与其他器官相比，Bt转基因棉棉铃中杀虫蛋白含量最低。该文研究了盛花期喷施氨基酸对棉铃Bt蛋白浓度和产量形成的影响、相关的蛋白质合成和碳水化合物转化机制。2017-2018年棉花生长季节，以2个陆地棉品种（杂交种泗抗3号和常规种泗抗1号）为试验材料，设置三个处理（即CK，对照；LA1，组成Bt蛋白的5种主要氨基酸；LA2，21种氨基酸）于盛花期喷施棉铃。结果表明，棉铃Bt蛋白浓度提高5.2%-16.4%，籽棉产量提高5.5%-11.3%，2个氨基酸处理间没有差异。此外，由于氨基酸的应用，棉铃游离氨基酸和可溶性蛋白含量、谷氨酸丙酮酸转氨酶（GPT）和谷氨酸草酰乙酸转氨酶（GOT）活性、葡萄糖和果糖含量、可溶性酸性转化酶（SAI）活性均有所增加。同时发现，棉铃Bt蛋白含量、铃数增长量和铃重与碳氮代谢密切相关，Bt蛋白含量与游离氨基酸含量、可溶性蛋白含量呈显著以上水平线性正相关。花后15-25天，铃数增长量与GPT活性、GOT活性呈显著以上水平线性正相关。花后55-65日铃重与SAI活性呈显著以上水平线性正相关。这些结果表明，氨基酸的应用促进了棉铃蛋白质合成和碳水化合物转化，从而提高了棉铃Bt蛋白浓度和皮棉产量。

不利的生长条件会造成玉米产量的降低。当前，生育期内的高温胁迫是玉米生产过程中所面临的重要威胁之一。玉米在生育期内的所有生长阶段都可能遭受连续或者间断的高温胁迫。为了应对不同生育期阶段内高温胁迫对玉米生产的影响，需要进一步综述、对比不同生长阶段内高温胁迫造成的产量损失，以及潜在的机制。为此，本文将玉米生长周期划分为七个生长阶段，即发芽和幼苗期、拔节期、营养生长后期、开花期、滞后期和有效灌浆期，以及灌浆后期。本文介绍的主要内容是不同阶段高温胁迫引起的产量损失和潜在生理变化。同时，还比较和讨论了高温胁迫对不同生长阶段生理过程影响的共性和差异。最后，提出了一个理论框架来描述不同阶段内高温胁迫对产量及产量构成要素的主要影响，这也将为制定缓解高温胁迫造成的玉米产量损失的策略提供帮助。

2013-2016年于扬州大学试验田，本试验对短季棉品种中棉所50（CRRI50）进行了密度（12.0、13.5和15.0株﹒m^-2）和缩节胺剂量（180、270和360 g ha^-1）的组合处理。结果表明，在13.5株﹒m^-2和270g﹒ha^-1 缩节胺处理下，单位面积铃数最多，棉铃日增量最高，90%以上的棉铃均出现在离地面高45-80cm范围内。综上所述，麦后直播棉种植模式下，适宜的缩节胺剂量配合高种植密度可促进集中成铃，使中、上冠层棉铃分布较多，并且不减产，从而克服目前移栽棉种植模式下用工多的问题。

在棉花生产中，种植密度是用来控制棉铃分布、成铃情况和产量的常用栽培方法。2015年和2016年在大田条件下，研究了5种种植密度（PD1-PD5:15000；30000；45000；60000和75000株·ha^-1）对两个Bt棉品种泗抗1号（常规品种）和泗抗3号（杂交品种）Bt杀虫蛋白含量的影响。单株铃数、铃重、棉铃体积均随密度的增加而减少。当种植密度从15000株/hm2增加到75000株/hm2时，棉子中Bt杀虫蛋白含量增加，2015年花后40天SK-1和SK-3中Bt杀虫蛋白含量分别增加了66.5%和53.4%，2016年SK-1和SK-3分别提高了36.8%和38.6%。氮代谢结果分析表明，随着密度的增加，可溶性蛋白含量、谷氨酸丙酮酸转氨酶（GPT）和谷氨酸草酰乙酸转氨酶（GOT）活性增加，游离氨基酸含量、蛋白酶和肽酶活性降低。花后20天数据分析表明，棉子Bt杀虫蛋白含量与可溶性蛋白水平呈显著正相关，2015年在SK-1和SK-3中的相关系数分别为0.825**和0.926**，2016年在SK-1和SK-3中的相关系数分别为0.955**和0.965**。相比之下，棉子Bt杀虫蛋白水平与游离氨基酸含量呈显著负相关，2015年在SK-1和SK-3中的相关系数分别为-0.983**和-0.974**，2016年在SK-1和SK-3中的相关系数分别为-0.996**和-0.986**。为进一步证实Bt杀虫蛋白含量与氮代谢的关系，分析发现Bt杀虫蛋白含量与GPT和GOT活性呈正相关，与蛋白酶和肽酶活性呈负相关。综上所述，高种植密度增加了棉子Bt杀虫蛋白含量，该增加与单株铃数、铃重和铃体积的减少密切相关。此外，在高种植密度下，氮代谢的变化也有助于Bt杀虫蛋白含量的增加。

