Abstract:Dtype cyclin (CYCD) regulates the G1/S phase transition of the cell cycle. CYCD combines with CyclinDependent Kinase (CDK) to form CYCD/CDK complex. The activated CYCD/CDK complex regulates the cell cycle through phosphorylation of downstream cell cycle response factors, which in turn affects plant growth and development. In this study, ‘741 poplar’ was used as experimental material, and a D2type cyclin gene was identified(PtoCYCD2; 1). The results showed that: (1) Quantitative real time polymerase chain reaction (qRTPCR) showed that PtoCYCD2; 1 gene was expressed in roots, stems, leaves, petioles, bark, and xylem, with the highest relative expression in leaves. (2) Subcellular localization indicated that PtoCYCD2; 1 protein was localized in the nucleus. (3) Compared with the wildtype poplar (WT), ‘741 poplar’ overexpressing PtoCYCD2; 1 gene showed reduced plant height, reduced stem diameter, and significantly lower leaf volume. (4) Scanning Electron Microscope (SEM) analysis showed that cells of transgenic poplars were smaller and more numerous than those of WT. Resin section showed that, compared with WT, the intercellular space of the fence tissue and sponge tissue of the transgenic poplar leaves was loose. (5) qRTPCR showed that, overexpressing PtoCYCD2; 1 gene in ‘741 poplar’, the expression levels of CDKA; 1, CDKB1; 1 and CDKB2; 1 were significantly upregulated, while retinoblastomarelated protein1 (RBR1) gene, cyclindependent kiprelated protein (KRP) gene expression level were significantly downregulated. This study lays a foundation for further understanding the function of CYCD2 gene in woody plants.

Abstract:Because of the stagnation of hypocotyl elongation of Lepidium apetalum Willd, at low temperature, it can be used as a good material to study the effect of temperature on hypocotyl elongation. In order to investigate whether the transcription factor HY5 plays a key role of L. apetalum hypocotyl elongation under the low temperature, we cloned and sequenced the LaHY5 sequence from the seed transcriptome of L. apetalum Willd. The relationship between the gene expression and low temperature induction and germination stage were studied by realtime quantitative PCR, the effect of the gene expression on hypocotyl elongation under low temperature was analyzed by transformation of Arabidopsis. The results showed that： (1) the LaHY5 cDNA sequence contains 447 bp of complete reading frame sequence, and its coding product is a peptide chain composed of 149 amino acids rich in serine, which contains a typical BRLZ domain. The relative molecular weight is 16.830 kD, the molecular formula is C₆₉₂H₁₁₅₆N₂₂₈O₂₄₆S₇, and the theoretical isoelectric point is 8.73, which is highly consistent with the homologous sequence of L. apetalum Willd. (2) The gene was rapidly upregulated by low temperature induction in the seeds or seedlings during the germination of L. apetalum Willd. (3) Under normal or low temperature conditions, the hypocotyls of transgenic Arabidopsis seeds grew faster than those of wildtype Arabidopsis. These results indicate that LaHY5 transcription factor plays an important role in seed germination of L. apetalum Willd, and seedling tolerance to low temperature stress. However, it also proved that it was not the cause of low temperature stagnation for hypocotyls elongation of L. apetalum Willd.

Abstract:MwMYB4 gene is a member of the MYB transcription factor family cloned from Agropyron mongolicum Keng. The progeny of transgenic Arabidopsis with MwMYB4 gene were used as materials in this study. The phenotype analysis and molecular identification of transgenic plants under drought and low temperature stress were used to analyze and verify the function of MwMYB4 gene. The results showed that： (1) the MwMYB4 gene has been successfully integrated into the genome of transgenic T₁ A. thaliana and achieved transcriptionlevel expression. (2) Under drought stress， the transgenic A. thaliana plants showed less yellowing， and the relative conductivity was lower than that of the wild type， but the change was not significant. The content of proline was significantly higher than that of the wild type control. The expression level increased with the duration of drought stress. (3) Under low temperature stress， the paleness of transgenic Arabidopsis leaves was significantly lower than that of wild type， and the expression level of MwMYB4 gene increased with the increase of low temperature stress time. Studies have shown that overexpression of MwMYB4 gene from Agropyron mongolicum can increase the tolerance of transgenic Arabidopsis to drought and low temperature. This gene may play a regulatory role in the regulation mechanism of drought stress and low temperature stress, and can be an important candidate gene for improving drought and cold resistance of crops and other forages.

