冰核细菌对仁用杏胚珠超微结构的影响

 应用透射电镜对两个仁用杏品种‘白玉扁’和‘一窝蜂’接种冰核细菌并低温处理后的胚珠超微结构进行了观察, 发现冰核细菌对胚珠的超微结构有一定影响: (1) 使珠心细胞发生严重的质壁分离,细胞质中存在大量泡状结构, 线粒体的内部结构完全被破坏, 呈透明状, 而且有些珠心细胞中形成同心圆状的多膜内含物; (2) 使胚囊中卵细胞的细胞核外膜膨胀, 甚至核膜局部解体, 细胞质中细胞器减少。这些变化致使胚珠发育不正常, 影响受精而导致减产或绝收。接种冰核细菌并低温处理比单纯低温处理对胚珠超微结构的破坏程度重。     

崇测冰帽冰芯记录与塔克拉玛干周缘观测的相逆降水趋势——兼论大气尘埃含量对高海拔山地冰川物质平衡的贡献

对钻自西昆仑山崇测冰帽6530m处18.7m长冰芯的分析得到:尘埃含量的变化影响着崇测冰帽钻点处的物质平衡———与其它气溶胶相比,沙尘微粒是冰帽钻点处降雪的主要贡献因子;以沙尘作为冰核的降雪是钻点处降水的主导形式。与塔克拉玛干沙漠周缘地区地面观测资料比较显示:近60a来的冰芯积累量所反映出的冰帽降水量在减少,同时显示塔克拉玛干沙漠周缘地区暖季降水量在增加,而沙尘恰是连接沙漠周缘地区和附近冰川区气候变化的中介。值得注意的是,本研究对于崇测冰帽冰芯中降雪积累率与尘埃沉降通量一致降低的发现具有区域范围,甚至全球范围气候变化的意义。     

Is the decline of soil microbial biomass in late winter coupled to changes in the physical state of cold soils?

During winter when the active layer of Arctic and alpine soils is below 0 °C, soil microbes are alive but metabolizing slowly, presumably in contact with unfrozen water. This unfrozen water is at the same negative chemical potential as the ice. While both the hydrostatic and the osmotic components of the chemical potential will contribute to this negative value, we argue that the osmotic component (osmotic potential) is the significant contributor. Hence, the soil microorganisms need to be at least halotolerant and psychrotolerant to survive in seasonally frozen soils. The low osmotic potential of unfrozen soil water will lead to the withdrawal of cell water, unless balanced by accumulation of compatible solutes. Many microbes appear to survive this dehydration, since microbial biomass in some situations is high, and rising, in winter. In late winter however, before the soil temperature rises above zero, there can be a considerable decline in soil microbial biomass due to the loss of compatible solutes from viable cells or to cell rupture. This decline may be caused by changes in the physical state of the system, specifically by sudden fluxes of melt water down channels in frozen soil, rapidly raising the chemical potential. The dehydrated cells may be unable to accommodate a rapid rise in osmotic potential so that cell membranes rupture and cells lyse. The exhaustion of soluble substrates released from senescing plant and microbial tissues in autumn and winter may also limit microbial growth, while in addition the rising temperatures may terminate a winter bloom of psychrophiles.Climate change is predicted to cause a decline in plant production in these northern soils, due to summer drought and to an increase in freeze-thaw cycles. Both of these may be expected to reduce soil microbial biomass in late winter. After lysis of microbial cells this biomass provides nutrients for plant growth in early spring. These feedbacks, in turn, could affect herbivory and production at higher trophic levels.     

温室透光覆盖材料流滴性测试方法

作为温室透光覆盖材料的塑料薄膜的流滴性日益受到关注，为此，已开发出各种无滴膜、无滴板，以改善温室透光覆盖材料的流滴性。但国内外对材料流滴性的监测与判断规则却很不统一，给温室用户带来了困难。该文分析了目前几种常用的流滴性检测方法的原理及其适用性，在此基础上，结合温室生产的实际条件，提出在15°～30°倾斜面上形成露滴后，材料表面凝结水滴面积占整个测试面积比例的检测方法——倾斜面上滞留水滴面积比法，并通过对塑料薄膜和聚碳酸酯板的分析测试，提出了将材料表面上计算水滴滞留面积小于10%作为透光覆盖材料流滴性的判别标准，为标准化检测覆盖材料的流滴性提供了依据。     

Geomorphological significance of lichen colonization in a present snow hollow: Hoya del Cuchillar de las Navajas, Sierra de Gredos (Spain)

