轮牧被自然科学家认为是保护草地的自然解决方案之一。然而，当牧民采用轮牧时，其对改善草地质量的效果尚不明确。基于中国两个主要牧区的牧户面板数据，本文利用固定效应模型、工具变量法实证分析轮牧对草地质量的影响。结果显示，轮牧在短期内对草地质量的影响不显著，但在长期内具有显著的正向效果。当村庄投资能提高生产效率的公共基础设施或牧民采取轮牧相关的支持措施时，轮牧可以更好地改善草地质量。进一步分析表明，采用轮牧措施的牧民具有更高的放牧强度、更高的补饲强度和更多的圈养牲畜天数，这表明牧民可以在不增加对天然草地压力的情况下更有效地管理牲畜。此外我们还发现，牧业收入和轮牧采用相辅相成，这也是牧户采取轮牧的经济原因。这些研究结果为在发展中国家推广协调生态系统保护和资源利用的基层政策提供了参考。

调节鸡肌纤维类型特异性和维持性的机制还很不清楚。在哺乳动物中，CSRP3在维持典型的肌肉结构和功能方面起着非常重要的作用。本研究探讨了CSRP3在鸡骨骼肌中的作用。首先，制备了鸡CSRP3抗体，比较了四种不同肌纤维组成的鸡骨骼肌中CSRP3基因的mRNA和蛋白表达水平。然后分析CSRP3沉默后对鸡成肌细胞转录组表达谱的影响。结果表明，鸡骨骼肌中CSRP3基因的mRNA和蛋白表达水平均与其肌纤维类型组成相关。以Q<0.05，差异倍数大于1.5为筛选条件，共鉴定出650个差异基因。CSRP3沉默后，255个基因表达上调，395个基因表达下调。功能富集分析结果表明，心肌细胞肾上腺素能信号、脂肪细胞因子信号和apelin信号等多种通路在差异表达基因和所有表达基因中均显著（P<0.05）富集。共表达基因网络结果表明，CSRP3沉默后引起与肌原纤维组装、肌肉分化和收缩相关基因的代偿性上调（Q<0.05）。同时，CSRP3沉默后，两个快速肌球蛋白重链基因（MyH1B和MyH1E）表达上调（Q<0.05）。这些结果表明，CSRP3在鸡肌纤维组成中发挥着重要作用，并可能通过调节MyH1B和MyH1E的表达从而影响鸡肌纤维类型的分布。

Plant growth regulators (PGRs) are artificially synthesized compounds that have become an important technical guarantee for agricultural production. EDAH (containing 27% ethephon and 3% DA-6) has been proven to inhibit stalk elongation, promote stalk bold and increase mechanical strength and number of vascular bundles. DA-6 could enhance plant photosynthetic capacity and promote cell division and growth. In our study, experiments were performed at summer maize growing season during 2018–2019. The result showed that plant height, ear height and center of gravity height of maize with EDAH+DA-6 treatment were decreased by 10.18, 16.77 and 13.21%, respectively; leaf area and leaf area index also significantly (P<0.001) decreased by 24.11 and 60.15%, respectively; the value of mean tilt angle significantly (P<0.001) increased by 16.72% compared with the control plants, which meant that EDAH+DA-6 could shape more compact plant type. Therefore, lodging rate of maize with EDAH+DA-6 treatment decreased by 6.95% compared with control plants, and the grain yield was increased by 15.51%. In addition, EDAH+DA-6 treatment significantly improved the quality of maize base stalks, such as improving mechanical properties, which increased maize base stalk crushing strength by 22.23%; increased the hemicellulose, cellulose and lignin contents by 6.93, 3.87 and 30.21%, respectively. In conclusion, EDAH+DA-6 treatment could improve summer maize yield by shaping plant morphological characteristics and group photosynthesis.

棉花的脱叶催熟技术在机械收获中必不可少，尤其是在华北平原，由于热量资源不足，导致收获时残留绿叶和未开裂棉铃的比例较大，棉花机械收获受到限制。确定棉花脱叶催熟剂最佳用量，同时最大程度地减少产量和品质的损失至关重要。本文主要研究一种新型脱叶催熟剂-欣噻利（XSL，10%噻苯隆和40%乙烯利的复配剂）对棉花叶片和棉铃的空间分布，以及产量和品质的影响。本试验共设置了四个处理：不同的XSL剂量（1800和2700 mL ha^-1），应用两次（分为两次应用，每次1350 mL ha^-1）和无XSL（清水）对照。该大田试验于2016-2017年在中国河北进行。结果表明：与清水对照相比，所有脱叶催熟处理均未显著影响棉花的产量和纤维品质。两年数据显示，2700 mL ha^-1 XSL一次性喷施的棉花吐絮率比清水对照高13.5％，而其他两个处理均未达到显著水平。三个XSL处理的脱叶率之间没有显著差异，但平均比清水对照高42.2％。年份对XSL应用效果较为显著，表明气候因素会影响XSL的应用。我们得出的结论是，在黄河流域棉区使用XSL的最佳剂量为2700 mL ha^-1，而且无需分成两次应用。我们的结果将促进棉花机械化收获并降低棉花生产的人工成本。