Abstract:DNA methylation is one of the epigenetic mechanisms that regulate plant growth, development and stress gene expression. In this study, we used 5azaC, a DNA methylation inhibitor with different concentrations, to treat spring wheat seeds with different salt treatments. We analyzed the effects of 5azaC on seed germination and DNA methylation changes after salt stress to explore the correlation between DNA methylation and salt tolerance of wheat. The results showed that: (1) 5azaC can significantly inhibit root length and reduce fresh weight and dry weight. (2) MSAP analysis showed that the methylation levels increased after salt stress alone, but the methylation level of 5azaC pretreated materials after salt stress showed a downward trend. (3) After salt stress, DNA demethylation and DNA methylation occurred simultaneously in the genome. The rate of DNA demethylation increased for saltsensitive cultivar ‘Xinchun 6’, while the DNA methylation rate decreased. Both rates of DNA demethylation and DNA methylation increased for salttolerant cultivar ‘Xinchun 11’, but the rate of demethylation was higher than that of DNA methylation. The results showed that the main change of DNA methylation in wheat leaves was DNA demethylation after salt stress. 5azaC increased the rate of DNA demethylation under salt stress. (4) Sequence analysis of DNA methylation modification sites found that DNA methylation modifications were present in ribosomal subunit proteins, protein kinases, and transposon sequences, indicating that salt stress could be resisted by multiple metabolic pathways.

Abstract:4coumarate: CoA ligase (4CL) plays an important regulatory role in the phenylaprapanoid metabolism. In this study, 11 4CL genes named Ib4CL1-Ib4CL11 were identified in sweet potato (Ipomoea batatas) based on transcriptome data. The results of sequence alignment and functional domain analysis showed that all Ib4CL had typical 4CL structural feature, containing the conserved Box Ⅰ and Box Ⅱ domains. Evolutionary and conserved motif analysis suggested that Ib4CL1 and Ib4CL2 belong to Class Ⅰ, Ib4CL3 belongs to Class Ⅱ, and Ib4CL4Ib4CL11 belong to 4CLlike proteins. Transcriptome data and quantitative realtime PCR analysis showed that the transcriptional levels of Ib4CL3 and Ib4CL10 in leaves were significantly higher than that in stems and roots, which were positively related to the accumulation of chlorogenic acid; Ib4CL4 and Ib4CL8 were higher expressed in young leaves, closely related to the accumulation of anthocyanins. The results laid the foundation for further revealing possible function of 4CL genes in phenylaprapanoid metabolism of sweet potato.

