Search

In order to further understand the effects of drought stress on hydraulic characteristics and the relationship between hydraulic conductivity and aquaporins or water channels of root systems of three wolfberry cultivars (Lycium chinense Mill.), hydraulic conductivity of 2-year-old pot-grown seedlings was measured under drought stress, rewatering, and treatment with exogenous mercuric chloride and β-mercaptoethanol. Under moderate and severe drought stress levels, the most significant decrease of hydraulic conductivity was 37.3% and 24.0%, respectively, in the ‘Ningqi 5’ cultivar compared with the non-stressed control. After rewatering, the rate of recovery in specific conductivity was most rapid in the ‘Mengqi 1’ cultivar, at 0.058 and 0.072 kg MPa−1 m−2 s−1 h−1 under moderate and severe drought stress levels, respectively. The ‘Mengqi 1’ cultivar had the highest recovery degree of hydraulic conductivity under two concentrations of β-ME (500 or 1000 μmol L− 1), reaching 82.4% and 88.5%, respectively, of the initial conductivity. The adaptive capacity of hydraulic conductivity in the ‘Ningqi 5’ cultivar was weaker than in the ‘Ningqi 1’ and ‘Mengqi 1’ cultivars under drought stress. The recovery capacity of hydraulic conductivity in ‘Mengqi 1’ cultivar was stronger than the ‘Ningqi 1’ and ‘Ningqi 5’ cultivars after rewatering. Aquaporins of the ‘Ningqi 1’ cultivar root systems had the highest binding affinity with mercuric chloride, which was the most likely cause in the decrease in hydraulic conductivity, whereas aquaporins of ‘Mengqi 1’ root systems had the weakest binding affinity. The inhibitory effect of mercuric chloride was readily eliminated by β-mercaptoethanol in the ‘Mengqi 1’ cultivar. The hydraulic characteristics of this cultivar were more sensitive to drought, mercuric chloride and β-mercaptoethanol than the other cultivars.

Monitoring of drinking water has shown an increase in nitrate-nitrogen (NO 3 − -N) concentration in groundwater in some areas of the Heihe River Basin, Northwest China. A combination of careful irrigation and nitrogen (N) management is needed to improve N uptake efficiency and to minimize fertilizer N loss. A 2-year experiment investigated the effects of different irrigation and N application rates on soil NO 3 − -N distribution and fertilizer N loss, wheat grain yield and N uptake on recently reclaimed sandy farmland. The experiment followed a completely randomized split-plot design, taking flood irrigation (0.6, 0.8 and 1.0 of the estimated evapotranspiration) as main plot treatment and N-supply as split-plot treatment (with five levels of 0, 79, 140, 221, 300 kg N ha−1). Fertilizer N loss was calculated according to N balance equation. Our results showed that, under deficit irrigation conditions, N fertilizer application at a rate of 300 kg ha−1 promoted NO 3 − -N concentration in 0–200 cm depth soil profiles, and treatments with 221 kg N ha−1 also increased soil NO 3 − -N concentrations only in the surface layers. Fertilizer N rates of 70 and 140 kg ha−1 did not increase NO 3 − -N concentration in the 0–200 cm soil profile remaining after the spring wheat growing season. The amount of residual NO 3 − -N in soil profiles decreased with the amount of irrigation. Compared with N0, the increases of fertilizer N loss, in N79, N140, N221 and N300 respectively, were 59.9, 104.6, 143.5 and 210.6 kg ha−1 over 2 years. Under these experimental conditions, a N rate of 221 kg ha−1 obtained the highest values of grain yield (2775 kg ha−1), above-ground dry matter (5310 kg ha−1) and plant N uptake (103.8 kg ha−1) over 2 years. The results clearly showed that the relative high grain yield and irrigation water productivity, and relative low N loss were achieved with application of 221 kg N ha−1 and low irrigation, the recommendation should be for those farmers who use the upper range of the recommended 150–400 kg N ha−1, that they can save about 45% of their N and 40% of their irrigation water application.

In this work, a simple two-step route has been developed to synthesize ultrafine barium titanate (BaTiO 3 ) with size ranging from 30 nm to 100nm by reacting barium hydroxide with tetrabutyl titanate in mixing solvent. This method facilitates the process-control and the property tailoring of the particles. The effect of 1,4-butylene glycol on hydrolysis rate of tetrabutyl titanate, temperature, solvent ratio between isopropanol and water, the particle size, the crystalline phase have been investigated. The prepared BaTiO 3 nanoparticles were characterized using X-ray diffraction and scanning electron microscopy (SEM). The results show that the particle size can be easily tuned by adjusting the ratio of 1, 4-butylene glycol, isopropanol and water in solution. The dielectric behavior of the BaTiO 3 /PVDF at low frequency show that the interfacial polarization acts as an important role for the high dielectric constant (e r ).

Intercropping of bread wheat (Triticum aestivum L.), maize (Zea mays L.) and potato (Solanum tuberosum)has been practiced in North-West China in the last several decades; however, the effects of this intercropping and phosphorus addition on crop yield and some wheat-grain components have not been adequately investigated. A 2-year field experiment was conducted from 2002 to 2003 in irrigated areas in North-West of China to investigate how phosphorus fertilizer application and intercropping of wheat/maize/potato impact on the crop yield and wheat-grain components such as protein content, wet gluten and sodium dodecyl sulphate (SDS) sedimentation. The results indicated that bread wheat and maize achieved higher yields in the intercropping system than in the monoculture system over the 2 years, and the wheat-grain had higher protein content, wet gluten and sodium dodecyl sulphate (SDS) sedimentation in the intercropping system than in the monoculture system. Better utilization of resources through border row effect and preventing competition between species over growing period have been indicated as the major factors contributing to the increased crop yield and wheat-grain components. Phosphorus application significantly increased crop yields and improved wheat-grain components; however, the optimal application rate for achieving highest protein content was at 150 kg ha-1. The practical implication of the present study was that to obtain good yield and better wheat-grain components, a combination of intercropping and application of phosphorus fertilizer at a rate of approximately 150 kg ha-1 was found as one of the most practical options. Key words: Border-row effect, intercropping, phosphorus, wheat-grain components, wheat/maize/potato, yield.