在转Bt基因抗虫棉（Bt棉）所有器官中，棉铃中杀虫蛋白含量最低。这也影响了Bt棉高产的获得。本文主要探讨了喷施不同浓度氮素（尿素）对Bt棉棉子中杀虫蛋白含量和籽棉产量的影响及其相关的生理机制。2017-2018年以泗抗3号（杂交种）和泗抗1号（常规种）为材料，在棉铃形成期，喷施不同浓度尿素。2017年设置0%、2%、4%、6%、8%、10% 等6个浓度；2018年设置0%、1%、3%、5%、7%、9%等6个浓度。尿素浓度对Bt棉棉子中杀虫蛋白含量和最终籽棉产量均有明显影响，其中喷施5%-6%尿素处理可显著提高供试品种棉子中杀虫蛋白含量且籽棉产量最高。进一步分析表明，喷施5%-6%尿素处理下，泗抗3号和泗抗1号棉铃中游离氨基酸和可溶性蛋白含量、谷氨酸丙酮酸转氨酶(GPT)和谷氨酸草酰乙酸转氨酶(GOT)活性均较高，但肽酶和蛋白酶活性却显著降低。相关性分析表明，游离氨基酸含量、GPT活性与棉子中杀虫蛋白含量呈显著线性正相关关系。此外，喷施5%-6%尿素后，供试品种田间棉铃虫数量及蛀铃率均显著降低，这也为最终高产的获得奠定了基础。喷施外源氮素可显著影响Bt棉棉子中杀虫蛋白含量，进而提高其对棉铃虫的抗性。其中喷施5%-6%尿素效果最为明显。

为了阐明减氮施肥对抗虫棉棉蕾中Bt杀虫蛋白含量的影响，在2015-2016棉花生长季，以常规种泗抗1号（SK-1）和杂交种泗抗3号（SK-3）为试验材料，分别进行了0、75、150、225、300 kg/公顷的施氮量处理。在不同施氮量处理下，随着施氮量从常规施氮量（300kg/公顷）降低到0 kg/公顷，单株蕾数、棉蕾体积和棉蕾干重均呈下降趋势，同时棉蕾Bt杀虫蛋白含量也相应下降。氮代谢分析结果表明，减氮条件下可溶性蛋白含量、GPT和GOT活性降低，游离氨基酸含量、肽酶和蛋白酶活性升高。相关性分析结果表明，缺氮条件下Bt蛋白含量的降低与氮代谢生理变化相关。综上所述，减氮条件下，棉蕾生长和棉蕾中Bt杀虫蛋白含量均呈下降趋势，因此在蕾期适当的施氮量在促进棉蕾生长的同时也可提高棉花抗虫性。在人间游历 爱是最壮观的迁徙。

