Ovulate Strobili Research Articles

Reestablishment of Zamia lawsoniana (Zamiaceae, Cycadales), an endemic species of Mexico, with first description of the ovulate strobilus

Background and Aims: Zamia, with 86 species, is the most diverse Neotropical cycad genus. In Mexico, 18 species occur, of which 15 are endemics. These taxa are distributed from sea level to 1200 m a.s.l. Recently, the phenology of Zamia in wild populations from southern Veracruz and Tabasco was studied to evaluate the morphological patterns of reproductive structures. While these records have been considered as Z. loddigesii, a species with a wide distribution along the Gulf of Mexico, different populations do possess morphological differences. Based on these data, we reevaluated the synonymy of Z. lawsoniana, which was described in 1884 and synonymized with Z. loddigesii in 1995. Methods: Botanical material was collected from three populations in Tabasco, ten in Veracruz and two in Oaxaca previously considered part of Z. loddigesii. Reproductive structures were measured at maturity in habitat. Populations were visited during 2022 and 2023 to record reproductive phenology. Herbarium specimens of Zamia lawsoniana and morphologically similar species (Z. loddigesii, Z. spartea and Z. stenophyllidia) were examined. A morphological description and an illustration for Z. lawsoniana were prepared. In addition, an identification key that included related species in terms of morphology, geography and phylogenetics was made. Key results: Zamia lawsoniana is removed from synonymy and some taxonomic clarifications are made. In this context, we provide a complete description of pollen strobili, including the microsporophylls, range of vegetative morphological variation, and a botanical illustration. Additionally, the ovulate strobilus is described for the first time and a preliminary conservation status is proposed. Conclusions: Based on morphological evidence of reproductive structures and vegetative characters, we propose the reestablishment of Zamia lawsoniana and its removal from synonymy with Z. loddigesii.

Evolutionary trends of reproductive phenotype in Cycadales: an analysis of morphological evolution in Ceratozamia.

The size and shape of reproductive structures is especially relevant in evolution because these characters are directly related to the capacity for pollination and seed dispersal, a process that plays a basic role in evolutionary patterns. The evolutionary trajectories of reproductive phenotypes in gymnosperms have received special attention in terms of pollination and innovations related to the emergence of the spermatophytes. However, variability of reproductive structures, evolutionary trends and the role of environment in the evolution of cycad species have not been well documented and explored. This study considered this topic under an explicitly phylogenetic and evolutionary approach that included a broad sampling of reproductive structures in the genus Ceratozamia. We sampled 1400 individuals of 36 Ceratozamia species to explore the evolutionary pattern and identify and evaluate factors that potentially drove their evolution. We analysed characters for both pollen and ovulate strobili within a phylogenetic framework using different methods and characters (i.e. molecular and both quantitative and qualitative morphological) to infer phylogenetic relationships. Using this phylogenetic framework, evolutionary models of trait evolution for strobilar size were evaluated. In addition, quantitative morphological variation and its relation to environmental variables across species were analysed. We found contrasting phylogenetic signals between characters of pollen and ovulate strobili. These structures exhibited high morphological disparity in several characters related to size. Results of analyses of evolutionary trajectories suggested a stabilizing selection model. With regard to phenotype-environment, the analysis produced mixed results and differences for groups in the vegetation type where the species occur; however, a positive relationship with climatic variables was found. The integrated approach synthesized reproductive phenotypic variation with current phylogenetic hypotheses and provided explicit statements of character evolution. The characters of volume for ovulate strobili were the most informative, and could provide a reference for further study of the evolutionary complexity in Ceratozamia. Finally, heterogeneous environments, which are under changing weather conditions, promote variability of reproductive structures.

