不同光照条件对脱镁叶绿酸钠光敏抑菌活性的影响

脱镁叶绿酸钠是叶绿素代谢中间产物脱镁叶绿酸a的水溶性钠盐,具有良好的光敏抑菌活性。为探索光照条件对其抑菌活性的影响,采用菌丝生长速率法,研究在不同光照度、光波长及光照时间条件下,脱镁叶绿酸钠对忽视拟盘多毛孢Pestalotiopsis neglecta的抑制作用。结果表明:20 mg/mL的脱镁叶绿酸钠在照度为2 000 lx的白光照射下对菌丝生长的抑制率为83.7%,在黑暗条件下抑制率为77.0%,表明光照对脱镁叶绿酸钠抑菌活性有显著影响 (P < 0.05);此外,白光的效果好于单色光;光照度及光照时间对抑菌活性也有显著影响,其中当照度为16 000 lx且光照时间为24 h时抑菌作用最强。     

isopropylstilbene发酵条件优化及其对灰葡萄孢的抑制作用

isopropylstilbene (3, 5-二羟基-4-异丙基二苯乙烯) 是发光杆菌Photohabdus temperata产生的一种二苯乙烯类化合物,具有多种生物活性。为促进isopropylstilbene在农业抗生素领域应用价值的开发,采用固相萃取、柱层析等技术从发光杆菌P. temperata SN 35的发酵液中分离纯化得到1个化合物,通过核磁共振氢谱对其结构进行了确认,并采用高效液相色谱测定了其纯度;通过Plackett-Burman试验和响应面法对发光杆菌SN 35摇瓶发酵培养条件进行了优化,并初步研究了所分离化合物对灰葡萄孢Botrytis cinerea的离体抑菌活性及对灰霉病的防治效果。结果表明:所分离的化合物为isopropylstilbene,纯度为93%;对发光杆菌SN 35摇瓶发酵培养条件进行优化后,isopropylstilbene的产量是优化前的2.22倍。离体抑菌试验结果表明:isopropylstilbene对灰葡萄孢的菌丝生长具有较好的抑制作用,其EC₅₀值为 (9.17 ± 0.17) μg/mL,但低于对照药剂百菌清[EC₅₀值为 (0.90 ± 0.08) μg/mL];在10 μg/mL下,isopropylstilbene对灰葡萄孢孢子萌发的抑制率为63.01%。活体盆栽试验结果表明,在200 μg/mL下,isopropylstilbene对黄瓜灰霉病的防治效果达92.19%,与百菌清的防效 (97.63%) 相当,对番茄灰霉病的防治效果为72.12%,略低于百菌清 (81.61%)。本研究通过对isopropylstilbene发酵条件的优化,为其工业化生产奠定了理论基础。该化合物对灰霉病具有很好的防治效果,可为天然杀菌剂的研究与开发提供参考。     

烟草米根霉对6种杀菌剂的敏感性及菌株保存条件筛选

采用孢子萌发法测定了烟草上米根霉Rhizopus oryzae对6种杀菌剂 (代森锰锌、多菌灵、嘧霉胺、嘧菌酯、啶酰菌胺及氟啶胺) 的敏感性,并就其适宜的保存条件进行了筛选,同时采用离体叶片法测定了上述6种杀菌剂对烟叶霉烂病的防治效果。结果表明:6种杀菌剂对米根霉孢子萌发和烟叶霉烂病均表现出了不同的抑制活性。其中,抑制孢子萌发活性最为明显的是氟啶胺和啶酰菌胺,其EC₉₀值分别为0.67 和1.53 mg/L;其次为代森锰锌和嘧菌酯,15.16和17.66 mg/L;最弱为嘧霉胺和多菌灵,71.87和81.96 mg/L。对烟叶霉烂病防效最好的为嘧菌酯,50 mg/L处理的防效为85%;其次为啶酰菌胺,200 mg/L处理时防效为83%;氟啶胺的防效较差,1 000 mg/L处理时仅为48%;而代森锰锌、多菌灵和嘧霉胺在最高使用剂量 (分别为4 000、800和800 mg/L) 时防效均低于20%。病原菌保存方法筛选结果表明,保存后米根霉的孢子萌发率均发生了不同程度降低。其中,4 ℃保存于20%甘油组的孢子悬浮液萌发率为60%;4 ℃保存的孢子干样萌发率为36%;4 ℃保存的孢子悬浮液和 –20 ℃保存于20%甘油的孢子悬浮液萌发率均低于20%;20 ℃保存的孢子干样萌发率为11%;–20 ℃保存的孢子悬浮液萌发率为6%。研究结果可为烘烤期烟叶霉烂病防治和米根霉孢子的保存提供参考依据。     