Received  14 August, 2017    Accepted  20 December, 2017

Received  14 September, 2017    Accepted  21 December, 2017
; © 2018 CAAS. Publishing services by Elsevier B.V.  All rights reserved.
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Peanut (Arachis hypogaea L.), an improtant oil crop, usually encounters drought stress in the process of growth and development, especially at pre-flowering stage.  In order to gain insight into the drought tolerance potentials based on osmolyte accumulation and metabolism of proline aspects of peanut, pot experiments were conducted with a split-plot design in Tai’an, Shangdong Province, China in 2013 and 2014.  Pre-flowering drought (PFD) stress and optinum irrigation (control, CK) were served as the main plots and the two peanut cultivars Shanhua 11 and Hua 17 served as sub-plots.  Shanhua 11 was drought-tolerant cultivar and Hua 17 was drought-sensitive.  The content of soluble sugars, soluble protein, free proline and other free amino acids, the activities of enzymes involved in proline metabolism, and malondialdehyde (MDA) content and ion leakage were all investigated in the two cultivars at pre-flowering stage.  Results showed that PFD stress significantly increased the levels of soluble protein, free proline and free amino acid, and increased Δ¹-pyrroline-5-carboxylate synthetase (P-5-CS, EC 2.7.2.11) activity in the leaves of drought-tolerant and drought-sensitive cultivars.  The activity of proline dehydrogenase (proDH) (EC 1.5.99.8) decreased under PFD stress in both cultivars.  The leaves of the tolerant cultivar maintained higher increments of osmolyte levels, lower increments of MDA content and ion leakage, as well as a higher increased proportion of P-5-CS activity and higher inhibited proportion of proDH activity under water stress compared with the drought-sensitive cultivar.  The study suggests that proline accumulation in peanut leaves under PFD can be explained by the higher enhanced activities of P-5-CS and higher inhibition of proDH.  The results will provide useful information for genetic improvement of peanut under drought tolerance.

Aphid-borne Zucchini yellow mosaic virus (ZYMV) is one of the most economically important viruses of cucurbitaceous plants.  To survey and control this virus, it is necessary to develop an efficient detection technique.  Using purified ZYMV virion and the conventional hybridoma technology, three hybridoma cell lines (16A11, 5A7 and 3B8) secreting monoclonal antibodies (MAbs) against ZYMV Zhejiang isolate were obtained.  The working titers of the ascitic fluids secreted by the three hybridoma cell lines were up to 10^–7 by indirect enzyme-linked immunosorbent assay (ELISA).  All MAbs were isotyped as IgG1, kappa light chain.  Western blot analysis indicated that the MAb 3B8 could specifically react with the coat protein of ZYMV while MAbs 5A7 and 16A11 reacted strongly with a protein of approximately 51 kDa from the ZYMV-infected leaf tissues.  According to this molecular weight, we consider this reactive protein is likely to be the HC-Pro protein.  Using these three MAbs, we have now developed five detection assays, i.e., antigen-coated-plate ELISA (ACP-ELISA), dot-ELISA, tissue blot-ELISA, double-antibody sandwich ELISA (DAS-ELISA), and immunocapture-RT-PCR (IC-RT-PCR), for the sensitive, specific, and easy detection of ZYMV.  The sensitivity test revealed that ZYMV could be readily detected respectively by ACP-ELISA, dot-ELISA, DAS-ELISA and IC-RT-PCR in 1:163 840, 1:2 560, 1:327 680 and 1:1 310 720 (w/v, g mL^–1) diluted crude extracts from the ZYMV-infected plants.  We demonstrated in this study that the dot-ELISA could also be used to detect ZYMV in individual viruliferous aphids.  A total of 275 cucurbitaceous plant samples collected from the Zhejiang, Jiangsu, Shandong and Hainan provinces, China, were screened for the presence of ZYMV with the described assays.  Our results showed that 163 of the 275 samples (59%) were infected with ZYMV.  This finding indicates that ZYMV is now widely present in cucurbitaceous crops in China.  RT-PCR followed by DNA sequencing and sequence analyses confirmed the accuracy of the five assays.  We consider that these detection assays can significantly benefit the control of ZYMV in China.  

