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关键词： RNA   发育过程   细胞质   柱头   胞浆   雌蕊   植物种   花粉管   胚胎发育   种胚发育   合成速度   DNA   胚珠   胚囊   雌配子体   发育生物学  

摘要： 如果从意大利数学家兼天文学家Giovanni Amici在1824年首先发现马齿苋(Portulaca oleracea)的花粉在柱头上发芽算起,则植物受精与胚胎发育的研究已有一百五十多年历史;中间虽然曾有人认为受精是在花粉管中进行,胚是在花粉管中发育的;但至1849年经Hofmeister对19个属中的38种植物

摘要： Fifty orofacial abscesses were studied using culture techniques for both aerobic and anaerobic organisms. Eighty-six per cent of the specimens contained anaerobes; of this group, 39 per cent had organisms resistant to penicillin.

关键词： 胚发育   维管束   根冠   酶活性   酶活力   同工酶谱   唐锡华   过氧化物酶同工酶   幼胚   高等植物   茎叶体植物   胚胎  

摘要： 稻胚过氧化物酶活性随着胚的分化发育而增高,至成熟期趋于稳定。酶活性反应初期出现在幼胚表皮层及胚柄,以后又出现在胚芽、胚根及盾片的维管束原,根冠外缘与各器官原基表皮层的细胞外缘。过氧化物酶同工酶随胚发育期而变化,前期在靠阳极端有两条明显快带,至后期逐渐消失,但出现3～4条近阴极端的明显慢带。不同发育期的幼胚在离体强制萌发后则近阳端的过氧化物酶同工酶谱大体相同,只是较成熟胚近阴端的慢带增多。这些现象说明:过氧化物酶活力的出现与胚细胞分化成熟有关;稻胚发育过程中有遗传信息的顺序表达,而且它们表达的规律是与胚和它所处的内、外环境条件之间相互作用有关。

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。