Investigation and Analysis of Three Nitrogen Pollution in Groundwater in Ledong, Hainan Province

[Objectives]This study was conducted to systematically monitor the contents of "three nitrogen",including ammonia nitrogen (NH4^+-N),nitrate nitrogen (NO3^--N) and nitrite nitrogen (NO2^--N) in groundwater in Ledong and analyze the reasons.[Methods]A total of 30 sampling points were set up in Ledong,including 22 ground waters and 8 surface waters.NO3^--N,NH4^+-N,NO2^--N and pH indicators were detected.[Results]① There is a problem of excessive nitrogen in the groundwater of Ledong,Hainan.NH4^+-N and NO3^--N exceeded the standards severely,and the over-standard rates were 27.27% and 13.64%,respectively.NO2^--N didn't exceed the standard.Among them,the highest concentration of NH4^+-N was up to 2.692 mg/L;and the highest concentration of NO3^--N reached 24.071 mg/L.② The pollution trends of NH4^+-N and NO2^--N in Ledong County were similar,and NO3^--N had no similarity.③ There was a regional difference in the groundwater three nitrogen in Ledong,Hainan.The pollution level near the farmland was greater than that far from the farmland.The pollution level near the farm area was greater than that far from the farm area.In addition,in combination with the layout of the sampling points and the test results,it was not found that the area far from the coastline would be lower than the area near the coastline in the pollution level.④ The main reasons for the excessive nitrogen in the groundwater of Ledong,Hainan are farmland fertilization,random discharge of domestic sewage,discharge of aquaculture wastewater,and discharge of industrial water at will.[Conclusions]This study is of great significance to safe prevention and control of groundwater in Ledong.

Role and Mechanism of Action of Exogenous Salicylic Acid and Sodium Molybdate in Improving Cold Tolerance of Bougainvillea glabra

This study was conducted to comprehensively evaluate the effects of salicylic acid and sodium molybdate on cold tolerance of an ornamental plant Bougainvillea glabra and to provide a theoretical guidance for landscape maintenance.B.glabra plants were treated with 0.5 mmol/L salicylic acid and 2.0 μmol/L alone or in combination,and then exposed to low temperature stress before physiological indices were measured.The results showed that all salicylic acid and sodium molybdate treatments reduced the relative conductivity and malondialdehyde( MDA) content of B.glabra to varying extents under the stress of low temperature,and more significant effect was achieved by using the two agents in combination.Oxygen free radicals production rate increased with decreasing temperature from 20 to 6 ℃,but declined with temperature decreasing from 3 to-3 ℃.The SOD activity of the control( CK) was significantly lower than that of other treatments at 0 and-3 ℃.The treatments with salicylic acid and sodium molybdate alone and in combination increased POD activity of B.glabra plants,especially at 0 ℃,as the POD activity of treatments T1,T2 and T3 was significantly higher than that of CK at 0 ℃.In addition,under low temperature stress,the contents of soluble sugar,starch and proline increased initially and decreased subsequently with temperature decreasing.The soluble sugar content at 3 ℃,starch and proline contents at 0 and-3 ℃ in treatments with salicylic acid and sodium molybdate alone and in combination were significantly higher than those of CK.All above results proved that salicylic acid and sodium molybdate are able to improve cold tolerance of B.glabra,and better effect can be achieved by using them together.

Effects of Sodium Nitroprussiate on the Metabolites and Key Enzyme Activities of Carbon-nitrogen Metabolism from Seed Germination to Seedling Period of Cherry Tomato

