激光光漂恢复技术测定林蛙卵第一次卵裂前卵表面的运动

激光光漂恢复技术测定了异硫氰基荧光素标记的林蛀卵表面分子在第一次卵裂前的运动。发现固着在玻片上的剥离“细胞膜”的分子运动形式为扩散。扩散系数为(4.6±1.3)×10~(-12)cm~2/s,可动部份为15%。完整卵子上的分子运动形式为流动。细胞膜在不停地流动着。它可能起着协助细胞质运动的作用。细胞膜流动的速度随时间而异,卵裂前不久,在大多数的卵子上,出现两个流动较慢的谷,少数细胞只测到一个谷。这可能与光漂起始时间,光斑与未来分裂沟的距离,和卵子间的差异有关。也讨论了这种速度变化与表面收缩波的关系。     

电刺激大鼠延髓头端腹外侧区对交感节前神经元单位放电的影响

本实验用氨基甲酸乙酯麻醉和箭毒化的雄性大鼠,细胞外记录脊髓胸2节段的交感节前神经元(SPN)单位放电,电刺激同侧颈交感干,逆向激活 SPN,以确定所记录的神经元为交感节前神经元。共分析了80个 SPN 单位放电,其中有自发活动和无自发活动的单位各40个。SPN 轴突传导速度为0.59—3.75m/s。实验观察到电刺激同侧延髓头端腹外侧区(Rostralventrolateral medulla:RVL)可兴奋多数有自发活动的 SPN(19/25),并可使少数静止SPN 产生诱发反应(4/23),潜伏期为6—115ms。电刺激对侧 RVL 结果类似:多数自发活动的 SPN(6/9)呈兴奋反应,及少数静止 SPN(3/17)产生诱发反应,潜伏期为11—105ms。表明 RVL 对双侧 SPN 有兴奋性影响。     

Expression of C4-like photosynthesis in several species of Flaveria

Abstract Photosynthetic metabolism was investigated in leaves of five species of Flaveria (Asteraceac), all previously considered to be C₄ plants. Leaves were exposed to ¹⁴CO₂ for different intervals up to 16s. Extrapolation of ¹⁴C-product curves to zero time indicated that only F. trinervia and F.bidentis assimilated atmospheric CO₂ exclusively through phosphoenolpyruvate carboxylase. The proportion of direct fixation of ¹⁴CO₂ by ribulose-I, 5-bisphosphate carboxylase/oxygenase (Rubisco) ranged from 5 to 10% in leaves of F. australasica. F. palmeri and F. vaginata. Protoplasts of leaf mesophyll and bundle sheath cells were utilized to examine the intercellular compartmentation of principal photosynthetic enzymes. Leaves of F. australasica, F. palmeri and F. vaginata contained 5 to 7% of the leaf's Rubisco activity in the mesophyll cells, while leaves of F. trinervia and F. bidentis contained at most 0.2 to 0.8% of such activity in their mesophyll cells. Thus, F. trinervia and F. bidentis have the complete C₄ syndrome, while F. australasica, F. palmeri and F. vaginata are less advanced, C₄-like species.     

Distribution of Metabolites and Enzymes of Nitrogen Metabolism between the Mesophyll and Paraveinal Mesophyll of Non-Nodulated Glycine max

The distribution of amino acids and key enzymes involved innitrogen metabolism was determined in mesophyll cells (MC),mesophyll protoplasts (MP), and paraveinal mesophyll protoplasts(PVMP) isolated from fully expanded trifoliolate leaves of non-nodulatedsoybean. Qualitative and quantitative differences were foundin the distribution of amino acids, with MP containing the highestconcentrations. Activity of nitrate reductase, glycolate oxidase,glutamine synthetase and glutamate dehydrogenase was measuredin both tissue types and differences in activities between thetissue types were seen. PVMP had high glutamate dehydrogenaseactivity when compared to MP. Activities of glycolate oxidaseand glutamine synthetase were much higher in MP on a protoplastbasis while nitrate reductase activity was similar between thetwo protoplast types. These results, on the distribution ofmetabolites and associated enzymes, are discussed as to theirpossible significance to nitrogen metabolism in the soybeanleaf. Key words: Amino acids, glutamate dehydrogenase, Glycine max, nitrate reductase, nitrogen metabolism, paraveinal mesophyll, protoplasts     

