Search Results (12)

In this study, the morphological and anatomical characteristics of the growth of the internal ovules and the dynamic changes in the content of endogenous hormones during the development of Korean pine (Pinus koraiensis Siebold & Zucc.) cones were investigated in detail and their interrelationships determined. In addition, morphological examinations, paraffin section, analysis and enzyme immunoassays were performed to observe the growth and development as well as the fertilization stages of the ovules of P. koraiensis from July of the pollination year to June of the following year. From July of the pollination year to May of the next year, the increase in the content of indoleacetic acid (IAA) and gibberellin and a decrease in the content of abscisic acid (ABA) in the pollination year correlated with the division of the gametophyte free nuclei. It was observed that the levels of IAA, ABA, zeatin riboside (ZR) and isopentenyl adenosine (IPA) initially decreased and then increased during overwintering, which was interpreted as a symptom of adaptation of P. koraiensis ovules to low temperatures. At the end of overwintering, the increase in IPA, ZR and ABA levels was associated with the development of the female gametophyte. The week before fertilization was identified as the stage of oocyte division, in which growth-promoting hormones dominate. During the week of fertilization, the increase in the level of growth-inhibiting hormones correlated with fertilization. After fertilization, the increase in the level of growth-promoting hormones also correlated with early embryonic development. The levels of endogenous hormones were observed to change dynamically with the development of P. koraiensis oocytes, indicating their important role. The results of this study provide the morphological and anatomical basis for related studies on the development of the ovarian strobilus in gymnosperms. Full article

Experimental manipulations of the balance between leaves as source organs and reproductive structures as sink organs have contributed greatly to our understanding of the assimilate partitioning and regulation of leaf photosynthesis. In order to add cycads to this research agenda, the full range in natural variation in leaf:seed ratio and incident light level of in situ Cycas micronesica was augmented with the experimental manipulation of leaf:seed ratios of C. micronesica and Cycas edentata in Guam and the Philippines. In every study, individual seed size and concentrations of megagametophyte carbon, starch, and sugars were not influenced by leaf:seed ratio. The leaf net photosynthesis (Pn) and operational efficiency of photosystem II were also quantified for the in situ studies, and leaf:seed ratio did not influence these leaf physiology traits. The natural variation in incident light revealed increased net Pn for C. micronesica trees receiving greater levels of light, but the sink traits of seeds were not influenced by these differences in source strength. The findings indicated that the size and sink activity of individual cycad seeds are constitutive traits that are not influenced by the relative balance between leaf source and seed sink size at the individual plant level. The results also reveal that upregulation or downregulation of cycad leaf Pn is not influenced by sink size or source:sink ratio. The massive amounts of nonstructural carbohydrates in cycad stems and roots may explain these findings, as these organs may be the primary source for strobilus and seed growth independently from leaf Pn. Full article

Calamitaceae was the predominant arborescent element of the Late Paleozoic plant assemblages. However, there is currently controversy surrounding the evolutionary relationships of their four reproductive organs, and there is no unified understanding of the geographical distribution and species richness characteristics. This paper is based on the detailed description of the macro- and microstructures of Calamites and Macrostachya discovered in the Shanxi Formation of the Cisuralian in the eastern Hexi Corridor of northwestern China, and it discusses the evolutionary patterns of calamitean reproductive organs. The results indicate that the current specimens can be identified as the Calamites cistii and Macrostachya sp., and the in situ spores should exhibit distinct trilete marks, indicating that they belong to the Punctatisporites punctatus. The abundant fossil records suggest that the “Calamostachys” type should be considered as the ancestral type of strobili. Additionally, Calamitaceae was widely distributed in mid to low latitudes globally from the Pennsylvanian to the Cisuralian and coupled with paleogeographic distribution characteristics. Full article

