Abstract:Protoporphyrinogen oxidase (PPOX1) is a key enzyme in the pathway of chlorophyll biosynthesis, and it is used to explore the function of PPOX1 gene in apple. In this study, Malus halliana, as a apple rootstock was used as the test material. The MhPPOX1 gene fragment was cloned by PCR and bioinformatics analysis and functional identification were conducted. Using the method of agrobacterium mediated genetic transformation of Nicotiana tabacum L. and Arabidopsis thaliana, the function of MhPPOX1 under iron deficiency stress was further analyzed, and resistance analysis of transgenic N. tabacum L. and A. thaliana were conducted. The results show that: (1) the MhPPOX1 gene fragment of M. halliana was successfully cloned and identified as apples MhPPOX1 (serial number: loc103444480). The open reading frame of MhPPOX1 gene is 1 644 bp, encoding 547 amino acids, and the isoelectric point is 8.98. Phylogenetic tree analysis showed that the amino acid sequence encoded by MhPPOX1 gene was closely related to the amino acid in Pyrus bretschneideri. (2) Successfully cloning of the MhPPOX1 promoter fragment of M. halliana (2 016 bp). The New PLACE database was used to predict and analyze the cis acting elements of the promoter. There were response elements such as drought, low temperature, light, auxin and chlorophyll in MhPPOX1 promoter sequence. (3) The overexpression vector MhPPOX1pRI101 was successfully constructed, and transgenic N. tabacum L. and A. thaliana were successfully obtained. (4) qRTPCR analysis showed that under iron deficiency stress (Fe) the leaves of M. halliana seedlings turned yellow and died, and the expression level of MhPPOX1 gene was significantly higher than that of the control. Compared with wild type, under iron deficiency stress transgenic N. tabacum L. and A. thaliana grew well and not easy yellowing. The total chlorophyll a, chlorophyll b and total iron contents of transgenic N. tabacum L. and A. thaliana were significantly higher than those of wild type plants, which indicated that overexpression of MhPPOX1 gene improved the resistance of N. tabacum L. and A. thaliana to iron deficiency stress. The study suggested that MhPPOX1 gene plays an important role in plant resistance to iron deficiency stress.

Abstract:Malic acid is one of the most important organic acids in strawberry fruits, and its content significantly affects the flavor of strawberry fruits. In this study, using Fragaria × ananassa ‘Benohoppe’ as material, we cloned a new MYB transcription factor (TF)FaMYB73 by RTPCR including 756 bp open reading frame, encoding 252 amino acids. It was predicted that the molecular mass of this protein was 27.6 kD, and pI was 6.8. The FaMYB73 protein contained the conserved R2R3MYB domain and microscopy analysis showed that 35SFaMYB73GFP was located exclusively in the nucleus as expected. Quantitative realtime PCR (qRTPCR) analysis demonstrated that the expression of FaMYB73 had tissue specific and stage specific. FaMYB73 was expressed in different tissues and four developmental stages of fruits. The expression level of FaMYB73 was relatively higher in leaves and flowers, the highest at the white fruit stage and decreased with maturity. The malic acid content detected by HPLC reached the highest at the white fruit stage and decreased thereafter, and was positively correlated with the expression of the FaMYB73 gene. The homologous expression in strawberries found that FaMYB73 overexpression significantly promoted the accumulation of malic acid, and silence distinctly reduced the amounts of malic acid. Two transgenic tobacco lines having the malic acid overaccumulation phenotype were obtained and the transformation was confirmed using quantitative realtime PCR (qRTPCR). The results indicated that FaMYB73 was involved in regulating the synthesis of malic acid in strawberry fruits and provided a theoretical foundation for further exploring the mechanism of FaMYB73 regulating malic acid in strawberry fruits.

