters found in the two extant subfamilies Castaneoideae and Fagoideae of Fagaceae. Comparison with cladograms based on modern taxa suggests that these extinct taxa were similar to the ancestors of subfamily Fagoideae and may have been intermediate between Fagus and the modern trigonobalanoid genera. Pollen types isolated from the fossil staminate catkins provide unique character states that are transitional between modern pollen types in Fagaceae and are important in understanding the evolution of exine micromorphology within the family. This analysis provides a striking example of the use of character data from fossils to determine character-state adjacency prior to polarization of characters using outgroup comparison. Because of the mosaic nature of their character complexes, these fossils support monophyly in both the family Fagaceae and the subfamily Fagoideae. In addition, the occurrence of trigonobalanoid fossils in the Oligocene of North America has interesting biogeographic implications and provides insights into the nature of North American Fagaceae during the Tertiary.

Multivariate analyses of hybridization between Betula cordifolia and B. populifolia (Betulaceae)

Multivariate analyses of Betula cordifolia Regel, B. populifolia Marsh., and B. × caerulea Blanchard in a mixed population in northern Maine show that the latter is a hybrid between the former two species. Hybrid status of B. × caerulea is further supported by the fact that two putative hybrid individuals have the same chromosome number as reports for the two parental species and that all three taxa have overlapping flowering times at this site. Studies of pollen germination and stainability and seed germination show that the putative hybrids are fertile. Betula papyrifera Marsh., which is also present in this mixed population and was included in the analyses, flowers earlier than B. cordifolia and B. populifolia, and it apparently does not hybridize with the latter species at this site. Characters that have not been used prior to this study and that are among the best discriminators between B. cordifolia, B. papyrifera, and B. populifolia are number and width of preformed staminate catkins and length and diameter of overwintering vegetative buds.

EARLIEST MEGAFOSSIL EVIDENCE OF FAGACEAE: PHYLOGENETIC AND BIOGEOGRAPHIC IMPLICATIONS

Fossil evidence of Fagaceae from the Paleocene/Eocene boundary of western Tennessee is described and discussed. These fossils include a newly discovered pistillate inflorescence and dispersed fruits of subfamily Castaneoideae as well as a taxon that resembles modern trigonobalanoids (pistillate inflorescences and dispersed mature fruits). Fossil staminate catkins with fagaceous pollen, which we suggest may be conspecific with the trigonobalanoid infructescences, are also found at the locality. Two distinct types of fagaceous leaves are present at the locality. The reproductive structures are the oldest megafossils unequivocally assignable to Fagaceae and represent the oldest remains of subfamily Fagoideae and the oldest megafossil remains of Castaneoideae. In addition, the fossils provide insights into the chronology of diversification, biogeography, and phylogeny of Fagaceae. The trigonobalanoid remains may also provide insights into the timing and circumstances of the evolution of wind pollination in Fagaceae.

Earliest Megafossil Evidence of Fagaceae: Phylogenetic and Biogeographic Implications

Fossil evidence of Fagaceae from the Paleocene/Eocene boundary of western Tennessee is described and discussed. These fossils include a newly discovered pistillate inflorescence and dispersed fruits of subfamily Castaneoideae as well as a taxon that resembles modern trigonobalanoids (pistillate inflorescences and dispersed mature fruits). Fossil staminate catkins with fagaceous pollen, which we suggest may be conspecific with the trigonobalanoid infructescences, are also found at the locality. Two distinct types of fagaceous leaves are present at the locality. The reproductive structures are the oldest megafossils unequivocally assignable to Fagaceae and represent the oldest remains of subfamily Fagoideae and the oldest megafossil remains of Castaneoideae. In addition, the fossils provide insights into the chronology of diversification, biogeography, and phylogeny of Fagaceae. The trigonobalanoid remains may also provide insights into the timing and circumstances of the evolution of wind pollination in Fagaceae.

The role of growth regulators in the differentiation of flowers and inflorescences

Growth regulators participate in the differentiation of floral parts, determining the developmental path of the respective type of inflorescence. The effect depends on the expression of the peculiarities of floral part differentiation, the recognition of the character of endogenous substances in certain stages and the choice of the suitable regulator for application. In the primitive flower ofPapaver petals and stamens are formed from the peripheral meristem with a lower content of auxins and a higher level of gibberellic substances. The pistil arises later from central tissues with a higher level of auxins and inhibitory substances. The stamens are more sensitive to the higher level of auxin substances, and by a suitable application of GA3 and BAP they can be transformed into petals; in this way double flower forms arise. In the differentiation of floral parts ofCampanula, Rosa andMelandrium similar regularities assert themselves in time successions, but in another spatial arrangement. Sex differentiation of diclinous flowers ofMelandrium is based on differences in heterochromosomes XY and XX. The rise of the zygomorphic flower ofVeronica is accompanied by a different distribution of endogenous substances which affect the development of petals, stamens and the pistil. The differentiation of flowers in the racemose inflorescence occurs in the acropetal succession, and lateral primordia inCampanula develop into actinomorphic regular flowers, whereas inDigitalis they are zygomorphic and only the terminal flower is peloric. In the initial phases the staminate tassel and the pistillate ear in maize are identical. Earlier differentiation of the terminal pistillate tassel is connected with a higher level of gibberellins and the later development of the lateral pistillate ear is accompanied by the increase in auxin-like substances and inhibitions. Similar correlations were found in the development of staminate catkins and the differentiation of pistillate flowers in terminal buds ofJuglans regia. By the application of auxin-like substances it is possible to achieve the transformation of primordia of the staminate tassel into the pistillate ear in maize or to regulate the number of staminate catkins and pistillate flowers on twigs of the walnut tree. In the capitulum of the sunflower differences arise between peripheral pistillate ray flowers and hermaphrodite tubular ones. By applying GA3 and BAP the number of ray flowers is increased. If the normal course of inflorescence differentiation is affected with a suitable type of regulator, a range of floral abnormalities appears which permit to assess the intervention in different developmental stages and the reaction of the primordium to the applied type of regulator. Abnormalities also suggest some phylogenetic correlations.