玉米植株抗弯特性对分禾器结构的影响分析

玉米收获机分禾器结构直接影响玉米植株的分禾和输送效果,是决定机具能否正常作业的重要因素。通过田间试验,对玉米植株抗弯特性进行了测定,测量出玉米植株的横向最大偏移量,并计算出玉米植株偏折角。得出了分禾器宽度与玉米植株抗弯特性之间的关系方程,找到了影响分禾输送效果的一个重要因素——植株自身的抗弯特性,为分禾器的设计提供了新的依据。在理论上解释了作业时分禾器离地越高越不易碰伤植株的现象,且对比了不同地区品种玉米植株抗弯强度的差异性,结论是最佳收获期内山东省、北京市地区品种的玉米植株抗弯能力比吉林省地区品种强。     

螺旋齿辊式秸秆调质装置性能试验

利用所研制的螺旋齿辊式秸秆调质装置试验台,采用调质齿辊差速转动方式对摘穗后玉米秸秆进行压裂、破节的连续调质正交试验,分析了调质齿辊工作间隙、调质齿辊转速及秸秆喂入速度对秸秆调质性能的影响.试验结果表明,调质齿辊工作间隙对秸秆调质作业性能影响显著,最优参数组合为调质齿辊工作间隙2 mm,调质齿辊转速65 r/min,秸秆喂入速度4 km/h.     

基于热交换的漂浮育苗温室除湿系统研究

基于热力学第二定律,设计了热交换式漂浮育苗温室保温除湿系统。该系统主要由热交换换气机和环境监控系统组成,通过将温室大棚外新风与棚内空气强制对流交换进行换气除湿,使新风温度升高,实现温室热能回收。环境监控系统可现场和远程了解温室大棚内部环境和除湿系统工作状态,实时自动对温室湿度进行调控。将系统应用于烟草漂浮育苗温室,运行结果表明,系统具有良好的保温、除湿能力,试验大棚较对照大棚平均相对湿度降低6.7%,系统平均热回收效率为59.35%,烟苗平均茎高增加0.4 mm、茎围增加0.6 mm。     

绵羊妊娠期胎儿垂体促性腺激素细胞的发生发育与血浆B-LH浓度的变化关系

为了研究绵羊胚胎期垂体中促性腺激素细胞的发育及功能变化，分别在胎儿发育的第60、90、120天和出生期采集垂体和血液，利用免疫荧光标记和生物学测定方法研究了垂体中促黄体激素β亚单位（LH-β)的表达和血液中LH生物活性的变化。结果证明：在胚胎发育的第60天，在腺垂体可观察到少量散在的LH-β阳性细胞；在胎儿发育的90d，LH-β阳性细胞率显著高于60d(P＜0．01)时，且均匀分布于整个腺垂体；在胎儿发育的120d，LH-β阳性细胞率达到高峰，但出生期又显著降低。胚胎发育过程中，垂体的LH-β细胞阳性率与血液中B-LH浓度呈现相似的变化趋势，且无显著的性别差异。以上研究征明绵羊垂体促性腺激素细胞的功能在胚胎中期之后最活跃，在后期垂体中LH-β阳性细胞率和血浆BLLH浓度都有降低，这种波动可能与胎儿垂体-性腺物的负反馈调节机制的建立有关。     

Impact of grassland contract policy on soil organic carbon losses from alpine grassland on the Qinghai–Tibetan Plateau

Carbon storage in the soils on the Qinghai–Tibetan Plateau plays a very important role in the global carbon budget. In the 1990s, a policy of contracting collective grasslands to smaller units was implemented, resulting in a change from the traditional collective grassland management to two new management patterns: a multi‐household management pattern (MMP: grassland shared by several households without enclosures) and a single‐household management pattern (SMP: grassland enclosed and used by only one household). In 2016, 50 MMP and 54 SMP winter pastures on the Qinghai–Tibetan Plateau were sampled to assess the differences in soil organic carbon (SOC) between the two management patterns. Results showed that average SOC was significantly greater under MMP than under SMP, with an estimated 0.41 Mg C/ha/yr lost due to SMP following the new grassland contract. Based on the government's grassland policy, four grassland utilization scenarios were developed for both summer and winter pastures. We found that if the grassland were managed under SMP, likely C losses ranged between 0.31 × 10⁷ and 6.15 × 10⁷ Mg C/yr across the Qinghai–Tibetan Plateau relative to MMP, which more closely resembles pre‐1990s grassland management. Previous estimates of C losses have only considered land use change (with cover change) and ignored the impacts driven by land management pattern changes (without cover change). The new data suggest that C losses from the Qinghai–Tibetan Plateau are greater than previously estimated, and therefore that the grassland contract policy should be reviewed and SMP households should be encouraged to reunite into the MMP. These findings have potential implications for land management strategies not only on the Qinghai–Tibetan Plateau but also other grazing regions globally where such practices may exist.     