红颈常室茧蜂雌性生殖系统及卵巢管形态学观察

利用光学显微镜和透射电镜观察红颈常室茧蜂Peristenus spretus Chen et van Achterberg雌性生殖系统结构、卵巢发育和卵子发生、卵子超微结构,并对15℃和23℃饲养条件下不同日龄的雌蜂卵巢管长度、卵巢管内卵室大小与成熟度进行了比较,揭示了该茧蜂雌性生殖系统结构与特征。结果表明：1）红颈常室茧蜂生殖系统结构主要包括一对卵巢、2条输卵管、中输卵管等;2）雌成虫在羽化前期（1～3 d）卵巢内的成熟卵粒较少,卵巢管内含有大量的卵原细胞,卵子内充满了大量的脂滴,中后期（5～11 d）随着脂肪体的降解吸收,卵子内逐渐新生一些线粒体、高尔基体等细胞器,其内存在滋养细胞、卵母细胞,并且滋养细胞无细胞膜存在。3）同一温度不同日龄红颈常室茧蜂卵粒数、成熟卵子数均差异显著,23℃下红颈常室茧蜂每条卵巢管内的日均卵子数20.70粒,显著高于15℃的日均卵子数18.65粒。     

花生田施用绿僵菌对土壤微生物群落的影响

昆虫病原真菌绿僵菌对地下害虫防治具有良好应用前景,而大量释放绿僵菌可能引起土著微生物群落变化,从而影响其植物保护的综合效果。本文研究了花生播种期施用绿僵菌后,在根际和根围土壤中绿僵菌自身种群及土著细菌、真菌和放线菌种群的消长和群落结构变化。结果表明,绿僵菌种群在30 d内快速下降,之后降速减缓,以低密度持续存活。随花生生长,土壤微生物自身有消长过程,施用绿僵菌对放线菌影响最大、真菌其次、细菌最小,在根际的影响大于在根围的影响。分别地,绿僵菌处理对根际和根围细菌、根围真菌无显著影响;使根际真菌种群初期的下降速度减缓,到达谷底时间由15 d推迟到30 d,但回升速度加快,达峰顶由60 d提前到45 d,峰值降低1/3;绿僵菌明显抑制了根际放线菌种群,使其消长变化周期与对照完全相反,且45 d时回落至低点后不再回升;绿僵菌减缓了根围放线菌种群下降,使达谷底时间由30 d推迟到45 d,且回升幅度减小。土壤微生物群落结构在施菌后15～30 d的幼苗至初花期有明显变化,细菌种群总体占比显著下降,但与对照相比,施菌后的根际细菌占比提高,真菌占比下降,放线菌占比显著地先抑后扬。在根围的变化相对较小。45 d即盛花期后,三类微生物结构逐渐恢复趋近原来状态。     