  Calcineurin (Cn or CaN) is implicated in the control of skeletal muscle fiber phenotype and hypertrophy. However, little information is available concerning the expression of Cn in chickens. In the present study, the expression of two Cn subunit genes (CnAα and CnB1) was quantified by qPCR in the lateral gastrocnemius (LG, mainly composing of red fast-twitch myofibers), the soleus (mainly composing of red slow-twitch myofibers) and the extensor digitorum longus (EDL, mainly composing of white fast-twitch myofibers) from Qingyuan partridge chickens (QY, slow-growing chicken breed) and Recessive White chickens (RW, fast-growing chicken breed) on different days (1, 8, 22, 36, 50 and 64 days post-hatching). Although CnAα and CnB1 gene expressions were variable with different trends in different skeletal muscles in the two chicken breeds during postnatal growth, it is highly muscle phenotype and breed specific. In general, the levels of CnAα and CnB1 gene expressions of the soleus were lower than those of EDL and LG in both chicken breeds at the same stages. Compared between the two chicken breeds, the levels of CnAα gene expression of the three skeletal muscles in QY chickens were higher than those in RW chickens on days 1 and 22. However, on day 64, the levels of both CnAα and CnB1 gene expressions of the three skeletal muscles were lower in QY chickens than those in RW chickens. Correlation analysis of the levels of CnAα and CnB1 gene expressions of the same skeletal muscle showed that there were positive correlations for all three skeletal muscle tissues in two chicken breeds. These results provide some valuable clues to understand the role of Cn in the development of chicken skeletal muscles, with a function that may be related to meat quality.

Increasing attentions have been paid to mineral concentration decrease in milled rice grains caused by CO2 enrichment, but the mechanisms still remain unclear. Therefore, mineral (Ca, Mg, Fe, Zn and Mn) translocation in plant-soil system with a FACE (Free-air CO2 enrichment) experiment were investigated in Eastern China after 4-yr operation. Results mainly showed that: (1) elevated CO2 significantly increased the biomass of stem and panicle by 21.9 and 24.0%, respectively, but did not affect the leaf biomass. (2) Elevated CO2 significantly increased the contents of Ca, Mg, Fe, Zn, and Mn in panicle by 61.2, 28.9, 87.0, 36.7, and 66.0%, respectively, and in stem by 13.2, 21.3, 47.2, 91.8, and 25.2%, respectively, but did not affect them in leaf. (3) Elevated CO2 had positive effects on the weight ratio of mineral/biomass in stem and panicle. Our results suggest that elevated CO2 can favor the translocation of Ca, Mg, Fe, Zn, and Mn from soil to stem and panicle. The CO2-led mineral decline in milled rice grains may mainly attribute to the CO2-led unbalanced stimulations on the translocations of minerals and carbohydrates from vegetative parts (e.g., leaf, stem, branch and husk) to the grains.

Understanding the relationship between the timing of N fertilizer applications and crop primary production is crucial for achieving high yield and N use efficiency in agriculture. This study investigated the effects of starting-N plus topdressing N applications (as compared to the common practice of all basal application) on soybean photosynthetic capacity under different planting densities. A field experiment was conducted in two growing seasons (2011 and 2012), and the soybean (Glycine max L. Merrill) cultivar was Dongnong 52, three planting densities (20, 25 and 30 plants m-2), and four N fertilizer application patterns (all N fertilizer of 6 g N m-2 as basal fertilizer, all N fertilizer as topdressing at beginning pod stage (R3), 1.8 g N m-2 as basal fertilizer and 4.2 g N m-2 as topdressing at stage R3 and full pod stage (R4), respectively). The results indicated that under the same planting density, compared to applying all N as basal fertilizer, the application of starter-N plus topdressing N substantially reduced the rate of pod abscission, and enhanced leaf area index (LAI) significantly at beginning seed stage (R5) (P<0.05), net assimilation rate (NAR) during stages R4-full seed stage (R6) (P<0.05), contribution rate of post-seed filling assimilate to seed (CPA) (P<0.05), and yield (P<0.05). Applying topdressing N at stage R4 resulted in higher net primary production and yield than applying topdressing N at stage R3. When applying starter-N plus topdressing N at planting density of 25 plants m-2, LAI after stage R5 and NAR after stage R4 were increased by 5.92-16.3% (P<0.05) and 13.7-26.6% (P<0.05) with the planting density of 20 plants m-2, respectively, and yield was 8.46-14.0% (P<0.05) higher than that under 20 plants m-2. When planting density increased to 30 plants m-2, only LAI during stages R4-R5 and NAR during stages R4-R5 increased by applying starter-N plus topdressing N, while the other indexes declined. Overall, results of this study demonstrated that applying starter-N plus topdressing N could significantly enhance soybean photosynthetic capacity after stage R5 at planting density of 25 plants m-2.