Aulacaspis yasumatsui Takagi invaded Guam in 2003 and caused the widespread mortality of the indigenous Cycas micronesica K.D. Hill population. The regeneration of the surviving tree population continues to be constrained 20 years later, and a look at the changes in megastrobili traits may inform future conservation management decisions concerning regeneration. We quantified megastrobilus reproductive effort and output from 2001 to 2022 to address this need. The reproductive effort of each megastrobilus was immediately reduced by the invasion, as the number of megasporophylls declined by 29%, and the number of ovules declined by 73% in 2006. Reproductive output was also damaged, as the percent seed set declined by 56% and the number of seeds per strobilus declined by 88%. These fecundity metrics have shown few signs of recovery through 2022. Our results reveal that chronic A. yasumatsui infestations, combined with other invasive herbivore threats, have damaged the host C. micronesica population through a sustained reduction in ovule production and the percent seed set for each megastrobilus, thereby impairing regeneration. This plant response to the biotic threats is distinct from the ongoing mortality of mature trees and emerging seedlings. Conservation interventions may be required to foster a return to adequate regeneration during future attempts to aid C. micronesica recovery. Full article

The primary metabolism and respiration of the hop strobilus has not been quantified in response to daily temperature fluctuations. The objective of this study was to assess strobilus gas exchange, specifically the response to temperature fluctuations. Hop strobilus were measured under controlled environment conditions to assess the organ’s contribution to carbon assimilation and respiration during the maturation phase. Strobilus-specific daily carbon budgets were estimated in response to temperature fluctuation. The optimal temperature for net carbon gain occurred at 15.7 °C. Estimated strobilus carbon uptake decreased approximately 41% per 5 °C increase in temperature above 20 °C. Daily temperatures within 10–27 °C resulted in a net positive strobilus daily carbon balance, whereas temperature increases beyond 27 °C increasingly exhaust strobilus carbon reserves. The Q₁₀ temperature coefficient (the rate respiration increases every 10 °C rise in temperature) approximately doubled per 10 °C rise in temperature from 7–40 °C (1.94–2) with slightly reduced values at lower temperatures. In conclusion, we show that photosynthetically active bracts maintain a positive strobilus carbon balance at moderate temperatures and as mean daily temperatures progressively exceed 27 °C, strobilus net carbon reserves are precipitously exhausted due to ever-increasing respiration rates. Full article

The economic value of Humulus lupulus L. (hop) is recognized, but the primary metabolism of the hop strobilus has not been quantified in response to elevated CO₂. The photosynthetic contribution of hop strobili to reproductive effort may be important for growth and crop yield. This component could be useful in hop breeding for enhanced performance in response to environmental signals. The objective of this study was to assess strobilus gas exchange, specifically the response to CO₂ and light. Hop strobili were measured under controlled environment conditions to assess the organ’s contribution to carbon assimilation and lupulin gland filling during the maturation phase. Leaf defoliation and bract photosynthetic inhibition were deployed to investigate the glandular trichome lupulin carbon source. Strobilus-level physiological response parameters were extrapolated to estimate strobilus-specific carbon budgets under current and future atmospheric CO₂ conditions. Under ambient atmospheric CO₂, the strobilus carbon balance was 92% autonomous. Estimated strobilus carbon uptake increased by 21% from 415 to 600 µmol mol⁻¹ CO₂, 14% from 600 to 900 µmol mol⁻¹, and another 8%, 4%, and 3% from 900 to 1200, 1500, and 1800 µmol mol⁻¹, respectively. We show that photosynthetically active bracts are a major source of carbon assimilation and that leaf defoliation had no effect on lupulin production or strobilus photosynthesis, whereas individual bract photosynthesis was linked to lupulin production. In conclusion, hop strobili can self-generate enough carbon assimilation under elevated CO₂ conditions to function autonomously, and strobilus bracts are the primary carbon source for lupulin biosynthesis. Full article

