快速干燥对黄皮胚轴贮藏寿命及抗氧化酶活性的影响

以黄皮种子离体胚轴为材料 ,研究了快速干燥对胚轴贮藏寿命的影响及与抗氧化酶活性的关系。未经脱水的胚轴在 15℃贮藏 12 8d仍具有较高的存活率和活力指数。快速脱水 1.5和 3.0h后胚轴的存活率和活力指数并未因脱水而下降 ,但它们在 15℃贮藏的寿命分别只有 8和 2d。未经脱水胚轴的抗氧化酶(SOD、POD、CAT)活性在贮藏过程中能较好地保持 ,但经快速脱水后其抗氧化酶活性在贮藏过程中则迅速下降 ,脱水时间越长 ,酶活性在贮藏过程中的下降就越快。     

Purification and characterization of protein phosphatase-1 from two cold-hardy goldenrod gall insects.

The catalytic subunit of protein phosphatase-1 (PP-1) was purified to homogeneity from final instar larvae (the overwintering stage) of freeze avoiding (Epiblema scudderiana) and freeze tolerant (Eurosta solidaginis) cold-hardy insects. Arrhenius plots showed that activity of PP-1 from both species was strongly suppressed at low temperature. Acidic shifts in pH optima and increased inhibition by okadaic acid were also observed when the enzymes were assayed at 4 degrees C compared with 24 degrees C. The data identify multiple ways by which PP-1 can be inhibited at low temperature and this inhibition appears to be key to sustaining high glycogen phosphorylase activity in support of polyol synthesis at low temperatures.     

Ultrastructural aspects of the development of the hyaline layer and extracellular matrix lining the gastrointestinal tract in embryos and larvae of the starfish Pisaster ochraceus preserved by freeze substitution.

Embryos and larvae of the starfish Pisaster ochraceus are surrounded by a complex extracellular matrix (ECM) layer called the hyaline layer (HL). A similar but less well-organized ECM layer lines some regions of the larval gut. Examination of material preserved by freeze substitution shows that the HL consists of a coarse outer meshwork, a boundary layer, a supporting layer, which is divided into three sublayers, H1, H2, and H3, and an intervillus layer. The development of the HL has been studied in material preserved by freeze substitution. Development begins at fertilization when exocytosis of the cortical granules releases ECM into the perivitelline space and elevates the fertilization membrane. Shortly after, plaques of dense material with attached fibers are present on the outer surface of the egg plasmalemma. Following this, these plaques and fibers are associated with the tips of short microvilli, suggesting that they may induce microvillus formation. Next, the tips of some of the microvilli are joined by short regions of the H1 sublayer. Some of these H1 regions have short segments of boundary layer material associated with their outer surfaces while others are naked. Just prior to hatching, the H1 and boundary layers completely surround the embryo, separating the developing coarse meshwork and intervillus layers. Short segments of the H2 and H3 sublayers are also present. Posthatching, the microvilli and all HL layers increase in thickness and density, particularly the H2, boundary, and coarse outer meshwork layers. The results suggest a sequential organization of HL components from ECM that is secreted into the perivitelline space.     

潮汐作用下干湿交替对黄河三角洲盐沼湿地净生态系统CO2交换的影响

潮汐作用作为盐沼湿地独特的水文特征能在短时间内强烈影响盐沼湿地的碳平衡.利用涡度相关和微气象监测技术,对黄河三角洲盐沼湿地净生态系统CO₂交换(NEE)和环境因子进行监测,并同步监测潮汐变化,探究潮汐过程及潮汐作用下干湿交替对NEE的影响.结果表明: 潮汐过程促进了白天生态系统CO₂的吸收但未对夜晚CO₂的释放产生显著影响,潮汐淹水成为影响白天NEE的主要因子.干旱阶段和湿润阶段NEE的日平均动态均呈“U”型曲线,但干旱阶段NEE的变幅较小.干湿交替增强了白天生态系统CO₂的吸收,干旱阶段最大光合速率(A_max)、表观量子产量(α)和生态系统呼吸(R_eco)的均值均高于湿润阶段.此外,干湿交替减少了盐沼湿地夜晚NEE释放的同时增强了其温度敏感性.     

Mechanisms underlying insect freeze tolerance

Freeze tolerance – the ability to survive internal ice formation – has evolved repeatedly in insects, facilitating survival in environments with low temperatures and/or high risk of freezing. Surviving internal ice formation poses several challenges because freezing can cause cellular dehydration and mechanical damage, and restricts the opportunity to metabolise and respond to environmental challenges. While freeze‐tolerant insects accumulate many potentially protective molecules, there is no apparent ‘magic bullet’ – a molecule or class of molecules that appears to be necessary or sufficient to support this cold‐tolerance strategy. In addition, the mechanisms underlying freeze tolerance have been minimally explored. Herein, we frame freeze tolerance as the ability to survive a process: freeze‐tolerant insects must withstand the challenges associated with cooling (low temperatures), freezing (internal ice formation), and thawing. To do so, we hypothesise that freeze‐tolerant insects control the quality and quantity of ice, prevent or repair damage to cells and macromolecules, manage biochemical processes while frozen/thawing, and restore physiological processes post‐thaw. Many of the molecules that can facilitate freeze tolerance are also accumulated by other cold‐ and desiccation‐tolerant insects. We suggest that, when freezing offered a physiological advantage, freeze tolerance evolved in insects that were already adapted to low temperatures or desiccation, or in insects that could withstand small amounts of internal ice formation. Although freeze tolerance is a complex cold‐tolerance strategy that has evolved multiple times, we suggest that a process‐focused approach (in combination with appropriate techniques and model organisms) will facilitate hypothesis‐driven research to understand better how insects survive internal ice formation.     

Kinetics and mathematical modeling of infrared thin-layer drying of garlic slices

Drying of garlic slices in thin-layer have been studied with Infrared (IR) at 0.075, 0.15, 0.225 and 0.3 W cm^?2 radiation intensity and 0.75 and 1.25 m s^?1 air flow velocity. The results showed increasing in drying rate and decreasing at the time of drying with decreasing air flow velocity and increasing IR radiation intensity. The effective moisture diffusivity (D_eff) was obtained using Fick’s diffusion equation and its mean values ranged between 5.83×10^?11 and 7.66×10^?10 m² s^?1 for all investigated conditions. In addition, a third-order polynomial equation linking the effective moisture diffusivity and moisture content was found. Average activation energy increased with the decrease of IR radiation and increase of air flow velocity. Thirteen different mathematical models were verified with non-linear regression analysis for describing the garlic drying process. Modified Henderson and Pabis model presented the best prediction of the drying of garlic slices.