Screening and identification of miRNAs related to sexual differentiation of strobili in Ginkgo biloba by integration analysis of small RNA, RNA, and degradome sequencing

BackgroundGinkgo biloba, a typical dioecious plant, is a traditional medicinal plant widely planted. However, it has a long juvenile period, which severely affected the breeding and cultivation of superior ginkgo varieties.ResultsIn order to clarify the complex mechanism of sexual differentiation in G. biloba strobili. Here, a total of 3293 miRNAs were identified in buds and strobili of G. biloba, including 1085 known miRNAs and 2208 novel miRNAs using the three sequencing approaches of transcriptome, small RNA, and degradome. Comparative transcriptome analysis screened 4346 and 7087 differentially expressed genes (DEGs) in male buds (MB) _vs_ female buds (FB) and microstrobilus (MS) _vs_ ovulate strobilus (OS), respectively. A total of 6032 target genes were predicted for differentially expressed miRNA. The combined analysis of both small RNA and transcriptome datasets identified 51 miRNA-mRNA interaction pairs that may be involved in the process of G. biloba strobili sexual differentiation, of which 15 pairs were verified in the analysis of degradome sequencing.ConclusionsThe comprehensive analysis of the small RNA, RNA and degradome sequencing data in this study provided candidate genes and clarified the regulatory mechanism of sexual differentiation of G. biloba strobili from multiple perspectives.

Pollination of cycads in an urban environment

Research on urban systems has documented the contributions of cities as sites where insect pollinators undergo their life cycles, contributing to the reproduction of many groups of plants. However, reports of plants whose reproduction is assisted by specialist pollinators under conditions prevalent in cities are scarce. Cycads and insect pollinators are threatened mainly by loss and modification of their habitats. Here, we describe two cases in which cycad species from two genera distributed in Mexico (Ceratozamia tenuis (Dyer) D.W. Stev. & Vovides and Dioon edule Lindl.) reproduce and germinate successfully in urban areas, aided by insects, near their natural distribution areas. The plants examined were artificially planted in different gardens within the city of Xalapa-Enríquez. We found that specimens two genera of insect pollinators, Pharaxonotha sp. (Erotylidae: Pharaxonothinae) on C. tenuis, and Parallocorynus sp., (Belidae: Oxycoryninae) on D. edule, can survive in cycad pollen strobili, maintaining ecological interactions as they would occur in wild, conserved environments. In addition, we found beetles in ovulate strobili during the pollen receptivity phase, which suggests that they effectively reach ovulate strobili with pollen from pollen strobili. Characterization of this gymnosperm–beetle pollination system, which is unexpected in urban areas due the effects of human disturbance on insect communities, could promote new conservation biology research on flagship species in environments and landscapes shaped by anthropogenic impacts.

Qualitative and quantitative morphological evidence for recognition of a new species within Ceratozamia (Zamiaceae) from Mexico

Several Ceratozamia populations from the “Carso Huasteco” region in Mexico have a controversial circumscription and have been historically identified as Ceratozamia fuscoviridis. In this paper, we present a review of the taxonomic history of this species and provide taxa circumscriptions based on analyses of herbarium specimens from this region and supplemented with fieldwork. For this, we have studied qualitative and quantitative morphological variation at population level. We recognize two species in this group: C. fuscoviridis and a new species, C. chamberlainii. Here, we provide two lines of qualitative and quantitative morphological evidence showing that plants of C. chamberlainii from southern San Luis Potosí to northern Hidalgo are distinct from C. fuscoviridis of central Hidalgo east of Veracruz. These species can be identified by leaflet form, leaf emergence color, color of the ovulate strobilus, and form of the megasporophyll, along with a combination of quantitative morphological characters.

A new Species of Ceratozamia (Zamiaceae) from the Sierra Norte of Puebla, Mexico

Recent collections of Ceratozamia from the Sierra Norte of Puebla, Mexico, point to a new undescribed species, which was previously subsumed under the concept of C. mexicana. Identification of this new species resulted from a review of three associated species: C. mexicana, C. tenuis, and C. delucana. Here we describe Ceratozamia totonacorum and provide information regarding its distribution and natural history. The Ceratozamia species from the Sierra Madre Oriental, Mexico, are circumscribed using morphological characters, including a detailed evaluation of reproductive structures such as the apex, position, color and shape of the ovulate strobilus.