Abstract:The cDNA and promoter sequence of FnMYB24 gene were cloned from Fragaria nilgerrensis Schltdl. by RTPCR. Bioinformatics analysis showed that the cDNA sequence of FnMYB24 was 1 033 bp (GenBank accession number MN879283) length, and its open reading frame (ORF) was 609 bp length, encoding 202 amino acids, including a conserved MYB_DNAbinding domain. Homogeneous analysis showed that the amino acid sequence encoded by FnMYB24 gene was 92.75% similar to that of encoded by Fragaria vesca. The promoter sequence of 718 bp upstream of the transcription initiation site (GenBank accession number MN879285) was further cloned, which was predicted to contain several cisacting elements such as hormone response elements and optical regulation elements. By constructing pFnMYB24∷GUS expression vector and carrying out instantaneous tobacco transformation, it was found that the pFnMYB24 promoter had transcriptional activity and could drive the expression of FnMYB24 gene. Realtime quantitative PCR results showed that the expression of MYB24 gene in the leaves of resistant variety F. nilgerrensis Schltdl. and susceptible cultivar ‘Miaoxiang No.3’ was upregulated after inoculation with Colletotrichum gloeosporioides, but the expression level of MYB24 in ‘Miaoxiang No.3’ was always lower than that in F. nilgerrensis Schltdl. This gene was also induced by SA since the MYB24 expression levels in two strawberry varieties after SA treatment were higher than those of controls. Our results suggest that MYB24 may involved in regulate resistance to strawberry anthracnose, this study laid foundation for further investigate the function of MYB24 confers resistance to strawberry anthracnose.

Abstract:In order to explore the molecular mechanism of NBSLRR genes in hulless barley(Hordeum vulgare L. var. nudum)resistance to barley leaf stripe, in this study, we isolated HvtRGA gene from leaves of the striperesistant hulless barley variety ‘Kunlun 14’ and the susceptible variety ‘Z1141’ and obtained a 3 544 bp sequence. HvtRGA gene contained a 3 306 bp open reading frame (ORF), encoding 1 101 amino acids. After sequencing and comparison, it was found that the similarity of base sequences of ‘Kunlun 14’ and ‘Z1141’ was 99.89% since the bases of ‘Z1141’ were replaced from G to A at position of 1196 and 1945, whereas the similarity of amino acid was 100%. Protein sequence analysis showed that HvtRGA was a hydrophilic unstable acidic protein containing NBARC conserved domain and five LRR domains, belonging to the NBSLRR family. The amino acid sequence similarity between HvtRGA protein and the NBSLRR encoded by rgaS9217 and rgaS226 of barley were 96.55% and 88.72%. Phylogenetic tree analysis showed that NBSLRR of hulless barley and barley of the wheat family, durum wheat, Brachypodium distachyon were clustered into one branch. Moreover, HvtRGA has the closest genetic relationship with the barley rgas9217 encoded protein, followed by the barley rgas226 encoded protein, while far away from Setaria viridis and Setaria italica. Quantitative PCR results showed that, under the stress of barley leaf stripe, the expression levels of HvtRGA gene in resistant and susceptible varieties were extremely significantly increased, and the gene expression levels in resistant varieties‘Kunlun 14’ were significantly higher than that in susceptible varieties‘Z1141’. It is speculated that HvtRGA gene may play an important role in the regulation of barley leaf stripe in hulless barley.

Abstract:The lysophosphatidic acid acyltransferase (LPAT) family genes were screened and identified from the transcriptome database of perilla. The sequence characteristics and protein structures of the family genes were analyzed using bioinformatics methods and the spatiotemporal expression characteristics of genes were studied using qRTPCR technology. The research provides a basis for better understanding the mechanism of perilla oil synthesis. The results showed that: (1) a total of 11 LPAT family genes were detected, including PfLPAT1, PfLPAT21, PfLPAT22, PfLPAT23, PfLPAT24, PfLPAT41, PfLPAT42, PfLPAT51, PfLPAT52, PfLPAT53 and PfLPAT54. The length of amino acids encoded by PfLPATs genes ranged from 250 to 384 aa, and the theoretical isoelectric point varied from 7.6 to 9.6. (2) The analysis of gene sequence comparison showed that 11 PfLPATs proteins belonged to three subclasses, respectively, among which type 1 LPAT contained one gene, type 2/3 LPAT contained four genes and type 4/5 LPAT contained six genes. (3)Realtime fluorescent quantitative PCR results indicated that 11 LPAT family genes were expressed in different tissues of ‘Jin Zisu 1’. Among them, LPAT21, LPAT22 and LPAT23 expressed highly in seeds. It was speculated that they play an key role in the process of perilla seed oil synthesis and metabolism. The results of this study provided important genetic information for further study on the functions of LPAT family genes.