The cotton direct seeding after wheat (rape) harvested is under trial and would be the future direction at the Yangtze River Valley region of China.  The objective of this study was to quantify the effects of branch and stem architecture on cotton yield and identify the optimal cotton architecture to compensate the yield loss due to the reduction of individual production capacity under high planting density in the direst seeding after wheat harvested cropping system.  The characteristics of the stem and branch architecture and the relationships between architecture of the stem and branch with yield formation were studied on eight short season cotton cultivars during 2015 and 2016 cotton growth seasons.  Based on the two years results, three cultivars with different architectures of stem and branch were selected to investigate the effect of mepiquat chloride (MC) application on the architecture of the stem and branch, boll retention, and the yield in 2017.  Significant differences were observed on plant height, all fruiting nodes to branches ratio (NBR) in the cotton plant, and the curvature of the fruiting branch (CFB) among the studied cultivars.  There were three types of stem and fruiting branch structures: Zhong425 with stable and suitable plant height and NBR (about 90 cm and 2.5, respectively), high CFB (more than 10.0), and high boll retention speed and seed cotton yield; Siyang 822 with excessive plant height and NBR, low CFB, and low boll retention speed and seed cotton yield; and other studied cultivars with unstable structure of stem and branch, boll retention speed, and seed cotton yield across years.  And MC application could promote the appropriate plant height and NBR and high CFB and thus resulted in high boll retention speed and the yield.  The results suggested that the suitable plant height and NBR (about 90 cm and 2.5 respectively), and high CFB (more than 10.0), which was related to both genotype and cultural practice, could promote the higher boll retention speed and seed cotton yield.

This study was conducted to investigate the effects of alternating high temperature on Cry1Ac protein content on Bt cotton cultivars Sikang 1 (SK-1, a conventional cultivar) and Sikang 3 (SK-3, a hybrid cultivar). In 2011 and 2012, cotton plants were subjected to high temperature treatments ranging from 32 to 40°C in climate chambers to investigate the effects of high temperature on boll shell insecticidal protein expression. The experiments showed that significant decline of the boll shell insecticidal protein was detected at temperatures higher than 38°C after 24 h. Based on the results, the cotton plants were treated with the threshold temperature of 38°C from 6:00 a.m. to 6:00 p.m. followed by a normal temperature of 27°C during the remaining night hours (DH/NN) in 2012 and 2013. These treatments were conducted at peak boll growth stage for both cultivars in study periods of 0, 4, 7, and 10 d. Temperature treatment of 32°C from 6:00 a.m. to 6:00 p.m. and 27°C in the remaining hours was set as control. The results showed that, compared with the control, after the DH/NN stress treatment applied for 7 d, the boll shell Cry1Ac protein content level was significantly decreased by 19.1 and 17.5% for SK-1 and by 15.3 and 13.7% for SK-3 in 2012 and 2013, respectively. Further analysis of nitrogen metabolic physiology under DH/NN showed that the soluble protein content and the glutamic pyruvic transaminase (GPT) activities decreased slightly after 4 d, and then decreased sharply after 7 d. The free amino acid content and the protease content increased sharply after 7 d. The changes in SK-1 were greater than those in SK-3. These results suggest that under DH/NN stress, boll shell Cry1Ac protein content decline was delayed. Reduced protein synthesis and increased protein degradation in the boll shell decreased protein content, including Bt protein, which may reduce resistance to the cotton bollworm.

Cotton cultivars with brown (Xiangcaimian 2), green (Wanmian 39) and white (Sumian 9) fiber were investigated to study fiber developmental characteristics of natural-colored cotton and the effect of hormones on fiber quality at different stages after anthesis. Fiber lengths of both natural-colored cottons were lower than the white-fibered control, with brown-fibered cotton longer than green. Fiber strength, micronaire and maturation of natural-colored cotton were also lower than the control. The shorter fiber of the green cultivar was due to slower growth during 10 to 30 days post-anthesis (DPA). Likewise, the lower fiber strength, micronaire and maturation of natured-colored cotton were also due to slower growth during this pivotal stage. Indole-3-acetic acid (IAA) content at 10 DPA, and abscisic acid (ABA) content at 30 to 40 DPA were lower in the fibers of the natural-colored than that of the white-fibered cotton. After applying 20 mg L^–1 gibberellic acid (GA3), the IAA content at 20 DPA in the brown and green-fibered cottons increased by 51.07 and 64.33%, fiber ABA content increased by 38.96 and 24.40%, and fiber length increased by 8.13 and 13.96%, respectively. Fiber strength, micronaire and maturation were also enhanced at boll opening stage. Those results suggest that the level of endogenous hormones affect fiber quality. Application of external hormones can increase hormone content in natural-colored cotton fiber, improving its quality.

