High nitrogen application rate and planting density reduce wheat grain yield by reducing filling rate of inferior grain in middle spikelets

Excessive use of nitrogen fertilizer and high planting density reduce grain weight in wheat.However,the effects of high nitrogen and planting density on the filling of grain located in different positions of the wheat spikelet are unknown.A two-year field experiment was conducted to investigate this question and the underlying mechanisms with respect to hormone and carbohydrate activity.Both high nitrogen application and planting density significantly increased spike density,while reducing kernel number per spike and 1000-kernel weight.However,the effects of high nitrogen and high plant density on kernel number per spike and 1000-kernel weight were different.The inhibitory effect of high nitrogen application and high planting density on kernel number per spike was achieved mainly by a reduction in kernel number per spikelet in the top and bottom spikelets.However,the decrease in 1000-kernel weight was contributed mainly by the reduced weight of grain in the middle spikelets.The grain-filling rate of inferior grain in the middle spikelets was significantly decreased under high nitrogen input and high planting density conditions,particularly during the early and middle grain-filling periods,leading to the suppression of grain filling and consequent decrease in grain weight.This effect resulted mainly from inhibited sucrose transport to and starch accumulation in inferior grain in the middle spikelets via reduction of the abscisic acid/ethylene ratio.This mechanism may explain how high nitrogen application and high planting density inhibit the grain filling of inferior wheat grain.

Two Ultraviolet Radiation Datasets that Cover China

Ultraviolet（UV） radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization＇s measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.

Multiple nano-drug delivery systems for intervertebral disc degeneration: Current status and future perspectives

Low back pain(LBP)is a common disease that imposes a huge social and economic burden on people.Intervertebral disc(IVD)degeneration(IVDD)is often considered to be the leading cause of LBP and further aggravate and cause serious spinal problems.The established treatment strategy for IVDD consists of physiotherapy,pain medication by drug therapy,and,if necessary,surgery,but none of them can be treated from the etiology;that is,it cannot fundamentally reverse IVD and reconstruct the mechanical function of the spine.With the development of nanotechnology and regenerative medicine,nano-drug delivery systems(NDDSs)have improved treatment results because of their good biodegradability,biocompatibility,precise targeted specific drug delivery,prolonged drug release time,and enhanced drug efficacy,and various new NDDSs for drugs,proteins,cells,and genes have brought light and hope for the treatment of IVDD.This review summarizes the research progress of NDDSs in the treatment of IVDD and provides prospects for using NDDSs to address the challenges of IVDD.We hope that the ideas generated in this review will provide insight into the precise treatment of IVDD.

煤化工废水中二元酚处理方法的研究进展

介绍了含二元酚废水处理方法的研究现状,主要包括吸附法、乳状液膜分离法、溶剂萃取法、焚烧法、酚醛缩合法、化学氧化法、蒸汽脱酚法、臭氧氧化法和高级氧化技术等,分析比较了各种处理方法的优缺点和应用前景,重点介绍了目前工业上常用的溶剂萃取法、溶剂的选择及其影响因素,展望了含二元酚废水处理技术的发展方向,提出多种技术联用是今后处理含二元酚废水的趋势.

Soil temperature and moisture sensitivities of soil CO_2 efflux before and after tillage in a wheat field of Loess Plateau,China

As a conventional farming practice, tillage has lasted for thousands of years in Loess Plateau, China. Although recent studies show that tillage is a prominent culprit to soil carbon loss in croplands, few studies have investigated the influences of tillage on the responses of soil CO2 efflux （SCE） to soil temperature and moisture. Using a multi-channel automated CO2 efflux chamber system, we measured SCE in situ continuously before and after the conventional tillage in a rain fed wheat field of Loess Plateau, China. The changes in soil temperature and moisture sensitivities of SCE, denoted by the Q10 value and linear regression slope respectively, were compared in the same range of soil temperature and moisture before and after the tillage. The results showed that, after the tillage, SCE increased by 1.2-2.2 times; the soil temperature sensitivity increased by 36.1%-37.5%; and the soil moisture sensitivity increased by 140%-166%. Thus, the tillage-induced increase in SCE might partially be attributed to the increases in temperature and moisture sensitivity of SCE.