Abstract:We used Optic Microscopic and Electron Microscopic to observe the formation and development of the interxylarycork in the roots of threeyearold Scutellaria baicalensis, to reveal the characteristics of interxylarycork formation and the changes of the vessels and surrounding parenchyma cells during the development of interxylarycork, in order to provide theoretical basis and experimental evidence for the formation of pithdecayed products of Radix Scutellariae.The results showed that: (1) the secondary structure of S. baicalensis root was composed of periderm, cortex and secondary vascular tissue; Interxylarycork occurred around the abnormal vessels in the xylem. First, tylosis or other substances appear in the vessels, and then some substances also appear in the parenchyma cells adjacent to these vessels. Subsequently, the normal parenchyma cells around the vessels recovered their meristematic ability and produced cork cambium, which formed interxylarycork. (2) Interxylarycork separated healthy tissues from these abnormal vessels and parenchyma cells, and the isolated tissues will gradually become dead tissues. (3) In the transection section, these small interxylarycorks can occur at different positions of xylem at the same time or successively, they gradually expand from inside to outside and connected with the surrounding interxylarycork, and finally, they formed a large interxylarycork. (4) In the longitudinal section, interxylarycorks which exist in some S. baicalensis roots within 3 cm below the root head extend downward from the head of the roots in tubular form.

Abstract:The materials used in this research is ‘Benihoppe’, a popular cultivar in strawberry production with weak resistance to black rot disease. We isolated and identified the pathogen of black rot disease from sick strawberry plants. Then, we further studied on the effect and mechanism of exogenous melatonin on improving the resistance of strawberry to black rot. We detected the pathogenicity of strawberry black rot, the bacteriostatic effect, the antibacterial ability of melatonin on strawberry, the changes of related enzymes activities and expression level of resistancerelated genes in the leaves with spraying exogenous melatonin and inoculating the pathogen of strawberry black rot. The results showed that: (1) the separation, sequence analysis and infection test proved that the pathogen was Alternaria alternate, which can result in black rot disease in ‘Benihoppe’ strawberry. (2) The hyphae growth rate of A. alternate was inhibited to different degrees on PDA media containing different concentrations of melatonin 1, 2, 4 and 8 mmol/L. It had slower growth rate with higher melatonin concentration. The inhibition rate of hyphae of A. alternate on the medium containing 8 mmol/L melatonin was 68.9%. (3) We found that exogenous melatonin had the function of delaying the infected onset process of pathogen (A. alternate) in leaves and stolons after they were pretreated for 24 hours. The inhibitory effect increased with the increase of melatonin concentration and 0.5 mmol/L melatonin was the most effective in inhibiting pathogen infection. (4) Biochemical analysis showed that 0.5 mmol/L exogenous melatonin pretreatment could improve the activities of diseaserelated enzymes such as CAT, POD, PAL and PPO after the strawberry leaves infected with pathogen, among which the activity of PPO changed most significantly, with a 23.8% higher inhibition rate than that of the control group. (5) 0.5 mmol/L exogenous melatonin treatment could significantly increase the expression levels of diseaserelated genes such as PR1Alike, PR10, WRKY1, PPO and CCR in strawberry. It suggested that exogenous melatonin could effectively inhibit the hyphae growth rate of A. alternate and delay the onset process. The best concentration was 0.5 mmol/L. And WRKY1 transcription factor plays an important regulatory role during the process of improving strawberry resistance to black rot disease. Exogenous melatonin may improve strawberry resistance to black rot by activating the expression of this transcription factor to regulate the expression of related genes and the activities of related antioxidant enzymes and defense enzymes.