Gayal is a rare semi-wild bovine species found in the Indo-China. They can graze grasses, including bamboo leaves, as well as reeds and other plant species, and grow to higher mature live weights than Yunnan Yellow cattle maintained in similar harsh environments. The aim of this study was to identify specific cellulase in the gayal rumen. A metagenomic fosmid library was constructed using genomic DNA isolated from the ruminal contents of four adult gayals. This library contained 38 400 clones with an average insert size of 35.5 kb. The Umcel-1 gene was isolated from this library. Investigation of the cellulase activity of 24 random clones led to the identification of the Umcel-1 gene, which exhibited the most potent cellulase activity. Sequencing the Umcel-1 gene revealed that it contained an open reading frame of 942 base pairs that encoded a product of 313 amino acids. The putative gene Umcel-1 product belonged to the glycosyl hydrolase family 5 and showed the highest homology to the cellulase (GenBank accession no. YP_004310852.1) from Clostridium lentocellum DSM 5427, with 44% identity and 62% similarity. The Umcel-1 gene was heterologously expressed in Escherichia coli BL21, and recombinant Umcel-1 was purified. The activity of purified recombinant Umcel-1 was assessed, and the results revealed that it hydrolyzed carboxymethyl cellulose with optimal activity at pH 5.5 and 45°C. To our knowledge, this study provides the first evidence for a cellulase produced by bacteria in gayal rumen.

High-temperature stress (HTS) at the grain-filling stage in spring maize (Zea mays L.) is the main obstacle to increasing productivity in the North China Plain (NCP). To solve this problem, the physiological mechanisms of HTS, and its causes and impacts, must be understood. The HTS threshold of the duration and rate in grain filling, photosynthetic characteristics (e.g., the thermal stability of thylakoid membrane, chlorophyll and electron transfer, photosynthetic carbon assimilation), water status (e.g., leaf water potential, turgor and leaf relative water content) and signal transduction in maize are reviewed. The HTS threshold for spring maize is highly desirable to be appraised to prevent damages by unfavorable temperatures during grain filling in this region. HTS has negative impacts on maize photosynthesis by damaging the stability of the thylakoid membrane structure and degrading chlorophyll, which reduces light energy absorption, transfer and photosynthetic carbon assimilation. In addition, photosynthesis can be deleteriously affected due to inhibited root growth under HTS in which plants decrease their water-absorbing capacity, leaf water potential, turgor, leaf relative water content, and stomatal conductance. Inhibited photosynthesis decrease the supply of photosynthates to the grain, leading to falling of kernel weight and even grain yield. However, maize does not respond passively to HTS. The plant transduces the abscisic acid (ABA) signal to express heat shock proteins (HSPs), which are molecular chaperones that participate in protein refolding and degradation caused by HTS. HSPs stabilize target protein configurations and indirectly improve thylakoid membrane structure stability, light energy absorption and passing, electron transport, and fixed carbon assimilation, leading to improved photosynthesis. ABA also induces stomatal closure to maintain a good water status for photosynthesis. Based on understanding of such mechanisms, strategies for alleviating HTS at the grain-filling stage in spring maize are summarized. Eight strategies have the potential to improve the ability of spring maize to avoid or tolerate HTS in this study, e.g., adjusting sowing date to avoid HTS, breeding heat-tolerance varieties, and tillage methods, optimizing irrigation, heat acclimation, regulating chemicals, nutritional management, and planting geometric design to tolerate HTS. Based on the single technology breakthrough, a comprehensive integrated technical system is needed to improve heat tolerance and increase the spring maize yield in the NCP.  

Cotton (Gossypium hirsutum L.) plants produce more ethylene when subjected to abiotic stresses, such as high temperatures and drought, which result in premature leaf senescence, reduced photosynthetic efficiency, and thus decreased yield. This study was conducted to test the hypothesis that the ethylene-inhibiting compound 1-methylcyclopropene (1-MCP) treatment of cotton plants can delay leaf senescence under high temperature, drought, and the aging process in controlled environmental conditions. Potted cotton plants were exposed to 1-MCP treatment at the early square stage of development. The protective effect of 1-MCP against membrane damage was found on older compared to younger leaves, indicating 1-MCP could lower the stress level caused by aging. Application of 1-MCP resulted in reduction of lipid peroxidation, membrane leakage, soluble sugar content, and increased chlorophyll content, in contrast to the untreated plants under heat stress, suggesting that 1-MCP treatment of cotton plants may also have the potential to reduce the effect of heat stress in terms of delayed senescence. Application of 1-MCP caused reductions of lipid peroxidation, membrane leakage, and soluble sugar content, together with increases in water use efficiency (WUE), water potential, chlorophyll content, and fluorescence quantum efficiency, compared to the untreated plants under drought, suggesting that 1-MCP treatment of cotton plants may also have the ability to reduce the level of stress under drought conditions. In conclusion, 1-MCP treatment of cotton should have the potential to delay senescence under heat and drought stress, and the aging process. Additionally, 1-MCP is more effective under stress than under non-stress conditions.

