Water storage in the wood and xylem cavitation in 1-year-old twigs of Populus deltoides Bartr.

The possible role of water expelled from cavitated xylem conduits in the rehydration of water-stressed leaves has been studied in one-year-old twigs of populus deltoides Bartr. Twigs were dehydrated in air. At desired values of leaf water potential (Ψ_l) (between near full turgor and -1.62 MPa), twigs were placed in black plastic bags for 1–2h. Leaf water content was measured every 3–5 min before bagging and every 10 min in the dark. Hydraulic conductivity and xylem cavitation were measured both in the open and in the dark. Cavitation was monitored as ultrasound acoustic emissions (AE). A critical Ψ_l value of -0.96 MPa was found, at which AE increased significantly while the leaf water deficit decreased by gain of water. Since the twigs were no longer attached to roots, it was concluded that water expelled from cavitated xylem conduits was transported to the leaves, thus contributing to their rehydration. Xylem cavitation is discussed in terms of a ‘leaf water deficit buffer mechanism’, under not very severe water stress conditions.     

黑翅土白蚁的跟踪信息素

黑翅土白蚁Odontotermes formosanus(Shiraki)严重危害堤坝,有明显跟踪行为,其分泌跟踪物质的腹板腺位于腹部第5节腹板前沿中部,分泌细胞呈长形,与腹板呈垂直方向排列。用滤纸双圈法测定黑翅土白蚁跟踪行为。跟踪物质的抽提以正己烷较好,丙酮和二氯甲烷次之。从抽提液柱层析、薄层层析和微化学反应结果推测,其跟踪物质可能是含有双键的醇类化合物。密褐褶孔菌及其感染的腐木块抽提液及白蚁跟踪信息化合物——顺,顺-3,6-十二碳双烯醇都对黑翅土白蚁有较强的跟踪活性。肖若散白蚁和家白蚁抽提液均对黑翅土白蚁有跟踪活性,但肖若散白蚁和家白蚁对黑翅土白蚁抽提液及其柱层析和薄层层析的活性馏份无活性反应。     

流行性乙型脑炎抗原重复浸清试验初步结果

1．按照Casals氏醋酮乙醚浸渍法制乙型脑炎病毒抗原过程中,将病毒鼠脑组几重复以生理鹽水浸渍制作抗原。 2．经第2次浸出的抗原舆初次浸出者分别做補髓结合试验,结果在效价上无顯著的差刖亦无抗補體的理象的发生。 3．此种第2次漫出抗原,在抗原敏感性测定及抗原特異性的的试验,均初步证明可供宝際補體结合试验的应用。因而在不增加成本及复稚步骤条件下,可加倍抗原的产量供应。     

Drought Avoidance Strategy in Ceratonia siliqua L., a Mesomorphic-leaved Tree in the Xeric Mediterranean Area

We report measurements of diurnal changes in leaf relative watercontent (RWC), water potential (     

意蜂与中蜂血淋巴蛋白质成份的研究

本实验用聚丙烯酰胺凝胶电泳分析了两个蜂种的血淋巴蛋白质成分。意蜂和中蜂都是Apis属,血淋巴蛋白质电泳谱相似。但是,两蜂种以及同一蜂种不同级别、不同发育阶段的电泳谱又各有特点。根据实验,我们把成年蜂血淋巴电泳谱分为11条带,雌蜂电泳谱上的带5是卵黄原蛋白;雄蜂卵黄原蛋白含量很少或测不出。 用Thorun方法,在聚丙烯酰胺凝胶平板电泳上测得意蜂卵黄原蛋白的分子量为185,000。     

不同频率电刺激猫中央中核对丘脑束旁核痛放电的抑制效应

用清醒的肌肉麻痹的猫进行实验。观察到:以4Hz、8Hz 和60Hz 的电脉冲刺激中央中核,均可抑制束旁核的痛放电。频率为8Hz 的刺激能产生最强的抑制效应,4Hz 的效应稍差,60Hz 的最差。抑制的表现方式有二:(1)跟随着每个刺激脉冲出现痛放电的短暂遏制,遏制时间约为120ms,而且不随刺激强度的加强而相应延长。这种方式只有在低频刺激时才出现。(2)痛放电的整个时程缩短,高频和低频刺激时均可出现,特別是在使用高强度(5.4—8.5V)刺激时表现得更加明显。刺激丘脑中央中核与刺激外周深部神经或“穴位”,对束旁核痛放电有非常相似的抑制时程和适宜频率。此外,刺激中央中核选择性地抑制束旁核内痛敏细胞的活动,而不抑制非痛敏细胞的活动。实验结果提示我们:中央中核可能在远距离穴位镇痛机制中占重要地位。