凝集素抑制林蛙卵裂沟新膜外露的作用

剥去受精膜的林蛙卵分裂时,分裂沟中的新膜会暴露出来。林蛙老膜上有大量均匀分布的麦胚和大豆凝集素受体。卵裂前,将剥去受精膜的蛙卵浸于上述的凝集素溶液中,新膜的外露就被抑制。凝集素愈浓,浸泡时间愈长,抑制愈大。在这些卵的表面可看到一层较厚的由凝集素引起的外被。碱处理过的受精卵表面,凝集素受体减少,凝集素抑制新膜外露的作用亦减弱,由凝集素引起的外被亦薄。凝集素是多价的,会在细胞表面产生交链,形成“外骨骼”,抑制新膜外露。凝集素也可通过受体,影响微丝,产生作用。     

Genetic control of dwarfism in hexaploid triticale (Triticosecale wittm.)

The genetic control of plant height has been studied in hexaploid forms of triticale (2n = 42) with genomic structure AABBRR. Thirty-four specimens from the world collection of triticale at the Vavilov All-Russia Research Institute of Plant Breeding with plant heights from 70 to 180 cm have been used in the study. The hybrid analysis of the first, second, and third generations, as well as backcross offsprings, has demonstrated that the given trait is characterized by different modes of inheritance: dominance of dwarfism, dominance of tallness, and intermediate inheritance. It has been found that triticale cultivars of middle and large height differ from short ones in alleles of one or two major genes.     

Dependence of the Post-Illumination Burst of CO2 on Temperature, Light, CO2, and O2 Concentration in Wheat (Triticum aestivum)

The effect of environmental factors on the post-illumination burst of CO₂ (PIB) and O₂ inhibition of apparent photosynthesis (APS) in wheat (Triticum aestivum L.) was studied in an open gas exchange system utilizing the mathematics of non-steady-state systems. Two components of inhibition by O₂ are suggested: one is caused by photorespiration as measured from the maximum rate of the PIB, and the second is direct inhibition as taken as APS_2%O2— (APS_x%O2+ PIB_x%O2) where X is the oxygen concentration. A primary PIB which occurred from 16–28 s after the darkening of the foliage was attributed to photorespiration. No primary PIB was observed at 2% O₂. At a CO₂ concentration of 100 μ/1 in the atmosphere (about 2.5 μM based on leaf intercellular concentration) and at 30°C and 145 nE/cm² nE/cm²·s, APS decreased curve-linearly with increasing O₂ and reached an O₂ compensation point of 560 μM (48% by volume), above which there was a net loss of CO₂ in the light. The PIB increased with increasing O₂ and became saturated at about 500 μM O₂ but decreased above 900 μM O₂. Direct inhibition of photosynthesis by O₂ increased with increasing O₂ concentration. Decreasing CO₂ concentration had an effect on the magnitude of the PIB similar to that of increasing O₂. At 30°C and 21% O₂, the PIB increased with decreasing CO₂ down to the CO₂ compensation point (I) of 1.4 μM (47 μM/l). Below Γ, both PIB and CO₂ evolution into the air in the light (at 21% O₂) increased and then decreased at CO₂ below 0.8 μM. The ratio of the PIB to APS_{2% o} O₂ increased linearly with increasing O₂/CO₂ ratio where O₂ was held constant at 21% and CO₂ was varied from 1.4 to 8.5 μM, while direct inhibition of photosynthesis expressed as a proportion of APS_2%O2 remained constant over this range. At low CO₂ concentration photorespiration as estimated by the PIB is the major part of O₂ photosynthesis, while at atmospheric CO₂ levels, direct inhibition is the major component. The PIB and APS at 2% and 21% O₂ increased hyperbolically with increasing irradiance and all became light-saturated at about 65 nE/cm₂ s. The percentage total O₂ inhibition of photosynthesis remained constant with increasing irradiance as did the relative contribution of direct O₂ inhibition or photorespiration (PIB) to total O₂ inhibition. The PIB and APS at 21% O₂ had similar temperature optima of 30°C when experimental conditions were adjusted to provide a constant internal O₂/CO₂ solubility ratio at varying temperatures. However, with a constant external CO₂ concentration, the temperature optimum for the PIB shifted upward to 35°C while that for APS at 21% O₂ remained at 30°C, which may be due to an increased O₂/CO₂ concentration in the leaf with increasing temperature.