Deficit Subsurface Drip Irrigation Improves Water Use Efficiency and Stabilizes Yield by Enhancing Subsoil Water Extraction in Winter Wheat.

Understanding the temporal and spatial patterns of soil water extraction and their impacts on growth response of winter wheat to deficit subsurface drip irrigation (SDI) conditions is critical for managing water scarcity and stabilizing yield. A field experiment was conducted from 2016 to 2018 involving five SDI amounts: 0.25, 0.4, 0.6, 0.8, and 1.0 ETc, representing 25, 40, 60, 80, and 100% of crop evapotranspiration (ETc), respectively. The results showed that the 0.6 ETc treatment significantly increased soil water extraction from 40-80 and 80-140-cm from jointing to maturity as compared to the 1.0 ETc treatment. Whereas the 0.8 ETc treatment significantly increased soil water extraction from 80-140-cm deep soil from flowering to maturity in the first growing season. The crop was most water-stressed under the 0.25 and 0.4 ETc treatments, thus extracted more soil water from 0-140-cm soil profile. However, both treatments exhibited minimum plant tillers, lowest leaf water content, leaf area index (LAI), photosynthetic rate (P n ), and transpiration rate (T r ) as well as grain yield. All these parameters, except for leaf water content, P n after the flowering stage, and grain productivity, were also reduced in the 0.6 ETc treatment than the 1.0 ETc treatment. The differences between the 0.8 and 1.0 ETc treatments were minor in terms of plant height, LAI, spike number, P n and T r , but infertile tillers were fewer in the 0.8 ETc treatment. We obtained high yield from the 0.8 ETc treatment, and the 0.6ETc treatment resulted in the highest harvest index with improved WUE than other treatments. Integrating deficit irrigation into SDI can save water in winter wheat production in water-limited regions, which can not only enhance soil water extraction from deep soil layers, but also sustained yield by stimulating crop growth. Therefore, a deficit SDI system would be used to conserve water in water-limited regions.

[Effects of postponing nitrogen application on photosynthetic characteristics and grain yield of winter wheat subjected to water stress after heading stage].

A pot culture experiment was conducted to study the effects of postponing nitrogen (N) application on photosynthetic characteristics and grain yield of winter wheat subjected to water stress after heading stage. Equal in the total N rate in winter wheat growth season, N application was split before sowing, and/or at jointing and /or at anthesis at the ratio of 10:0:0 (N1), 6:4:0 (N2) and 4:3:3 (N3), combined with unfavorable water condition (either waterlogged or drought) with the sufficient water condition as control. The results showed that, under each of the water condition, both N2 and N3 treatments significantly improved the leaf photosynthetic rate and the SPAD value of flag leaf compared with N1 treatment during grain filling stage, and also the crop ear number, grain number per spike and above-ground biomass were increased. Although postponing nitrogen application increased water consumption, both grain yield and water use efficiency were increased. Compared with sufficient water supply, drought stress and waterlogging stress significantly reduced the photosynthetic rate of flag leaves at anthesis and grain filling stages, ear number, 1000-grain mass and yield under all of the N application patterns. The decline of photosynthetic rate under either drought stress or waterlogging stress was much less in N2 and N3 than in N1 treatments, just the same as the grain yield. The results indicated that postponing nitrogen application could regulate winter wheat yield as well as its components to alleviate the damages, caused by unfavorable water stress by increasing flag leaf SPAD and maintaining flag leaf photosynthetic rate after anthesis, and promoting above-ground dry matter accumulation.

[Effects of stubble-standing mode on the grain yield and water use efficiency of wheat and maize in wheat/maize intercropping system].

Wheat/maize intercropping is the main intercropping pattern in the irrigation region of Hexi Oasis, Northwest China, but the traditional intercropping needs much water, making the regional water resource lacked increasingly. In 2010, a field experiment was conducted in the irrigation region of Shiyang River basin oasis, Gansu Province of Northwest China, aimed to study the effects of traditional stubble-burning, stubble-returning, and stubble-standing on the grain yield, water use efficiency (WUE), and economical benefits of wheat and maize in wheat/maize inter-cropping system. Compared with stubble-burning and stubble-returning, stubble-standing increased the grain yield of mono- and intercropped wheat by 7.2% and 5.1% , and 6.2%, 5.1%, and that of mono- and intercropped maize by 4.7% and 2.5%, and 7.2% and 3.3%, and increased the WUE of mono- and intercropped wheat by 20.4% and 16.2%, and 17.9% and 14.6%, and that of mono- and intercropping maize by 16.7% and 10.9%, and 11. 8% and 17.0%, respectively. As for the mono- and intercropped wheat and maize, their average net economical benefits under stubble-burning, stubble- returning, and stubble-standing were 10946, 11471, and 13454 RMB.hm-2, respectively. In considering the grain yield, WUE, and economic benefits, stubble- standing would be the optimal mode of wheat/maize intercropping in the oasis of Hexi irrigation region, Northwest China.

Transplantation of human limbal cells cultivated on amniotic membrane for reconstruction of rat corneal epithelium after alkaline burn.

BACKGROUND: The transplantation of limbal epithelial cells cultivated on amniotic membrane is a newly developed treatment for limbal stem cell deficiency. The purpose of our study was to investigate the biological characteristics of limbal epithelial cells and evaluate the effect of transplantation of cultivated human limbal epithelial cells on ocular surface reconstruction in limbal stem cell deficiency rat model. METHODS: Human limbal cells were isolated and cultivated in vitro. Cytokeratins 3, 12, and 19 (K3, K12 and K19) and p63 were detected by immunofluorescent staining or RT-PCR. BrdU labelling test was used to identify the slow cycling cells in the cultures. Limbal stem cell deficiency was established in rat cornea by alkali burn. Two weeks after injury, the rats received transplants of human limbal stem cells cultivated on amniotic membrane carrier. The therapeutic effect was evaluated by slit lamp observation, Hemotoxin and Eosin (HE) staining and immunofluorescent staining. RESULTS: On day 7 in primary culture, p63 and K19 were strongly expressed by most cells but only a few cells expressed K3. On days 14 and 21, p63 and K19 were still expressed by a majority of cells, but the expressive intensity of p63 decreased in a number of cells, while the proportion of K3 positive cells increased slightly and some cells coexpressed p63 and K3. RT-PCR showed that gene expression of both p63 and K12 were positive in cultivated limbal cells, but in mature superficial epithelial cells, only K12 was detected. BrdU labelling test showed that most cells were labelled with BrdU after 7 days' labelling and BrdU label retaining cells were observed after chasing for 21 days with BrdU free medium. For in vivo test, slit lamp observation, HE staining and immunofluorescent staining showed that the rats receiving transplant of human limbal stem cells cultivated on amniotic membrane grew reconstructed corneas with intact epithelium, improved transparency and slight or no neovascularization. A majority of epithelial cells of the reconstructed cornea were positive to antihuman nuclear antibody and cells expressing K3 were found mainly in superfacial epithelium. CONCLUSIONS: Limbal stem cells can be cultivated in vitro: the cells are characterized by high proliferation and slow cycling and identified as p63/K19 positive and K3/K12 negative. During culture, some stem cells can proliferate and differentiate into mature cornea epithelial cells. Amniotic membrane is a suitable carrier for limbal stem cells. Transplantation of human limbal stem cells cultivated on amniotic membrane can functionally reconstruct rat cornea with limbal stem cell deficiency.