To make recycling utilization of organic materials produced in various agricultural systems, five kinds of organic materials were applied in a field test, including crop straw (CS), biogas residue (BR), mushroom residue (MR), wine residue (WR), pig manure (PM), with a mineral fertilizer (CF) and a no-fertilizer (CK) treatment as a control. Our objectives were: i) to quantify the effects of organic materials on soil C and N accumulation; ii) to evaluate the effects of organic materials on soil aggregate stability, along with the total organic carbon (TOC), and N in different aggregate fractions; and iii) to assess the relationships among the organic material components, soil C and N, and C, N in aggregate fractions. The trial was conducted in Wuqiao County, Hebei Province, China. The organic materials were incorporated at an equal rate of C, and combined with a mineral fertilizer in amounts of 150 kg N ha-1, 26 kg P ha-1 and 124 kg K ha-1 respectively during each crop season of a wheat-maize rotation system. The inputted C quantity of each organic material treatment was equivalent to the total amount of C contained in the crop straw harvested in CS treatement in the previous season. TOC, N, water-stable aggregates, and aggregate-associated TOC and N were investigated. The results showed that organic material incorporation increased soil aggregation and stabilization. On average, the soil macroaggregate proportion increased by 14%, the microaggregate proportion increased by 3%, and mean-weight diameter (MWD) increased by 20%. TOC content followed the order of PM>WR>MR>BR>CS>CK>CF; N content followed the order WR>PM>MR>BR>CS>CF>CK. No significant correlation was found between TOC, N, and the quality of organic material. Soil silt and clay particles contained the largest part of TOC, whereas the small macroaggregate fraction was the most sensitive to organic materials. Our results indicate that PM and WR exerted better effects on soil C and N accumulation, followed by MR and BR, suggesting that organic materials from ex situ farmland could promote soil quality more as compared to straw returned in situ.

Higher boll worm survival rates were detected after high temperature presented during square period in Bt cotton. The objective of this study was to investigate the effects of high temperature level on the Bt efficacy of two different types of Bt cotton cultivars at squaring stage. During the 2011 to 2013 cotton growth seasons, high temperature treatments ranged from 34 to 44°C in climate chambers, and field experiments under high temperature weather with various temperature levels were conducted to investigate the effects of the high temperature level on square Bt protein concentration and nitrogen metabolism. The climate chamber experiments showed that the square insecticidal protein contents reduced after 24 h elevated temperature treatments for both cultivars, whereas significant declines of the square insecticidal protein contents were detected at temperature >38°C, and only slightly numerical reductions were observed when temperature below 38°C. Similar high temperature responses were also observed at the two field experimental sites in 2013. Correspondingly, high temperature below 38°C seems have little effect on the square amino acid concentrations, soluble protein contents, glutamic- pyruvic transaminase (GPT) and glutamic-oxalacetic transaminase (GOT) activities as well as protease and peptidase activities; however, when the temperature was above 38°C, reduced soluble protein contents, enhanced amino acid concentrations, decreased GPT and GOT activities, bolstered protease and peptidase activities in square were detected. In general, the higher the temperature is (>38°C), the larger the changes for the above compound contents and key enzymes activities of the square protein cycle. The findings indicated that the unstable insect resistance of the square was related to high temperature level during square stage.