A new arborescent species of Zamia from the Central Cordillera of Tolima, Colombia (Cycadales, Zamiaceae), with comments on the Z. poeppigiana species complex

Zamia tolimensis, a large arborescent species from the Central Cordillera of Tolima, Colombia, is described and illustrated. It is compared to Z. lindenii and Z. poeppigiana, the two most similar species. From these it is distinguished by leaflets with fewer teeth, sparse prickles on its petioles, beige-yellow ovulate strobili with shorter peduncles, and more microsporangia aggregated into a single group on the abaxial surface of the microsporophyll. Brief descriptions of Z. lindenii and Z. poeppigiana are also provided, as well as a key to separate the three species.

Phylogenetic Relationships in Ephedra (Gnetales): Evidence from Nuclear and Chloroplast DNA Sequence Data

Sequences from the nuclear ribosomal internal transcribed spacer region 1 (nrDNA ITS1) and the plastid rps4 gene from the genus Ephedra (Ephedraceae, Gnetales) were obtained in order to infer phylogenetic relationships, character evolution, and historical biogeography in the genus. Within Ephedra the length of the nrDNA ITS1 varied from 1,081 to 1,143 basepairs (bp), in contrast to dramatically shorter lengths in the outgroups (Gnetum, Welwitschia, and Pinus). The rps4 locus varied in length from 645 to 661 bp in the same set of taxa. Both parsimony and maximum likelihood analyses of these sequences resulted in a well-resolved phylogeny that supports the monophyly of Ephedra, but not its subdivision into the traditional sections Ephedra, Asarca, and Alatae. The resulting phylogeny also indicates a derivation of the New World clade from among the Old World taxa. Among the Old World species three highly-supported monophyletic groups are recognized that are highly concordant with morphological evidence. The New World clade includes two main subclades of North and South American species that are strongly supported, while the position of two, mostly Mexican species E. pedunculata and E. compacta remains unresolved. Character reconstruction of ovulate strobilus types in Ephedra indicates that fleshy bracts are ancestral, with shifts to dry, winged bracts having occurred multiple times. Low levels of sequence divergence within the North American clade suggest either recent and rapid ecological radiation or highly conservative ribosomal DNA evolution within the clade.

Pollination of Picea orientalis (Pinaceae): saccus morphology governs pollen buoyancy

Sacci of conifer pollen do not function primarily to increase the efficiency of wind pollination as is widely thought. Rather, they are bladders and cause pollen to float upwards in a liquid drop into the ovules. This observation is seemingly unsupported in the case of oriental spruce (Picea orientalis (L.) Link), which has saccate pollen. Ovulate cones are pendant at the time of pollination, which requires that pollen sink into the ovules. Pollen of oriental spruce floats at first but within 1-2 min sinks into the ovule. As sinking does not occur in saccate pollen of other Pinaceae, a variety of techniques was used to determine anatomical differences leading to this uncharacteristic tendency. Light, scanning electron, and confocal microscopy of the pollen surface yielded no significant appearing difference between pollen of oriental spruce and white spruce. However, transmission electron microscopy of freeze-fixed/freeze-substituted hydrated pollen revealed that the ektexine of oriental spruce pollen sacci is porous compared to that of white spruce. Confocal microscopy allowed examination of pollen hydration dynamics. Water enters pollen at the distal pole between sacci, and resulting rapid expansion of the tube cell forces air out of the saccate space. White spruce pollen remains buoyant because of enclosed air pockets in the saccus ektexine. Evolutionary change in pollen wall anatomy with resultant loss of saccus function is correlated with a change in ovulate strobilus orientation at pollination in oriental spruce. A suite of characters interact in the conifer pollination mechanism, and concerted change in these characters may lead to speciation.

The acceleration of jack pine seed development

The time from emergence of an ovulate strobilus to collection of viable seeds can be reduced to as little as 9 months instead of the usual 16 months spread over two growing seasons. The procedure is called the "shortened reproductive cycle." Two-year-old jack pine (Pinusbanksiana Lamb.) seedlings, grown under accelerated growth conditions, were brought into a greenhouse in the fall, where the environment simulated natural photoperiod and temperature conditions encountered during a growing season, including the approach of fall and winter. Ovulate strobili that subsequently emerged were pollinated and "2nd-year" cones, derived from those strobili, were collected the following September. The yield of filled seeds per cone was low and germination success was variable. The seedlings derived from the shortened reproductive cycle appeared to be normal and produced their own ovulate strobili 14 months after germination. Exposure to the greenhouse environment stimulated pollen production but decreased production of ovulate strobili 1 year after transplanting to the nursery. Flowering during the shortened reproductive cycle procedure was further promoted with gibberellin A4/7 application at the end of terminal shoot elongation in the greenhouse during the winter. Ovulate strobili were observed 6 months later in the nursery.

