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Response of Leaf Amino Acids of Understory Shrubs to Nitrogen Addition in Primary Forest and Secondary Forest of Mt. Jianfengling

LI Xiuping, AN Lihua, NI Xiaofeng, JI Chengjun

Acta Scientiarum Naturalium Universitatis Pekinensis 2021, 57 (4): 660-670. DOI: 10.13209/j.0479-8023.2021.043

Abstract （609）

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In order to further understand of the plants response and adaptation mechanism to nitrogen addition in primary and secondary tropical montane rain forests, the authors conducted a nitrogen addition experiment in the primary and secondary forests in Mt. Jianfengling respectively, setting three nitrogen addition treatments (0, 50 and 100 kg N/(ha·yr)) in each forest, to explore the effects of enhanced nitrogen addition on amino acid content in leaves of understory shrubs. The results showed that when no nitrogen was added, the contents of total amino acids and hydrolyzed amino acids in primary forest and secondary forest were not significant, while the content of free amino acids in primary forest was significantly higher than that in secondary forest. When middle nitrogen was added, the response of leaf amino acid content of understory plants in secondary forests was higher than that in primary forests. When high nitrogen was added, there was no significant difference in the response of hydrolyzed amino acids of understory shrubs in primary forest and secondary forest, but the response of free amino acids in understory shrubs in primary forests was higher than that in secondary forests.

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Late Smithian (Early Triassic) Fish-bearing Concretions from Chaohu Area: Geochemistry and Its Significance

YU Xin, SUN Zuoyu, MENG Qingqiang, JI Cheng, ZHOU Min

Acta Scientiarum Naturalium Universitatis Pekinensis 2021, 57 (2): 225-240. DOI: 10.13209/j.0479-8023.2020.117

Abstract （1073）

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Fish-bearing carbonate concretions are found in the organic-rich shale at the top of Helongshan Formation, Lower Triassic in Chaohu area, Anhui Province. In order to study the formation mechanism and environmental significance of the carbonate concretions, petrography, major and trace elements, carbon and oxygen isotopes and environmental minerals were analyzed for the concretions and surrounding rocks. The 3D-preserved fish fossils and high carbonate content (80%) in the center of concretions indicate that concretions were formed in the early diagenetic stage. Concretions have a concentric zoning structure inside. From the center to the edge, the content of carbonate decreases, the content of siliceous clastic increases and laminae gradually appears, the content of Fe and S elements increases, δ¹³C values increase, δ¹⁸O values decrease, and TOC contents gradually increases, all indicating a concentric growth of concretions. The analysis of the size of framboidal pyrites in the host rock indicates a euxinic environment where concretions were formed. The level of concretions appears 1 m below the Smithian-Spathian boundary (SSB), consistent with the increased burial of organic carbon, rapid positive excursion of δ¹³C (-1.3‰ to 1.9‰) and seawater euxinic event. The concretions have the potential to be regarded as an auxiliary identification marker of SSB in South China.

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Leaf Stomatal Traits of Woody Plants and Their Response to Nitrogen Addition in Typical Forests in Eastern China

JIANG Xingxing, ZOU Anlong, WANG Yuanyuan, ZHOU Xuli, JI Chengjun

Acta Scientiarum Naturalium Universitatis Pekinensis 2018, 54 (4): 839-847. DOI: 10.13209/j.0479-8023.2018.003

Abstract （568）

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The stomatal traits of eighteen dominant woody plants in the Nutrient Enrichment Experiments in Chinese Forests (NEECF) were compared. The results showed that the lifeform affects stomatal features of the woody plants significantly (P<0.05). There is a visible latitudinal pattern of stomatal traits of dominant woody plants in eastern China and MAT, MAP, PET are important influent factors. All woody plants’ stomatal traits have significant correlation. The stomatal length and density showed negative correlation, and the stomatal conductance increased with increasing stomatal length and decreased with increasing stomatal density. Woody plants of different climate zones and lifeform showed diverse response with nitrogen addition.