Many studies have focused on various agricultural management measures to reduce agricultural nitrous oxide (N2O) emission. However, few studies have investigated soil N2O emissions in intercropping systems in the North China Plain. Thus, we conducted a field experiment to compare N2O emissions under monoculture and maize-legume intercropping systems. In 2010, five treatments, including monocultured maize (M), maize-peanut (MP), maize-alfalfa (MA), maize-soybean (MS), and maize-sweet clover (MSC) intercropping were designed to investigate this issue using the static chamber technique. In 2011, M, MP, and MS remained, and monocultured peanuts (P) and soybean (S) were added to the trial. The results showed that total production of N2O from different treatments ranged from (0.87±0.12) to (1.17±0.11) kg ha-1 in 2010, while those ranged from (3.35±0.30) to (9.10±2.09) kg ha-1 in 2011. MA and MSC had no significant effect on soil N2O production compared to that of M (P<0.05). Cumulative N2O emissions from MP in 2010 were significantly lower than those from M, but the result was the opposite in 2011 (P<0.05). MS significantly reduced soil N2O emissions by 25.55 and 48.84% in 2010 and 2011, respectively (P<0.05). Soil N2O emissions were significantly correlated with soil water content, soil temperature, nitrification potential, soil NH4 +, and soil NO3 - content (R2=0.160-0.764, P<0.01). A stepwise linear regression analysis indicated that soil N2O release was mainly controlled by the interaction between soil moisture and soil NO3 - content (R2=0.828, P<0.001). These results indicate that MS had a coincident effect on soil N2O flux and significantly reduced soil N2O production compared to that of M over two growing seasons.

Expression of insecticidal protein for transgenic Bacillus thuringiensis (Bt) cotton is unstable and related to nitrogen metabolism. The objective of this study was to investigate the relationship between leaf carbon nitrogen ratio (C/N) and insecticidal efficacy of two Bt cotton cultivars. C/N ratio and Bt protein content were both measured at peak square period and peak boll period respectively under 5-7 d high temperature and different nitrogen fertilizer rates on the Yangzhou University Farm and the Ludong Cotton Farm, China. All plants were grown in field. The results showed that the C/N ratio enhanced slightly and the Bt protein content remained stable at peak square period, but significant increases for the C/N ratio and decreases markedly for the leaf Bt protein concentration were detected at the peak boll period. The similar patterns at the two growth periods were found for the leaf C/N ratio and Bt protein content by different N fertilizer treatments. When nitrogen rate was from 0 to 600 kg ha-1, the C/N ratio was reduced by 0.017 and 0.006 for Sikang 1 and Sikang 3 at peak square period, compared to the 1.350 to 1.143 reduction for Sikang 1 and Sikang 3 at peak boll period, respectively. Correspondingly, the leaf Bt protein contents were bolstered by 2.6-11.8 and 26.9-36.9% at the two different growth periods, respectively. The results suggested that enhanced C/N ratio by high temperature and nitrogen application may result in the reduction of insectiocidal efficacy in Bt cotton, especially in peak boll period.

High temperature stress (HTS) on spring maize (Zea mays L.) during the filling stage is the key factor that limits the yield increase in the North China Plain (NCP). Subsoiling (SS) and ridge tillage (R) were introduced to enhance the ability of spring maize to resist HTS during the filling stage. The field experiments were conducted during the 2011 and 2012 maize growing seasons at Wuqiao County, Hebei Province, China. Compared with rotary tillage (RT), the net photosynthetic rate, stomatal conductance, transpiration rate, and chlorophyll relative content (SPAD) of maize leaves was increased by 40.0, 42.6, 12.8, and 29.7% under SS, and increased by 20.4, 20.0, 5.4, and 14.2% under R, repectively. However, the treatments reduce the intercellular CO2 concentration under HTS. The SS and R treatments increased the relative water content (RWC) by 11.9 and 6.2%, and the water use efficiency (WUE) by 24.3 and 14.3%, respectively, compared with RT. The SS treatment increased the root length density and soil moisture in the 0-80 cm soil profile, whereas the R treatment increased the root length density and soil moisture in the 0-40 cm soil profile compared with the RT treatment. Compared with 2011, the number of days with temperatures 33°C was more 2 d and the mean day temperature was higher 0.9°C than that in 2012, whereas the plant yield decreased by 2.5, 8.5 and 10.9%, the net photosynthetic rate reduced by 7.5, 10.5 and 18.0%, the RWC reduced by 3.9, 5.6 and 6.2%, and the WUE at leaf level reduced by 1.8, 5.2 and 13.1% in the SS, R and RT treatments, respectively. Both the root length density and the soil moisture also decreased at different levels. The yield, photosynthetic rate, plant water status, root length density, and soil moisture under the SS and R treatments declined less than that under the RT treatment. The results indicated that SS and R can enhance the HTS resistance of spring maize during the filling stage, and led to higher yield by directly improving soil moisture and root growth and indirectly improving plant water status, photosynthesis and grain filling. The study can provide a theoretical basis for improving yield of maize by adjusting soil tillage in the NCP.