Insecticide Applications During the Pollination Period Do Not Adversely Affect Seed Yields of Loblolly Pine

Abstract Three insecticides--Guthion® (azinphosmethyl), Pydrin® (fenvalerate), and Ambush® (permethrin)--were applied to catkins and to ovulate strobili of loblolly pines (Pinus taeda) at the time of maximum ovulate receptivity to determine their effects upon pollen viability, ovulate strobili survival, seed set, seed yields, and seed viability. Concentrations recommended for seed orchard use did not significantly reduce the number of pollen grains/ovule, in vitro or in vivo pollen germination, survival of ovulate strobili, number of developed seeds/cone, number of filled seeds/cone, germination of full seed, or cause an increase in abnormal seed germination. Operational applications of these insecticides to control the webbing coneworm (Dioryctria disclusa) should not cause adverse effects during this sensitive period of seed development in loblolly pine seed orchards.

White spruce (Piceaglauca) flowering in response to spray application of gibberellin A4/7

Experiments were conducted on three populations of white spruce (Piceaglauca (Moench) Voss) to determine if calendar dates could be used as guidelines to spray gibberellin A4/7 in an Aromox–ethanol solution to increase flowering and to determine if early flushing (EF) and late flushing (LF) clones, sprayed on the same dates, responded differently. Spraying from July 8 to September 9 was ineffective, but spraying from May 7 to July 1 gave a significant response. Elongating shoots sprayed from May 13 to June 3 produced significantly more ovulate and staminate strobili than did elongating shoots sprayed from June 10 to July 1, and both produced significantly more than the control. Gibberellin A4/7 significantly increased production of ovulate and staminate strobili in the EF and LF clones that were sprayed only from June 2 to June 30. LF clones produced significantly more ovulate strobili than the EF clones, but there was no significant difference between them in staminate strobilus production. The studies demonstrated that the timing of gibberellin A4/7 spray application affects the flowering response in white spruce.

Applied gibberellin A4/7 increases ovulate strobili production in accelerated growth jack pine seedlings

Jack pine (Pinusbanksiana Lamb.) seeds were sown in October, January, and March, and the seedlings were cultured under accelerated growth conditions in a greenhouse. At biweekly intervals, from May 15 to August 15, they were transplanted to a nearby nursery and sprayed with GA4/7 or GA4/7 + NAA. The following spring a fourfold increase in flowering was noted in trees receiving either of the GA4/7 treatments. Trees in the March sowing did not flower. The data suggest that the increased flowering was caused by GA4/7-mediated differentiation of lateral long-branch primordia into ovulate strobili.

MORE EVIDENCE FOR CONIFER DIVERSITY IN THE UPPER TRIASSIC OF NORTH CAROLINA

An ovulate strobilus from the Upper Triassic Deep River Basin, North Carolina, has helically arranged, loosely aggregated, elongated, spatulate bracts with axillary ovule‐bearing appendages with about 8–10 ovules attached in two lateral rows, with outwardly directed micropyles. The axillary ovuliferous appendage is homologous with the voltzialean fertile dwarf shoot, but probably not directly evolved from it. More credible is a suggested origin from a completely fertile axillary appendage such as that of the Lower Permian Trichopitys. The occurrence of this cone, Metridiostrobus palissyaeoides, gen. and sp. nov., along with Compsostrobus neotericus and Voltzia andrewsii, reflects considerable diversity among conifer ovulate cones during the Upper Triassic.

More Evidence for Conifer Diversity in the Upper Triassic of North Carolina

An ovulate strobilus from the Upper Triassic Deep River Basin, North Carolina, has helically arranged, loosely aggregated, elongated, spatulate bracts with axillary ovule-bearing appendages with about 8–10 ovules attached in two lateral rows, with outwardly directed micropyles. The axillary ovuliferous appendage is homologous with the voltzialean fertile dwarf shoot, but probably not directly evolved from it. More credible is a suggested origin from a completely fertile axillary appendage such as that of the Lower Permian Trichopitys. The occurrence of this cone, Metridiostrobus palissyaeoides, gen. and sp. nov., along with Compsostrobus neotericus and Voltzia andrewsii, reflects considerable diversity among conifer ovulate cones during the Upper Triassic.

