Photosynthetic Apparatus Responses to Short‐term low‐temperature Flooding May Contribute to Freezing Tolerance Changes in Forage Grasses

Winter conditions are subjected to rapid climate changes. Increased precipitation and snow melting during warmer winters may result in low‐temperature flooding. These factors probably affect plant overwintering strategies. This study investigated the relationships between the photosynthetic adjustment and freezing tolerance following a short‐term low‐temperature flooding in two forage grasses (Lolium perenne and Festuca pratensis). The effect of flooding on the photosynthetic apparatus acclimation to cold was determined using chlorophyll a fluorescence measurements. Freezing tolerance was estimated using an electrolyte leakage test. It has been shown that genotypes activating non‐photochemical mechanisms of photosynthetic acclimation to cold during low‐temperature flooding may show increased freezing tolerance. Freezing tolerance reduction observed in Festuca pratensis was probably connected with decreased photochemical activity and photoinhibition of photosynthesis. It can be concluded that photosynthetic apparatus response to low‐temperature flooding may contribute to changes in the freezing tolerance. The direction of the changes is associated with different photosynthetic apparatus performance.     

无柄小叶榕等4种容器苗质量评价中关键生理因子筛选的初步研究

本研究通过栽培无柄小叶榕等4种乔木在15种轻基质中不同组合的苗圃期和出圃实验，建立容器苗质量评价及预测线性回归模型，探讨了苗圃期植株生理指标在解释苗圃期生长表现（干重总生物量、干重根茎比）和预测出圃生长表现中（存活率、株高、地径、相对生长速率）的作用，推荐叶片总叶绿素含量为容器苗质量评价体系中的最关键生理因子。     

激光光致发光光谱分析系统的设计及应用

在微区紫外-可见阴极荧光分析系统成功研制的基础上,采用532nm固体激光器作为激发源研制了一套计算机自动控制的微区光致发光分析系统。该系统不仅可探测可见波段的激光光致荧光,并且将荧光的研究波段扩展至红外区域。对来自于不同地区金刚石样品的900～1010nm波段红外光致发光光谱进行探测,结果发现不同样品在946nm、957nm左右2个宽峰处呈现不同光谱特征,能有效地对样品的生长条件和受外界影响等因素进行分析和研究。该分析系统能在更宽的波段上获取更多更新的样品内在信息,为样品的测试提供了一种有效方法。     

X射线在防腐木材有效成分测定中的应用

采用X射线荧光光谱仪与原子吸收分光光度计,分别测定铬化砷酸铜(CCA)以及氨/胺溶铜季胺盐(ACQ)处理木材中活性成分的含量,并将两者的结果进行了比较和分析。结果表明,用这2种方法所测得的结果差异较小,但前者具备检测速度快、分析精度高、操作简便等优点,可在实际应用中推广。     

Methyl Jasmonate Counteract UV-B Stress in Barley Seedlings

The role of exogenously applied phytohormone methyl jasmonate (MeJA) in counteracting the ultraviolet B (UV‐B) stress in barley seedlings was investigated. Barley seedlings (Hordeum vulgare L., cv. Alfa) 4 days old were supplied with 5 × 10^?5 m MeJA through the roots for 3 days and then exposed for 2 days for 5 h per day to UV‐B (312 nm, biological effectiveness of UV‐B radiation 28.8 kJ m^?2day^?1). The rate of ¹⁴CO₂ fixation, PSI and PSII activities and chlorophyll content decreased, but flavonoids, H₂O₂, malondialdehyde, proline and UV‐B induced compounds increased after UV‐B treatment. The rate of photosynthetic oxygen evolution was more strongly inhibited by UV‐B‐irradiation than PSI and PSII efficiency. MeJA itself increased the content of free proline, which acts as a stress protector due to its radical scavenging ability. Increased superoxide dismutase, catalase and peroxidase (POX) activities in the leaves and in the roots and the POX isoforms induction revealed the MeJA involvement in plant tolerance to oxidative stress caused by UV‐B irradiation. It was shown that pre‐treatment with MeJA counteracted UV‐B stress. Therefore, it was suggested that MeJA could acts as a mediator in plant defense responses to UV‐B irradiation by enhancing the activity of antioxidant system and free radical scavenging capability of plant cells.     