A 2-yr field experiment was conducted on a calcareous alluvial soil with four summer maize intercropping systems at Shangzhuang Experiment Station (116.3°E, 39.9°N) in the North China Plain. The objective was to determine nitrate leaching from intercropping systems involving maize (Zea mays L.): sole maize (CK), maize + soybean (CST), maize + groundnut (CGT), maize+ ryegrass (CHM), and maize + alfalfa (CMX). Intercropping greatly reduced nitrate accumulation in the 100-200 cm soil layers compared with maize monoculture. Nitrate accumulation under intercropping systems decreased significantly at the 140-200 cm soil depth; the accumulation varied in the order CK>CST>CMX>CHM>CGT. However, compared to the CK treatment, nitrate leaching losses during the maize growing period were reduced by 20.9- 174.8 (CGT), 35.2-130.8 (CHM), 60.4-122.0 (CMX), and 30.6-82.4 kg ha-1 (CST). The results also suggested that intercropping is an effective way to reduce nitrogen leaching in fields with N fertilizer over-dose.

Weed control is one of the major constraint factors in crop production around the world. Field experiments were conducted during 2008-2009 under intercropping systems involving alfalfa (Medicago sativa L.), sweet potato (Ipomoea batatas [L.] Lam.), peanut (Arachis hypogaea L.), and sunflower (Helianthus annuus L.) in maize (Zea mays L.) without any weeds control methods taken. The results demonstrate that maize||sunflower is most effective on weed suppression and that it also has a more competitively inhibitory effect on Xanthium compared with the other patterns by evaluating the Xanthium density and dry weight under different intercropping systems with maize. Maize||peanut, maize||alfalfa and maize||sweet potato intercrops have no apparent inhibitory effect on weeds. To further investigate the effect of maize||sunflower on weed control, indoor pot experiments were conducted by determining the effect of extractions on germination rate (GR), root vigor, MDA (malondialdehyde), SOD (superoxide dismutase) and POD (peroxidase) content of Xanthium. The results better prove that maize||sunflower extractions have more significant inhibitory effect on GR and young root vigor of Xanthium than maize monocrop extractions.

The higher survival rates of Helicoverpa amigera larvae were usually observed after adverse climate which was related to extreme temperature (T) and relative humidity (RH) stresses in transgenic Bacillus thuringiensis (Bt) cotton. The unstable resistance of Bt cotton to bollworms has been correlated with the reduced expression of CryIAc d-endotoxin. The objective of this study was to investigate the effects of combined temperature and relative humidity stresses on the leaf CryIAc insecticidal protein expression during critical developmental stages. The study was undertaken on two transgenic cotton cultivars that share same parental background, Sikang 1 (a conventional cultivar) and Sikang 3 (a hybrid cultivar), during the 2007 and 2008 growing seasons at the Yangzhou University Farm, Yangzhou, China. The study was arranged with two factors that consisted of temperature (two levels) and relative humidity (three levels). The six T/RH treatments were 37°C/95%, 37°C/70%, 37°C/50%, 18°C/95%, 18°C/70%, and 18°C/50%. In 2007, the six treatments were imposed to the plants at peak flowering stage for 24 h; in 2008, the six treatments were applied to the plants at peak square, peak flowering, and peak boll stages for 48 h. The results of the study indicated that the leaf insecticidal protein expression in CryIAc was significantly affected by extreme temperature only at peak flowering stage, and by both extreme temperature and relative humidity during boll filling stage. The greatest reductions were observed when the stresses were applied at peak boll stage. In 2008, after 48 h stress treatment, the leaf Bt endotoxin expression reduced by 25.9-36.7 and 23.6-40.5% at peak boll stage, but only by 14.9-26.5 and 12.8-24.0% at peak flowering stage for Sikang 1 and Sikang 3, respectively. The greatest reduction was found under the low temperature combined with low relative humidity condition for both years. It is believed that the temperature and relative humidity stresses may be attributed to the reduced efficacy of Bt cotton in growing conditions in China, where extreme temperatures often increase up to 35-40°C and/or decrease down to 15-20°C, and relative humidity may reach to 85-95% and/or reduce to 40-55% during the cotton growing season.