CmRT1, a Ty3-gypsy-like retrotransposon in Castanea mollissima,is associated with a short-catkin mutation

Summary

Retrotransposons are major components of the genomes of most eukaryotic organisms and have resulted in the introduction of desirable traits in many crops, including fruit trees. Here, we describe a Ty3-gypsy-like retrotransposon associated with a short-catkin mutant in Chinese chestnut (Castanea mollissima), resulting in catkins that are < 20% the length of normal staminate catkins. A partial sequence of the retrotransposon, named CmRT1, detected by amplified fragment length polymorphism (AFLP) analysis, and its complete sequence were determined from the genome of Chinese chestnut (Castanea mollissima) using improved Tail-PCR. CmRT1 was 10,067 bp in length and shared high homology in its predicted amino acid sequence and motifs with other Ty3/gypsy-like retrotransposons. The 5’ long terminal repeat (LTR) of CmRT1 contained a TATA box and several cis-elements that were predicted to be important for processes involving abscisic acid, gibberellic acid, and auxins and in stress-mediated responses. Further characterisation of the transposition event that led to the short-catkin phenotype was performed using two pairs of primers that aligned with the flanking region of the LTRs. The expected PCR bands were observed only in genomic DNA from plants that showed the mutation. Finally, cloning and real-time qPCR analysis of an NADP-dependent alkenal double-bond reductase (CmADBR) target gene that was adjacent to CmRT1, revealed that CmADBR expression was significantly down-regulated in the short-catkin mutant. Taken together, these results suggest that the CmRT1 retrotransposon is responsible for the short-catkin phenotype.     

几种造纸用丛生竹秆节育苗试验

在福建省邵武市对椽竹、孝顺竹、坭竹等几种造纸用丛生竹进行秆节育苗试验表明，用平埋方法育苗显著优于斜埋和直插，竹蔸平埋效果更佳；不同竹种秆节育苗成活率存在明显差异；不同年龄的秆节育苗成活率在不同竹种间表现不同；不同育苗时间（３月或５月）的成活率差异不显著。竹秆不同粗细、不同部位、单节段或双节段育苗对比试验，结果以细秆（胸径２．５ｃｍ）、上部节段、双节段育苗成活率较粗秆（胸径４．６ｃｍ）、下部节段、单节段的为高。椽竹秆节径用不同激素处理后，处理间成苗率差异显著，以２，４－Ｄ２０ｍｇ／ｋｇ处理５ｈ和硼酸２０ｍｇ／ｋｇ处理２４ｈ的效果最佳。几种造纸用丛生竹秆节育苗试验＊张文燕周道三马乃训叶长青曹德友张华明     

切流式花生全喂入联合收获机清选机构设计

针对切流式花生全喂入联合收获机清选环节果杂分离不清、损失率高、缠膜挂秧、筛面堵塞等难题,该文设计了一种风筛组合、无阻滞、大小杂并除的清选机构,其主要由上层筛(杆筛)、下层筛(多阶弹性筛和后筛)、抖草轮、偏心套、风机等组成。该文运用动态静力学方法研究了筛面物料的相对运动,分析了物料相对筛面上滑、下滑、从筛面跃起的极限条件,确定了振动筛主要运动参数的理论值域;运用达朗伯原理开展了交变载荷下筛体的受力分析,确定了筛体关键结构参数。该文对影响清选作业质量主要因素开展了试验研究,试验结果表明:影响清选机构综合作业质量的主次作用因素为主风机转速、振动筛振幅、振动频率,较优参数组合为主风机转速2 100 r/min、振动筛振幅12.5 mm、振动频率9Hz,此时清选损失率5.03%、荚果含杂率5.39%;清选机构作业顺畅性较好,较少出现缠膜挂秧、筛面堵塞现象。研究结论可为切流式花生全喂入联合收获机清选机构的设计提供理论参考。     

基于耕地质量成果的上海市耕地占补平衡运行机制研究

在对我国耕地占补平衡问题分析的基础上,结合占补平衡耕地质量内涵和上海市耕地质量成果应用条件分析,构建以数量平衡为前提的耕地质量占补平衡运行机制。该机制框架包括耕地质量评估和监测机制、占补平衡指标储备机制、占补平衡指标跨区使用机制和占补平衡实施经济保障机制等4个方面,以为完善耕地占补平衡制度提供依据。