Bud Initiation, Microsporogenesis, Megasporogenesis, and Cone Development in Platycladus orientalis

As a native tree species with a strong adaptability, Platycladus orientalis is a species of choice for afforestation and landscaping in northern China. However, it develops mostly male cones and few female cones. In addition, its reproductive characteristics are not yet clear, which limits further breeding work. To systematically clarify the reproductive biology characteristic and fertilization mechanism of P. orientalis, the present study comprehensively investigated the process of micro and macro-sporogenesis in male and female cones from bud initiation to fertilization, and seed development. The specific time in each developmental stage, including bud initiation, microsporogenesis, megasporogenesis, and cone and seed development, was determined, and the abortive phenomenon during development was discovered in both male and female cones. In addition, this research showed that the microspore mother cells were dormant in winter at meiosis stage, and the male gametophyte started to develop when dormancy ended. The tapetum developed normally and belonged to the secretory type. The optimal treatment time for male and female cones transformation by artificial induction was from late June to mid-July. This finding provided a theoretical basis for hybridization, breeding, improvement of seed yield and quality, and artificial induction of male and female cone transformation in P. orientalis.

The Transcriptome of Cunninghamia lanceolata male/female cone reveal the association between MIKC MADS-box genes and reproductive organs development

Background Cunninghamia lanceolata (Chinese fir), a member of the conifer family Cupressaceae, is one of the most popular cultivated trees for wood production in China. Continuous research is being performed to improve C. lanceolata breeding values. Given the high rate of seed abortion (one of the reasons being the failure of ovule and pollen development) in C. lanceolata, the proper formation of female/male cones could theoretically increase the number of offspring in future generations. MIKC MADS-box genes are well-known for their roles in the flower/cone development and comprise the typical/atypical floral development model for both angiosperms and gymnosperms. Results We performed a transcriptomic analysis to find genes differentially expressed between female and male cones at a single, carefully determined developmental stage, focusing on the MIKC MADS-box genes. We finally obtained 47 unique MIKC MADS-box genes from C. lanceolata and divided these genes into separate branches. 27 out of the 47 MIKC MADS-box genes showed differential expression between female and male cones, and most of them were not expressed in leaves. Out of these 27 genes, most B-class genes (AP3/PI) were up-regulated in the male cone, while TM8 genes were up-regulated in the female cone. Then, with no obvious overall preference for AG (class C + D) genes in female/male cones, it seems likely that these genes are involved in the development of both cones. Finally, a small number of genes such as GGM7, SVP, AGL15, that were specifically expressed in female/male cones, making them candidate genes for sex-specific cone development. Conclusions Our study identified a number of MIKC MADS-box genes showing differential expression between female and male cones in C. lanceolata, illustrating a potential link of these genes with C. lanceolata cone development. On the basis of this, we postulated a possible cone development model for C. lanceolata. The gene expression library showing differential expression between female and male cones shown here, can be used to discover unknown regulatory networks related to sex-specific cone development in the future.

Effects of Light Intensity and Girdling Treatments on the Production of Female Cones in Japanese Larch (Larix kaempferi (Lamb.) Carr.): Implications for the Management of Seed Orchards

To ensure sustainable forestry, it is important to establish an efficient management procedure for improving the seed production capacity of seed orchards. In this study, we evaluated the effects of girdling and increasing light intensity on female cone production in an old L. kaempferi (Lamb.) Carr. seed orchard. We also evaluated whether there is a genotype-specific reproductive response to these factors among clones. The results showed that female cone production was augmented by girdling and increasing light intensity. There was a difference in the effectiveness of girdling treatment levels, and the probability of producing female cones increased markedly at higher girdling levels. At light intensities where the relative photosynthetic photon flux density was higher than 50%, more than half of the trees tended to produce female cones, even in intact (ungirdled) trees, and the genotype-specific response to light intensity was more apparent in less-reproductive clones. These findings suggested that girdling less-reproductive trees combined with increasing light intensity was an effective management strategy for improving cone production in old seed orchards.

Climate and size of previous cone crops contribute to large-scale synchronous cone production in balsam fir

Mast year occurrence in trees is often synchronized across large regions. In this study, we used dendrochronological methods to reconstruct male and female cone production in balsam fir during the period 1987-2018, using cone scar characteristics on tree branches. Results indicate that mast years generally occur every second year, and can be synchronized across distances > 1000 km. The main predictors of current year cone abundance were cone abundance during the two previous years, which can be considered as a proxy for resource availability for cone bud development during the current year, together with relatively warm temperature during cone bud development. Presence of aborted male cones was positively correlated with the occurrence of relatively cold episodes during cone bud development. This suggests that weather influence on cone crop abundance is at least partly mediated by growth cessation in the developing cone buds. We also suggests that a change in weather patterns before and after the 2005-2010 period is responsible for a switch of mast years from even to uneven calendar years around that time.

Author Correction: De novo assembly of the Platycladus orientalis (L.) Franco transcriptome provides insight into the development and pollination mechanism of female cone based on RNA-Seq data

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

ARAUCARIA GOROENSIS (ARAUCARIACEAE), A NEW MONKEY PUZZLE FROM NEW CALEDONIA, AND NOMENCLATURAL NOTES ON ARAUCARIA MUELLERI

Araucaria goroensis R.R.Mill & Ruhsam sp. nov., a new monkey puzzle species from New Caledonia, is described and illustrated with photographs from the field and from herbarium specimens. Previously confused with Araucaria muelleri, it is more similar to A. rulei. It is distinguished from the latter species by its larger leaves, microsporophylls without a shouldered base, and shorter female cone bracts. It occurs in a very limited area of south-east New Caledonia, where its existence is threatened by nickel mining. Using the guidelines of the International Union for Conservation of Nature, we propose an assessment of Endangered for the new species and reassess Araucaria muelleri also as Endangered. A key to the seven species in the ‘large-leaved clade’ of New Caledonian species of Araucaria is given. The name Eutassa latifolia de Laub. is synonymised with Araucaria muelleri, and the recent typification of the latter name by Vieillard 1276 is rejected. Detailed reasoning is given for these nomenclatural acts.

New findings of seeds and fruits from Cenomanian–Turonian deposits of Western Siberia

Three-dimensional remains of seeds and fruits originating from Cenomanian–Turonian deposits of the Simonovo Suite are reported from one locality at the Kem’ River near the village Maslennikovo (58°11'24.8"N, 91°54'24.2"E) and from six localities at the Kiya River near the village Kubayevo (56°04'27.5"N, 87°52'22.4"E; 56°04'39.6"N 87°52'19.0"E; 56°04'39.6"N, 87°52'20.9"E), from the south of Western Siberia. The majority of the findings studied belong to undescribed genera of gymnosperms and flowering plants. The Maslennikovo collection has yielded seeds of Alapaja cf. uralensis Dorofeev (Cupressaceae) and Liriodendroidea Knobloch et Mai (Magnoliaceae), fruits of Porosia cf. verrucosa (Lesq.) Hickey, as well as platanaceous heads. The Kubayevo collections contain seeds and remains of a female cone of cf. Krassilovidendron fecundum Sokolova, Gordenko et Zavialova (Cupressaceae), seeds of Saccospermum cf. trebecense Knobloch et Mai and fruits or seeds of Spirellea Knobloch et Mai (angiosperms of unknown affinities). Despite having originated from deposits of the same suite, the Maslennikovo and Kubayevo collections almost don’t have overlapping forms.