Abstract:The genome constitution of Elymus dahuricus and E. nutans were characterized using 12 repetitive sequence by a technique of fluorescence in situ hybridization (FISH) probes, which include probes of nine trinucleotide simple sequence repeat (SSR) motifs and two satellite DNA repeats sequences pAs1 and pSc119.2, and ribosomal 5S rDNA. This study provided a new evidence for the speciation and evolution of E. nutans and E. dahuricus at the level of molecular cytogenetics. The results suggested that: (1) all sequences produce detectable hybridization signals on the chromosomes of both species. In both species, (AAC)₁₀, (ACT)₁₀, and (CAT)₁₀ were revealed to be colocalized, whereas AAG and AGG also revealed an approximately colocalized. All repetitive sequences except 5S rDNA, produced highintensity and multiple hybridization sites on the H chromosomes. The hybridization sites of different repeat sequence on the both St and Y chromosomes are varied. It showed that 5S rDNA, pSc119.2, (AAC)₁₀, (CAT)₁₀, (ACT)₁₀, (CAC)₁₀ have fewer or no signal distribution, while the remainders have more signal sites. (2) E. dahuricus included a hybridization site of (AAC)₁₀, (ACT)₁₀, (CAT)₁₀, (CAC)₁₀ on St genome. It is distinct from E. nutans which includes none of them on its St genome. E. hahuricus has one unique pSc119.2 hybridization on the terminal position of a pair of chromosome, in contrast to the E. nutans involving it on the intercalary region of a pair chromosome of St genome. E. nutans contains more repetitive sequences hybridization sites in St and Y genome than E. dahuricus. (3) A unique H/Y intergenomic translocation was stably detected between different materials in E. dahuricus. It implies a relative genome stability of E. dahuricus. However, more polymorphic hybridization sites in H genome than in St and Y genome were still observed in E.dahuricus between different materials. E. nutans present higher number of polymorphic hybridization sites between different materials than E. dahuricus. According to the study, both H genomes of E. nutans and E. dahuricus are derived from H. bogdanii, and St genome may be originated from different species of Pseudoroegneria. Compared with E. dahuricus, St and Y genomes of E. nutans may have higher chromosomal structural variability, and the reason for the large variation of St and Y genomes of E. nutans may be the introgression hybridizations with the species which contains St and Y genomes distributed in the same region.

Abstract:In this study, we constructed an F₂ isolated population derived from a cross between a dwarf wild rice mutant with shortgrain and a cultivar variety KJ01 with longgrain. And the genetic analysis for grain length of the F₂ population was performed. By using 132 pairs of polymorphic molecular markers evenly distributed on 12 chromosomes of rice, we conducted QTL mapping and major QTLs analysis, which would establish a foundation of further cloning the novel major grain length gene and provide a theoretical basis for grain shape breeding of rice. The results were as follows: (1) grain length trait of the isolated population F₂ was quantitative trait controlled by multiple genes. (2) By QTL linkage analysis of 543 F₂ individuals, a linkage map of 1 713.94 cM controlling rice grain length was constructed, and a total of 24 QTLs were detected, and only 3 QTLs showed additive genetic effects, the others showed negative genetic effects. (3) The three major QTLs located in interval markers of PSM379-RID24455, RID24455-RM15689, and RM571-RM16238 on chromosome 3, which explained phenotypic variation for 54.85%, 31.02%, and 7.62, respectively. (4) The grain length QTL located in interval markers of PSM379-RID24455 was the major QTL newly discovered in this study.

Abstract:In this study， we subjected Arabidopsis thaliana wild type and related transgenic lines to the concentration of 0, 50, 100, 200 and 400 μg/mL cefotaxime， investigated the effects of cefotaxime on the elongation of primary root, meristem activities, auxin distribution and transport and stem cell activities， explored the toxic mechanism of cefotaxime on the growth and development of primary root. The results showed that: (1) cefotaxime remarkably inhibited primary root growth of A. thaliana in a concentrationdependent manner. It also repressed the meristem size and the expression of CYCB1; 1， suggesting that cefotaxime can inhibit the meristem activities of root tips. (2) Cefotaxime reduced the expression of auxin reporter genes DR5∷GUS，DR5∷GFP and auxin polar transport proteins PIN1, PIN2, PIN3, PIN7 and AUX1， indicating that it can inhibit the auxin distribution and polar transport of root tips. (3) Cefotaxime downregulated the expression of quiescent center marker lines WOX5∷GFP, QC25 and QC46, as well as the expression of SHR and SCR proteins， indicating that it can inhibit the stem cell activity of root tips. Collectively, cefotaxime regulates the growth and development primary root in A. thaliana by repressing the auxin distribution and transport， stem cell activity and meristem activity.

