Zhao-Pu Liu

Anthropogenic Impact on Surface Water Quality in Taihu Lake Region, China

Abstract Taihu Lake region is one of the most industrialized areas in China, and the surface water is progressively susceptible to anthropogenic pollution. The physicochemical parameters of surface water quality were determined at 20 sampling sites in Taihu Lake region, China in spring, summer, autumn, and winter seasons of 2005–2006 to assess the effect of human activities on the surface water quality. Principal component analysis (PCA) and cluster analysis (CA) were used to identify characteristics of the water quality in the studied water bodies. PCA extracted the first three principal components (PCs), explaining 80.84% of the total variance of the raw data. Especially, PC1 (38.91%) was associated with NH 4 -N, total N, soluble reactive phosphorus, and total P. PC2 (22.70%) was characterized by NO 3 -N and temperature. PC3 (19.23%) was mainly associated with pH and dissolved organic carbon. CA showed that streams were influenced by urban residential subsistence and livestock farming contributed significantly to PC1 throughout the year. The streams influenced by farmland runoff contributed most to PC2 in spring and winter compared with other streams. PC3 was affected mainly by aquiculture in spring, rural residential subsistence in summer, and livestock farming in fall and winter seasons. Further analyses showed that farmlands contributed significantly to nitrogen pollution of Taihu Lake, while urban residential subsistence and livestock farming also polluted water quality of Taihu Lake in rainy season. The results would be helpful for the authorities to take sound actions for an effective management of water quality in Taihu Lake region.

Effect of NO−3 -N Enrichment on Seawater Stress Tolerance of Jerusalem Artichoke (Helianthus tuberosus)

Abstract A hydroponic experiment with six treatments, i.e., 0% seawater (control), 10% seawater, 25% seawater, 0% seawater + N (7.5 mmol L −1 NaNO 3 ), 10% seawater + N (7.5 mmol L −1 NaNO 3 ), and 25% seawater + N (7.5 mmol L −1 NaNO 3 ), was carried out to study the effect of nitrogen addition on the growth and physiological and biochemical characteristics of Jerusalem artichoke ( Helianthus tuberosus ) seedlings under seawater stress. The 10% seawater stress treatment had the least effect on plant growth while at 25% seawater growth was significantly inhibited. The malondialdehyde content and electrolyte leakage in leaves under 10% seawater were similar to those of the control, but significantly higher under the 25% seawater stress. The activities of superoxide dismutase, peroxidase and catalase in the leaves increased concomitantly with increasing seawater concentration and time. Proline and soluble-sugars in the leaves and Na + , K + , and CL − contents in shoots and roots increased significantly with the concentration of seawater increasing. Nitrogen addition resulted in increasing fresh and dry weights of shoots and roots compared with seawater treatment without N. Nitrogen supplementation also significantly enhanced the activities of antioxidant enzymes in leaves. Addition of N to seawater enhanced the contents of proline and soluble-sugars in the leaves and K + and total-N in the aerial parts and roots of H. tuberosus, but it resulted in declined concentrations of Na + and CL − in the aerial parts and roots. Nitrogen addition ameliorated the toxicity of seawater by improving the antioxidative enzymes, accumulating of proline and soluble-sugars, and altering the distribution of inorganic ions in H. tuberosus .

Overexpression of Arabidopsis thaliana Na+/H+ antiporter gene enhanced salt resistance in transgenic poplar (Populus × euramericana ‘Neva’)

Salinity is a major abiotic stress factor limiting plant growth and productivity. One possible method to enhance plant salt-resistance is to compartmentalize sodium ions away from the cytosol. In the present work, a vacuolar Na+/H+ antiporter gene AtNHX1 from Arabidopsis thaliana, was transferred into Populusxa0×xa0euramericana ‘Neva’ by Agrobacterium tumefaciens in order to enhance poplar salt-resistance. The results showed that the transgenic poplar were more resistant to NaCl than the wild-type (WT) in greenhouse condition. Compared with the WT, plant growth and photosynthetic capacity of the transgenic plants were enhanced, and the transgenic plants accumulated more Na+ and K+ in roots and leaves under the same NaCl condition, whereas malondialdehyde and relative electrical conductivity were lower. All of these properties of the transgenic poplar were likely to be a consequence of the overexpression of AtNHX1 caused Na+ sequestration in the vacuoles and improved K+ absorption, thus reducing their toxic effects. These results indicated overexpression of the AtNHX1 enhanced salt-resistance of poplar, and AtNHX1 played an important role in the compartmentation of Na+ into the vacuoles. Therefore, this study provides an effective way for improving salt resistance in trees.

Effect of Seawater Stress on Physiological and Biochemical Responses of Five Jerusalem Artichoke Ecotypes

Abstract Three treatments consisting of 0%, 15%, and 30% seawater were investigated to analyse the ecotypic variabilities among five populations of Jerusalem artichoke (Helianthus tuberosus) regarding their responses to seawater stress under a hydroponic culture system. Analyses were done 2, 4, and 6 days after treatments. The 15% and 30% seawater treatments reduced the growth rates of roots and shoots of H. tuberosus populations. The activities of superoxide dismutase, peroxidase, and catalase majored in the leaves were stimulated under the seawater stress. The electrolyte leakage and malondialdehyde contents of the leaves were also stimulated owing to seawater stress. The contents of proline and soluble-sugars in the leaves increased significantly with increasing seawater concentrations. The concentrations of Na+, K+, and Cl−in the aerial parts and roots increased with an increase in the seawater concentration throughout the experimental period. There were ecotypic differences among the five populations of H. tuberosus as evidenced by the analyses of the above items in both aerial parts and roots under seawater treatment. The magnitude of the ecotypic variance components indicated that a substantial proportion of the total variation for these physiological and biochemical responses were owing to ecotype, indicating the possibility of improvement through hybridization and selection.