Ellagic acid attenuates hypoxic-ischemic brain injury by alleviating autophagy

AIM:To investigate whether ellagic acid (EA) attenuates hypoxic-ischemic encephalopathy (HIE) by down-regulating autophagy. METHODS:In vivo, Sprague-Dawley rats (n=17) were randomly divided into 3 groups:5 rats for sham group, 6 rats for HIE group and 6 rats for HIE+EA pretreatment group. The rats in HIE+EA pretreatment group were treated with EA (10 mg/kg, 10 mL/kg, suspended in corn oil, ig). After 24 h of operation, the rats from each group were sacrificed and their brains were collected. TTC staining and HE staining were used to define the infarct areas and brain structure. The autophagy-related proteins beclin-1, P62, LC3-Ⅱ/-I and Atg5 in the cortex in each group were compared by Western blot. In vitro, PC12 cells were divided into 3 groups:control group, CoCl₂ group and CoCl₂+EA pretreatment group. CoCl₂ at 800 μmol/L was added to the PC12 cells to induce an anoxic environment. The PC12 cells were pretreated with EA at 8 μmol/L and the cell viability was measured by CCK-8 assay. The production of reactive oxidative species (ROS) in the cells was detected by flow cytometry with DCFH-DA staining. MDC staining and TMRE staining were applied to reflect the extent of autophagy and the state of apoptosis, respectively. The autophagy-related proteins in PC12 cells were also investigated. RESULTS:In HIE group, 7-day-old rats were given the operations and the their large infarct areas in the hemisphere were observed by TTC staining. HE staining displayed the injured hemispheres which contained few neurons, and exhibited edema status and serious structural damage. EA pretreatment decreased the infarct area and alleviated the damage to hemisphere with more visible neurons, compared with HIE group. Compared with sham group, the levels of autophagy-related proteins Atg5, beclin-1 and LC3-Ⅱ/-I in the cortex were increased (P<0.01), and P62 protein expression was decreased (P<0.01) in HIE group. Compared with HIE group, the protein expression of Atg5, beclin-1 and LC3-Ⅱ/-I was decreased (P<0.01) and P62 protein expression was increased in HIE+EA pretreatment group (P<0.01). In vitro, compared with CoCl₂ group, the PC12 cells in CoCl₂+EA pretreatment group showed a lower ROS level. Moreover, the cells in CoCl₂+EA pretreatment group exhibited higher mitochondrial membrane potential than that in CoCl₂ group. MDC staining in CoCl₂ group showed high value of fluorescence and increased number of autophagosomes. EA pretreatment reduced the number of autophagosomes and the extent of autophagy to protect PC12 cells. Furthermore, the protein levels of Atg5, beclin-1 and LC3-Ⅱ/-I in CoCl₂ group were higher (P<0.01), and the protein expression of P62 was lower (P<0.01) than those in control group. In CoCl₂+EA pretreatment group, the protein levels of Atg5, beclin-1 and LC3-Ⅱ/-I were decreased (P<0.01) and the protein expression of P62 was increased as compared with CoCl₂ group (P<0.01). CONCLUSION:EA pretreatment attenuates autophagy to protect the neurons against HIE injury.     

Ethanol extract from Cortex Albiziae attenuates mouse acute liver injury induced by carbon tetrachloride via modulation of NF-κB pathway

AIM:To investigate the protective effect of ethanol extract from Cortex Albiziae on acute liver injury, and to explore its possible mechanism. METHODS:Acute liver injury in mice was induced by single intraperitoneal injection of 25% carbon tetrachloride (olive oil solubilization). The effective parts of ethanol extract from Cortex Albizziae against acute liver injury were screened. The pathological changes of the liver tissues were examined by pathological sections with HE staining. The activity of total superoxide dismutase (T-SOD) and the content of malondialdehyde (MDA) of the liver tissues were detected, the serum levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were mea-sured by ELISA, and the protein expression levels of NF-κB p65, Bcl-2 and Bax in the liver cells of the mice in each group were determined by Western blot. RESULTS:Compared with model group, the serum levels of AST and ALT in low-dose n-butanol phase of ethanol extract from Cortex Albiziae (AB-L, 4 mg·kg^-1·d^-1) group and high-dose n-butanol phase of ethanol extract from Cortex Albiziae (AB-H, 8 mg·kg^-1·d^-1) group were significantly decreased. The necrosis extent and degree of the hepatocytes and infiltration of inflammatory cells were significantly lower than that in model group. Compared with model group, the serum levels of TNF-α and IL-6 in AB-H group and AB-L group were significantly decreased (P<0.05). The protein level of NF-κB p65 in the nuclei of mouse liver cells in AB-H group and AB-L group were also decreased significantly (P<0.05). Compared with model group, the protein expression of Bax was decreased, the protein expression of Bcl-2 was increased, and the Bcl-2/Bax ratio was increased in AB-L group and AB-H group. CONCLUSION:The n-butanol phase of ethanol extract from Cortex Albiziae may protect the liver by reducing the activation of NF-κB p65, inhibiting the excessive release of inflammatory cytokines IL-6 and TNF-α, and decreasing hepatocyte apoptosis via regulating Bcl-2 and Bax expression.     