Abstract:In order to provide theoretical basis and effective way to alleviate the continuous cropping obstacle of cucumber, we studied the effects of different concentrations of exogenous silicon (0, 0.5, 1.0, 1.5 and 2.0 mmol/L) on the growth, photosynthesis and chlorophyll fluorescence parameters of ‘Lübo 6’ cucumber seedlings under autotoxicity (3.0 mmol/L cinnamic acid, CA) by nutrient solution culture method. Our results indicated that: (1) autotoxic stress significantly inhibited the growth of cucumber seedlings, root morphogenesis and biomass accumulation, significantly reduced the net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s) and chlorophyll (Chl a, Chl b and Chl t) contents. At the same time, PSⅡ electron transport rate (ETR), PSⅡ actual photochemical efficiency ［Y_(Ⅱ)］ and light chemical quenching coefficient (qP) of cucumber leavers were markedly decreased. (2) Adding appropriate concentration of exogenous silicon can effectively alleviate the effect of CA stress on the growth of cucumber seedlings, improve the values of P_n, G_s, T_r and chlorophyll contents, so as to maintain the stability of the photosynthetic system of leaves to a certain extent. (3) Under CA stress, adding suitable concentration of exogenous silicon significantly increased F_v/F_m, ETR, Y_(Ⅱ), and qP in leaves of cucumber seedlings, rather than the coefficient of photochemical quenching (NPQ) dropped significantly. The results showed that the contents of chlorophyll, F_v/F_m, ETR, Y_(Ⅱ) and qP of cucumber seedlings under CA stress were increased by adding appropriate concentration of exogenous silicon, which made the photosynthetic apparatus stable, inhibited the decline of P_n, and alleviated the damage of autotoxicity on the photosynthetic system, so as to improve the resistance of cucumber seedlings to CA stress. The optimal concentration of exogenous silicon was 1.0 mmol/L.

Abstract:In this study, five sweet cherry (Prunus avium) varieties, including ‘Brooks’, ‘Tieton’, ‘Hongmi’, were used as plant materials to detect the stigma receptivity of sweet cherry at different stages of flower development. Additionally, we simulated low temperature (2 ℃/10 ℃), normal temperature (6 ℃/18 ℃), high temperature (12 ℃/24 ℃) and ultrahigh temperature (12 ℃/24 ℃/30 ℃) using the artificial climate box to check the influence of temperature treatment on stigma receptivity in different sweet cherry varieties. The results show that: (1) ‘Tieton’, ‘Van’ and ‘Summit’ are suitable for pollination under simulated normal temperature (6 ℃/18 ℃), while ‘Hongmi’ is suitable for pollination under simulated high temperature (12 ℃/24 ℃). In comparison, ‘Brooks’ showed a broad range of suitable pollination temperatures, having high activity of stigma at normal temperature (6 ℃/18 ℃) and high temperature (12 ℃/24 ℃). (2) ‘Hongmi’ has strong resistance to simulated low temperature (2 ℃/10 ℃) and ultrahigh temperature (12 ℃/24 ℃/30 ℃); while ‘Brooks’ and ‘Summit’ have poor resistance to ultrahigh temperature (12 ℃/24 ℃/30 ℃). ‘Tieton’ has strong resistance to simulated low temperature (6 ℃/10 ℃), whereas it has poor resistance to simulated high temperature (12 ℃/24 ℃). ‘Van’ has no obvious resistance to simulated low temperature (6 ℃/10 ℃) and ultrahigh temperature (12 ℃/24 ℃/30 ℃). Low temperature (2℃/10℃) mainly affects the stigma receptivity of sweet cherry after flowering, while ultrahigh temperature (12 ℃/24 ℃/30 ℃) has a great influence on the stigma receptivity during the whole flowering process.

Abstract:Using variety ‘Yanke No. 2’ as the test material, we used the pot water to set normal water supply (75% field water holding capacity), moderate drought stress (60% field water holding capacity and severe drought stress (45% field water holding capacity). Chlorophyll fluorescence technology was used to study the growth of oats and the changes of leaf photoreaction system Ⅱ (PSⅡ) function under different water gradients, and to explore the effect of drought stress on the photosynthetic performance of oat leaves. The results showed that: (1) drought stress caused the height of the oat plant to become shorter, the number of leaves, main stems, and ears decreased, the leaves became green and yellow, and the grain yield decreased significantly. (2) Compared with normal water supply, the maximum photochemical efficiency (F_v/F_m) and photosynthetic performance index (PI_ABS) of oat leaves were significantly reduced under severe drought stress. (3) Severe drought stress caused the light energy absorbed by the unit reaction center (ABS/RC) and the energy dissipated by the unit reaction center (DI₀/RC) of the oat leaves to decrease significantly. The energy used by the unit reaction center for electron transfer (ET₀/RC) and the light energy captured by the unit reaction center (TR₀/RC) increased significantly; the openness of the active reaction center (Ψ₀) and the quantum yield of the electron transfer chain (φ_E0) decreased significantly, and the maximum quantum yield was nonphotochemically quenched The forehead (φ_D0) is significantly increased, the relative fluorescence intensity at the three sites of V_J, V_K, and V_L is significantly increased, and the initial slope M_o of the OJIP curve is significantly increased. The study found that the PSⅡ of oat leaves has a strong adaptability to moderate drought stress, and severe drought stress severely damages the PSⅡ reaction center of its leaves, resulting in an imbalance in the energy flow distribution of its reaction center, blocked electron transfer and weakened PSⅡ stability, which in turn affects the photosynthesis of oats eventually leads to the inhibition of oat growth.