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Structural and Behavioral Characters of the Early Triassic Ichthyosauriformes from Chaohu, Anhui Province, and Their Implications on the Origin of Ichthyopterygia

LU Hao, JI Cheng, NI Peigang, ZHOU Min, FU Wanlu

Acta Scientiarum Naturalium Universitatis Pekinensis 2016, 52 (2): 234-240. DOI: 10.13209/j.0479-8023.2015.115

Abstract （1358）

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Ichthyosaurs, firstly appeared at the end of the Early Triassic. The previously reported Ichthyosaurs show very high level of adaptability to life in water, and their osteology shows structural characters that are fully adapted to life in water without any terrestrial characters that can relate them to their terrestrial ancestor. Two specimens are studied, one belonging to Cartorhynchus and the other to Chaohusaurus with embryos found from the Lower Triassic (Olenekian) of Chaohu, Anhui Province, South China. Based on studies of the number of presacral vertebra (i.e. 31), the ratio of snout length to skull length (i.e. 0.35), the ratio of forelimb length to presacral vertebra length (i.e. 0.45), and comparisons of these measurements and morphological characters with the derived Ichthyosaurs, Cartorhynchus is considered to be primitive in structural features and to have an amphibianlike habit. Combined with the analyses of the embryo-bearing specimens of the Early Triassic Chaohusaurus and the Jurassic Stenopterygius, Chaohusaurus appears more derives than Cartorhynchus in body structural characters and is fully adapted to life in water; however, Chaohusaurus retained a head-first birth posture when giving birth to offsprings. Therefore, during the evolution of Ichthyosaurs from terrestrial ancestors to marine types, the adaptive structural characters (such as flipper, and elongate snout) and the adaptive behavioral characters (such as the mode of reproduction) might have evolved in different tempo, and the former changed earlier.

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A New Species of Qianichthyosaurus (Reptilia: Ichthyosauria) from Xingyi Fauna (Ladinian, Middle Triassic) of Guizhou

YANG Pengfei,JI Cheng,JIANG Dayong,Ryosuke Motani,Andrea Tintori,SUN Yuanlin,SUN Zuoyu

Acta Scientiarum Naturalium Universitatis Pekinensis

Abstract （1203）

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A new species of Qianichthyosaurus Li, 1999 from the Zhuganpo Member of the Falang Formation (Ladinian, Middle Triassic), Wusha Town, Xingyi City of Guizhou is described here, namely Qianichthyosaurus xingyiensis sp. nov. The recognition of the new species revises the diagnosis of the genus: tooth size relative to the skull width slightly below 0.1; ulna peripheral “shaft” notched or largely reduced; hindlimb nearly equal or longer than forelimb; tibia peripheral “shaft” notched or largely reduced. Qianichthyosaurus xingyiensis sp. nov. differs from the type species in having relatively longer snout (snout length/skull length over 60%); humerus radial facet being prominently larger than ulnar facet; unenclosed obturator foramen on pubis; fibula posterior process on the posterior margin and the ischium sub-triangular lacking shaft. The new species is stratigraphically older than Q. zhoui, the specimens of which were exclusively known from the Wayao Member of the Falang Formation (Carnian, Late Triassic). Along with askeptosaurid thalattosaur Anshunsaurus and shastasaurid ichthyosaur Guizhouich- thyosaurus, the occurrence of Q. xingyiensis sp. nov. in Xingyi Fauna suggests a closer relationship between Xingyi Fauna (late Ladinian, Middle Triassic) and Guanling Biota (Carnian, Late Triassic).

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Morphology of Keichousaurus hui from the Middle Triassic of Xingyi, Guizhou Province with Comments on Its Reproduction Mode

FU Wanlu,ZHANG Xuan,JI Cheng,JIANG Dayong,SUN Zuoyu,HAO Weicheng

Acta Scientiarum Naturalium Universitatis Pekinensis

Abstract （810）

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On the basis of detailed morphological description and anatomy comparison of two specimens of Keichousaurus hui, the diagnostic characters of Keichousaurus hui have been reconfirmed: small upper temporal fenestra, large orbits, thickened proximal end of ribs and extremely broad ulnae; and more morphological information of Keichousaurus hui is added. The sexual dimorphism of three adults and the ontogenetic stage of a juvenile have been identified through the measurement of different bones. Furthermore, from the paleogeographic information and observation of the embryos, it’s inferred that the reproduction mode is most likely viviparous, but the possibility of ovoviviparity cannot be totally ruled out.

