教学课程资源库 更多>>

摘要： Chlorophyll distribution within the carpets, CO₂ gas exchange under controlled conditions, and heat resistance of the snowbed bryophyte Anthelia juratzkana (Limpr.) Trev. were investigated. Also the gas-exchange parameters of the co-occurring Polytrichum sexangulare Floercke were assessed. Only the uppermost 4 mm layer of Anthelia carpets contains sufficient pigments for photosynthesis. At light saturation and optimal temperatures (6–11°C) the maximum rates of CO₂ uptake are 0.7 mg CO₂ g^-1dw h^-1 in Anthelia and 1.5 mg CO₂ g^-1dw h^-1 in Polytrichum. Gas exchange reaches light saturation at about 300 μE m^-2s^-1 in both species. At +2°C the light compensation point is reached at ca. 10μE m^-2s^-1 and increases significantly with increasing temperature. The lower temperature compensation point is reached at-4°C in Anthelia and does not drop much below-5°C in Polytrichum. Anthelia cannot sustain net photosynthesis beyond 30°C and Polytrichum not beyond 32°C. Nine month storage under dark, cold and wet conditions does not affect the photosynthetic capability of Anthelia. As a response, however, the net photosynthesis rate is depressed due to an increase of the respiration rates. Polytrichum sexangulare did not tolerate the storage so well. The heat resistance limit of Anthelia is low (39°C). There is evidence that the distribution of the two bryophytes within snowbed communities is determined by their capability to make use of low light intensities and their low temperature demand for optimal photosynthetic rates. Being resistant to long lasting cold, wet, and dark conditions, Anthelia is particularly adapted t

关键词： 愈伤组织块   胚乳   蓖麻   初步观察   向日葵   小麦   向日葵属   麦类作物   生长素   吲哚乙酸   生物学效应   植物组织培养   植物组培   激素  

摘要： 植物激素,按作用性质分为二大类:一为生长素类(如吲哚乙酸,奈乙酸,2,4—D等),一为激动素类(kinetin)(如6—苄基嘌呤,甲氨基嘌呤等)。从石油废渣中提取的长春产C—751激素是相当于哪一类激素呢?通过胡萝卜,菊芋,蓖麻胚乳的诱导愈伤组织实验和通过对小麦,向日葵,绿豆的发芽、生根实验,我们做了同6—苄基嘌呤,6—(?)基嘌呤,吲哚乙酸,萘乙酸,2,4—D药剂的作用对比,实验初步结果:C—751激素在诱导愈伤组织形成和生长以及种子发芽和幼苗生根中,其性质多接近生长素类。

关键词： Plant Sciences   Plant Genetics and Genomics   Plant Pathology   Plant Physiology   Biotechnology  

摘要： Flowering behavior and the morphology of flowers in white yam, D. rotundata Poir. is described in relation to hand pollination. Plants flowered between June and Sept. with flowering intensity depending largely on factors associated with shoot vigor in genotypes. The high predominance of male plants coupled with irregular flowering necessitate the establishment of many plants to ensure sufficient flowering individuals for a hybridization program. In order to achieve good fruit set and seed yields, pollen should be collected from open male flowers around 1400 h and mature female flowers pollinated within a week after they are bagged particularly during the early flowering months. Low fruit set in white yam (12%) is primarily due to inefficient pollination by insects. With hand pollination fruit set is improved 3-fold.

关键词： 固沙植物   经济植物   沙坡头地区   小叶锦鸡儿   锦鸡儿属   生理学   基础医学   生物学  

摘要： 我们在沙坡头地区进行了引种栽植试验,选择出抗逆性及适应性较强的优良固沙植物种,并运用电子显微镜及一些分析手段,研究它们的抗旱机理。据研究,在形态结构方面,旱生型肉质植物红砂、沙拐枣,叶表皮覆盖有蜡质且细胞壁和角质层较厚,气孔下陷。旱生型的柠条、猫头刺、叶形变小,叶表面被稠密的灰白色的绒毛所覆盖,借以掩盖气孔,减少蒸腾,使叶肉组织免于灼伤。在生理特性方面,这些旱生型植物细胞的原生质粘滞性较高,弹性强,透性大,抗脱水能力强,抗热性好,蒸腾强度小,过氧化氢酶的活性强,可溶性糖的含量高,束缚水含量多,束缚水与自由水的比值大等,从而构成耐干旱的特性。

关键词： 古生物学  

摘要： 本书简要地介绍了古生物学的研究历史、对象、目的、意义和发展趋势,重点在古无脊椎动物与古植物。

关键词： 粳稻   蛋白质   RNA   发育进程   水稻   唐锡华   铁骨矮   蛋白质含量   淀粉含量   高等植物   茎叶体植物   干重   胚发育   分化发育   发育生物学   胚胎  

摘要： 鉴测了粳稻胚的发育进程及不同分化发育时期中DNA、RNA、蛋白质、淀粉含量和鲜重、干重、细胞数的变化。 开花后6～13天(胚分化第一到第四叶原基期间)胚细胞数增加时,DNA、RNA含量迅速上升。此后细胞数和DNA、RNA含量都趋于稳定,但RNA在18～25天再次增长。每胚蛋白质和干重基本上随RNA含量相应地变化。 每毫克胚于重的核酸和蛋白质含量在13天出现明显的转折。平均每细胞的DNA含量在整个发育期保持稳定,RNA第一阶段的增长只持续到分化完成的前夕,而蛋白质在25天以前一直增加。 胚内淀粉的累积在整个胚形成期呈现三段斜率不同的直线。以单位干重表示时则在8天左右和21天出现两个高峰,先于RNA和蛋白质两次积累的高峰。 在大分子物质的变化与胚胎发育进程相互关系并与籼稻比较的基础上,将稻胚发育划分为原胚期、分化期、成熟期和休止期。

关键词： Carbon felt dosimetry   FRP boat production   Mandelic acid   Phenylglyoxylic acid   Styrene  

摘要： A survey on styrene exposure was conducted in 5 small to medium-sized fiber-reinforced plastic (FRP) boat plants utilizing carbon felt dosimeters as personal and stationary samplers to measure 4 h (TWA [time-weighted average]) exposure during workday afternoons. The heaviest exposure, up to 256 ppm by personal sampling and 174 ppm by stationary sampling, took place during the lamination on a mold to produce a boat shell, and the work inside narrow holds also resulted in exposures of a comparable degree. Styrene levels were lower in other auxiliary works. The TWA of exposure in an entire boat production was 40-50 ppm. Installation of several flexible hoses as an exhaust system was effective in decreasing the vapor concentration. Gas masks were also useful in reducing the exposure. Urine samples were collected from 96 male workers at the end of 8-h work (4 h in the morning and 4 h in the afternoon) and from 22 nonexposed male subjects, and analyzed for mandelic acid (MA), phenylglyoxylic acid (PhGA) and hippuric acid (HA). When the results of urinalyses were compared with 4-h styrene TWA as monitored by personal sampling, the best correlation was obtained with MA+PhGA/creatinine (r = 0.88), followed by MA (0.84). For these 2 cases, regression lines and 95% confidence limits for the group means and for the individual values were calculated. The urinary levels of MA, PhGA and HA in the 22 nonexposed male subjects were also tabulated.