Quantitative assessment of development sustainability could be a challenge to regional management and planning, especially for areas facing great risks of water shortage. Surface-water decline and groundwater over-pumping have caused serious environmental problems and limited economic development in many regions all around the world. In this paper, a framework for quantitatively evaluating development sustainability was established with water-related eco-environmental carrying capacity (EECC) as the core measure. As a case study, the developed approach was applied to data of the Haihe River Basin, China, during 1998 through 2007. The overall sustainable development degree (SDD) is determined to be 0.39, suggesting that this rate of development is not sustainable. Results of scenario analysis revealed that overshoot, or resource over- exploitation, of the Basin’s EECC is about 20% for both population and economy. Based on conditions in the study area in 2007, in order to achieve sustainable development, i.e., SDD>0.70 in this study, the EECC could support a population of 108 million and gross domestic product (GDP) of 2.72 trillion CNY. The newly developed approach in quantifying eco- environmental carrying capacity is anticipated to facilitate sustainable development oriented resource management in water- deficient areas.

Timing of harvest is critical for mechanical picking in cotton production, especially in those regions with double cropping system. Appropriate and safe harvest aids will improve timing and facilitate harvest of cotton in the double cropping system. Three defoliants (dimethipin, thidiazuron, and thidiazuron-diuron) and one boll opener (ethephon) were included in this research. They were evaluated for their effects on defoliation, boll opening, seedcotton yield, seed quality, and fiber quality of field grown cotton when used alone or as a mixture in 2009 and 2010. Defoliation and/or boll opening were increased by all three defoliants and ethephon, especially by mixtures of a defoliant and ethephon. First harvest of seedcotton was significantly increased with defoliant-ethephon mixtures. No significant adverse effects were observed on boll weight, lint percentage, seed quality, and fiber properties. It was estimated that tank mixes of ethephon and one of the three defoliants can improve the adjusted gross revenue. Boll opening can be used as an alternative indicator for the adjusted gross revenue, because, it was linearly and positively correlated with the relative adjusted gross revenue and convenient in measurements. Wheat seedling growth was not affected by thidiazuron, whereas its seedling emergence, root dry weight, relative water content, and electrolyte leakage were adversely affected by dimethipin and thidiazurondiuron when concentration was above 340 and 100 g (a.i.) ha-1, respectively. 90% defoliation and 80% boll opening were observed with the high rate of thidiazuron-ethephon mixture, but no adverse effects on winter wheat. The results suggested that tank mixes of ethephon with thidiazuron can be used effectively and safely in the cotton-winter wheat double cropping system to improve yield without adverse effects on seed quality and fiber quality.

China is one of the most important rapeseed producing countries in the world. Effective mechanical harvesting time for decreasing harvesting loss of winter oilseed rape has been becoming a critical factor. An elite cultivar Zhongshuang 11 (Brassica napus L.) was employed in two rounds of field experiments from 2009 to 2011. Seeds were sown with machine, three combine harvesting times namely combine harvesting A, B, and C (CHA, CHB, and CHC) were designed and manual harvesting (MH) as control was performed at maturity. The harvesting treatments were determined according to color of pod and seed in the field. Seed yield loss and quality in different treatments were evaluated. Results showed that both seed yields and harvesting losses in 2009-2010 were higher than that in 2010-2011, whereas seed oil contents in 2010-2011 were higher than that in 2009-2010. The highest yield appeared in CHB, which was significantly higher than that in MH. Furthermore, harvesting loss in CHB were 50% that in MH. Seed oil content and chlorophyll exhibited no obvious difference between CHB and MH. Economic profit analysis demonstrated that mechanical sowing/combine harvesting (MS/CH) showed an input/output ratio of 1:1.6, and it was 1:1.2 in mechanical sowing/manual harvesting (MS/MH). Labor-cost accounted for more than 70% of the total cost in MS/MH, which led to low profitability to a great extent. Our results suggested that CHB was the optimum harvesting time for winter oilseed rape along the Yangtze River.