Abstract:The phenotypic plasticity of plant leaves under drought stress can reveal the ecological significance of plants in different natural environments and understand their adaptive evolution mechanism. Indigofera is the third genus of Leguminosae, and its habitat is diverse and complex, so there are many problems in its classification and evolution. In this study, we chose I. bungeana, which has the widest ecological amplitude and the largest morphological variation in Indigofera. Oneyearold seedlings of I. bungeana from Shimian of Sichuan Province, Mengzi, Yanshan of Yunnan Province were treated with the gradient drought stress. The results were as follows: as the stress of drought was intensified and last, the leaf length and area kept on decreasing, the petiole length appeared much smaller for all three populations of I. bungeana. The density of trichomes on abaxially increased significantly, the length of trichomes on abaxially decreased significantly, the length of trichomes on adaxially change significantly in the populations from Yanshan and Shimian. There was no significant difference on the density of trichomes on adaxially in the populations from Shimian and Mengzi, while the length of trichomes on adaxially did not change in the population from Mengzi. The results of this study can not only provide the evidence for the classification of I. bungeana, but also lay a foundation for the studies on its adaptation and evolution.

Abstract:The pot experiment was carried out by the lowtemperature stress under controlled conditions. We selected the annual dormant stems in five species (strains) of Euonymus as the experimental materials, aiming to study the physiological mechanisms and coldtolerance under controlled conditions. The temperature gradients were established of 0 ℃, -10 ℃, -20 ℃ and -30 ℃, respectively, by a temperature/humidity chamber in this study. The properties of cell membrane permeability, contents of osmotic regulators, protective enzymes activities and other physiological indexes in different Euonymus species were tested by the lab. analysis when suffered to various temperature conditions. Otherwise, leaf anatomical structure and subordinate function were used to evaluate the resistance capability of five species (strains) under cold condition. The results showed that: (1) E. japonicus ‘CuZhi’ NO.6 had three close layers of palisade cell, while E. japonicus ‘CuZhi’, E. kiautschovicus, E. japonicus had two close and one loose ones. In contrast, E. fortunei had only two close layers of palisade cell. Lowtemperature stress led to varieties in leaf tissue tightness of the five E. species, and the order indicated that E. japonicus ‘CuZhi’ NO.6 > E. japonicus ‘Cu Zhi’ > E. kiautschovicus > E. japonicus > E. fortunei. (2) The logistic equation was applied to analyze the relative conductivity of five E. species and the lethal temperature of 50% (LT₅₀), and the arrangement was as follows: E. japonicus ‘CuZhi’ NO.6 (-19.69 ℃) < E. japonicus ‘CuZhi’ (-17.41 ℃) < E. kiautschovicus (-16.03 ℃) < E. japonicus (-13.33 ℃) < E. fortunei (-10.45 ℃). (3) The contents of permeability regulate substances indicated a continuously increase with the decrease of treated temperature, while the soluble sugar content of E. japonicus ‘CuZhi’ NO.6 and E. japonicus ‘CuZhi’ improved the most at -30 ℃. Similarly, the soluble protein content of E. kiautschovicus and E. japonicus also largely increased. In contrast, the both former substance contents in E. fortune had the opposite trend. (4) The activities of antioxidant enzymes revealed the process of ascending firstly and then descending under the control condition. The activities of SOD, POD and PPO in E. fortunei and E. fortune reached to the maximum at -10 ℃. Different from that, the enzyme activities in the blade of E. japonicus ‘CuZhi’ NO.6, E. japonicus ‘CuZhi’ and E. kiautschovicus were at -20 ℃. And this changes were in accordance with the results of LT₅₀. (5) According to the changes of each index induced by coldstress, the results on resistance ability of five species were obtained by using membership function. The sequences indicated that E. japonicus ‘CuZhi’ NO.6 > E. japonicus ‘CuZhi’ > E. kiautschovicus > E. japonicus > E. fortunei. From the above results, we could see that there were two ways to reveal the impacts of coldstress on various E. species. One side, it could regulate the osmotic potential through the synthesis of osmoregulation substances of the plants under cold stress. On the other side, the promoted activities of antioxidant enzymes could be benefit to the hazardous substances removal like the reactive oxygen species and polyphenol material etc. In conclusion, the adaptive ability to the lowtemperature stress to five E. species was evaluated correctly by studying leaf anatomical structure, lethal temperature of 50% and subordinate function. Hence, the mentioned conclusions could provide a theoretical basis for cold resistant screening and the application in city afforestation of E. germplasm resources.