Abstract:‘Xuxiang’ kiwifruit were pretreated with 1.0 mmol·L^-1 salicylic acid (SA) and then weight loss, firmness, polygalacturonase (PG) activity, malondialdehyde (MDA) content, as well as enzyme activities and substances contents related to arginine catabolism were measured during ambient storage (23±2) ℃ for investigating the mechanism of SA on delaying postharvest senescence of kiwifruit. The results showed: (1) weight loss and firmness of SA treated fruit were 13.77% lower and 78.25% higher than that of control at 20 d, indicating that SA treatment effectively inhibited the decrease of firmness and fresh weight. (2) At 20 d, the PG activity of SApretreated fruit (13.61 μg·g^-1·h^-1) was significantly lower than that of the control (16.77 μg·g^-1·h^-1); The difference of MDA content in kiwifruit reached the maximum at 15 d of storage, and the MDA content of SA treatment was 33.40% lower than that of control. (3) Compared to control, SA treatment markedly improved the content of ornithine and the activities of arginine decarboxylase and ornithine decarboxylase. Meanwhile, SA treatment inhibited the activities of polyamine oxidase and diamine oxidase, and prominently increased the accumulation of polyamines (putrescine, spermine, spermidine) in kiwifruit during the whole storage. (4) In comparison with control fruit, SA treatment notably induced the enhancement of nitric oxide synthase activity in kiwifruit and promoted the accumulation of nitric oxide (NO) in fruit, and the content of NO in fruit was significantly higher than that of control after the 5 d of storage. The above results showed that SAmediated delay of postharvest senescence in kiwifruit at ambient storage, which may be associated with its trigger of different pathways of arginine catabolism.

Abstract:The objectives of this experiment were to study the effects of foliarspraying nitric oxide (NO) on N metabolism enzyme activities and nutrients of Reaumuria soongorica seedlings leaves and roots under NaCl stress and to determine the ability of exogenous NO to alleviate NaCl stress in R. soongorica seedlings. The currentyear R. soongorica seedlings were used as test material to measure the activities of glutamine synthetase (GS), glutamate synthetase (GOGAT) and nitrate reductase (NR), the concentrations of soluble protein, free amino acid and NO^-₃ N in roots and leaves by different concentrations of NO (0, 0.01, 0.10, 0.25, 0.50 and 1.00 mmol·L^-1 sodium nitroprusside) under 300 mmol·L^-1 NaCl stress in this pot experiment. Principal component and subordinate function analysis were used to select the best N metabolism indexes and optimal NO concentration for evaluating the ability of NO to alleviate NaCl stress in R. soongorica seedlings. The results showed that: (1) GS, GOGAT and NR activities and soluble protein and NO^-₃ N concentrations all decreased significantly under 300 mmol·L^-1 NaCl stress. (2) Exogenous NO can significantly increase GS, GOGAT and NR activities and nitrate nitrogen concentrations in R. soongorica roots and leaves, and increase soluble protein and free amino acid concentrations in roots. (3) NR and GOGAT activities can be used to evaluate the mitigation effect of NO on R. soongorica seedlings under NaCl stress and order of the mitigating effect of exogenous NO on R. soongorica seedlings under NaCl stress is 0.25 mmol·L^-1SNP > 0.50 mmol·L^-1 SNP > 0.10 mmol·L^-1SNP > 1.00 mmol·L^-1SNP > 0.01 mmol·L^-1SNP by principal component and subordinate function analysis. The study found that 300 mmol·L^-1 NaCl stress inhibited N metabolism. Exogenous NO helped R. soongorica seedlings adapt to NaCl stress by increasing NR activities and promoting NO^-₃N transformate to NH⁺₄ and by promoting the assimilation of NH⁺₄ via the GS/GOGAT cycle in R. soongorica roots and leaves. The results showed that 0.25 mmol·L^-1SNP treatment was the most effective for alleviating NaCl stress in R. soongorica seedlings. NR and GOGAT activities can be used to evaluate the ability of NO to alleviate NaCl stress in R. soongorica.