Knowledge of the formation and correlation of reproductive structures with dendro/morphometric variables of the Araucaria angustifolia tree species is a tool for its conservation and viability for sustainable forest management. We counted visually in araucaria trees the number of male strobili in RGB images acquired by Remotely Piloted Aircraft System (RPAs) over forest remnants. The diameter at the breast height (d), total height (h), crown radii (cr), crown base height (cbh), periodic annual increment in d based on increment rolls were measured, and the morphometric indices and crown efficiency were calculated with these variables. The relationships of these variables with male strobili production were analyzed by Pearson’s correlation and multivariate analysis techniques (cluster, factorial analysis, and main components). The morphometric variables correlated with the production of male strobili were d (r = 0.58, p-0.0002), crown diameter (r = 0.62, p < 0.0001), crown area (r = 0.62, p < 0.0001), coverage index (r = 0.51, p-0.001) and slenderness (r = −0.39, p-0.01). We argue that the production of male strobili is related to the vitality, dimension, density, growth space, and position in the stratum of the tree inside the forest, inferring a relationship between reproductive structures with the shape, size, growth space, and tree density. Such aspects shall be considered in future forest management initiatives in Southern Brazil. Full article

Taxodium Rich is well known for its flooding tolerance and has great ecological and economic potential. A comprehensive understanding of pollen characteristics and storage capacity is important for breeding and genetic resource conservation of the genus. In this study, we observed the microsporogenesis and pollen ornamentation, studied the conditions of in vitro pollen germination, compared the difference in pollen viability of T. distichum var. distichum measured by in vitro germination and TTC staining, analyzed the change in pollen viability after different storage times and the feasibility of using stored pollen for cross breeding. Results indicated that the pollen mother cells of T. distichum var. distichum begin to enter the meiosis stage one month before the male strobilus disperse, reach metaphase 10 days after meiosis and form pollen grains three to five days after tetrad development. Pollen germination rate topped in the culture medium of 0.012% boric acid under 30 °C after 48 h, reaching 66.81%. The TTC staining demonstrated that the pollen viability of T. distichum var. distichum TD-4 and TD-5 were 97.78% and 80.54%, 98.96% and 91.67%, and 83.67% and 21.75% after one-, two- and three-year storage at −20 °C, which is significantly higher than (p < 0.05) that of 17.02 and 27.04%, 2.77% and 12.82%, and 0 determined by the in vitro cultivation. It is feasible to use pollen of T. distichum var. distichum TD-4 and TD-5 stored at −20 °C for one year for artificial hybridization, and the fruit setting rate and seed germination rate were 10.94 and 36.79%, and 11.47 and 65.76%, respectively. Full article

Japanese cedar (Cryptomeria japonica) is the most important timber species in Japan; however, its pollen is the primary cause of pollinosis in Japan. The total number of pollen grains produced by a single tree is determined by the number of male strobili (male flowers) and the number of pollen grains per male strobilus. While the number of male strobili is a visible and well-investigated trait, little is known about the number of pollen grains per male strobilus. We hypothesized that genetic and environmental factors affect the pollen number per male strobilus and explored the factors that affect pollen production and genetic variation among clones. We counted pollen numbers of 523 male strobili from 26 clones using a cell counter method that we recently developed. Piecewise Structural Equation Modeling (pSEM) revealed that the pollen number is mostly affected by genetic variation, male strobilus weight, and pollen size. Although we collected samples from locations with different environmental conditions, statistical modeling succeeded in predicting pollen numbers for different clones sampled from branches facing different directions. Comparison of predicted pollen numbers revealed that they varied >3-fold among the 26 clones. The determination of the factors affecting pollen number and a precise evaluation of genetic variation will contribute to breeding strategies to counter pollinosis. Furthermore, the combination of our efficient counting method and statistical modeling will provide a powerful tool not only for Japanese cedar but also for other plant species. Full article