Abstract:In this experiment, we used melting flesh peach (Zhongyoutao13, Chunmei and Zhongyoutao 4) and stony hard (SH) flesh peach (Zhongyoutao18, Zhongtao 9 and Bairuyu) to analyze the changes of fruit quality and ethylene emission during cold storage, and to explore the mechanism of chilling injury in peaches with different textures. The results showed that： (1) flesh browning was a mainly chilling injury of SH peach， while wooliness of melting peach. (2) Compared with storing at ambient temperature， the ethylene production of melting peach would be repressed when storing at low temperature for a short period， while the extended cold storage would induce the development of chilling injury and ethylene burst； For SH flesh peach， ethylene production increased sharply when kept at low temperature for a long time. It was also found that during cold storage, the ethylene release peak in peach was 5 to 10 days later than that of nectarine of the same flesh texture, and peaches were more tolerant to low temperature than nectarines. (3) The melting peach softened rapidly after harvest, but the decline rate of firmness was significantly inhibited at low temperature and maintained at about 15N in the later stage of cold storage, while the firmness of stony hard peach fruit was less affected during low temperature and ambient temperature storage. (4) The soluble solids content of different fleshy peaches changed slightly during storage. The above results showed that the symptoms of chilling injury and the mode of ethylene release of different flesh textures are diverse, which provides theory basis for reasonable low temperature storage of peach with different textures in the future.

Abstract:Our objective was to study the influence of methyl jasmonate (MJ) on biosynthesis of gallic acid (GA) in cell suspension of Acer ginnala. MJ was added into A. ginnala suspension and the cells were sampled at a series of time points after induction. The content of GA was determined by an HPLC method, the conductivity of the media was measured by a conductivity meter, the dissolvable protein content of the cells was determined by spectrophotometry and the cell shape was recorded by confocal microscopy. The results showed that: (1) induced by MJ 100 μmol·L^-1 for 24 hours, the production of GA reached the peak (12.49 mg·g^-1) which is about twice of that of control. (2) The pH value and conductivity of the media were dynamic after induction by MJ. The cell membrane was damaged, with increased permeability. Few cells had several nuclei. (3) The soluable protein content of the cell had three peaks at 24 h, 72 h and 5 d after induced, respectively, which are 1.4, 1.67 and 2.07 times of those of control, respectively. (4) The activity of phenylalanine ammonialyase (PAL) reached the peak at 25 h and 5 d of postinduction, respectively, which were twice and 3.75 times of control, respectively. These results indicate that after shorttime induction, the GA content is accumulated, the activity of PAL and the content of soluable proteins also increased, whereas the pH value and conductivity of the media did not alter significantly.

Abstract:Taking winter wheat cultivar ‘Yunong 211’ as materials, we carried out a pot experiment that set up to control water for 12 days and rewater for 2 days after drought to study the effects of root application of 15 mmol·L^-1 propionic acid on plant morphology, leaf relative water content, electrical conductivity, malondialdehyde content and the dynamic changes of leaf proline content and its key metabolic enzyme activities, to explore the mechanism of proline metabolism of exogenous propionic acid in improving drought resistance of wheat. The results showed that: (1) under drought stress (the relative water content of soil decreased to 20%), the root application of propionic acid could significantly increase the relative water content of wheat leaves, and reduce the relative conductivity and malondialdehyde content of wheat leaves. The wilting degree of wheat seedlings treated with propionic acid was significantly lower than that of control, and the biomass accumulation in the shoot increased by 13.3% (P < 0.05). (2) Under mild water stress (soil relative water content decreased to 45%-55%), the root propionic acid treatment led to a significant accumulation of proline than control. With the increase of drought stress (soil relative water content decreased to below 20%), it could still maintain at the normal level (about 300 μg·g^-1), while the proline content in control leaves increased sharply; and the proline content in leaves of wheat treated with propionic acid could recover to normal level rapidly. (3) During the whole process from water control to rewatering, the activities of the key enzymes Δ 1pyrroline5carboxylate synthetase (P5CS) and ornithine aminotransferase (σOAT) of proline biosynthesis increased firstly and then decreased. The activity of pyrroline5carboxylic acid reductase (P5CR) decreased firstly and then increased, while the activity of proline dehydrogenase (PDH), the key enzyme of proline degradation, increased. These results suggested that under drought stress, applying propionic acid to roots could regulate the key enzyme activities of proline synthesis and degradation pathway in the process of proline metabolism to maintain the stability of proline level in leaf cells, and effectively reduce the degree of water loss and peroxidation damage of leaves, so as to improve the drought resistance of winter wheat seedlings.