Direct non-thermal plasma treatment for the sanitation of fresh corn salad leaves: Evaluation of physical and physiological effects and antimicrobial efficacy

Current problems with outbreaks of serious infections caused by human pathogens on fresh-cut greens highlight the need for new, optimized postharvest sanitation treatments to effectively meet recent food safety standards. In contrast to various chemical treatments, non-thermal plasma (NTP) has a high potential as a gentle target sanitation technique. However, possible interactions between NTP and the physiology of treated fresh products have not been investigated in detail. Here, chlorophyll fluorescence image analysis (CFIA) was used to study the potential impacts of non-thermal plasma on the photosynthetic activity of highly perishable corn salad leaves as a model produce. For this purpose, an atmospheric pressure plasma jet, driven at radio frequency, and transforming argon with flow rates of 20 L min⁻¹ into non-thermal plasma at 10, 20, 30, and 40 W generator power was applied for various times to the surface of corn salad leaves. Thermographic measurements indicated maximum temperatures of 39.0 °C, 44.4 °C, 60.1 °C, and 66.0 °C, respectively, on treated leaf surfaces. CFIA revealed that treatment at moderate generator power of 20 W for up to 1 min was the maximum setting for quality retention. Furthermore, the microbial inactivation efficiency of the plasma jet system at these operating parameters was successfully tested on Escherichia coli bacteria, inoculated on corn salad surface at 10⁷ cfu cm⁻² and 10⁴ cfu cm⁻². At 20 W, bacteria with lower initial load could be inactivated by 3.6 (±0.6) log-cycles within 15 s of treatment duration; whereas at the higher initial load of 10⁷ cfu cm⁻², bacteria were reduced by 2.1 (±0.2) log-cycles after 30 s.     

西葫芦银叶病发病叶片叶绿素代谢及其荧光特性

 研究了西葫芦银叶病发病叶片和叶柄叶绿素代谢特性和叶片叶绿素荧光参数的变化。与对照相比，发病叶片和叶柄叶绿素总量(Chl.a+b)，叶绿素a (Chl.a)，叶绿素b (Chl.b)含量均下降；轻度与重度发病叶片叶绿素a/b增加，中度发病叶片与对照差异不显著，而叶柄比对照降低。西葫芦银叶病对叶片Chl.b的影响比Chl.a大，而对叶柄Chl.a的影响比Chl.b大。发病叶片和叶柄叶绿素酶活性升高，从而使叶绿素降解加速，叶绿素合成中间产物Protoporphyrin IX (Proto IX)，Magnesium protoporphyrin IX (Mg-Proto IX)，Protochlorophyllide (Pchlide)含量降低，Uroporphyrinogen Ⅲ (Uro Ⅲ)含量增加，表明叶绿素合成在 Uro Ⅲ到 Proto Ⅸ受阻。发病叶片最大光化学量子产量(Fv/Fm)，光系统Ⅱ(PSⅡ)的潜在活性(F_v/F_o)，实际光化学效率(φPSⅡ)，光化学淬灭系数(q_P)降低，非光化学淬灭系数(NPQ)增加。试验结果表明，西葫芦银叶病破坏了叶绿素合成和降解的动态平衡，叶绿素合成受阻和叶绿素降解加速是导致叶片叶绿素含量降低的原因；发病叶片叶绿体PSⅡ活性受到抑制。     

基于纳米材料的免疫层析试纸在兽药残留检测中的应用

兽药残留是食品安全的重要影响因素,开发兽药残留检测方法是保证食品安全的重要手段。免疫层析试纸是一种操作简单、生产成本低且具有良好灵敏度的检测方法,适用于现场检测、大规模食品筛选,在兽药残留检测中具有巨大的应用价值。纳米材料可提供特殊的检测信号,是影响免疫层析试纸检测灵敏度和定量分析的关键因素。文章主要对胶体金、磁性纳米材料、量子点以及时间分辨荧光微球这几种纳米标记材料进行介绍,指出各自的优缺点及应用情况,并对该技术在兽药残留检测中的应用趋势进行展望。     

美国山核桃无性系叶绿素的荧光特性

研究了12个不同品种美国山核桃无性系嫁接苗的叶绿素荧光特性.结果表明:不同品种间的初始荧光(Fo)、最大荧光(Fm)、PS II原初光能转化效率(Fv/Fm)、PS II潜在活性(Fv/Fo)、非光化学猝灭系数(qN)均存在显著或极显著差异;光合量子产额(Y ield)和光化学猝灭系数(qP)未达显著差异.初步聚类分析表明,不同无性系嫁接苗中的所有西部品种和国内优系金华1号具有较好的光合性能.