Abstract:Sodium (Na⁺), potassium (K⁺) contents and Na⁺/K⁺ ratio are the key indexes that affect the salt tolerance of rice. The salt tolerance of rice is controlled by quantitative trait loci (QTLs). At present, a number of quantitative trait loci for Na⁺ and K⁺ contents, as well as the Na⁺/K⁺ ratio, have been identified at the seedling stage, but few have been identified at the field growth stage. In this study, using a recombinant inbred line (RIL) population derived from a cross between ‘Dongnong 425’ and ‘Changbai 10’, dynamic QTLs for Na⁺ content, K⁺ content and the Na⁺/K⁺ ratio were identified by a combined analysis of salt stress and control conditions at different developmental stages during the field growth stage of rice. The additive (A), epistatic (AA), and QTL × environmental interaction effects (QE) of these QTLs were analyzed using a mixed linear model (MCIM). The results show that: (1) under the salt stress condition, the Na⁺ content of stems (SNC), Na⁺/K⁺ ratio of stems (SN/K), Na⁺ content of leaves (LNC) and Na⁺/K⁺ ratio of leaves (LN/K) in parents and RIL population were all higher than those of the control at each stage, while the K⁺content of stems (SKC) and K⁺ content of leaves (LKC) were all lower than those of the control. There was no significant difference of traits between parents at most stages under control condition. Under the salt stress, a number of traits of the two parents were significantly different at different development stages, among which SNC and LKC were significantly different at four stages, SN/K and LN/K were significantly different at three stages, and SKC and LNC were significantly different at two stages. (2) In total, 13 additive and 11 epistatic QTLs, including 14 unconditional and 10 conditional QTLs were detected using unconditional and conditional QTL mapping methods. We noted that 8 out of 13 additive QTLs and 7 out of 11 epistatic QTLs had significant QE effects. (3) qSKC51 was detected at four developmental stages, suggesting a key role in regulating the salt tolerance of rice. The additive × QE effect was detected in all QTLs of SNC, SN/K and LN/K, and the epistatic × QE effect was detected in all QTLs controlling SNC, indicating that the QTLs of these traits were more sensitive to salt environment. The present study demonstrates that the expression of QTLs for Na⁺ content, K⁺ content and Na⁺/K⁺ ratio in rice during the field growth stage was closely related to the developmental stages. The heredity of salt tolerance of rice under field growth condition is very complex. Epistatic and QE effects should be considered in producing new salttolerant rice materials by molecular markerassisted selection (MAS).

Abstract:To explore the native and exotic species of adaptability to different environmental pollution in the city, in this study, we selected 10 tree species in the industrial area, road, mining area and park green space of Fuxin City as the research objects. We measured the dust retention per leaf area of tree species and the changes of physiological indexes of leaves before and after dust retention by the elution method, and discussed the dust detention effect of leaves in different trees and the influence of leaves on physiological activities of plants after the dust detention effect. The results indicate that: (1) different tree species have different dust retention per unit area. The dust retention of Populus bolleana was 1.45 g/m² which is higher than that of others and Ginkgo biloba was only 0.92 g/m2 which is lower than that of others in all 10 tree species. (2) SPAD value of leaves showed a significant downward trend, contents of osmotic regulatory substances (proline, soluble protein, soluble sugar) and membrane permeability (MDA, Rec) showed an upward trend, while activities of antioxidant enzymes (SOD and POD) showed a downward trend, but the rate of decline was not obvious. (3) There was a significant correlation between the amount of dust held by G. biloba and Acer mono. It was more suitable to detect the indicators of urban dust pollution from the physiological aspect. (4) According to the clustering analysis of dust retention and dust resistance of different tree species in four functional areas, the dust retention and dust resistance of P. bolleana, Syringa oblata, Gleditsia japonica and Ailanthus altissima were both strong.The dust retention and dust resistance of foreign tree species in Fuxin City were similar to that of native tree species. Therefore, under the longterm dust pollution stress, each tree species may alleviate the damage of dust pollution by increasing the contents of osmotic regulation substances and the activities of antioxidant enzymes. The foreign tree species and native tree species both show strong adaptability and are not sensitive to environmental pollution. Therefore, it is a strong guarantee for the safe and healthy development of urban landscape in arid areas to introduce foreign tree species which can effectively hold dust and control sand and prevent wind without causing biological invasion.