Abstract:We studied the effect of continuous soil natural drought on the growth, physiological indexes of stress tolerance and the contents of main medicinal components of Uncaria rhynchophylla seedlings by pot experiment of soil water control for 12 days. The results showed that: (1) with the extension of drought stress time, the biomass of roots, stems and leaves and the relative water content (RWC) of leaves decreased significantly (P < 0.05), while the content of MDA and the relative electrical conductivity (REC) increased gradually. (2) Along with the time of drought stress extended, the contents of chlorophyll a and chlorophyll b in leaves increased firstly and then decreased. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) increased firstly and then decreased. The activity of POD firstly reached the peak, and the increase of CAT activity was the largest. The contents of proline (Pro), soluble sugar (SS) and soluble protein (SP) in leaves increased gradually, and Pro showed stronger osmotic regulation ability. (3) The contents of rhynchophylline and isorhynchophylline in leaves, main stems and branches of U.rhynchophylla seedlings increased firstly and then decreased with the extension of drought stress time. The response time in order was leaves, main stems and branches with hooks. The alkaloid content in order was branches with hooks, leaves and main stems from high to low. It was found that the growth of U. rhynchophylla seedlings was affected by the continuous natural drought in the soil, but the plants could improve their water absorption and retention capacity by increasing their antioxidant enzyme activity and accumulation of osmoregulation substances to resist the drought stress effectively. In addition, the 4th-8th day of drought was beneficial to the accumulation of the main medicinal components, rhynchophylline and isorhynchophylline. Generally speaking, when the relative water content of soil was 42%-53%, U. rhynchophylla had stronger drought resistance and higher contents of rhynchophylline and isorhynchophylline.

Abstract:We conducted a pot experiment using 5monthold Phoebe bournei seedlings with twofactor including four light treatments (100%, 41.3%, 14.3%, 3.6% Nature Source light) and four nitrogen levels (0, 0.5, 1, 2 mol/L) to study the photosynthetic physiological characteristics of Phoebe bournei under the interaction of light and nitrogen, to explore the physiological mechanism of its adaptability to the environment. The results showed that: (1) shading and nitrogen could significantly improve the photosynthetic pigment content of P. bournei. With the decrease of light intensity, the soluble sugar (SS), soluble protein (SP), net photosynthetic rate (P_n), stomatal conductance (G_s), maximum net photosynthetic rate (P_max), dark respiration rate (R_d), apparent quantum coefficient (AQY) in leaves of P. bournei seedlings increased firstly and then decreased under the same nitrogen, and the highest was at 41.3% natural light level. The intercellular CO₂ concentration (C_i), transpiration rate (T_r), light saturation point (LSP) and light compensation point (LCP) decreased at the same term. The maximum photochemical efficiency (F_v/F_m) and potential activity (F_v/F_o) of PSⅡ increased with the decrease of light intensity. (2) With the increase of nitrogen application, SS, SP, photosynthetic gas exchange parameters and characteristic parameters of light response curve of P. bournei leaves increased firstly and then decreased, F_v/F_m and F_v/F_o decreased then ascend. (3) There was a significant interaction between different light and nitrogen levels. Membership function analysis results showed that 41.3% natural light and 0.5 mol/L pure N treatment had the best effect, the research indicated that the P. bournei seedlings were photophilous and shade plant, and the combination of suitable shading and nitrogen application can significantly improve the osmotic adjustment ability, improve the utilization rate of light energy, and promote photosynthesis of P. bournei, while full light, excessive shading, nitrogen deficiency, or excessive nitrogen application were not conducive to the normal physiological metabolism of P. bournei.