This study was conducted to elucidate the regulating mechanism of sodium nitroprussiate on seed germination and seedling growth of cherry tomato. After the treatment with different concentrations of sodium nitroprusside, the effects on the metabolites and key enzyme activities in carbon-nitrogen metabolism of cherry tomato cuhivar Zhuyun as an experimental material were investigated. The results showed that from seed germination to seedling period, the contents of starch and total nitrogen decreased, but the contents of soluble sugar, reducing sugar, sucrose and soluble protein increased firstly and then decreased; and free amino acids content increased gradually. Sodium nitroprusside made the contents of starch, sucrose and free amino acids higher than CK. From seed germination to seedling period in cherry tomato, the activities of amylase, glutamine synthetase （GS） and sucrose phosphate synthase （SPS） decreased; the activities of nitrate reductase （NR） and glutamate synthase （GOGAT） increased at first and decreased then; and the CK and the 0.25 mmol/L sodium nitroprusside treatments exhibited de- creased sucrose synthase （SS） activity, and the trend was increasing at first and decreasing then after the treatment with 0.50 and 1.00 mmol/L sodium nitroprus- side. Sodium nitroprusside treatment improved amylase activity; and the carbon-nitrogen ratio of the CK increased at first and decreased then, while the values of other treatments tended to decrease. In addition, sodium nitroprusside did not affect seed germination potential and germination rate, but significantly improved biomass accumulation, root length and height of seedlings. These data suggest that sodium nitroprusside could affect the conversion of starch and sugar accumulation, delay the decomposition of total nitrogen and soluble protein, and achieve the effects of accelerating the accumulation of free amino acids, and promoting seed germination and seedling growth, and 0.50 mmol/L sodium nitroprusside has the best effect.

Analyses on Community Composition and Diversity of Endophytic Bacteria in Different Tissues of Anoectochilus roxburghii

[Objective] This study aimed to investigate the diversity of community composition and diversity of endophytic bacteria in Anoectochilus roxburghii.[Method] By using Illumina MiSeq high-throughput sequencing technology, the 16S rDNA-V4 region of endophytic bacteria in ^4. roxburghii was sequenced. Qiime and Mothur software packages were used to sort and count the number of sequences and operational taxonomic units （OTUs） and analyze the species abundance and distribution, Alpha diversity and differences of species abundance among samples. [Result] The number of effective sequences/OTUs for each sample was 110485/247 （stem） and 98524/259 （leaf） , respectively. The rarefaction curve showed that adequate sampling was performed. The number of OTUs had almost reached a saturation point. Endophytic bacteria in A. roxburghii mainly belonged to the genera Acidovorax, Pseudomonas, Sphingomonas and Halomonas. [Conclusions] Illumi-na MiSeq high-throughput sequencing technology provides more accurate and scientific data resources for the study of endophytic bacteria in A. roxburghii.

Effects of Formaldehyde and Low-light Stress on Growth and Nutrition of Hedera spp.

Potted seedlings of Hedera nepalensis and H. helix were exposed to formaldehyde and low light alone or in combination for four months, before the morphological and nutritive indices of the plants were measured to assess the effects of formaldehyde and low-light stress on the growth and nutrient accumulation of Hedera species. The results showed that treatment with either formaldehyde or low-light stress reduced leaf length, leaf width, stem length, stem diameter, root length and biomass, but increased leaf shape index of the two Hedera species. Treatment with formaldehyde alone increased root-shoot ratio, while treatment with formaldehyde ＋ low light or low light alone decreased root-shoot ratio of the two Hedera species. Under the stress of formaldehyde, soluble sugar content decreased, while starch content increased in roots, stems and leaves of the two Hedera species; total carbon content, proline content and carbon-to-nitrogen （C/N） ratio increased, while protein content and phosphorus content decreased in roots of the two Hedera species; the contents of total carbon, protein and total nitrogen in leaves of the two Hedera species; C/N ratio in roots of H. nepalensis increased; the C/N ratio in roots of H. nepalensis and that in leaves of the two Hedera species significantly increased. Under formaldehyde ＋ low light stress, the soluble sugar content decreased, while starch content increased in stems and leaves of the two Hedera species; starch content in roots of the two Hedera species decreased; the contents of protein and total nitrogen decreased, while C/N ratio increased in leaves of H. nepalensis ; proline content in roots and stems of the two Hedera species significantly increased.