Abstract:The evaluation index system of swamp degradation is an important scientific issue in swamp degradation research. We used Longbao swamp areas to investigate the changes of vegetation during degradation and use principal component analysis method with multiple vegetation indexes to construct the vegetation evaluation index of swamp degradation. The results showed that： (1) the importance value of the helophyte decreased at the degradation process of swamp, but importance values of the hygrophyte and mesophyte had an increase. Carex parva, the dominant plant in the nondegradation and light degradation was succeeded by Kobresia tibetica in the heavy degradation. (2) The diversity index, evenness index and species richness of plant community increased with the degradation of the swamp, and the difference was significant between the nondegradation and heavy degradation (P<0.05). (3) The aboveground biomass decreased significantly with swamp degradation (P<0.05). The belowground biomass in the 0-30 cm soil layer showed a change trend of first increasing and then decreasing with the degradation of the swamp, in which the heavy degradation in 10-20 cm and 20-30 cm soil layers were significantly less than the light degradation (P<0.05). (4) Principal component analysis showed that the nine plant community indices were simplified into the first and second principal components, with the cumulative percentage of variation explained reaching 91.7%. The coverage, aboveground biomass and important values of the helophyte and the mesophyte had a higher load of more than 0.9 in the first principal component, which were well indicators of swamp degradation. (5) The swamp vegetation evaluation indexes (SVEI) are -3.23 ~ -1.98 in the nondegradation, -0.54 ~ 0.51 in the light degradation and 2.15 ~ 3.26 in the heavy degradation, respectively. The present results suggest that the swamp vegetation evaluation index established by using multiple vegetation indexes could well indicate the degradation degree of Longbao swamp. The higher the SVEI value showed the more severe degradation of swamp. SVEI<-1 represented the nondegradation, -1≤SVEI≤1 represented the light degradation, SVEI>1 represented the heavy degradation.

Abstract:In order to provide reference for the protection of local species diversity and cultivation of economic crops as well as provide a basis for the ecosystem service function assessment of Juniperus, we investigated the coverage, abundance, frequency, etc and analyzed the responses of species composition, α diversity and β diversity to elevation gradient in the communities of Juniperus przewalskii natural forest in Maxiu forest centre and Zhongtie forest centre in Three River Headwater based on the field investigation. The results indicated that: (1) a total of 72 species were investigated in the sample plot, belonging to 27 families and 58 genera. Among them, 1 species of gymnosperms belong to 1 family and 1 genus, 61 species of dicotyledonous belong to 21 families and 48 genera, 10 species of monocotyledonous belong to 5 families and 9 genera. For Juniperus przewalskii forest, Compositae are dominant. (2) The species richness of vegetation layer was as follows: herb layer > shrub layer > arbor layer. The arbor layer was dominated by J. przewalskii, while the species richness of shrub and herb layer showed an obvious “lateral pattern” on the elevation gradient, both reaching the maximum value at 3 150 m. (3) With the rise of altitude, shrub layer and herb layer α diversity showed a “wave” shaped change trend, reaching the lowest value at 3 550 m. (4) The Cody index of shrub layer reached its peak at 2 950-3 150 m, and that of herb layer reached its peak at 3 150-3 350 m. The Sorenson index of shrub layer peaks at 2 950-3 150 m and 3 350-3 550 m, while herb layer peaks at 2 950-3 150 m. Therefore, in the process of ecological restoration, the degree of human disturbance should be controlled at low altitudes and the cultivation and utilization of local economic plants should be increased for enhancing the income of farmers and herders.