Seasonal changes in the macro- and micro-nutrient composition of ovulate strobili and seeds of Pinus resinosa

Seasonal changes in N, P, K, Ca, Mg, Fe, B, Cu, Zn, Mn, Na, and Al of first- and second-year ovulate strobili and developing seeds of Pinus resinosa Ait. were investigated. During the first year, the major macronutrients moved steadily into developing strobili. Nitrogen and P accumulated in high amounts and Ca and Mg in low amounts. Micronutrients also moved into strobili throughout the first year as did Na and Al.The seasonal pattern of uptake and accumulation of nutrients during the second year of strobilus development differed from the first-year pattern. During the period of rapid growth of strobili following fertilization, macro- and micro-nutrients continued to move into cone tissue. However, movement of Mn into strobili stopped abruptly during mid-June when strobili reached maximum size. Beginning in mid-July, N, P, and K began moving out of maturing strobili. Other macro- and micro-nutrients continued to accumulate in strobili during the entire second year.At the same time that mature strobili were beginning to senesce, N, P, K, Mg, Mn, Zn, and Fe rapidly moved into developing seeds. Nitrogen particularly accumulated in high concentrations. Senescing cone tissue appeared to supply much of the N, P, and K that was translocated into seeds. Calcium was present in very low concentrations in seeds whereas Na accumulated in high amounts. Aluminum did not move into seeds after fertilization occurred.

Seasonal growth patterns of ovulate strobili of Pinus resinosa in central Wisconsin

Seasonal growth patterns and water balance of first- and second-year strobili and seeds of Pinus resinosa Ait. were studied. Strobili emerged from the bud in late May or early June and grew slowly during the first season, reaching approximately 1/40 the weight of mature strobili. After a rapid period of hydration which lasted until mid-June, the weight of water in first-year strobili remained stable, but percentage of moisture decreased, primarily because of increasing dry weight. Strobili resumed growth in mid-April of the second year and grew slowly until June. Then, at about the time that fertilization of ovules occurred, dry weight increment of strobili increased greatly until a final weight of 6 to 8 g was reached early in August. However, strobili reached final size in mid-July. After mid-June, both the weight of water and percentage of moisture of second-year strobili decreased greatly, reflecting characteristic dehydration of cones during maturation. Seeds increased rapidly in dry weight after fertilization, but decreased sharply in percentage of moisture and weight of water.Continuous monitoring of strobilus diameters with dendrographs showed that, during the first year, strobili expanded slowly and showed diurnal fluctuations in diameter during periods of water stress. Second-year strobili showed three growth phases: an initial phase characterized by net diameter increment; a second phase in which no large net diameter increment took place although diurnal fluctuations regularly occurred; and a third, dehydration, phase during which time strobilus diameters decreased, accompanied by diurnal contraction and partial reexpansion.

Development of the gibberellin-induced ovulate strobilus of western red cedar: quantitative requirement for long-day → short-day → long-day

The induction of flowering in western red cedar (Thuja plicata Donn.) by gibberellin (GA3) has a quantitative requirement for long-day (LD). However, the strobilus does not develop fully under LD. Full development does occur though, if the photoperiod sequence of short-day (SD) → LD is given after an initial period of 3+ months under LD for induction. For the male, continued development entails a slight expansion and the shedding of pollen. For the female, it involves expansion from a tight 2-mm bud to a 15-mm cone, even without pollination. Cold increased the number of developing strobili, although it did not affect the date of first expansion. GA3 concentration had little effect on continued strobilus development under SD or LD. The present study indicates that continued development of the strobilus has a photoperiodic requirement that can be likened to the requirement of SD → LD of some flowers for anthesis. The requirement for SD is quantitative rather than qualitative, an increasing number of short-days will increase the number of expanding strobili, and eventually (18 to 30 months) some strobili will develop even under continuous LD. Continued development of the strobilus will not take place under SD alone, LD must follow. Therefore, the LD requirement in the sequence SD → LD appears to be qualitative in nature. This does not appear to be true for another conifer, Arizona cypress (Cupressus arizonica Greene). These strobili will develop under SD, but their development is enhanced by the sequence SD → LD.