Abstract:Based on a field experiment involving five precipitation treatments (50% reduction, 30% reduction, control, 30% increase, and 50% increase) and two N addition treatments (0 and 5 g·m^-2·a^-1) conducted in a desert steppe of Ningxia in 2017, the C∶N∶P ecological stoichiometry in both plants and soil microbes were studied, and their relationships with soil C∶N∶P ecological stoichiometry and other indices were also analyzed. Our main objectives were to determine the C∶N∶P balance characteristics both in plants and soil microbes and their key influencing factors. The results showed that: (1) decreasing precipitation had little effects on the C∶N∶P stoichiometry in both plants and soil microbes, reflecting their adaptations to shortterm drought; increasing precipitation decreased N and P contents in both plants and soil microbes, and thus increased C∶N and C∶P. However, these effects were simultaneously influenced by N addition. (2) Under reduced and increased precipitation conditions, N addition had less effect on plant C∶N∶P stoichiometry, whereas it greatly changed soil microbial C∶N∶P stoichiometry, especially under increased precipitation treatments, indicating that precipitation promotes the effect of N addition. (3) Compared with other indices, plant total N content and N∶P and soil microbial biomass N∶P had lower internal stabilities, indicating that these indices could better reflect the N supply and N and P limitation in soils. (4) Among all soil factors, plant C∶N∶P stoichiometry was more affected by available P concentration, phosphatase activity, conductivity, C∶P and organic C content, while soil microbial C∶N∶P ecological stoichiometry more tightly related to conductivity, water content, sucrase activity, and phosphatase activity, indicating that the C∶N∶P ecological stoichiometry of plants and soil microbes are mainly regulated by other soil factors, rather than soil C∶N∶P ecological stoichiometry.

Abstract:Precipitation is the most important limiting factor for the processes and functions of desert ecosystems, and desert plant seedlings are extremely sensitive to precipitation changes during the growing season. In order to explore the response of desert plant seedlings to future precipitation patterns changes, we selected two typical desert plant seedlings (Nitraria tangutorum and Artemisia ordosica) in UlanBuh desert as research objects. The stoichiometric characteristics of two plant seedlings were studied with artificial simulated precipitation addition experiment, including different gradients (CK. natural precipitation, A. +25% precipitation, B. +50% precipitation, C. +75% precipitation, D. +100% precipitation) according to the precipitation of growing season (June to September). The result showed that: (1) for the distribution of C, N and P contents in different organs of seedlings, increase precipitation significantly reduced the C content of stems and C and P contents of roots of N. tangutorum seedlings, and increased C and P contents of leaves and the N content of roots(P<0.05), while it significantly increased C content in stems and leaves of A. ordosica seedlings, and decreased N content in leaves and roots and the P content in stems, leaves and roots(P<0.05). (2) For the stoichiometric ratio, the N∶P of stems, leaves and roots of N. tangutorum seedlings is relatively constant, and the ratio is greater than 16, indicating that the relative growth rate of N. tangutorum seedlings is lower under the environment of precipitation addition, and is obviously restricted by P element. However, the N∶P of A. ordosica seedlings showed a significant negative correlation with the increase of precipitation. The relative growth rate increased with the increase of precipitation. Therefore, simulated precipitation addition had a significant effect on the stoichiometric characteristics of the desert plant. Increasing precipitation is not conducive to the growth of N. tangutorum seedlings, but is more conducive to the rapid growth of A. ordosica seedlings.