Abstract:In order to understand the plant resources and flora characteristics of the Bijie karst rocky desertification area, we surveyed the wild plant resources in the study area by sampling lines and sampling methods in 2018 and 2019, and the research was conducted through methods such as specimen collection and literature review. The plant resources and flora of the district were analyzed for providing theoretical basis for karst rocky desertification control and ecological protection. The results showed that: (1) there were 721 species of 438 genera and 133 families in the study area, including 10 families, 13 genera, 16 species of pteridophytes, 7 families, 9 genera and 11 species of gymnosperms, 116 families, 417 genera and 695 species of angiosperms. Among angiosperms, there are 15 families, 75 genera, 121 species of monocotyledonous plants, and 101 families, 342 genera, 574 species of dicotyledons. There are 35 species of rare and endangered species, belonging to 14 families and 24 genera. (2) Among the classification of resource plants, there are 516 species of medicinal plants in 121 families, 339 genera and 333 species of nectar plants in 74 families, 180 genera, 75 species of edible plants in 37 families, 60 genera, 209 species of ornamental plants in 75 families, 146 genera, 89 species of fibers in 42 families, 82 genera, 59 species of starches and sugars in 21 families, 37 genera, and 132 species of aromatic oils in 25 families, 88 genera. There are 144 species of grease in 63 families, 117 genera, 22 species of resins and gums in 17 families, 17 genera, 87 species of tanning in 63 genera and 38 families and 155 species of other plant resources total in 68 families, 128 genera. (3) On the flora, the families and genera of pteridophytes are slightly differentiated. The flora of the seed plant family is divided into 9 distribution types and 9 subtypes, mainly tropical components; 15 distribution types and 20 subtypes at the genus level, temperate elements dominate at the genus level. Studies have shown that the study area is rich in plant resources, and the flora has the dual nature and transitional characteristics of temperate and tropical zones.

Abstract:A new species of Quercus (Fagaceae), Quercas dehangensis G. X. Chen, D. G. Zhang & B. Z. Wang, sp. nov. from Dehang of Xiangxi World Geopark, Hunan Province of China, is described and illustrated. The new species belongs to the Quercus, with bracts imbricate. Q. dehangensis is most similar to Q. engleriana Seemen, but differs from the Q. engleriana in its plant usually 3-5 m tall, secondary veins 7-10 on each side of midvein, young branchlets, petiole and abaxial leaf blade are covered with scaled stellate hair and early deciduous stipules. According to IUCN Red List Categories and Criteria, the Q. dehangensis should be regarded as Critically Endangered (CR).

Abstract:This paper thoroughly studies the specimens of two biraphid diatom species reported from China for the first time ——Prestauroneis tumida and Placoneis anglophila var. signata, which were collected from the East Dongting Lake National Nature Reserve, were studied with light and scanning electric microscopy. The results show that: (1) Pr. tumida possesses four identifying characters: ① valve outline lanceolate in larger specimens, and ellipticlanceolate in smaller specimens; ② striae radiate on the middle valve part and spaced wider than on other parts; ③ a pseudoseptum occurring at both apices; ④ the inner areola openings covered by hymens. (2) Pl. anglophila var. signata also possesses four identifying characters: ① linearelliptic or elliptic valve outline; ② striae radiate in most middle part where stria density is 10-14/10 μm, except at the apices where striae are parallel; ③ a stigma present at the center of the valve; ④ the internal areola opening covered by a velum which is supported by four props and the areola density is 35-40/10 μm. The detailed descriptions and clear illustrations in this paper provide a basis for the correct identification of Pr. tumida and Pl. anglophila var. signata for the future researchers.

Abstract:Plant adaptation to drought environment is a complex biological process, involving cross regulation of multiple signal pathways, in which transcription factors play an important role in regulating resistance to drought. The main transcription factors involved in plant drought stress response are AP2/EREBP, MYB, NAC, bZIP and WRKY. Studies have shown that a single transcription factor can activate or inhibit the transcription of a large number of downstream target genes, and a single target gene is regulated by different transcription factors. The crosstalk between transcription factors is common in plant drought regulation network. This paper summarized the main signal pathways (ABA pathway, Ca²⁺ pathway and MAPKs pathway) involved in plant response to drought stress, and reviewed the structure and classifications of the above five transcription factors and their regulation of drought stress. Some deep research directions in this area were also put forward．