Pseudotaxus chienii, a rare tertiary relict species with economic and ecological value, is a representative of the monotypic genus Pseudotaxus that is endemic to China. P. chienii can adapt well to habitat isolation and ecological heterogeneity under a variety of climate and soil conditions, and is able to survive in harsh environments. However, little is known about the molecular and genetic resources of this long-lived conifer. Herein, we sequenced the transcriptomes of four organs of P. chienii using the PacBio Isoform Sequencing and Illumina RNA Sequencing platforms. Based on the PacBio Iso-Seq data, we obtained 44,896, 58,082, 50,485, and 67,638 full-length unigenes from the root, stem, leaf, and strobilus, respectively, with a mean length of 2692 bp, and a mean N50 length of 3010.75 bp. We then comprehensively annotated these unigenes. The number of organ-specific expressed unigenes ranged from 4393 in leaf to 9124 in strobilus, suggesting their special roles in physiological processes, organ development, and adaptability in the different four organs. A total of 16,562 differentially expressed genes (DEGs) were identified among the four organs and clustered into six subclusters. The gene families related to biotic/abiotic factors, including the TPS, CYP450, and HSP families, were characterized. The expression levels of most DEGs in the phenylpropanoid biosynthesis pathway and plant–pathogen interactions were higher in the root than in the three other organs, suggesting that root constitutes the main organ of defensive compound synthesis and accumulation and has a stronger ability to respond to stress. The sequences were analyzed to predict transcription factors, long non-coding RNAs, and alternative splicing events. The expression levels of most DEGs of C2H2, C3H, bHLH, and bZIP families in the root and stem were higher than those in the leaf and strobilus, indicating that these TFs may play a crucial role in the survival of the root and stem. These results comprise the first comprehensive gene expression profiles obtained for different organs of P. chienii. Our findings will facilitate further studies on the functional genomics, adaptive evolution, and phylogeny of P. chienii, and lay the foundation for the development of conservation strategies for this endangered conifer. Full article

The plant hormone gibberellin (GA) is known to regulate elongating growth, seed germination, and the initiation of flower bud formation, and it has been postulated that GAs originally had functions in reproductive processes. Studies on the mechanism of induction of flowering by GA have been performed in Arabidopsis and other model plants. In coniferous trees, reproductive organ induction by GAs is known to occur, but there are few reports on the molecular mechanism in this system. To clarify the gene expression dynamics of the GA induction of the male strobilus in Cryptomeria japonica, we performed comprehensive gene expression analysis using a microarray. A GA-treated group and a nontreated group were allowed to set, and individual trees were sampled over a 6-week time course. A total of 881 genes exhibiting changed expression was identified. In the GA-treated group, genes related to ‘stress response’ and to ‘cell wall’ were initially enriched, and genes related to ‘transcription’ and ‘transcription factor activity’ were enriched at later stages. This analysis also clarified the dynamics of the expression of genes related to GA signaling transduction following GA treatment, permitting us to compare and contrast with the expression dynamics of genes implicated in signal transduction responses to other plant hormones. These results suggested that various plant hormones have complex influences on the male strobilus induction. Additionally, principal component analysis (PCA) using expression patterns of the genes that exhibited sequence similarity with flower bud or floral organ formation-related genes of Arabidopsis was performed. PCA suggested that gene expression leading to male strobilus formation in C. japonica became conspicuous within one week of GA treatment. Together, these findings help to clarify the evolution of the mechanism of induction of reproductive organs by GA. Full article

Fraser fir (Abies fraseri [Pursh] Poir.) is an important Christmas tree species in the United States, and understanding its phenology is important for managing Fraser fir trees in plantations or forests. Many management decisions are informed by and dependent on shoot phenology, from late spring frost protection to shearing, and from timing pesticide sprays to managing cone production. The ability to predict important phenological stages will become increasingly important as the climate warms, as is predicted for the primary regions where Fraser fir is grown for Christmas trees. Here, we report on the development of a model of shoot phenology in Fraser fir, and present one example of how this model may be applied to the problem of managing cone production. We surveyed shoot phenology at nine Christmas tree plantations in Michigan over three years, and used the data obtained to develop a phenology model of shoot growth. Derived from the beta sigmoid function and based on growing degree days, this phenology model offers a high predictive power and is robust to extremes of temperature and precipitation. When applied to cone production, our model provides guidance for timing practices that influence cone bud formation, both for reducing nuisance cones in Christmas tree plantations and for enhancing cone production in seed orchards. In addition, the model may assist with timing other practices tied to shoot phenology. The performance of our model under extreme heat and drought conditions suggests a role for this and other phenology models in predicting and mitigating the effects of climate change on tree growth and development. Full article