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True Tailbend Occurred in the Late Triassic: Evidence from Ichthyosaur Skeletons of South China

JI Cheng,JIANG Dayong,HAO Weicheng,SUN Yuanlin,SUN Zuoyu

Acta Scientiarum Naturalium Universitatis Pekinensis

Abstract （780）

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Here the true tailbends are reported in two complete skeletons of Guanlingsaurus from the late triassic of Guizhou Province, southwestern China after accurate observations, measurements and comparisons with Ichthyosaur of early jurassic. They have acquired the wedge-shaped centra and the angles in these tailbends are around 15°while those in jurassic types are around 60°. This study shows for the first time that wedge-shaped tailbend centra already existed in merriamosaurs as early as late triassic time, probably being a result of coevolution between ichthyosaurs and the environment. The occurrence of the true tailbend connected triassic and jurassic ichthyosaurs that used to be considered as separate groups in previous literature. The present finding also suggests the monophyly of ichthyopterygia.

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RAPD Analyses of Fagus Species in China

JI Chengjun,SHEN Haihua,FANG Jingyun,XIE Changfu,FAN Yongjun

Acta Scientiarum Naturalium Universitatis Pekinensis

Abstract （640）

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Random amplified polymorphic DNA (RAPD) technique was applied to assess six Fagus species in China. Fifty-six of eighty tested arbitrary primers generated obvious bands with size ranging from 250 to 3050bp. An index of genetic similarity(F)was calculated and the value of (1-F) was used to evaluate genetic distances between species to construct dendrogram. The result suggested that three species，F.pashanica, F.hayaatae and F.hayatae var.zhejiangensis, had closer relationship and should be clustered into a single species. This was in good agreement with our morphological work. Based on RAPD markers,we suggested that Chinese beech species should be divided into four species, F.longipetiolata, F.engleriana, F.lucida and F.hayaatae (including F. pashanica and F.hayatae var.zhejiangensis).

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Ultrastructural Studies on Megasporogenesis in Triticum aestivum L.

LI Ling,JI Chengjun,YOU Ruilin

Acta Scientiarum Naturalium Universitatis Pekinensis

Abstract （602）

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Ultrastructural changes of the megasporogenesis of Triticum aestivum L were studied. During the meiotic process of megasporocyte, the ribosome population diminished greatly in prophase I and restored in metaphase I; plastids and mitochondria turned unclear (dedifferentiation) in prophase I and recovered their normal structures (redifferentiation) in metaphase I. All these proved that cytoplasmic reorganization took place during the megasporogenesis of Triticum aestivum. It was also found that the nuclear envelope disappeared earlier at the micropylar end than that at the chalazal end. The speed of the programmed cell death were different in three nonfunctional megaspores at the micropylar end and their relationships with the neighboring cells were also different. The biological significance was discussed about these phenomenon.

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Cytological Studies on the Formation of Female Gametophyte and Development of Archegonia in Ginkgo Biloba

JI Chengjun,YANG Xiong,LI ZhengliLee CL

Acta Scientiarum Naturalium Universitatis Pekinensis

Abstract （817）

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Following approximately a dozen of multiple divisions of producing about 2000 nuclei, the cell wall of the female gametophyte of Ginkgo biloba began to form centripedally. The archegonial initials could be distinguished from the peripheral cells at the micropyle end of the female gametophyte before the completion of the wall formation where the cell wall had reached the center of the gametophyte. Usually there were two archegonia in a female gametophyte which developed asynchronously at first, and gradually developed in concert. Great structural and morphological changes in the neck cell and the central cell took place during the archegonial development. The two neck cells of the archegonium divided to form four neck cells before fertilization, this division happened prior to the division of the central cell, but at times they divided synchronously. The initiation and development of archegonia in Gingko, compared with those of cycads, were liked to be more primitive at the evolutional level.

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