博落回对铅的耐性、富集及生理响应研究

以草本植物博落回（Macleaya cordata）为供试植物,采用沙培盆栽实验研究其对重金属铅（Pb）的耐性、富集及生理响应机制。结果表明：博落回能耐受500 mg/L的Pb胁迫而其生长发育不受影响,高于此浓度时植株生长发育受到抑制。不同组织对Pb的富集能力表现为根>茎>叶,博落回对Pb的富集与转运能力皆随Pb胁迫浓度的升高而减弱。Pb胁迫引起丙二醛（Malondialdehyde, MDA）在植物体内累积。低于500 mg/L的Pb促进叶绿素、可溶性蛋白的合成和抗氧化酶活性的提高,高于此浓度时,则表现为抑制,且导致膜脂过氧化与生物膜的损伤。Pb主要以迁移活性低的化学形态存在于细胞壁和可溶性组分中,浓度升高会导致Pb向迁移毒性强的形态转化。透射电子显微镜（TEM）观察到高浓度的Pb胁迫会损害细胞壁结构,使Pb进入细胞内部,对细胞造成毒害。傅里叶红外光谱仪（FTIR）分析表明,Pb胁迫会提高细胞内-OH、-COOH等基团和有机酸、蛋白质的含量,在低浓度时可与Pb结合,削弱其对博落回的毒性。     

耕地细碎化、耕地质量认知与化肥施用效率 ——基于湖北省水稻种植户的调查数据

在中国倡导农业农村绿色发展的大背景下,化肥投入的政策导向逐渐由增量增产转变为减量增效,如何提高化肥施用效率成为当前重点关注的问题。本文依据湖北省水稻种植户微观调查数据,运用随机前沿法测算水稻种植户化肥施用效率,并在此基础上运用CLAD模型进一步分析耕地细碎化程度与耕地质量认知对化肥施用效率的影响。结果表明:当前水稻种植户化肥施用效率仅为63.85%,若完全消除效率损失,化肥施用效率仍有36.15%的提升空间;耕地细碎化程度显著降低了化肥施用效率,可能与农户的避险行为有关;耕地质量认知显著促进了化肥施用效率提升,说明农户对耕地质量的科学认识能够改善化肥施用效率。因此,提出加快耕地整合与耕地连片经营法律法规建设,加速耕地细碎化治理经验与创新结合,加强引导农户对化肥施用的正确认知,推行科学种植生产模式以提升化肥施用效率的政策建议。     

数字技能如何影响农民电商参与行为？——基于信息获取的中介效应分析

为探究数字技能对农民电商参与行为的影响及作用机制,基于2020年中国乡村振兴综合调查（CRRS）数据,立足“手段-自由-成就”的可行信息能力理论,构建“数字技能-信息获取-电商参与”的理论分析框架,采用二元Probit、Tobit和中介效应等分析方法,从信息获取的中介视角实证检验数字技能对农民电商参与决策及程度的影响,并进行稳健性检验和异质性分析。结果表明：1）数字技能对农民电商参与决策和程度均具有显著正向影响;2）信息获取在数字技能对农民电商参与决策和程度的影响中存在部分中介效应,中介效应占总效应的比重分别为11.76%和11.73%;3）数字技能对收入水平较高、受教育水平较高的农民,电商参与决策和参与程度的正向影响更为显著。政府应从有效提升农民数字技能水平,稳步实现信息获取自由,加强关注农民内部分化3方面提升农民电商参与率和程度。