Protective Role of Ca Against NaCl Toxicity in Jerusalem Artichoke by Up-Regulation of Antioxidant Enzymes

Abstract The ameliorative effect of external Ca 2+ on Jerusalem artichoke (Helianthus tuberosus L.) under salt stress was studied through biochemical and physiological analyses of Jerusalem artichoke seedlings treated with or without 10 mol L −1 CaCl 2 , 150 mmol L −1 NaCl, and/or 5 mmol L −1 ethylene-bis(oxyethylenenitrilo)-tetraacetic acid (EGTA) for five days. Exposure to NaCl (150 mmol L −1 ) decreased growth, leaf chlorophyll content, and photosynthetic rate of Jerusalem artichoke seedlings. NaCl treatment showed 59% and 37% higher lipid peroxidation and electrolyte leakage, respectively, than the control. The activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were decreased by NaCl, indicating an impeded antioxidant defense mechanism of Jerusalem artichoke grown under salt stress. Addition of 10 mmol L −1 CaCl 2 to the salt solutions significantly decreased the damaging effect of NaCl on growth and chlorophyll content and simultaneously restored the rate of photosynthesis almost to the level of the control. Ca 2+ addition decreased the leaf malondialdehyde (MDA) content and electrolyte leakage from NaCl-treated seedlings by 47% and 24%, respectively, and significantly improved the activities of SOD, POD, and CAT in NaCl-treated plants. Addition of EGTA, a specific chelator of Ca 2+ , decreased the growth, chlorophyll content, and photosynthesis, and increased level of MDA and electrolyte leakage from NaCl-treated plants and from the control plants. EGTA addition to the growth medium also repressed the activities of SOD, POD, and CAT in NaCl-treated and control seedlings. External Ca 2+ might protect Jerusalem artichoke against NaCl stress by up-regulating the activities of antioxidant enzymes and thereby decreasing the oxidative stress.

Soil Properties and Yield of Jerusalem Artichoke (Helianthus tuberosus L.) with Seawater Irrigation in North China Plain

Abstract Irrigation with various dilutions of seawater can act as an alternate water resource and thus plays an important role in saving freshwater resources as well as promoting agriculture in the coastal semi-arid areas of the North China Plain. Jerusalem artichoke ( Helianthus tuberosus L.) grown in a field experiment was irrigated with seawater diluted with freshwater from 2001 to 2003 to determine the feasibility of seawater irrigation in the Laizhou area. For treatments of CK (non-irrigation) along with seawater concentrations of 25%, 50%, and 75%, total dissolved solid (TDS) in the non-irrigated soil significantly increased ( P ≤ 0.05) in both 2002 and 2003 and was 1.3 times higher in 2003 than in 2001. In the 25% and 50% seawater concentration treatments, TDS in 2001 was significantly greater ( P ≤ 0.05) than CK; however, TDS in these two treatments decreased by 34.9% and 40.1%, respectively, in 2003 compared with 2001. The sodium adsorption ratio (SAR) remained below 10 mmol 1/2 L −1/2 , indicating that alkalization was low with seawater irrigation. In 2001 and 2002, compared to CK and the irrigation treatment with 75% seawater, irrigation with 25% and 50% seawater increased the yields of Jerusalem artichoke. This meant that Jerusalem artichoke could be safely grown in salt-affected land of Laizhou area with 25% and 50% seawater irrigation.

Effect of Saline Aquaculture Effluent on Salt-Tolerant Jerusalem Artichoke (Helianthus tuberosus L.) in a Semi-Arid Coastal Area of China

An experiment with six treatments: CK1 (rainfed), CK2 (irrigated with freshwater), and 4 treatments of saline aquaculture effluent blended with brackish groundwater at different ratios of 1:1, 1:2, 1:3, and 1:4 (v/v) was carried out during 2004 to assess the effect of saline aquaculture effluent on plant growth and soil properties in the Laizhou region, Shandong Province, China and to determine an optimal salinity threshold for aquaculture effluent. Cumulative evapotranspiration for the saline aquaculture effluent irrigation and non-irrigation treatments was lower than that for the freshwater irrigation treatment. Soil electrical conductivity was higher with respect to saline aquaculture effluent irrigation treatment compared to that with respect to non-irrigation or freshwater irrigation treatment. For Jerusalem artichoke (Helianthus tuberosus L.), in comparison to the freshwater treatment, plant height and aboveground biomass for the 1:3 and 1:4 treatments were constrained, whereas stem width and root biomass were enhanced. Concomitantly, higher tuber yield was obtained for the 1:3 and 1:4 treatments compared to that for CK1 and 1:1 treatments. Nitrogen and phosphorus were higher in tubers of the 1:4 treatment. This study demonstrated that saline aquaculture effluent could be used successfully to irrigate Jerusalem artichoke with higher tuber yield and nutrient removal.