This paper discusses the results of a lichenometrical and geomorphological study of one of the few remaining active snow hollows in the central region of the Iberian Peninsula. The study area, located on a glacial shoulder, is called Hoya del Cuchillar de las Navajas. A protalus rampart occurs at the base of the hollow. Our studies, conducted between 1992 and 1998, were designed to determine the geomorphological characteristics of Hoya, the mobility of the deposits, and the characteristics of the snow cover. These data formed the basis for a study of the lichen colonization on the blocks and on the wall surrounding the snow hollow. All of the lichen species found were analyzed according to their abundance, distribution and the extent of their surface cover. Measurements of the diameter of the thalli of the species Rhizocarpon geographicum were also obtained. Thalli of this species were found to require a mean snow-free growing season of at least 95 days (13.5 weeks) per year. Maximum mean thallus diameters indicate that the protalus rampart was formed during the Little Ice Age and became inactive 130 years ago.     

Effects of Low Temperature Stress and INA Bacteria on Chlorophyll a Fluorescence Induction Kinetics in Young Fruit of Two Apricot Cultivars

Effects of low temperature and INA bacteria on the change of chlorophyll a fluorescence inyoung fruit from two apricot cultivars were investigated. Low temperature decreased the potential activity(Fv/Fo) ,conversion efficiency of primary light energy (Fv/Fm)of PS Ⅱ and photochemical quenching (qP) inyoung fruit of two apricot cultivars. Low temperature enhanced non-photochemical quenching qN, decreasingthe quantum yield of photosynthetic electron transfer. The presence of ice nucleating active (INA) bacteria in-tensified the effects of low temperature, raised the injury temperature threshold from - 4℃ to - 2 - - 3℃.INA bacteria can be a factor to induce frost susceptibility of apricot fruit. The amount of damaged PS Ⅱ activi-ty center was related to apricot fruit size and cultivar.     

黄河凌汛检测系统分析

根据清洁水体、浑浊水体和冰体在不同波段的反射率不同,运用C语言编写黄河凌汛检测系统程序,将清洁水体、浑浊水体和冰体检测出来,运用GIS的地图控件计算出清洁水体、浑浊水体和冰体面积以及它们的中心经纬度,以实现对黄河凌汛的动态检测。     

黄瓜光合色素与抗寒性相关关系研究

[目的]通过对黄瓜在短时不同强度光照低温条件下的表现,探讨低温胁迫下不同品种间光合色素的表现。[方法]选用本实验室经过多年选育的高代自交纯合系M16、M18、M19、M21、M25和M59为实验材料,设冰水浴光照5个处理:T1为1 h冰水浴光照、T2为3 h冰水浴光照、T3为5 h冰水浴光照、T4为3 h冰水浴避光和T5为7 d低温弱光,研究了黄瓜主要光合色素的含量与抗寒性的相关关系。[结果]T4中类胡萝卜素含量与T5中黄瓜的抗寒指数存在显著负相关,与T5的MDA含量呈显著正相关;T2中叶绿素含量与T5的抗寒指数和MDA含量都呈显著负相关。[结论]抗寒能力的维持需要合适的光照条件。该结果为建立黄瓜抗寒性的快速鉴定方法提供了理论依据。     

2008年娄底冰雪灾害成因分析

2008年1月13日~2月5日,娄底市出现了有气象记录以来强度最强、持续时间最长的冰冻雨雪灾害。在此通过天气形势及各物理量分析,研究发生此次天气过程的主要原因。结果表明,欧亚大陆长时间维持两槽一脊形势,有利中高纬度冷空气南下,中纬度地区长时间维持浅槽天气形势,槽前强盛的西南气流为娄底市冰雪天气提供充沛的水汽来源,对流层中低层冷暖气流形成的辐合带是影响娄底市冰雪天气稳定的天气系统;湖南中南部对流层中低层长时间存在次级环流、深厚的逆温层、逆温层中低层的水汽辐合,这些对娄底市长时间维持冰雪天气起主要作用。     

常温泡沫箱加冰运输条件下荔枝的温度、品质、呼吸和乙烯释放变化

常温泡沫箱加冰密封技术已经广泛应用于荔枝的国内运输。以淮枝为材料，探讨加冰与预冷处理对果实温度、品质以及某些生理指标的影响。结果表明：29～31℃室温下72　h后，对照与5℃预冷处理的果实温度相近，达33℃，高于室温。加冰处理使果实温度先下降，至最低点后回升。加冰量达50％时，果实最低温度降至6℃，72　h后回升至27℃，低于室温。对不同加冰比例的荔枝可溶性固形物含量、好果率、果实失重、酶活性以及箱内乙烯、二氧化碳等气体成分动态进行了比较研究。