Abstract:Based on the theory and method of dendrochronology, we studied the response relationship between the radial growth of Populus euphratica and the temperature and runoff in the middle reaches of Tarim River by means of interdecadal mean, correlation analysis and multiple linear regression, in order to understand the radial growth law of P. euphratica and its response to environmental change, and finally to provide a theoretical basis for the protection and management of P. euphratica forest. The results show that: (1) during the period from 1983 to 2014, the periods with the highest temperature and the lowest runoff in the middle reaches of the Tarim River occurred between 2005 and 2009, and the annual ring width of P. euphratica reached the minimum during this period; From 2010 to 2014, the width of the annual rings of P. euphratica appeared to be the largest and narrower. (2) The radial growth of P. euphratica in the section of Shazihekou is mainly affected by the runoff in the growing season from April to September. The runoff in the previous year also has a certain lag effect, but the effect of temperature is not obvious. The radial growth of P. euphratica in the section of Aqike was greatly affected by the runoff from January to March. The high temperature in June of that year and November of the previous year became the limiting factor for its radial growth. (3) Sufficient runoff in spring and summer and the autumn of the previous year are the ideal conditions for the radial growth of P. euphratica in the section of Shazihekou. However, in some of these three seasons, the runoff is small and the rest is sufficient. It is still possible to form a wide treering, but if the runoff in these three seasons is not sufficient, narrow treering will inevitably be formed. The ideal condition for the radial growth of P. euphratica in Aqike section is that the lower temperature is more favorable for the radial growth of P. euphratica in the next year when the runoff at the end of autumn is small. The results show that the radial growth of P. euphratica in the middle reaches of Tarim River has a positive correlation response to runoff, a negative correlation response to temperature when runoff is small, and both of them have a lag response.

Abstract:Ammopiptanthus mongolicus is a rare and endangered species in northwest China. It is of great significance to explore floristic composition and community characteristics to maintain the fragile ecosystem in the arid desert area of northwest China. In this paper, 26 sample sites of A. mongolicus were investigated. We used TWINSPAN to classify the communities, and canonical correspondence analysis (CCA) to analyze the relationship between species composition and ecological factors of A. mongolicus. The results showed that: (1) the species composition of A. mongolicus was mainly leguminous, gramineae, compositae and chenopodiaceae, belonging to 28 families, 63 genera and 90 species, and the floristic composition was mainly distributed in Mediterranean, north temperate zone and the world. (2) TWINSPAN classification can divide 26 A. mongolicus sample plots into 9 community types. (3) According to the ranking analysis of CCA, average annual rainfall (F = 2.8, P = 0.002), the growing season rainfall (F = 2.6, P = 0.002), available nitrogen (F = 2.1, P = 0.006), solar radiation (F = 2.1, P = 0.008), the vapor pressure (F = 1.9, P = 0.006), soil organic matter (F = 1.7, P = 0.04), latitude (F = 1.7, P = 0.006) are the main ecological factors affecting the A. mongolicus community composition, the results can provide the protection of the rare and endangered plants of Mongolia sand Holly with basic data.

Abstract:The fern flora was analyzed in terms of floristic composition, distribution types and ecotypes through field investigation and consulting literature, and meanwhile similarity coefficient among the flora and other 7 floras were compared. The results showed that： (1) the flora was composed of 109 species, 47 genera and 28 families. The representative families are Dryopteridaceae, Thelypteridaceae and Athyriaceae, and the main genera are Dryopteris, Asplenium and Arachniodes. There are 14 species endemic in Ningzhen Mountain. (2) The families and genera distribution types mainly belong to tropical elements, and the species distribution type belongs to East Asia, indicating the fern flora of Ninzhen Mountain was featured with subtropics transition to temperated area. (3) Similarity coefficient of families, genera and species showed the genetic relationship of Ningzhen Mountain is intimate to Jigong Shan in Henan, and followed by Fengyang Shan in Zhejiang and Wuyi Shan in Fujian. (4) The ferns in Ningzhen Mountain range can be divided into three types: the wet, the stone and the soil, and there are 31, 8 and 70 species, respectively.

Abstract:A new record family of Pteridophyta, Diplaziopsidaceae, and its species Diplaziopsis cavaleriana are reported from Qinling Mountain area in Shaanxi Province. A brief description and photos are provided. The voucher specimens were deposited in Herbarium of Shaanxi University of Technology (HZTC).