EXPERIMENTS ON THE PRECOCIOUS FLOWERING OF WESTERN RED CEDAR AND FOUR SPECIES OF CUPRESSUS WITH GIBBERELLINS A3 AND A4/A7 MIXTURE

Induction of staminate and ovulate strobili was obtained on western red cedar (Thuja plicata Donn) by foliar application of gibberellin A3. Staminate strobili could be induced as early as age 4 months after 3.5 months of treatment under long-day conditions, but further development of the strobilus required a photoperiodic sequence of long-day — short-day — long-day. Induction of the ovulate strobilus may also have occurred under long-day conditions at an early age, but development did not become apparent until the above photoperiodic sequence had been given. Age at this time was 12 months. It is concluded that induction and development of the strobilus is under photoperiodic as well as hormonal control.Foliar application of gibberellin A3 and a gibberellin A4/A7 mixture to pygmy cypress (Cupressus pygmaea Sarg.), Portuguese cypress (Cupressus lusitanica Mill.), and Arizona cypress (Cupressus arizonica Greene) at age 7–9 months resulted in induction of staminate strobili on all plants. Length of time to flowering varied both with species of plant and gibberellin. Application of gibberellin A3 to Arizona and Portuguese cypress seedlings resulted in production of ovulate as well as staminate strobili at ages 21 and 10 months respectively. Mourning cypress (Cupressus funebris Endl.) still in a juvenile needle stage at age 9 months has proved unresponsive to foliar application of gibberellin A3 for at least 100 days.

Vascular Anatomy of the Megasporophylls of Conifers

1. In the evolution of the ovulate strobilus in members of the Coniferales, two general tendencies are apparent: (1) the reduction in number of sporophylls in the strobilus; (2) the modification of a compound sporophyll into an apparently simple sporophyll; the latter appears in diverse disguises, but in general implies loss of one of the sporophyll members or welding of the two. 2. Strobilus reduction has reached its highest expression in members of the Cupressineae, Taxineae, and Podocarpineae; one type of strobilus reduction is represented by the general sterilization and reduction of parts in the lower sporophylls of Pinus. 3. Simplification of a compound sporophyll has been attained to fullest extent in Arthrotaxis selaginoides, Agathis, and Saxegothaea, and possibly others; an extensive reduction of bract occurs in Cedrus Libani and the lower sporophylls of Pinus maritima; the scale in Phyllocladus is probably reduced so as to be represented only by a distinct ovular supply; the welding of the two organs is complete in Juniperus communis and Chamaecyparis Lawsoniana. 4. Fusion of bract and scale vascular supplies does not directly parallel fusion of bract and scale. 5. Separate origin of bract and scale vascular supplies occurs most generally in the Podocarpineae and Abietineae; fusion of bract and scale supplies has reached its highest expression in the Araucarineae; both types of bundle origin are represented in the same strobilus in Cryptomeria japonica, Cupressus Benthamii, and the lower sporophylls of Pinus. 6. The bract bundle in plants with uninerved vegetative leaves divides only slightly if at all; the extent of the scale bundle system is directly related to the size of the organ supplied. 7. The scale bundles in the Abietineae and Chamaecyparis Lawsoniana form in the expanded portion of the organ a straight row or arc; in members of the Taxodineae and Cupressineae scale bundles swing around so as to lie at each side of the bract bundle. 8. In Cryptomeria japonica and Cupressus Benthamii and perhaps Cunninghamia Davidiana scale bundles accompany the bract bundle into the free portion of the bract. 9. A branching bundle in the vegetative leaf in Araucaria and Agathis probably implies a branching bundle in the bract of the sporophyll; the vascular system in the megasporophyll is probably a complex of bract and scale bundles. 10. In species of Podocarpus the scale bundles continue in the portion of the scale folded toward the dorsal side, forming the epimatium of the ovule.